NEW OSE IM31 Turn Fins!!

[Darin Jordan]

Hey Gang,

I sent Steven the drawings for these awhile back, and he sent me some prototypes to verify last week.

I developed these for my IM31's prior to the 2012 Nats after having issues maintaining the proper "ride orientation" under race conditions.... (In other words... I couldn't keep the boat from FLIPPING in race water in the turns!! )....

The stock, teardrop shaped turn-fins don't hold. I built a couple of sets of these new designs and it transformed my IM31's to a completely new boat. Literally a night-and-day difference. Boat is more stable in the straights, and holds the turns in rough water, and under a good head of steam.

As soon as Steven has a link for them on his store, I'll post it here (or he will)... They are a bolt-on, and have a bit of depth adjustment as well.

A bit of a design flaw on my part... these will correct it!

Nicely done, Steven!

[Mike Caruso]

Nice improvement and thanks for sharing to make the next person have a better change of winning a race.
You're a stand up guy Darin!

[Darin Jordan]

Nice improvement and thanks for sharing to make the next person have a better change of winning a race.
You're a stand up guy Darin!

You are all welcome, Mike... Not enough of us out there to get too hung up on keeping this stuff to ones self.

These truely are a VAST improvement. It really surprised me how much better the boat is with just this bolt-on. Really a different boat with more than the stock prop or power system, and a real pleasure to drive.

[Fluid]

I am often amazed at how poorly many monos will turn with stock or aftermarket "shark fins". The racers will concentrate on prop and rudder size and CG and strut depth - when simply putting on a fin with greater side area may cure the issue. Most mono turn fins seem to be shaped to 'look cool' rather than to perform best - while some of my monos run "shark fins" many work better with rectangular fins as Darin as developed. I have used some ridiculously large square turn fins on a few monos to improve their cornering performance.

The Europeans seem to have a better handle on this than NA racers do.
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[Darin Jordan]

I am often amazed at how poorly many monos will turn with stock or aftermarket "shark fins". The racers will concentrate on prop and rudder size and CG and strut depth - when simply putting on a fin with greater side area may cure the issue. Most mono turn fins seem to be shaped to 'look cool' rather than to perform best - while some of my monos run "shark fins" many work better with rectangular fins as Darin as developed. I have used some ridiculously large square turn fins on a few monos to improve their cornering performance.

The Europeans seem to have a better handle on this than NA racers do.
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I agree, Jay... Looking back on it, I think this may have been the issue with my 32" WildThing Mono in P-Mono.... I kept going larger on the fins as I went faster, but I kept going bigger with TEARDROP fins... A set of the square ones would have certainly made a night-and-day difference.

I guess that's why it's called "development"... Learn something new every day.

[Darin Jordan]

Steven now has the fins for sale on his site.

http://www.offshoreelectrics.com/pro...+Upgrade+parts



Hopefully you all enjoy the upgrade!

[mannytx1]

Thank you very much Darin, 74f today with sunshine in Renton, WA

Manny

[Cap'n Bill]

Darin,

Why square? Why not something with a high aspect ratio like the rudder on the IM31? Or would that generate too much drag? Fluid's pic shows something closer to what I am describing.

[Darin Jordan]

Darin,

Why square? Why not something with a high aspect ratio like the rudder on the IM31? Or would that generate too much drag? Fluid's pic shows something closer to what I am describing.

I don't know about the rest of what you are asking, but for the fins... square... because it works!

No further analysis needed!

[Cap'n Bill]

Darin,

I'm sure they work as advertised. I'm just asking about the design approach. Additional analysis usually results in optimization. In this case, I'd be looking for reduced drag while maintaining the stability that you've achieved.


-Bill

Ps note the new addition in the signature line. I've finally made the jump after a lot of reading forums.