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I know this is too late to be of any help to JAL3. but since the issue of Swing Wing hinges came up, I decided to start a new thread about just that.

There is “just something” about flying 6 to 10.5 foot wingspan swing-wings tend to make you learn how to make stronger, more robust (and to me, easier) ways to pivot the wings. And those methods down-scale well too. I even did some 1/4A Swing-wings, long ago.

So, for new discussion of swing wing hinges, check out this thread which includes the 6.5 foot span model below and drawings for what I have used for Swing Wing hinges:

https://www.rocketryforum.com/showthread.php?p=165789

- George Gassaway

I've been following that thread as you have posted it and it is something to be archived. Thanks for the information. I'd like to have the guts to do a big one like that some day.
 
Because I wanted maximum exposure to ask my questions.

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Ahah . . . So, you're a "Rocktry Exhibitionist", eh ? . . . LOL !

Actually, you have a very good point there. With contest rocketry isolated by itself, many rocketeers who don't currently fly competition might never get to see your questions.

After reading a thread like this, they might become curious and try flying NAR competition, or even just competition in their clubs or with friends !

BTW - It would be helpful if you signed your posts . . . Happy Flying !

Dave Fitch
 
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I'm afraid you've completely lost me in the second paragraph. If the vertical stabilizer is moveable, I completely missed that and need to go back and look at the plans again.

No. He said glue the rudder (vertical stab) wings and pod on, but NOT glue on the horizontal stab. Use a temporary attachment to figure out how much negative incidence to add before gluing the stab on permanently. Negative incidence in the horizontal stab is the front lower than the back.

kj
 
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BTW - It would be helpful if you signed your posts . . . Happy Flying !

Dave Fitch

????? My full name appears at the bottom of each post...doesn't it?
 
No. He said glue the rudder (vertical stab) wings and pod on, but NOT glue on the horizontal stab. Use a temporary attachment to figure out how much negative incidence to add before gluing the stab on permanently. Negative incidence in the horizontal stab is the front lower than the back.

kj

Thanks for clearing that up for me.
 
You can also adjust the incidence by cutting the trailing edge at the root (both sides) and warping the stab. Then superglue it in place--I've done this and had the adjustment hold for years.
 
Cutting BT5 to 1/8" lengths was a big one! I managed to ruin an entire 6" piece without getting one usable hub.

The secret to that one is to use tape to make something your sharp (even better- brand new) blade can run against, and use a spent motor as a mandrel when you are cutting.

Makes cutting those little slices a heck of a lot easier!

kj
 
The secret to that one is to use tape to make something your sharp (even better- brand new) blade can run against, and use a spent motor as a mandrel when you are cutting.

Makes cutting those little slices a heck of a lot easier!

kj

sez you!

That's how I mangled my BT5 tube. Like I said, though, I have a secret weapon: Sheryl at Semroc!
 
When last this thread was serviced, I had just cut out the template for the shoulders. Would it surprise anyone to learn that I traced one onto balsa and then cut it out?

shoulder-1.jpg

shoulder-2.jpg
 
I also cut out the template for the wingtips/stabilizers.

template-3.jpg

template-4.jpg
 
BIG QUESTION

I'm glad I did some checking before doing any actual cutting.

The instructions say to bore an 11/16 hole through the wings in order to mount the short, 1/8 inch BT tube for use as a hub. I had marked the point for the holes but decided to test on some scrap before actually cutting.

I set the BT on top of an 11/16 bit and found that the bit was quite a bit larger. I tried the next size down I had and then went down one more to 9/16. The 9/16 seemed like a perfect fit.

Was the 11/16 instruction a typo or is there something fundamental I am not getting

EDIT: I am adding some photos to show what I mean.
The first is the 11/16 called for, clearly too big.
The second is 5/8 which is better but still bigger
the last is 9/16 which looks just right.

I'm inclined to the typo theory but with my history I just may be missing some fundamental bit of understanding.

11-16.jpg

5-8.jpg

9-16.jpg
 
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My 1/8" wing stock was too wide so I used the template to mark the correct width and then ripped them to size with an x-acto and steel rule.

wings-3.jpg

wings-4.jpg
 
The wingtip template was then set on one end of a wing and the outline transferred.

wings-5.jpg

wings-6.jpg
 
The excess material at the wingtip was then cut off.

wings-7.jpg
 
The shoulder template was applied to the opposite end of the wing and that excess was cut off as well.

wings-8.jpg

wings-9.jpg
 
The process was then repeated with the other wing.

wings-10.jpg
 
BIG QUESTION

I set the BT on top of an 11/16 bit and found that the bit was quite a bit larger. I tried the next size down I had and then went down one more to 9/16. The 9/16 seemed like a perfect fit.

