sharpshooter... Sports Hydro.

[detox]

Too wet is a classic mistake...strut set too deep...too much weight up front.

Bottom of hull should be level with board (hull resting on rear of sponsons and strut). Sometimes I have to file strut slot to allow for less deep setting..

Hang hull sideways using finger at middle of turnfin . Ready to run hull should hang level or very slightly tail heavy. This is your balance.

Turnfins are tricky. Too much inward angle is slow.

Running too wet also caused my UL-1 nosecone to pop off when hitting waves (strong nose cone did not shatter). Adding a locator pad helped prevent nose cone from shifting and breaking tape. Pad shape looks just like Aquacraft's UL-1 version.




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[785boats]

Pete.
I was more than happy with it. A few more sessions of testing & she will be a happy little runner. I think the M447 was going to be best prop for the day but didn't really get to try it out because of the sudden deceleration issue with the buoy.

detox.
Not really a mistake running it a bit wet on the first runs. I like to start with it that way rather than watching it blow off the water the first time down the back straight because the set up was too loose.
I raise the strut a bit each run & /or change props to ones with less lift until the sponsons are just breathing on the water. That's just the way I like to test new boats.
I prefer to have the cog at about 1/3 the way forward from the trailing edge of the turn fin & that's where it was with the pack at the rear of the battery compartment.
The turn fin was working well. Nice tight turns at full noise with no loss of speed.
It was a good day.

[Shooter]

This boat is no doubt more prone to run wet. Every boat on the market at the time packed too much air for P sport IMO, so I threw everything at it to reduce the pressure under the hull (angled bleeds, low tunnel depth, etc...). As you reach speeds of 65+, this will be a huge benefit!!

BTW - I've raced this boat for two seasons. Never had a blow over. People tell me I'm running too wet, but I've also finished every race!!

[Speed810]

Paul....Sounds like you have a keeper there... Sorry about the incident with the buey. I hate those things sometimes....but trying to keep that depth perseption out there can be a pain....been there!

When you say:: I prefer to have the cog at about 1/3 the way forward from the trailing edge of the turn fin. Not sure I understand that. I have always measured back from the trailing edge of the sponson to the center of the turn fin. i.e. My 1/8 scale I have balanced out about 1"1/4 from the trailing edge of the sponson which puts it at about the center of the turn fin. Just wondering if this another way to balance these boats. I know my 1/8 scale does run somewhat wet.

During my balance process I used a 1/2" steel rod, placed it under the hull at equal points on each side and shifted weight around until I was able to hit the 1" to 1"1/4 mark.

In any case it will be great to see a video of yours running....

Mike

[785boats]

Mike.
I will post a video as soon as I can.
All I am saying is that instead of the cog being in the centre of the fin I have it a bit further back at 2/3 of the fin from the heel of the sponson.(in other words, 1/3 of the width of the fin forward from the trailing edge of the fin).
But the fin I'm using on this boat is only 1-3/4" wide & is mounted as close to the sponson as possible which puts the cog at about 1-1/2" behind the heel of the sponson.
In my other hydros, the little bit of extra weight behind the fin seems to help throw the tail out more easily in the corners with less rudder throw & therefore less drag & more speed in the corners.
But the aero effects of this hull seems to keep it well planted so I might have to slide the cog forward a bit to free it up a little. It never even felt as if it was going to lift off. We'll see in the next practice session.
Maybe I'm wrong with this Pete. Where do you have the COG on this hull?

[Shooter]

To be honest Paul, you guys probably know a lot more than me regarding trimming a boat. I do know that a fin forward of the CG will be more 'effective' than a fin behind the CG, but I prefer my fin to be right at the CG so the reactive force on the fin is acting through the CG (if the force is behind the CG, the moment arm is fighting the rudder in the turn and it will be more stable, if the force is in front of the CG, the moment arm is spinning the boat and adding more steering). My CG is at about 1" from the back of the sponson which is actually a little in front of the fin center.

[detox]

Changing COG is as simple as adding stick on lead weights...especially to rear of hull. Sometimes you can tell quickly if it works or not.


I wonder what works best, a lightweight hull running a tad tight, or a heavier hull running a tad loose? I think in most water conditions the heavier hull will work best.

[T.S.Davis]

To be honest Paul, you guys probably know a lot more than me regarding trimming a boat. I do know that a fin forward of the CG will be more 'effective' than a fin behind the CG, but I prefer my fin to be right at the CG so the reactive force on the fin is acting through the CG (if the force is behind the CG, the moment arm is fighting the rudder in the turn and it will be more stable, if the force is in front of the CG, the moment arm is spinning the boat and adding more steering). My CG is at about 1" from the back of the sponson which is actually a little in front of the fin center.

Didn't we talk about this one one of your early versions?

You can tune your turning by fiddling with the position of the fin in relationship to the CG. Slide the fin forward and the rudder has more effect etc.

[785boats]

^^ That's what I was trying to say in my post #80. GoG nearer the trailing edge of the fin helps with the turns.

Detox.
Weights are always an option, but I'll see what I can do with the strut depth, angle, & props first.
I must admit that most of my hydros needed weight added to the front. But this one might end up needing some at the rear.
Where we race the waters can be very choppy most of the time & you are right, the heavier boats certainly fare better in those conditions. That's why I don't mind if my boats are slightly on the heavy side.

[detox]

Getting the boat to track strait as possible without fighting rudder is important. I check this on water before and after turnfin is installed. Bending of strut (left or right) and turnfin bracket may be required.

Next I would check strait line speed by adjusting strut depth and COG.

Finally I would adjust turning. I like TSDavis's idea of moving turnfin forward and backward when testing.


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[Shooter]

Didn't we talk about this one one of your early versions?

You can tune your turning by fiddling with the position of the fin in relationship to the CG. Slide the fin forward and the rudder has more effect etc.

Yep. I remember we were out there one Saturday afternoon moving it forward and back. I was really surprised how much effect it had with only a 1/2" shift!