Can The People "In The Know" Answer Some Cat Questions?

[monkeyswrench]

Ok, not wanting to pollute someone else's thread, but would like some clarification as to why's and differences. We have terms "true cat", "true tunnel" and "center pod" floating around here like empty beer cans in the garage. I understand a center pod design would be for a single IO normally, and a hull designed without it would be more suited to twin IO's or OB's. Now, I can kind of see how lack of a center pod could make a hull turn sharper, like a big version of the tunnel boats. As for big water stuff, does the "true" whatever pack more air? It seems as though a center pod would actually create a higher pressure between the sponsons due to the restriction created by the pod. What speeds do these advantages take place at, and do they have any weird side effects on deceleration?

 

[Tooms22]

I believe you’re right and also wrong

I’m here for the info too. Subscribed.

 

[monkeyswrench]

I believe you’re right and also wrong

I’m here for the info too. Subscribed.

See my confusion!?

 

[zx14]

I’m a daytona guy, and what the Grandfather told me , (Bob Leach) , the center pod helps you get on plane. Pure and simple. You have a little more running surface when starting off and slower speeds. When your at speed, it is not touching, packing air like a none center pod tunnel. I won’t use the word , true tunnel, just because there is no center pod. I own a true tunnel. (It’s not a mod vp boat, a V bottom with 2 tunnel like inverted rails. These boats don’t really pack air, like a tunnel boat with sponsons, with a large flat area up front to scoop in and pack air, they are more of a Tri hull that slice trough waves better, up to the point when the waves are as tall as the depth of the tunnel.) Now this is on the bigger center pod tunnels, the center pod is not as deep as the sponsons, so you truly, pack air and it vents completely through the tunnel at speed. Single or twin I/O or wacker, and in some cases triple wacker, it does not matter. Then You have the 18’ and 19, Daytona, it’s center pod is deeper,(traditionally) , these boats originated as jet botes. Your center pod had to be deeper than sponsons, so it can still touch and suck water at speed.

My 2 cents.

 

[2FORCEFULL]

Ok, not wanting to pollute someone else's thread, but would like some clarification as to why's and differences. We have terms "true cat", "true tunnel" and "center pod" floating around here like empty beer cans in the garage. I understand a center pod design would be for a single IO normally, and a hull designed without it would be more suited to twin IO's or OB's. Now, I can kind of see how lack of a center pod could make a hull turn sharper, like a big version of the tunnel boats. As for big water stuff, does the "true" whatever pack more air? It seems as though a center pod would actually create a higher pressure between the sponsons due to the restriction created by the pod. What speeds do these advantages take place at, and do they have any weird side effects on deceleration?

I 've owned them all, Full tunnel (true tunnel) schiada river tunnel, mod V , cheetah tunnel, Carrera tunnl / force (same as Carrera stretched a foot)...most need to be around the 80 mph mark to pack enough air...the cheetahs, the tunnels are too big, and most of them never go fast enough to make the bottom work , so they have a harsh ride.. schiada RT 's handle better in the ruff, but not as good as the RC....the center pod provides the needed lift to get the boat off the big flat area of the tunnel at slower speeds to help with the pounding that happens ….. the math involved can get confusing , the outter sponsons have to be able to cause enough lift with out packing air...too big of tunnel just raises the speed that will allow the air lift...I remember Brad at force adding depth to the center pod of the 34'r trying to over come this problem...what happens is the boat will start to hop like a rabbit...and faster you go the more violent it gets...weight placement VS tunnel design can get catastrophic,.. people have lost there lives messing around with cats.... blow over and such....nasty crashes with tunnels and tunnel tabs....pretty much why stoker puts fixed tabs that won't adjust going across the water, Believe this or not, some people think it's cool to take tab indicators off,...same with sponson tabs, and center sponson tabs...placement at speed can get real critical...the confidence people have in 100 mph plus 29'rs is scarry… they think this... it'll never "BLOW OVER" till it does....then what..I did a full vert 90 degree's in my 29'r.... got lucky I didn't kill every body in the boat...respect for the boat was taugh quick..

 

[2FORCEFULL]

I remember years ago, I was working on a hi rise in vegas….we stocked a bunch of drywall on the upper floors before the walls were framed...wind kicked up that night... sheets of drywall scattered out all over the golf coarse the next morning...those of you that know drywall know of the recessed edge on both sides, as heavy as the sheets are, this allowed air to get between the sheets...the wind was enough to cause the sheets to kite and fly away...so again,....math problem..

 

[2FORCEFULL]

As you can tell...the subject of tabs and plates on boats to me is very serious...the wrong combo of tabs, plates, rollers,wind and speed … better known as driver error can take away life.....know your boat, and know where your tabs are..Lucky is a 3 legged one eye dog that always ran across the same freeway...till one day....

 

[Carlson-jet]

Center pods are for jets. Where else are you going to put the jet?

 

[lake p.a.l.]

