Primary Force rudder and/or engine offset?

[George Truett]

I'm just about to start final assembly on my first Primary Force.  The plans do not call out any offset on rudder or engine, what is working for you guys that are flying them?  I do have adjustable leadouts by the way.
 Thanks,  George T

[Mike Griffin]

George,  TY is right on the money with that advice.  I think over the years I have probably built a half dozen or so of the Primary Force.  I don't know what magic Mikey Pratt built into the design but it flies as good as any flapped stunter I ever flew, however, I am not a world class flyer like some of the guys on here are but for a duffer like me, it flies great.  I did not even put any engine offset on them and they still flew beautifully.  I have another one to build and Mikey told me that a K&B 28 sportster is a great engine for the model.  I don't own one but think I am going to try one on this one coming up.


Mike

[Dane Martin]

Agreed and agreed. Mine flys extremely stable. Although at the last contest I flew it, I didn't do well because I inadvertently switched handles. So don't take that score into account for my opinion. Haha. I have adjustable LO slider and a tip weight box also. I have no rudder or engine offset at all. Mine is also powered by an LA 25. Mine did come in nose heavy. I added 1oz to the tail for a total weight of 38oz.

[john e. holliday]

I still have my first Primary Force built according to the plans.  Needs recovering after the demented poodle did her little dance on the wing.  One of the best if not the best flying plane in the shop.

[James Holford]

.46LA flies one kinds nice

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[Guy B Jr]

Anyone tried an OS FP20 on one of these?

[Mike Griffin]

Anyone tried an OS FP20 on one of these?

Guy, I have not.  The smallest size engine I have tried on this model was a  .25 and it flew well with it.  I really don't know how a FP20 would pull it but I suspect, given the size of the model, you might be approaching an underpowered combination.  I am just guessing here based on that setup since I have never used that combination.

Mike

[MikeyPratt]

Anyone tried an OS FP20 on one of these?

Hi Guy,
I haven’t tried the FP 20 but it should be fine with the proper set up.  Just keep in mind if has the same mounting as a FP or LA 25.  At one time I had about a seven LA 25 and a three FP 25.  The FP 25 had more power than the LA’s and had the edge in my mind.  If you can find a K&B 28 Sportster works like a champ.

Rudder off set:  No more than 1/16” just to make sure it not pointing to the inside of the circle.  Lead-out position as shown on the plans.  Follow the bench trimming in the instruction book (And Do Exactly As Stated).

Later,
Mikey

[George Truett]

I bought my short kit here in the classifieds, it has plans but no instruction book.  I made templates and cut foam cores for mine.  Wing is completely sheeted and glassed with .6 ounce cloth, total all up weight with all airframe components and engine is 840 grams.  I still have to put the finish on and add tank and landing gear so I expect I will be between 32 and 40 ounces somewhere unless I get crazy with the spray gun.  I am thinking Brodak 40 with tongue muffler for power, it's a very light combination (and I don't have a 25).