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Lots of questions about my hydroplane.

f_inscreenname

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I will be the first to say I have no clue about this hydro stuff so I need help. Ran around with it for 28 miles yesterday and now I have a couple issues to figure out.
Does the boat sit right?

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I know its stupid question but I have to ask. It sits basically flat when stopped. Not sure if that means anything or not. I'm so used to the high bow deep V boats seeing a boat sitting flat almost seems weird. I was able to do some measuring todays thanks to running in a muddy river. If you run a string from the end of the sponson to the flat at the transom and another along the sitting still waterline at the transom its 9.5? and at the sponson is 8.75? between the two lines. Pretty flat.

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The boat takes off normal. The bow raises and the stern digs in but as you?re getting into it the stern starts to rise and then it's like an outboard ski boat that has a pad at the end of the hull, the prop breaks loose some but you just keep powering thru it and it grabs and off it goes. Does that sound right? If you run it like a drag boat 1/4 mile and just go it happens so fast that you never even notice it.
The only good take off shot I have is this one. Motor ran perfect all day except this one time the carb stumbled but you can still see the boat has no issue getting out of the hole and I wasn?t even trying after the stumble.

[video=youtube;2fn4aoGKrD4]http://www.youtube.com/watch?v=2fn4aoGKrD4[/video]

She takes off like a SOB. Jumps on top of the water and goes. No issues there.
It has a 13X15L Ron Hill prop (nothing special) on it and after it settles and all the way up to 3000rpm?s the prop slip numbers are in the mid-single digits (hard to believe). Past that and all the way up to 45/50mph turning/steering is not as good as it should be but is tolerable and can be compensated for. After 50 things start to get progressively worse unless the wind is just right and that only helped a couple times in straight line runs. It almost feels like its riding on the front sponsons. Not on the back edge but on the flat of the sponson. The best way I can put it is the stern is rising and the bow is rolling over on its nose. 50 to 60 the bow almost feels like it breaks loose and starts to slide back and forth like it?s drifting. This goes on for a couple seconds then one side will start to dig in (my side if by myself) and if you are not backing out it just gets worse pretty fast. Still does it if you are backing out but getting a little wet from spray is better than the alternative. You bring it back to 40mph and everything is normal again, well?.
With a big center fin she is not really into turning. It tends to push the left sponson down when turning right and vice versa. Water sprays out off the sponson as you are turning into it and it comes back at you. It's definitely not a circle boat. It is a little un-nerving when she digs in though at any speed. Again like it is bow heavy or something.

So now to the questions.
The front rolling over and digging in on turns. Think that could have something to do with it having a single center fin? All the pictures I?ve seen online of hydros have fins on the sponsons not in the center of the boat. The center one I have now starts at the end of the sponsons and is 11? long and sticks down below the sponsons by 5 inches. So I?m starting to think of it as the boat is on ice skates between the front fin and the rudder when riding on top of the water. Think I should take the center fin off and make/buy sponsons fins? If so any sugestions?
The next issue is, the boat sits and rides like it does. It was pretty much a consensus when building the boat to move the motor and transmission as far forward as possible because it was thought that the motor wouldn?t be strong enough to lift the back half of the boat and so I did. The driveshaft is a couple couplings and 4 u-joints. Now I?m thinking that the motor is too far forward and is lifting the stern too much. Anyone ever have this issue? In a hydro do you want to motor as far forward as possible?
From what I have read and watched on you tube when you are wide open you want just the rear edge of the sponson and the last edge of the transom (if that?) in the water?
 

mobboss

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Ok to start i am in no way an expert Hell im just learning about v drives myself! the lift your talking about is from the gear box, the angle , from what i understand there are 2 different ones. one is for skiing and one is for racing. the ski one has a greater angle ( i thing 12 degrees ) the race one is 10 degrees. with more power than what was original you can lift the boat out of the water. not sure if there is away to correct this or not, hell im not sure how to measure to see which one i have???? its basically your shaft angle , your prop is pushing the ass end out of the water!
 

CampbellCarl

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There's lots going on here. First, you're talking about an old four (4) point hydro so none of the current race hydro info applies to you application. Try finding info (youtube, google etc) on old 4 point hydros. The tunnels create the rear two points of the four.

Your comment about moving the motor as far as possible worries me. How far is it from when you got the boat?

The other concern is with the prop. Was the prop spec'd for a four point hydro? Kinda sounds like its creating too much tail lift and pushing the bow/nose too far down creating some steering issues. Hydros generally don't like to turn at all. Point it, stab it and hang on. Need to turn? Back off of plane then point it again and repeat.

