Bench Trimming

[Bill Little]

Hi All,

I pretty much am the epitomy of the "Even a Blind Squirrel can find an acorn every now and then" theory.

I realised while going through another thread that I have a bench trimmingh concept that I have been using over the years that I don't even think about.  I have general idea of where I think the balance point should be and stole Paul Walker's theory of a starting place for tip weight.  Lead outs centered about 1/2 inch behind the CG and they seem to be very flyable on the first flight.  Sometimes that first flight has been a contest official!  Bad planning!!!!!!! 

What do y'all do on the "bench" before that first flight??

Bill <><

[Zuriel Armstrong]

Hi Bill,

Pretty much the same thing on the tip weight.  I suspend the plane by the leadouts and adjust them until the nose hangs slightly down.  It has been a good starting point for me.  I haven't finished a new plane for two years now and my  "Friend"   Rootbeard has been after me to finish something.

I'm almost there buddy!!!

[L0U CRANE]

As usual, I do things differently.

Kit, plan, ARF, ARC or 100% scratch, I run the numbers through some stuff I've been developing for over 30 years. It helps me set things like:  CG, bellcrank and horn dimensions, line rake, weight, prop, RPM, line dia and length, tipweight, asymmetry -  for a best shot at a nice flying model.

Then, I build to those numbers.

Yeah, it means building tanks, bellcranks, horns, pushrods, as well as the big pieces everyone plays with.

Works for me.

There's no 'bench trimming,' as such, involved.  I trim the model before I build it, and build it to that configuration. For a fairly 'standard' layout, I don't use adjustable leadouts or tipweight - as I don't need them. 

[Charlie Pate]

Bill!
I put my vise in the middle and 1/4' shim under the right leg.
Worked great!
Seriously.........., I think this is a confusing term.
If you are building a plane that you have already built two of and like , you will
likely set it up just like the last one that flew so good you built another.
 If its a new Randy pipe job ,are you going to set it up according to the plans , or do it your way and the complain when iy doesn,t fly right.
 I feel tank ,wing warps, tip weight,C/g are a part of building ,not bench trimming.
 The trimming occurs after you fly the plane.

[Ron King]

Bill,

I'll go along with Charlie on trimming my bench. 

If it's one of my "standard" stunters, I have a pretty good idea on the starting spot for CG, tip weight, and leadouts. You still have to fly it to be sure, but I'm usually close.

I also like to start out slightly nose heavy, but learned a difficult lesson with the Roadrunner. I set it up nose heavy, then learned it didn't have enough stab or elevator to do a loop. 

My latest plane is a full tilt electric stunter. The nice thing about electrics is you can test fly them before you finish them, so I have already figured out where most of the trim stuff should start.

Take care. Hope to see you guys again soon.

[Randy Powell]

I always think I have a new plane bench trimmed well. Plane before the last one flew right off. I've actually done very little trimming except to shorten the pushrod a turn and I'm still not sure it's any better. Great plane.

The current plane I was WAY off. Tail heavy, way too much line spacing, tracking issues and a number or minor issues. It has 5 flights on it and I'm just getting into the "I can fly a whole pattern now" stage. Probably need another 20 flights with incremental changes before I'd feel comfortable flying it in a contest.

[john e. holliday]

Well now that I have read what people do, myself I usually follow the instructions wether it is plans or a kit.  I figure they know more than me.  Then I go from there.  Had a few anxious first flights, but, most flew better than me.  Ted Fancher's "Doctor" was still flying they way he said to set it up when I gave it away.  Later,  DOC Holliday

[Bill Little]

Bill!
I put my vise in the middle and 1/4' shim under the right leg.
Worked great!
Seriously.........., I think this is a confusing term.
If you are building a plane that you have already built two of and like , you will
likely set it up just like the last one that flew so good you built another.
 If its a new Randy pipe job ,are you going to set it up according to the plans , or do it your way and the complain when iy doesn,t fly right.
 I feel tank ,wing warps, tip weight,C/g are a part of building ,not bench trimming.
 The trimming occurs after you fly the plane.

Look out, Buddy.......... I'll run over you with the mule cart again!

I agree with what you're saying, But things like tip weight are not listed on Randy's plans. 

Glad to hear from you, haven't seen you in a month of Sundays.