Handling issues

[BulletMaster]

Guys..

I am looking for some informed opinions here. I have an electric outrigger hydro, about B-Hydro size (weighs 3Kg). It has a tracking issue. With the current turn fin in place, when I throttle up, it pulls badly into the course (to the right). Now if I remove the turn fin, and do some straight runs, it tracks dead straight with no rudder trim required.

The turn fin is located on the right sponson, with the leading edge of the fin starting at the trailing edge of the sponson. The rudder is located on the left side of the transom. The turn fin does have a hook in the bottom (holds great through the turns). Fin is 2mm T6 alloy and leading edge is sharpened on the outside (ie R/H side). I tried bending to the left, but it didn't make any difference. I am baffled. Any ideas guys?

The first photo is of an old turn fin I ran, but it lifted through the corners.

 

[anthony_marquart]

First thing,.. That's a cool boat. Is it a scratch build? Kit or purchased?

It looks like your turn fin needs to be rotated a little. Looks like it is digging in. This can cause the problem you mention. Someone told me this. take a long rod or tube like a 1/4 dowel 2-3 ft long and place it against the turn fin so that it rests in the root of the "hook". The tube should be level with the tube or the waterline for your boat. This will keep it from digging in or dragging...

just a thought but I think that's your problem.

 

[BulletMaster]

Anthony,

thanks mate, the boat is a scratchbuilt. I am using a 6S1P Lipo setup with a Neu motor and CC 180A ESC.

Ta for the hints, I will try what you suggested. I am also going to change the design so that the turn fin is not a 1 peice unit, but rather mounts to a strut off the sponson. Makes it heaps easier to try different fins.

 

[aaron alberico]

Tony

what steering servo are you using, i had the same issue with my new 67 rigger,

if i hit the throttle hard it would go right hard,[as if i was turn full right] if i feed the throttle on slowly

it was alot better, tried different turn fins still did the same,

went to more power full servo, problem fixed

regards Aaron

 

[rhomodel]

Looks like a tilted forward turnfin. Another option can be that the right sponson is not paralel with the tub, but if you tried bending the fin and it didn't help I have to agree with Anthony, digging in the right sponson, causing more drag on the right side, and therefore making a right turn.

 

[Chris Wood]

how thick is your turn fin?? it could be flexing and causing it to track all over the place..

i try to used between 1/16 and .082 on my 21 boats i build.

chris

 

[Chris Wood]

oh and what grade aluminum is it?? if it is 6061 then that might be the problem.

chris

 

[BulletMaster]

Guys,

thanks for the input...

Aaron... the servo is a high torque Hextronic unit... should be bags of grunt there (but I will try a change if everything else fails).

Rhomodel.... yes, will be trying the method Anthony suggested.

Chris.... as stated, turnfin is 2mm T6 Aluminium. Plenty stiff enough for this application. The boat is heavier and larger than a 21. And also, it holds solid through corners, it just tracks to the right in the straight.

I have been talking with some other people too, and the suggestion has been made that the rudder may not be deep enough, or wide enough for this size boat. So will try that too.

 

[Preston_Hall]

I would try a longer rudder maybe. How about a pic from the side showing the rudder length. A good sharp edge on your prop will help reduce this as well. The sharpened angle on the turn fin is also a trick. The feathered type that you have will pull the boat into the coarse. Fins like CMDi have are shapened at about a 45 degree angle. This removes any airfoil effect. I personally like the feathered edge and compensate with rudder. One last thing is to lower the angle of attack on the left sponson. This creates more drag on the left to compensate for the drag of the turn fin.