The combination of power plant forward and too much tail lift in the prop may be combining to compound the issue.
 

f_inscreenname

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Mob,
454, B/W trans 1 to 1, HallCraft V-drive 21% over gears. According to my GPS, tach and a prop analyzer program when turning 3000rpms the prop slip #?s are in the single digits. So yes it?s hooking up. After that it?s too hard to get accurate numbers while holding on white knuckled. Lol. But I don?t think it loses but grabs better. After about 50mph it almost feels like its running downhill. Then she leans on one of the front corners a little to much and that front sponson will start to dig in. Most folks I?ve talked to that drive hydroplanes say they have to back off to get the sponsons in the water to so they can almost ?drift? the boat in the direction they want to go. Mine wants to dip the opposite side sponson of your turn and dig in .
Camp,
Very nice catch on the 4pt thing. I didn?t want to scare anyone away by mentioning that but since you brought it up?..
Let?s just leave that part out (lol) and treat this as a 3pt flat. I think this whole 4pt thing is way over blown. It?s a small channel and IMHO I think it was a way to getting a 1950?s heavy, underpowered motor and the rear end of the boat out of the water while still having some of the hull (the rear 2pts) riding on the water creating lift.
No the prop is not speced for a 4pt. There is nothing that?s speced for a 4pt hydro. Lol. It?s just a Ron hill test prop 13X15L. The motor was not in the boat and for that matter most of the stringers were not there either. I found the boat in the weeds in PA about 18 months ago. What was left of the set up looked like Swiss Cheese so I went on-line and asked and the few that dared to answer the question on set up thought the motor should be as far forward as possible to help with stern lift. I?ll give this one to you on the 4pt thing meaning something, I think stern lift is already built in this boat. Just riding on the rear 2pts has most of the hull behind the front sponsons out of the water. After that I would think the closer to the water the 2pts at the transom are without touching it would be better for how the front would ride (angle of the front sponsons to the water). So why not move the weight back and pick the front end up?
Something else I have noticed is I have never seen a hydro with a single center skid fin like this one. I?m thinking that when it gets up on top of the water, between the skid fin and rudder it?s like balancing on and ice skate. Think I need to put skid plates on the front sponsons make it more like a 3pt ice boat or would you just take it off?
 

harlanorrin

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I would find all the propellors you can beg, borrow, or steal, to try. I would start with a 11" diameter. When you could test the boat with different propellors, run the boat with different passenger and fuel loads. Depending how many porpellors you can find your tests could take some time. I have tested with 2 passengers setting on the rear deck. You are looking for performance/ride not engine rpms. Your propellor man can tune up or build a new propellor to your needs.
I would consider running a turn fin on the port-left sponson. Turn fins on both sponsons could steer the boat. This boat was not built to be a circle racer.
I ran a Stellings 12/15 ski boat prop on my hydroplane, with 16%od. I ran 107.14 with a 327 SBC on my record holding wood hydroplane.

HARLAN ORRIN
 

f_inscreenname

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I hear what you are saying. Just got done moving the motor back toward the transom almost 7"s (and it's not on rails) trying to get the balance a little more the way it should be. Since I've done that driving it has got a lot better and I think the center skid fin is OK for now but I do have a couple smaller skid fins in the garage if needed in the future. Also after I get the right prop on it I plan on moving a couple sand bags around until I get it prefect for me then make the weight that way permanently.
The real issue is the beg, borrow, steal, etc, etc. I'm on the east coast. These boats over here are about as rare as an off shore racer are over on your side and props are even harder to find. That?s why I was looking for a comparable prop to my OJ in a hydroplane prop because it looks like I will be buying them for testing on a hope and a prayer.
I figured that someone here would have done it and would say something like, "if you are running a 15P OJ then in a chopper you should be using a __ pitch or a 2 blade you should use this..." Just like the info that's everywhere for changing from a 3 blade to a 4 blade prop. Just can?t find anything on doing what I need to do.
 

vdcruiser

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I doubt you will find anybody with experience with this particular hull, and why do you want to think of it as a 3 point hydro if its not. Most of the flat bottom and semi V- bottom V-drives I've messed with like a smaller dia prop than 13", like an 11 or 11 1/2" . Also is yours a bronze prop, if so be careful spinning it above 4500 rpm or so. I have thrown blades off a bronze and even stainless props, blown motor though. I think moving the engine back was a good idea.
 

f_inscreenname

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The reason I went with a 3pt instead of a 4pt because that most don?t know what a 4pt is and even fewer have driven one.
Thanks for the info.
 
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