I'm no expert just owned a couple of boats. Had a 28 Silhouette deck "cat" hull, planed ok with 550 hp, didn't turn great & ran 70mph, probably not fast enough to experience any porpoise. Then we owned a 25 Daytona with 735hp 748lb/ft NA that ran 105 mph, didn't plane great but not terrible, turning was just a controlled drift AT BEST, porpoise from 60-70mph but hammer thru it & you wouldn't notice it, would handle 1-2' legitimate chop, cruiser & surf wakes you better slow down, was a good boat.
Now we've owned a 308 Skater with twin,bone stock, 300XS for 3 years. By FAR the best boat we have owned and best hull I've ridden in for all around performance. Planes quickly even with 200 gallons & 5 people, doesn't accelerate great when really loaded down, turns incredibly hard like it's on rails, porpoise from 50-70mph but easy to drive thru when lighter on fuel & passengers, runs 104mph max, ran 99mph last Sat with 100+ gallons & 5 people, laughs at surf & most cruiser wakes, handles SF Bay on most days, a truly amazing machine with just 600hp.

Once again, I'm no expert. If you put a true cat against the same size center pod with same power, the true cat will absolutely DESTROY the center pod boat in any kind of rough water or thru the turns of the Delta. Less than zero chance I'm going back to a center pod boat and can't imagine owning another big block either.

 

[zx14]

I'm no expert just owned a couple of boats. Had a 28 Silhouette deck "cat" hull, planed ok with 550 hp, didn't turn great & ran 70mph, probably not fast enough to experience any porpoise. Then we owned a 25 Daytona with 735hp 748lb/ft NA that ran 105 mph, didn't plane great but not terrible, turning was just a controlled drift AT BEST, porpoise from 60-70mph but hammer thru it & you wouldn't notice it, would handle 1-2' legitimate chop, cruiser & surf wakes you better slow down, was a good boat.
Now we've owned a 308 Skater with twin,bone stock, 300XS for 3 years. By FAR the best boat we have owned and best hull I've ridden in for all around performance. Planes quickly even with 200 gallons & 5 people, doesn't accelerate great when really loaded down, turns incredibly hard like it's on rails, porpoise from 50-70mph but easy to drive thru when lighter on fuel & passengers, runs 104mph max, ran 99mph last Sat with 100+ gallons & 5 people, laughs at surf & most cruiser wakes, handles SF Bay on most days, a truly amazing machine with just 600hp.

Once again, I'm no expert. If you put a true cat against the same size center pod with same power, the true cat will absolutely DESTROY the center pod boat in any kind of rough water or thru the turns of the Delta. Less than zero chance I'm going back to a center pod boat and can't imagine owning another big block either.

Porpoise from 50-70?,is that all through that 20mph zone?, or it does it somewhere in there? I always like the looks of 28-30 skaters and am a wacker fan.(had 3 over the years).
I boat a lot from 40-55 mph, what does your 308 do at those speeds? Yes I can go over 100 with a push of the stick, but really don’t do it much, I’m packing good air at 70-80, “you never know on the porpoise, sometimes it’s there, sometimes not” but to be honest, unless I’m in a hurry, I’m running under 60mph.

 

[lake p.a.l.]

Porpoise from 50-70?,is that all through that 20mph zone?, or it does it somewhere in there? I always like the looks of 28-30 skaters and am a wacker fan.(had 3 over the years).
I boat a lot from 40-55 mph, what does your 308 do at those speeds? Yes I can go over 100 with a push of the stick, but really don’t do it much, I’m packing good air at 70-80, “you never know on the porpoise, sometimes it’s there, sometimes not” but to be honest, unless I’m in a hurry, I’m running under 60mph.

In flat water & 6-10" wind ripple our 308 will porpoise from 50-70mph, not violent, but annoying. If its confused water from different directions there is no hop & rides great. Put it into a lil left or right turn & power right thru the hop. The 308 is a foot wide, foot taller & 1000lb heavier than the sports car 28.

 

[lake p.a.l.]

All of the outboard Skaters I've been on have a hop from 50-70 +/- mph depending on weight & wind direction, fyi.

 

[sirbob]

When you say porpoise, are you saying it is rising in the bow followed by rising in the stern?

Or is it just the bow going up and down?

 

[PlanB]

All of the outboard Skaters I've been on have a hop from 50-70 +/- mph depending on weight & wind direction, fyi.

Our 28 also had the hop, but you could get rid of it by lowering the tab. I rarely ran in the speed range where it hopped, so It was never really a problem.

I have owned a Daytona, 2 DCB's and a Skater. The Skater was hands down the best performing hull.

 

[River Runnin]

Both mine are litter box trained!??

 

[monkeyswrench]

Both mine are litter box trained!??

...but I'd bet they both get hop about 70mph!

 

[beaverretriever]

When you say porpoise, are you saying it is rising in the bow followed by rising in the stern?

Or is it just the bow going up and down?

