Flexible fuse

[Doug Moon]

I am working on this new plane.  

It is all up in one piece and ready for finish, sans the fillets, I start the filling the add them in later after first coats of carbon viel.

What you see here weighs 30.5 oz.

When I stand behind the plane and hold the tips of the stab and apply up and down pressure I can see the fuse twist a little bit before it starts to pick up the wing.  I think the stab tips probably go up a 1/4" before the plane starts to move all together.  Incidentally the stab does not flex at all!

Question is how far if any should it twist at this point?

This is a normal 60 sized stunter, geo bolt wing and 29" span on the solid foam stab stab.

I havent built a plane start to finish in several years and the last one, Furias, had a VERY LARGE fuse and was not flexible at all before the blocks were added.  I cant remember how it should be and if the finish will help tighten it up.

I will finish with carbon veil and dope, then automotive paint and clear.

What do you think?

[Mark Scarborough]

did you  do any diagonal bracing between formers? tha tmakes a huge diference.
If i were in your shoes and didnt want to cut in for more bracing, I would use silkspan on the fuse not CF, I think it will stiffen it more.

[Kim Doherty]

Doug,

I don't think you have anything to worry about. The fuselage cross section looks to be large enough for its intended purpose. Applying the finish will certainly stiffen up the wood but not to the point where you will not be able to deflect the stab. When you grab the tips with your hands, you are applying an unrealistic force over a relatively long moment arm in a manner nature can not duplicate. I would be surpried if the stab/fuselage DIDN'T twist.

The loading along the stab in flight will be failry uniform and will not likely twist.

Unless someone very tall and very fast runs after your model while in flight and grabs the tips of the stab with malice aforethought I see no problem  :-)

Kim.

[Dennis Adamisin]

Doug
Good looking bird, & nice weight too.  I seriously doubt you will have any reall issue with fuselage flex.    

BTW, what do you mean by "60 sized"?  Which AXI motor and what size battery pack do you have in mind??            

(sorry, just wanted to pull your chain a little  )

[Doug Moon]

I think it will be just fine.  I doped it last night, first coat.  What a difference just one coat made!!!  After the full finish it should be just fine.  I got to thinking about all the plane in the past with large cutouts in the fuse.  Once covered they hold up just fine.

Dennis, I sure wish I knew how to convert to what would be an elec motor for it.  I dont have a clue.  I am sure i could figure it out if i just took the time.

Kim that is a funny visual.  My brother and I got a kick out of that one.

[peabody]

Doug...it will be unflyable....the best thing to do is finish it and send it to me.
Way cool!