Was the 11/16 instruction a typo or is there something fundamental I am not getting

Wow. Last time I built one I just set a BT on the balsa, traced around it, and then cut it out with an xacto knife. I guess having more tools makes things more confusing.

Possibly a typo. You seem to have found the right size bit to use. I'd go with that.

kj
 
Wow. Last time I built one I just set a BT on the balsa, traced around it, and then cut it out with an xacto knife. I guess having more tools makes things more confusing.

Possibly a typo. You seem to have found the right size bit to use. I'd go with that.

kj

Thanks. I really was worried that I had conceptually missed something.

I tried an experiement with some scrap and learned that using a spade bit on balsa is definitely NOT the way to go. Its time to be off and buy more toys.:eyeroll:
 
I tried an experiement with some scrap and learned that using a spade bit on balsa is definitely NOT the way to go. Its time to be off and buy more toys.:eyeroll:
Uh, yeahhhh. I knew what the result was gonna be if/when you tried to use any sort of large diameter “cutting bit” on balsa (have not checked this thread in awhile). The only non-knife “tool” that would work well would be a computer controlled Laser cutter, but Lowe’s is always out of stock of those....... :)

As KJ said, the most practical way is to trace it and cut it by hand with an X-Acto knife. These hinges are much like the ancient “Groundhog” Swing-wings. And those were such a PITA and weak that I ended up developing the “pivoter” method so that a very small hole would suffice, among other things.

One of the weaknesses of that hole-thru-balsa hinge design is that the balsa will want to split along the grain, where the hole is. You may want to glue on a piece of 1/64” Plywood (or .005” G10/Waferglass) on the bottom of the wing (in the pivot area) to help reinforce it. Or even 1/32” balsa, glued at 90 degrees (gross-grain). If it is not too late.

- George Gassaway
 
Uh, yeahhhh. I knew what the result was gonna be if/when you tried to use any sort of large diameter “cutting bit” on balsa (have not checked this thread in awhile). The only non-knife “tool” that would work well would be a computer controlled Laser cutter, but Lowe’s is always out of stock of those....... :)

As KJ said, the most practical way is to trace it and cut it by hand with an X-Acto knife. These hinges are much like the ancient “Groundhog” Swing-wings. And those were such a PITA and weak that I ended up developing the “pivoter” method so that a very small hole would suffice, among other things.

One of the weaknesses of that hole-thru-balsa hinge design is that the balsa will want to split along the grain, where the hole is. You may want to glue on a piece of 1/64” Plywood (or .005” G10/Waferglass) on the bottom of the wing (in the pivot area) to help reinforce it. Or even 1/32” balsa, glued at 90 degrees (gross-grain). If it is not too late.

- George Gassaway

Oops.

It's been so long since I got any work done on it that I didn't check back.

Well... We'll see what happens.
 
The shoulder template was used to mark out spacing wedges which were then cut out.

shoulder-3.jpg

shoulder-4.jpg
 
After a good long while, I had a complete set of the shoulder pieces cut. I stacked them and regularized the ends with some sandpaper.

shoulder-5.jpg

shoulder-6.jpg
 
To mark the high point on the wing, I drew a line along its length 1/4 of the distance back from the front edge. For the rounded part, I made a series of 25% marks and joined them by drawing it in by hand.

wings-11.jpg
 
The sanding of the airfoils was accomplished by taping the wing down to a piece of plate glass and running masking tape lines along the boundaries to be protected. Sanding blocks were used do do the sanding.

wings-12.jpg
 
The launch lug was cut with a razor saw from a piece of 1/8" ID aluminum tubing.

lug-1.jpg
 
The instructions recommended to wrap the lug in thread to improve the bond with the parts to which it is joined. With that in mind, I used an overhand knot to start the thread at one end and secured the knot with some CA.

lug-2.jpg
 
The thread was then wrapped around the lug until it extended almost the full length. The tail end was tacked into place with CA as well.

lug-3.jpg
 
The two wings were taped together, back to back, and a sanding block was used to smooth out the ends that would fit in the shoulders.

wings-13.jpg
 
The location for the pivot was marked and then a small drill bit was hand twisted to establish a pilot hole.

wings-14.jpg
 
It seemed that even with the pilot hole, the big bit would have a tendency to wander so I repeated the procedure with a larger bit.

wings-15.jpg
 
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