My Skater based "true tunnel" hull would bounce right around 70mph two or three times but I would drive right through it. No rise in the stern area whatsoever. Just a few bumps in the front and that was it. 70 seemed so slow in my last boat so it was either 45 or 95 in it so not being able to run 70mph wasn't negative

 

[HighVoltage329]

If you don't want to drive 70+ consistently then center pod is the way to go. I like both center pod (DCB F29 & M31), and true tunnel (Skater 28) but in really rough water a true tunnel will do better.

 

[MK1MOD0]

I believe a more accurate way to describe a skater would be a “true catamaran “. And yes. A true cat will always outrun a canter pod tunnel boat in the rough. Take a look at a 36 Skater .... even next to a 40MTI you can see how much deeper the tunnel is compared to the MTI. That’s why the Skater is faster than the MTI when it gets really rough. On the calmer water it’s reversed. Tunnel depth makes a huge difference in ride quality when it’s rough, even between two different true catamarans

 

[lake p.a.l.]

When you say porpoise, are you saying it is rising in the bow followed by rising in the stern?

Or is it just the bow going up and down?

Just the bow. I just know I can't cruise between 50-70mph unless the water is sloppy.

 

[DrunkenSailor]

The silverwing tunnel is a true tunnel. At 20.5' it is the best turning boat that I have ever been in. You can take the wheel at 70 mph and complete a u turn in 20 feet and be back headed the other direction at 70 in seconds also does very well in the chop and is faster in messy water than on glass. It accelerates unlike anything else. The problem is low speed cruising. Without a center pod you have to pack air or you are gonna be taking water over the bow. This boat hates going under 40 mph. Get it over that speed though and it will float over just about everything.

https://images.app.goo.gl/9SVx4bEg13QudjVcA

 

[RiverDave]

Ok, not wanting to pollute someone else's thread, but would like some clarification as to why's and differences. We have terms "true cat", "true tunnel" and "center pod" floating around here like empty beer cans in the garage. I understand a center pod design would be for a single IO normally, and a hull designed without it would be more suited to twin IO's or OB's. Now, I can kind of see how lack of a center pod could make a hull turn sharper, like a big version of the tunnel boats. As for big water stuff, does the "true" whatever pack more air? It seems as though a center pod would actually create a higher pressure between the sponsons due to the restriction created by the pod. What speeds do these advantages take place at, and do they have any weird side effects on deceleration?

You are asking several questions pretty broadly.. It would take an entire book to accurately answer what you asked.. That said I'll throw in my .02. I've been waiting until I got to a keyboard because I'm not sure how long of an answer it's going to be, and it would be full of typos. That said expect some hater or "know it all" to come along and tell you everything I said is wrong in about 5 seconds.. LOL

In order to answer the question I think we should start at the very basics instead of pods vs true tunnels etc. The very basic thing is what is the difference between an air entrapment hull vs a traditional planing hull. They both start off the same getting onto plane with hydrodynamic lift. In the case of a vee bottom the boat is going to be running on hydrodynamic lift entirely throughout the entire speed range. In the case of an air entrapment hull you are going to start getting lift from aerodynamic lift. In both cases generally speaking the farther the boat comes out of the water (or less contact patch) the less drag and the faster it goes.

Now I'm going to start into primarily air entrapment because that's what you asked about and some of this is going to be in "generalities" as there's no way you can describe all of this in specifics as there are so many scenarios and so many different boats you can't pin point one thing onto all of them.

The Porpoise - Generally speaking most true air entrapment hulls that "work" are going to have some kind of porpoise at some speed somewhere. What that is is basically the "transition" point from hydrodynamic lift to some blend of hydrodynamic / aerodynamic lift. At that speed the boat is starting to work aerodynamically and lift is being built, however it isn't enough compression yet and the air will spill back out of the tunnel and the boat falls back into the water, which then the lifting strakes bring it back and the process repeats. A little slower and it's mostly on the hydrodynamic side (bottom of the boat), and once you cross this threshold it's going to be some blend of aerodynamic & hydrodynamic, the more compression the more aerodynamic. etc.. Once things begin lifting aerodynamically things start getting a lot more efficient as cutting through air is a lot easier than cutting through water. Without getting to next level on the thought process the laws of diminishing returns basically get pushed back quite a ways because the efficiency and lifting method is much more efficient. Think wing of an airplane vs a wing on a hydrofoil.. It's easier to push the wing through the air than it is the water.

So now you have your different types of bottoms that ride on "air" which typically are going to be a True Tunnel / A Center Pod Boat / A mod VP boat.

To start we will discuss the Mod VP. It originally started just what it sounds like. It's a modified "V" bottom with tunnels. There's about a million variations of that, and I'm quite sure people can argue until the cows come home of when and where a mod vp turns into a center pod boat and vice versa. I don't really care to argue it. I'm just putting this out as generalities.

Center Pod Boat - These have evolved over the years. Unlike a mod VP boat they didn't start life as a Modified V but rather were tooled as a catamaran from the get go but have a center sponson (pod). If you look throughout the history and evolution of these things they generally started out with the center pod below the sponsons and have inched up and up over the years.

