Sport Hydro Sponson vs. Strut Weight Distribution?

I'm having some frustration taming sponson dance on this DF Vortex34 . I've played with strut depth & angle, added air dam (untested as yet) and played with some CG variation. I seem to remember posts discussing % weight distribution between sponson (I'm assuming rear sponson transom location) and strut. Is there any general rule of thumb ?



Thanks,

Tony

Hey T.

Have you blue printed the sponson riding surfaces and make sure they are flat? Just throwing darts

* What about taking the turn fin completely off, make a couple of passes, and see if your getting the same behavior?

Mike has a good suggestion. Try a pass with no turn fin to see if there is an issue there. If there still is an issue...... is the whole boat lifting off the water and rocking side to side or is the transon still in the water and the front sponsons dancing? If the whole boat is lifting out of the water and dancing you need less angle on your strut. set it parallel to the water if it is not presently parallel. If the front sponsons are doing all the dancing and the prop is still in the water maybe the strut needs to be a tad deeper or the CG needs to be more forward. I would put the CG just behind the front sponson ride surface. I have a 1/8th scale roundnose electric hull where I had the same problem and it was the strut angle and the CG. The CG is 1/2 inch behind the front sponsons and the strut is now parallel and it runs great. I had to put the batteries up in the bow as far as they would go. I have found that the electric power is over powering these boats that were originally designed for nitro. My oberto 1/8th scale works great at 62 mph, but when you add another battery cell the boat jumps like crazy at 65 plus mph. At some point we are just over powering these huls and need larger boats.

Thanks Fella's.

I'm sure my initial strut depth was too shallow . Now lowered substantially + big rubber overkill air dam up front + 8 oz lead in left front sponson (LF sponson torque lift with X452 - now plan to test other props). Should test soon. It has a huge-ish turn fin (from in Insane boat) & I'm thinking I'll cut it down some. Oh and it's WAY overpowered because I wanted to try out the TP Power 40mm X 100mm 4070 2200KV monster mill out of curiosity. Eeekk- . John, I agree boat was probably not designed/destined for that much power/speed (especially with the full length air traps). Jay T and Howard T. are both working out similar issues with their Vortex 34's - we're commiserating/collaborating some. Boat basically has way too much AoA in dihedral config. I may do a little sanding. Howard completely re-config'd his AoA and vented the traps with good results.





Appreciate the input.

More will be revealed

Tony

Kinda looks like the fin is angled up, which can lift the right sponson out of the water. Or it may just be the photo angle. I had to rotate my fin (larger than yours) back a bit to smooth things out. Removing the fin for testing is a great idea!

My strut is lower than yours, this reduces the sponson aoa. And the boat did not like lifting props at all, rather than changing the strut angle I switched to ABC 17* props - much better.

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tony, if you haven't solved the sponson dancing i have a suggestion. Don Pinckert told me a trick many years ago. taper the front of the rudder blade maybe 3/16" smaller at the bottom than the top.front to back. and make the back of the rudder 90 degrees to the water or ever so slightly kicked back.

john urbowicz said:

tony, if you haven't solved the sponson dancing i have a suggestion. Don Pinckert told me a trick many years ago. taper the front of the rudder blade maybe 3/16" smaller at the bottom than the top.front to back. and make the back of the rudder 90 degrees to the water or ever so slightly kicked back.

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Thanks John. I'll be testing (hopefully) this coming Sunday after the SCSTA/Nitro/FE race. I'll post results.

properchopper said:

Oh and it's WAY overpowered because I wanted to try out the TP Power 40mm X 100mm 4070 2200KV monster mill out of curiosity. Eeekk-

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This is a bit of your problem. With more power, more prop, more torq, more dancing with a boat with a shorter wheel base.