Trimming a Shark 402 with LA 25

[Allen Eshleman]

I have a Shark 402 with an LA 25 on it.  The laps are around 4 seconds on 58 ft lines. It seems fast but also, it doesn't pull very much.  I didn't try any maneuvers today.  First time out this spring.  Any thoughts on how to make it pull more and slower laps. 

[Dan McEntee]

   It's a small model with an LA.25 on it, it's not going to pull very hard even in perfect trim. Try slowing it down with the needle. to the 5 second range and a few, simple loops and see if it will fly inverted with outside loops. First things first. You also don't give us any other factors like prop pitch and diameter and such. Need more info after you fly it some more.
   Type at you later,
  Dan McEntee

[Motorman]

I have one of those! Ok, list my set up.

Box stock OS LA 25
Venturi .240"
OS spraybar
factory muffler with the stinger filed off hole size .270"
APC 9-4 Sport prop
3oz uniflow tank
10% nitro 10% castor 10% klotz
one #4 flat washer under each front motor mount lug for out thrust
Balance point 1-3/4" behind leading edge
Tether point 3" behind leading edge
Rudder offset 11/16"
Lines are .015" x 60' handle to thrust line.
I run the engine flat rich in a 4 stroke for a 5.0 lap time.

Hope that helps
Motorman

[Brett Buck]

I have a Shark 402 with an LA 25 on it.  The laps are around 4 seconds on 58 ft lines. It seems fast but also, it doesn't pull very much.  I didn't try any maneuvers today.  First time out this spring.  Any thoughts on how to make it pull more and slower laps.

    It should be pulling pretty darn good at that speed. I think the standard steps apply - set the CG at about 15%, leadouts about an inch to an inch and a quarter behind the CG. Remove any rudder offset, but make sure that it is not inboard. Tweak the wings until level, add tip weight until it starts to hinge, then take the last adjustment you made (something like 1/8 ounce) back out.

   Slowing it down, I would start with at least 60' .015 lines. Change the lines and you have to go back through your trim adjustments, and just add 1/4 ounce of tipweight before you switch. If it's too much, remove it a little bit at a time.
     Brett

[Allen Eshleman]

Thanks for the tips.  Motorman and Brett.  I am using a 9X4 prop.