True Tunnel - This is just going to have two sponsons and a smooth tunnel from front to back. (generally speaking)

Now there's going to be variations on all this stuff where maybe they don't fit in any of the categories in particular.. For example a "CP" / "Gullwing" style boat is most definitely using aerodynamic lift and they work extremely well.. That said they don't trap air in the tunnels from the front to the back, but rather generate lift and then bleed it out the sides of the boat towards the transom. Someone else brought up a 19 Daytona earlier which does something very similar even though the tunnels run all the way to the back. That boat the center pod is lower than the outside sponsons. It's pretty rare to see one doing it outside of the drag races, but if you ever see one that is setup really well and hauls ass, they actually ride on the center sponson and the outside sponsons are slightly out of the water when running. Than you can get into a newer style boat like the Howard 255 VTX.. That boat works very similarly to the CP / Gull wing.. It generates lift the faster you go and spills it out the sides and the back when you are running.

Which is going to bring us over to something like the Talon bottom which almost all the west coast decks are some slight variant or direct copy. As Steve said earlier 99% of those boats aren't going to go fast enough to make that bottom work. In the vast majority of cases even though they are an air entrapment hull they are basically being used as a tri hull. The reason a lot of people say they ride smooth is because in moderate lake chop there's almost always some surface touching the water. Think about quartering wakes in a deck boat and the first sponson crosses the wake the middle sponson is now on that wake and it's entering touching the third. They kind of crab across water so there isn't a lot of up and down movement. Now if you start throwing some horsepower in them and get them running 80+ and those little tunnels start working and you can actually feel the boat getting lighter and coming out of the water. That bottom is an extremely stable & docile bottom which is why it was used for all these family rigs, as well as hotrods. Something that should be noted is that bottom primarily works on hydrodynamic lift and it's a great freakin bottom that is exceptionally efficient.

So the inverse of that is you start adding a bunch of aerodynamic lift and things are going to be a lot more efficient and go alot faster, but things can also get less stable. Take an HTM which is basically a 28 warlock shortened with some mods. That boat has a giant "wing" on the front of it and has a small center pod that then flares at the back and adds a ton of compression. HTM's are basically HP to HP one of the fastest west coast cats you are going to find. That said it's arguable that some of that performance comes at a cost of stability. If you look at the design of an HTM (even though it's an older design) they really put a lot of thought into the wing (portion in between the sponsons) of that boat to try and maximise lift. They damn near shaped it like an airplane wing.

Part 2 Coming.

 

[monkeyswrench]

Learning. A little more each day, which puts me ahead of some.

So, from what I'm gathering a tunnel and center pod deal both work on the concept of a wing in ground effect. The pod design though has a more consistant ride at varying speeds. Whereas a tunnel requires speed to transition cleanly from basically waterborn to airborn. Kinda?

If this is the case, why couldn't variably port the airflow to change the lift characteristics? Much the same way they can use trim tabs to adjust the attitude of the hull from a hydrodynamic standpoint.

 

[RiverDave]

If you are asking which "type" of air entrapment boat turns the best the answer is going to be a true tunnel. We are going to step out of the generalities here for one second and get into specifics and extremes.. Up until recently the hardest turning (most g forces) you could experience in any kind of vehicle would have been a "Champ Boat" which is basically a true tunnel outboard boat with a shallow tunnel depth. They are extremely efficient and I can't remember now but I think they pull something like 7G's in the corners when they are racing..

I picked this video for you as you get a pretty clear shot of the bottom (understatement) and I think it's rad the guy did a flip and kept rolling after..

Now if we are getting into the larger more modern stuff the same is going to hold true.. The big True Tunnel boats are going to have a "rail" down the insides of the sponsons. As the boat turned the inner sponson digs in and that "rail" for lack of a better term is what "Hooks it in" to the turn. The boats if driven correctly will actually lean into the turns like a vee bottom.

At the 7:52 mark in this video you can see what I'm talking about.. I didn't scrub the whole video that was just the first instance I saw. There's better examples out there.

Now a centerpod boat will also lean to the inside as well! Note the 45 second mark of this video you can see Tony rolling from left to right and the boat transfers smoothly..

So the pro's and cons?

The center pod boats generally ride a lot better at slower speeds.. If you are in a Spectre or a true tunnel boat and that thing isn't up and running the waves will actually smack the bottom of the tunnel and the things will kick you right in the ass like a bronco. In a pod boat when you are running slow the waves are generally "broken" by the centerpod and generally won't come up and hit the flats of the tunnel. Center pod boats tend to have a smaller porpoise window and are a lot more comfortable usually in smooth water / smoother waters. They are also a lot more forgiving and docile to drive, and have a broader trim window to work with.

True Tunnels - Once they are up and running they can handle a lot larger water than a center pod boat. They turn harder because there is no pod to block the inside sponson. Generally speaking they are going to be slightly faster HP to HP. The porpoise window (again generally speaking) is going to be larger, and it's harder to get them to run well in smoother water because of that.


