Best method to sand in dihedral?

[Rktman]

What’s the best method to sand in the dihedral on a flop wing? A. Bevel both sides of the wing by half the dihedral angle or B. Bevel the total dihedral angle on only the tip panel?

Does it make any difference at all in terms of strength? My concern is that on a previous model I built, the balsa where the two edges met eventually smushed and the angle kept increasing till the glider was unflyable.

 

[caveduck]

Dredging up oooold memories - for the sanding it doesn't really matter. IIRC I would just do all the dihedral angle on one side.

There are a lot of ways to do the hinge and travel limiters. One of the easiest is to harden up the edges of the balsa with CA. You can also use a wire or 3D printed travel limiter on the inside of the angle. If you use a really good hinge material on the outside angle (I've heard Tyvek mailing envelope material works) the hinge tape itself will limit any over-rotation.

If you know anybody who is building the FAI S4A RG swing/flop wings for internats competition, they have some really sophisticated ways of making those things today. Do a Google image search for "S4A boost glider" to get a few perhaps useful photos. There are a couple of pics of swing/flop gliders here: https://contestrockets.org/showthread.php?tid=13 but they don't show the mechanism details very well. Also a Russian one is here: https://www.rocketryforum.com/threads/s4a.2248/ with a little better view of the hinge areas.

 

[Rktman]

Dredging up oooold memories - for the sanding it doesn't really matter. IIRC I would just do all the dihedral angle on one side.

There are a lot of ways to do the hinge and travel limiters. One of the easiest is to harden up the edges of the balsa with CA. You can also use a wire or 3D printed travel limiter on the inside of the angle. If you use a really good hinge material on the outside angle (I've heard Tyvek mailing envelope material works) the hinge tape itself will limit any over-rotation.

If you know anybody who is building the FAI S4A RG swing/flop wings for internats competition, they have some really sophisticated ways of making those things today. Do a Google image search for "S4A boost glider" to get a few perhaps useful photos. There are a couple of pics of swing/flop gliders here: https://contestrockets.org/showthread.php?tid=13 but they don't show the mechanism details very well. Also a Russian one is here: https://www.rocketryforum.com/threads/s4a.2248/ with a little better view of the hinge areas.

Appreciate the feedback and links. I really like the Eastern European-style FAI S4A swing/flop glider design but there's precious little info and detail on their construction and methods like travel limiter design or rotary hinge mechanisms. That's why I like the Forum, so many more experienced builders like yourself that have probably run into the same problems and have found solutions (or know where to find them).

 

[Amsterdam]

The designs shown here seem to use both ways

The Giblet plan at the bottom is step by step instructions

 

[caveduck]

Yes good point. The Giblet plan is pretty accessible and is a good first read. The Jacomb plan is also worth reading but it's some serious Internats over-engineering and actually has wings that fold up longitudinally into a thin strip in addition to just swing/flop, but you can learn some useful construction techniques there. BTW the link to the Venus Rocketry plans inline in the discussion is dead - they are now an RC helo site. The links at the bottom of the NAR article all seem good.

 

[Rktman]

The designs shown here seem to use both ways

The Giblet plan at the bottom is step by step instructions

Yes good point. The Giblet plan is pretty accessible and is a good first read. The Jacomb plan is also worth reading but it's some serious Internats over-engineering and actually has wings that fold up longitudinally into a thin strip in addition to just swing/flop, but you can learn some useful construction techniques there. BTW the link to the Venus Rocketry plans inline in the discussion is dead - they are now an RC helo site. The links at the bottom of the NAR article all seem good.

Ended up sanding just the outboard wingtip panel and it works fine. In fact the angle was more accurate than trying to sand in half the angle on both sides (which I tried on a few previous models).