My new design and build P-Sport Hydro.

[jantagg]

I will have comments on the next Message.

Tom Taggart

[JimClark]

nice job Tom

[lenny]

Very nice piece of art work you have there.
What size is it and what setup do you have in it ?

[jantagg]

I haven't built a new race boat in several years because I wanted to build something different in style and design. The above attachments shown in the above message show the result of that endeavor. The design is similar to that of the current big Unlimited hydroplanes racing boats today in that the model has full length air-traps, a canoe-shaped sponson bow and multi-level sponsons. The angle of the flat bottom is a mere 1 degree while the sponsons are only 2 degrees (the big boats' sponsons are 1.5 degrees as they control the attitude by working the the front wing).

The problem, as it turns out, is that what works on a full-size boat doesn't necessarly work on a small RC boat, and the boat at Saturday's Club outing was an absolute embarassment. When the boat was first launched, it had to be thrown into the water gas-style and the rudder turned hard left to keep the right sponson from submerging. This was fixed to some extent by adding 1/4" wedges to the bottom of the sponsons. However, that didn't solve the right sponson problem, and in addition, the right sponson problem and was exacerbated when the boat went into a turn. The right sponson seemed to be sucked down, resulting in the boat doing a horrific spin. I tried everything to resolve the problem but to no avail--wedges on the front of the sponsons, strut adjustments and longer rudders but, it always ended with the same unpleasant results.

I had the suspicion all along that the air-traps were the culpit, but that was the reason for the box design and part of the unique design. It seems the when the boat went into the turn, either suction or friction or both caused the right sponson to sink. So, with either tears on my cheek or sweat from the Houston 100 degree heat, I removed the air-traps by planing them level with the bottom of the hull. That finally did the trick and now the boat now runs around my rather small pond at full throttle. It remains to be seen how it will stack up against M-L and Insane, but for now I'm happy.

[Fluid]

I'm glad you got the hydro sorted out Tom, it sure ran nice in the straights. Here are a few more pics.

[jantagg]

The boat is a full size P-Sport hydro being a little under 34". I hope to be able to run it as a small "Q" class if the weather conditions will permit. But, that remains to be seen.

[Doug Smock]

Very nice work as usual Tom!

[Sobie2]

I can't see the second series of pics, but I would put more of the blame on the bent in design of the turn fin wit the hook. Swap it out with a straight conventional one. If there was any twist in the fin you could be creating lift or suction.

Sobie2

[Chilli]

Looks like a standard sport hydro turn fin to me. If it's adjusted properly, it won't create lift or suction.

[jantagg]

After numerous times to the pond and much frustration, I finally got the boat to stop spinning out in the turns. It wasn't the skid fin or the air traps, rudder, angle or depth of the strut. The problem was that the design taken from the big boats did not afford enough lift to drag coefficient causing the right sponson to be sucked under water. I widened the right sponson riding surface (to a more normal RC shape) giving the sponson more lift and finally the boat behaved properly. The shape of the left sponson was left alone resulting in the great turning boat.

[Fluid]

Glad to hear it Tom! Wish you'd had it out Saturday.



.

[urbs00007]

could you tell me the builder of the boat to the left of yours? looks very interesting. thanks

[jantagg]

That is my little N2 design and build. I built it several years ago when we were using brush motors in LSH. It is my TOMCAT design.

Tom Taggart

[urbs00007]

thanks tom, what is N2, LSH< and TOMCAT? sorry for my ignorance. any chance to see more pictures? it caught my eye . thank you

[jantagg]

I call my design/builds TOMCATS. N2 class is a two cell boat as such a round nose boat works very well. LSH (Limited Sport Hydro) is a four cell class that has a minimum length of 24" and allows only certain manufactured motors. Since you asked, I'll will send a better picture.