Earlier someone mentioned they had a true tunnel and if it hopped they would lower the tab. They were referring to a large tab that goes across the entire tunnel and can be lowered or raised. That tab isn't to touch the water but rather to add or reduce tunnel compression. If there boat was hopping because it wasn't at the speed the boat desires they could lower that tab a bit and raise compression and get it to stop. To that effect on race boats if the water is smooth they can drop that tab and get the boat up "on a bubble" and increase the speeds dramatically via a reduction in drag. However if the water isn't smooth enough they'll break the tab etc.. Or in some cases it can cause crashes (as has happened plenty of times in smaller boats with tunnel tabs).


At the end of the day there isn't really one that's better than the other for all purposes.. There's a reason why DCB & Eliminator have always been the kings of the west coast, and the Skaters and MTI's etc have always been the kings of the east. We run them in different environments historically.

With the new outboard power though that's all changing. People are wanting a boat that they can run hard all day long with a ridiculous warranty.. Then because it's an outboard it's easy to flush so why not run it in the ocean and on the lakes. Right now you are seeing a shift where the MTI's and Skaters, and Doug Wrights are now permeating the west coast and buyers are really liking the idea of a true tunnel that offers that flexibility of rough / smooth water.

In response you are now seeing the west coast builders respond with true tunnels to answer the call and offer those same options to their current customers and offer their own twists on the builds.

 

[RiverDave]

Learning. A little more each day, which puts me ahead of some.

So, from what I'm gathering a tunnel and center pod deal both work on the concept of a wing in ground effect. The pod design though has a more consistant ride at varying speeds. Whereas a tunnel requires speed to transition cleanly from basically waterborn to airborn. Kinda?

If this is the case, why couldn't variably port the airflow to change the lift characteristics? Much the same way they can use trim tabs to adjust the attitude of the hull from a hydrodynamic standpoint.

They do.. With a tunnel tab.

RD

 

[RiverDave]

The Nordic is kind of a different beast all together which is why everyone is very curious as to how it runs. It is a wide sponson / narrow (but deep) tunnel.

Due to my injury I haven’t been in one yet, but I can speak for a lot of people to say that we are all interested on how it’s going to perform vs more traditional style bottoms.

Anyhow I hope some of that helps and at least answered some of your questions. If you want to know something specific just ask! If I don’t know I will find out.

 

[monkeyswrench]

The Nordic is kind of a different beast all together which is why everyone is very curious as to how it runs. It is a wide sponson / narrow (but deep) tunnel.

Due to my injury I haven’t been in one yet, but I can speak for a lot of people to say that we are all interested on how it’s going to perform vs more traditional style bottoms.

Anyhow I hope some of that helps and at least answered some of your questions. If you want to know something specific just ask! If I don’t know I will find out.

I am really new to the concept of larger boats going fast. I had gone to see GP tunnels at Puddingstone when I was a kid. Saw three blow over on the start. Was impressed by their cornering abilities. Flash forward a decade, buddies had jets and Vdrives. Fast as hell, but like skipping rocks. All were sub 21ft. Now, I've been around some 28ft boats, but all pretty anemic, 496ho family boats. Great boats, I like them, and will eventually end up with one. Now, in reading, most have had more capable hulls than power. I am pretty decent with motors. Built more than a couple. Boats are a different animal though. My questions are pretty general, because I am still learning the basics. As I learn more, there is more I don't know. There are a lot of people on here that know a lot of things...I'm not one of them. At least not when it comes to boating. Pretty bad, this being a boating site and all.

The questions will come. Some random and some mundane. As I figure more out, there will be more I need to figure out

 

[RiverDave]

I am really new to the concept of larger boats going fast. I had gone to see GP tunnels at Puddingstone when I was a kid. Saw three blow over on the start. Was impressed by their cornering abilities. Flash forward a decade, buddies had jets and Vdrives. Fast as hell, but like skipping rocks. All were sub 21ft. Now, I've been around some 28ft boats, but all pretty anemic, 496ho family boats. Great boats, I like them, and will eventually end up with one. Now, in reading, most have had more capable hulls than power. I am pretty decent with motors. Built more than a couple. Boats are a different animal though. My questions are pretty general, because I am still learning the basics. As I learn more, there is more I don't know. There are a lot of people on here that know a lot of things...I'm not one of them. At least not when it comes to boating. Pretty bad, this being a boating site and all.

The questions will come. Some random and some mundane. As I figure more out, there will be more I need to figure out

I'm no Naval Architect, but I've been around it my whole life, and I enjoy figuring out how things work and what makes things work better etc..

RD

 

[LHCBOY]

I'm no Naval Architect, but I've been around it my whole life, and I enjoy figuring out how things work and what makes things work better etc..

RD

Thank for taking us to school today Dave


Sent from my iPhone using Tapatalk

 

[MK1MOD0]

The Nordic is kind of a different beast all together which is why everyone is very curious as to how it runs. It is a wide sponson / narrow (but deep) tunnel.

