stunthanger.com

General control line discussion => Open Forum => Topic started by: Paul Taylor on July 21, 2007, 12:46:19 PM

Title: Foam wing question - center rib or not???
Post by: Paul Taylor on July 21, 2007, 12:46:19 PM

OK, I am getting close to gluing two wing halves together of a foam wing. I have seen pictures of foam wings with and without the bellcrank mounted on a center rib with hard wood blocks.

This wing will go in profile plane, and I am only doing 4 in sheeting on the leading edge and 1 in sheeting on the trailing edge with cap strips glued down on the foam wing between the sheeting. I will cover it with monokote.

So my question is center rib or not?

If no center rib is needed can someone post a picture here? I have a few pictures but it is hard to tell how it is done.

Thanks
Paul H^^

Title: Re: Foam wing question - center rib or not???
Post by: Leester on July 21, 2007, 01:32:26 PM

Paul: If your doing the Tom Dixon method on the wing you still sheet the center of the wing, and use ply top and bottom for the BC post support.

Title: Re: Foam wing question - center rib or not???
Post by: Paul Taylor on July 21, 2007, 03:10:02 PM

Not sure how Tom Dixon puts the bellcrank in.

I have this picture:
http://www.builtrightflyright.com/MiscHelpPgs/magnum/projects/projectspictures/IM001583a.JPG

Then one that Andy did on his profile Nobler with a center rib with the bellcrank mounted on it.

I am not sure what way to go.

Thanks for the help guys.
Paul H^^

Title: Re: Foam wing question - center rib or not???
Post by: Leester on July 21, 2007, 03:53:03 PM

Paul: Go to Tom Dixon's web site, he gives the dirrections for sheeting the wing his way using cap stips. I believe the bell crank mounting instructions are there also. When you get to is site click on wings and scroll down.

Title: Re: Foam wing question - center rib or not???
Post by: Paul Taylor on July 21, 2007, 05:25:27 PM

OK that cleared up a few things.
I think I need to add the rib because it is going in a profile.

Thanks
Paul

Title: Profile of full body, that is the question.
Post by: Paul Smith on July 21, 2007, 07:24:06 PM

The whole thing boils down to understanding how the wing attaches to the body.

On a full body plane, the fuse is glued onto the wing via two "airfoil holes" about 2" apart.  This makes for a very stable joint and obviously, a 1/2" rib in the middle wouldn't accomplish anything.

A profile is not so strong.  The 1/2" balsa fuse glues onto the wing via only one "airfoil hole" and lacks the stablity to two widely spaced ribs.  So on a profile, we need all the beef we can get , in the form of a "full-thickness" - (or thicker) center rib to give fuse something to glue onto.

Title: Re: Foam wing question - center rib or not???
Post by: Crist Rigotti on July 21, 2007, 07:55:33 PM

You do not need a center rib.

Title: Re: Foam wing question - center rib or not???
Post by: Chris McMillin on July 21, 2007, 09:53:32 PM

I never use a center rib or a spar in foamies. Profile or not.
Chris...

Title: Re: Foam wing question - center rib or not???
Post by: Paul Taylor on July 22, 2007, 07:23:49 AM

I am going to do the glass down the center.

Please post a picture of how install the bellcrank without the rib. Or point me to one. ;D HIHI%%
I am a have to see it guy of person. n~


Thanks H^^

Title: Re: Foam wing question - center rib or not???
Post by: Crist Rigotti on July 22, 2007, 07:31:34 AM

Here is one.  Ignore the center Lite Ply spar.

Title: Re: Foam wing question - center rib or not???
Post by: john e. holliday on July 22, 2007, 08:39:11 PM

I think you realize that after the wing is joined and in the fuselage that plywood pads will cut and drilled to fit over the bellcrank posts top and bottom.  I also make them fit to the fuselage side in a built up plane.    DOC Holliday

Title: Re: Foam wing question - center rib or not???
Post by: Bill Little on July 22, 2007, 08:59:38 PM

Yep, epoxy ply scabs on the top and bottom, 1/2 X 3/4, maybe 1/2 X 1.  Notch the fuse for them and you're set to go. 

I use a basswood tension spar on built up wings to mount the BC, suspended, then put a ply cap top and bottom to the inside fuselage side once the wing is mounted.

Title: Re: Foam wing question - center rib or not???
Post by: Wynn Robins on July 22, 2007, 09:12:09 PM

I use elongated diamond shapes of pine to mount the post to. cut the wing core so they are a tight fit with the longest part of the diamond inboard.
these should be flush with the top of the foam

glue the centre sheeting over top - this secures the mounting "pads" and locks them in.

you can glass over the sheeting for extra strength if you need to - but I never have .

Title: Re: Foam wing question - center rib or not???
Post by: Paul Taylor on July 22, 2007, 11:02:09 PM

Thanks Wynn. That is what I needed to see.

Paul H^^

Title: Re: Foam wing question - center rib or not???
Post by: phil c on July 23, 2007, 09:41:37 AM

By far and away the best way to build a profile(a takeoff on the old Veco Tomahawk).  NO hole in the fuse, the wings are joined by spar joiners and the leading edge and trailing edge going through the fuse.  The bc mount is a piece of 1/8 in. ply through the fuse and pinned with 1/8 in. dowels on the outboard side.