Due to my injury I haven’t been in one yet, but I can speak for a lot of people to say that we are all interested on how it’s going to perform vs more traditional style bottoms.

Anyhow I hope some of that helps and at least answered some of your questions. If you want to know something specific just ask! If I don’t know I will find out.

It’s interesting because then I was originally looking at the new Nordic the first boat that came to mind was a Skater 32 B. Wide deep sponsons with a fairly narrow tunnel. It’s known to be an amazing boat in the rough, so my bet is the Nordic will be as well.

 

[monkeyswrench]

I'm no Naval Architect, but I've been around it my whole life, and I enjoy figuring out how things work and what makes things work better etc..

RD

Well, I like going fast. Started playing with nitrous oxide at 18, and building motors shortly after...it was a learning curve. I like to know how things work. Boats are no different it seems. Different hulls for different purposes. The same as car designs, road, drag race and offroad. They share similar components, but used or sized differently. Powerband on the motor is the same, different goals, different setup.

Learning what makes a boat tick helps understand what is needed for what purpose.

 

[PlanB]

I have posted this before, but if you look at the 1:50 mark you can see the low speed "hop". As I pick up a little speed going away from the camera it smooths out. You can also see that on very flat water a true tunnel can still ride very smooth. This was a 117 MPH pass in our 28 Skater.

 

[RiverDave]

I have posted this before, but if you look at the 1:50 mark you can see the low speed "hop". As I pick up a little speed going away from the camera it smooths out. You can also see that on very flat water a true tunnel can still ride very smooth. This was a 117 MPH pass in our 28 Skater.

True tunnels can run well in smooth water so long as you keep them out of the porpoise zone.. it seems as things have progressed they are dialing them in better and better.

 

[Blackmagic94]

And no center pod has won a real race lol

 

[RiverDave]

And no center pod has won a real race lol

well I’m not sure I’d agree with that. Eliminator did some racing back in the day and were fairly successful at it as far as cats go.

Go in Advantages show room and there’s an awful lot of checkered flags and trophies.. granted that was vee’s

Lavey campaigned for awhile and held their own as well.

Schiada has won more ski race deals than pretty much everyone combined..

The east coast is mysterious and elusive to us West Coasters.. Because we don’t see a lot of it.. but pound for pound we are doing alright.

I’d take a 28 eco over a 29 OL. For my purposes.

For the rest though Roy’s one of one 28 skater (which we don’t even know if it works yet) is probably my favorite and sexiest boat of all time..

That new Nordic (never been in it so I can’t say how it runs) looks sexy from the outside

And on and on..

The point being there’s mystique and there’s reality.

Performance boating (IMO) was born out here and while there’s a lot of unknowns.. when you start measuring in quantifiable metrics things do tend to balance out for use vs performance.

That is changing quickly though with the larger cockpits some of these guys have come out with and the new outboard power. It’s enough to make your head spin.

There is proactive and there is reactive. The guys that are being proactive are going to do well in the upcoming years. I think Barron is they can tool their 30’ CC deal is gonna kill it, providing they put some innovation in its design do it better than everyone else.

So much I’d love to talk about, and theorize about.. but it’s late and I have one more thing to do before bed.

 

[Sigus]

Best thread ever!

 

[monkeyswrench]

Best thread ever!

It's a lot of info for us newbies to digest. Knowing what boats are fast is pretty easy, knowing what makes them fast is another.

Aerodynamics and hydrodynamics...not just the standard IO vs OB discussion​

 

[monkeyswrench]

Ok...watched some videos (boat porn) and came up with some thoughts on the hull and lift.
A cat is plowing through the water. As it builds speed, it comes up on plane. As more speed is build, the tunnel packs air, and lightens the craft. The goal is to have as little in the water as possible, as that is your primary drag...

How do they build boats that don't blow over? There are hulls that have power ranging from 500-1500hp. How do the builders compensate for both low and high power, as well as changing weight loads and water conditions? There are a lot of variables, but for the most part the hull is not easily changed. It seems it would be hard to build a hull that is efficient for all the power options offered by the builders.

 

[X-rated]

Quite likely why not everyone does it with Any amount of success

 

[FreeBird236]

Ok...watched some videos (boat porn) and came up with some thoughts on the hull and lift.
A cat is plowing through the water. As it builds speed, it comes up on plane. As more speed is build, the tunnel packs air, and lightens the craft. The goal is to have as little in the water as possible, as that is your primary drag...

How do they build boats that don't blow over? There are hulls that have power ranging from 500-1500hp. How do the builders compensate for both low and high power, as well as changing weight loads and water conditions? There are a lot of variables, but for the most part the hull is not easily changed. It seems it would be hard to build a hull that is efficient for all the power options offered by the builders.

There are some that do blow over, some more than others.

 

[RiverDave]

Ok...watched some videos (boat porn) and came up with some thoughts on the hull and lift.
A cat is plowing through the water. As it builds speed, it comes up on plane. As more speed is build, the tunnel packs air, and lightens the craft. The goal is to have as little in the water as possible, as that is your primary drag...

How do they build boats that don't blow over? There are hulls that have power ranging from 500-1500hp. How do the builders compensate for both low and high power, as well as changing weight loads and water conditions? There are a lot of variables, but for the most part the hull is not easily changed. It seems it would be hard to build a hull that is efficient for all the power options offered by the builders.

Typically (most cases) they don’t change the hull to accommodate the power. In high performance cat setups it’s not uncommon to change the setups to make best use of the power.

Take for example an old school Mach 26. If you were running mild or stock power they’d run a lower X dimension to help the boat get on plane and be more comfortable with the moderate speeds it would be running.

Now these are “custom” technically so a customer can order it with a higher x dimension with the intention of trying to get the most speed out of it as possible, and or possibly adding a blower after the warranty expires etc. That comes at a price for getting on plane and slow speed handling etc.

Or the same boat with a blower motor might run a higher X because the boat is going to live at a higher speed range. It reduces drag puts up better numbers and is more efficient overall. That puts less stress on the drive (part 2 coming on that) in normal circumstances etc..

To stick to the topic though there are true custom boat builders out there.

Schiada for example it isn’t uncommon for Lee to talk to the customer and actually change the hull to their needs. For a lower HP ski boat they might add a delta pad to help reduce wake and get a little more performance out of the hull. Etc.

For an example of Cats Skater is a true custom builder. The 388 is a common boat, most don’t know they lay up a hull and the first thing they do is cut it down the middle and widen the boat. The 38 is 38’ long. The second 8 is eight inches wider. Each boat is custom made and hand built / widened. You can order whatever you want and they will guide you through the process and make recommendations on what they feel will work or won’t.

If you look at Get Real performance’s boat is it’s a 28 Skater thst has been widened to a 10’ beam! And it is bad ass.. That is a custom one off one of one boat.

It is also going to be one of the sickest (if not the sickest) outboard builds thread on the history of the internet. Lol.


If you want to see an awesome build thread that is incorporating a lot of ingenuity and outside of the box thinking go check out hydroskreamin’s thread on here!

 

[Headless hula]

Ok...watched some videos (boat porn) and came up with some thoughts on the hull and lift.
A cat is plowing through the water. As it builds speed, it comes up on plane. As more speed is build, the tunnel packs air, and lightens the craft. The goal is to have as little in the water as possible, as that is your primary drag...

How do they build boats that don't blow over? There are hulls that have power ranging from 500-1500hp. How do the builders compensate for both low and high power, as well as changing weight loads and water conditions? There are a lot of variables, but for the most part the hull is not easily changed. It seems it would be hard to build a hull that is efficient for all the power options offered by the builders.

Typically (most cases) they don’t change the hull to accommodate the power. In high performance cat setups it’s not uncommon to change the setups to make best use of the power.

Take for example an old school Mach 26. If you were running mild or stock power they’d run a lower X dimension to help the boat get on plane and be more comfortable with the moderate speeds it would be running.

Now these are “custom” technically so a customer can order it with a higher x dimension with the intention of trying to get the most speed out of it as possible, and or possibly adding a blower after the warranty expires etc. That comes at a price for getting on plane and slow speed handling etc.

Or the same boat with a blower motor might run a higher X because the boat is going to live at a higher speed range. It reduces drag puts up better numbers and is more efficient overall. That puts less stress on the drive (part 2 coming on that) in normal circumstances etc..

To stick to the topic though there are true custom boat builders out there.

Schiada for example it isn’t uncommon for Lee to talk to the customer and actually change the hull to their needs. For a lower HP ski boat they might add a delta pad to help reduce wake and get a little more performance out of the hull. Etc.

For an example of Cats Skater is a true custom builder. The 388 is a common boat, most don’t know they lay up a hull and the first thing they do is cut it down the middle and widen the boat. The 38 is 38’ long. The second 8 is eight inches wider. Each boat is custom made and hand built / widened. You can order whatever you want and they will guide you through the process and make recommendations on what they feel will work or won’t.

If you look at Get Real performance’s boat is it’s a 28 Skater thst has been widened to a 10’ beam! And it is bad ass.. That is a custom one off one of one boat.

It is also going to be one of the sickest (if not the sickest) outboard builds thread on the history of the internet. Lol.


If you want to see an awesome build thread that is incorporating a lot of ingenuity and outside of the box thinking go check out hydroskreamin’s thread on here!

It's only 10 pages, and 3 years worth of posts to read, but come on Kevin, you needed some more reading to do.


https://www.riverdavesplace.com/forums/threads/project-stresseliminator-restomod-23-daytona.155360/

 

[zx14]

Ok...watched some videos (boat porn) and came up with some thoughts on the hull and lift.
A cat is plowing through the water. As it builds speed, it comes up on plane. As more speed is build, the tunnel packs air, and lightens the craft. The goal is to have as little in the water as possible, as that is your primary drag...

How do they build boats that don't blow over? There are hulls that have power ranging from 500-1500hp. How do the builders compensate for both low and high power, as well as changing weight loads and water conditions? There are a lot of variables, but for the most part the hull is not easily changed. It seems it would be hard to build a hull that is efficient for all the power options offered by the builders.

Driver input is one variable, on a 19-21’ Daytona you can blow it over pretty ez if you wanted too. Drive into the wind with 280 hp outboard, trim too high, and oops. On 26’ on up, you really would have to try, you need 1000hp and a good headwind. And of course trim too high. Now that being said, if you know what your doing, the faster you go the higher out of the water, thus the more “venting” out the rear releasing the pressure causing the lift, and it relative to speed. You “can” do stupid things in a cat. But you can also do some pretty cool things, one I really like is crossing a big set of rollers, if they are spread a bit further than my boat can ride across, and I’m going fast enough” not too fast but packing” I can trim up, grab a big gulp of air, then trim down just as the bow crest the first wave, not bury the bow but drop it, it squishes that air and you ride the bubble across the waves to the next, if you have a quest in your boat, they grab for something bracing for impact, and nothing happens, it’s like riding a marshmallow , do it wrong, and you launch. Cats are more of a drivers boat. I cut my teeth on the little ones. In my 21, it would actually go down the river a little crooked when halling ass, there was so little boat in the water, and only half the prop in the water, the torque of the prop would act like a paddle wheel and pull the assend to the right, making the right sponson in front of the left, like the boat was turning left, but your moving forward.

 

[monkeyswrench]

It's only 10 pages, and 3 years worth of posts to read, but come on Kevin, you needed some more reading to do.


https://www.riverdavesplace.com/forums/threads/project-stresseliminator-restomod-23-daytona.155360/

I'm a redneck with WiFi...at least I use the intraweb to learn stuff, not just look at the pretty girls

 

[Headless hula]

I'm a redneck with WiFi...at least I use the intraweb to learn stuff, not just look at the pretty girls

Hopefully you dont miss the part in his thread where we cut the bottom of his pod off the boat.....


(No worries, we glassed a new bottom back in place)....

 

[jimboat]

great thread with lot's of good thoughts.

 

[81Sprint]

Driver input is one variable, on a 19-21’ Daytona you can blow it over pretty ez if you wanted too. Drive into the wind with 280 hp outboard, trim too high, and oops. On 26’ on up, you really would have to try, you need 1000hp and a good headwind. And of course trim too high. Now that being said, if you know what your doing, the faster you go the higher out of the water, thus the more “venting” out the rear releasing the pressure causing the lift, and it relative to speed. You “can” do stupid things in a cat. But you can also do some pretty cool things, one I really like is crossing a big set of rollers, if they are spread a bit further than my boat can ride across, and I’m going fast enough” not too fast but packing” I can trim up, grab a big gulp of air, then trim down just as the bow crest the first wave, not bury the bow but drop it, it squishes that air and you ride the bubble across the waves to the next, if you have a quest in your boat, they grab for something bracing for impact, and nothing happens, it’s like riding a marshmallow , do it wrong, and you launch. Cats are more of a drivers boat. I cut my teeth on the little ones. In my 21, it would actually go down the river a little crooked when halling ass, there was so little boat in the water, and only half the prop in the water, the torque of the prop would act like a paddle wheel and pull the assend to the right, making the right sponson in front of the left, like the boat was turning left, but your moving forward.

I experienced this in my 19' took it out on the river with a pretty good blowing headwind, put some power to it and boy did that hull pick up outta the water quick. Nothing crazy but packed serious air and got a little squirrely. Definitely teaches you to respect the boat.

 

[Skinny Tire AH]

Here's a couple that show the entire process of the boat going thru the hop and up packing air and a perfect run.

 

[clarence]

I'm curious about safety and what 21-28' single outboard performance boat is best suited to someone without experience.

Cats are more of a drivers boat.

Moreso than a v-bottom with a pad?

The very basic thing is what is the difference between an air entrapment hull vs a traditional planing hull. They both start off the same getting onto plane with hydrodynamic lift. In the case of a vee bottom the boat is going to be running on hydrodynamic lift entirely throughout the entire speed range. In the case of an air entrapment hull you are going to start getting lift from aerodynamic lift. In both cases generally speaking the farther the boat comes out of the water (or less contact patch) the less drag and the faster it goes.

The difference seems to be narrowing?

“The only way to make a boat go faster is to get it up out of the water,” he said. “I’m trying to use aerodynamics and above under the boat to get that lift.”

Tuff Marine Adding New 24-Footer

Tuff Marine president Mark Weigl is so early in the process of designing his company’s next boat that he’s not even sure about the overall length, but that didn’t stop two customers from buying the first pair. “There’s already two pre-sold and I haven’t even shown anyone a picture of it,” said...

www.speedonthewater.com

 

[Mikemo_SDS]

RIP Garth and Jim