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Jan 04, 2014, 11:49 AM
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builderdude's Avatar
Quote:
Originally Posted by davidterrell80
Good suggestions all around. I've also had good experience making raw laminate bend with a weak ammonia solution.

Ammonia? Hmm, I'll have to try that next time. Never thought of that.
And the funny fairy image made me laugh.

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Jan 04, 2014, 12:12 PM
Ad eos qui nesciunt crepitus
Old_Pilot's Avatar
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Quote:
Originally Posted by builderdude
I know you've already chosen monokote, but I might suggest some ideas that would have worked for the undercamber.

If you used tissue instead of monokote, the degree of shrinkage would have been less, and it would not have pulled away from the ribs so bad. Monokote, being plastic, doesn't accept glue as well as tissue would. Monokote is also not used on real light airframes for the same reason, it shrinks too severely.

If you used silk, you could have not only glued it, but you could have also previously bored a couple of small holes in the wood and sewed it in place with thread to hold the material on the undercamber.

In fact, if you decide to, you could still go back and do that on the undercamber, using either tissue or silk, even if the top side is already monokoted.
But that's up to you.

BD,

I always build test frames for almost everything that I question or have never tried, which means I have a lot of test frames ! HA ! The wing section I did was only a 4-rib piece, just to see what would happen. My selection of a film cover has a much to do with my flying (in)ability as it does with technique. A couple of test glides of the Fighter Glider left her with several large puncture wounds, and she was covered with onion skin, which is a lot stronger than tissue....I'm at the stage now that I really want to fly these birds.....more than once ! LOL

Plus, I scored the mother load of MonoKote from my LHS. Seemingly he bought several private model collections that included at least 100 rolls of film, in all kinds of colors...and was selling them for $1.00 per roll. I've got 20 rolls of the stuff to use up !

Hard to find any of the fabric coverings here in Memphis..we only have two hobby stores, and neither are geared towards balsa aircraft, and I'm way too impatient for mail order. Lot's of foam Arf's, Barf's, and Rtf's.....very few balsa planes.

Maybe someday I'll try to cover with silk etc.

Needle and thread......me ??!!.......not a chance..don't have enough bandaids.
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Jan 04, 2014, 04:23 PM
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Old_Pilot's Avatar
Thread OP

Port wing


Roughed in the port wing.....Haven't cut the ailerons loose yet.......
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Jan 04, 2014, 05:22 PM
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Fly Wheel's Avatar
The kit I have recommends against the heavier shrink films like MonoCote (in fact they mention that brand by name). I did find this video on covering undercambered wings, you might wish to watch it; it may give you some ideas.
Covering a Wing With Polyspan (56 min 53 sec)


As far as the framework showing through the film, in one of the very few pictures of the actual plane the ribs show through quite clearly (even in the primitive grainy photograph). And this picture was taken indoors, not even in the air. In fact I cannot even find a photo of this plane actually flying.


So I would think the spars would be pretty much visible as well. In fact if you look closely at the photo full size you can see them. Remember these early planes were only covered with fabric (in fact they were built much like the pre foam, pre X-cote models) and few it seems were painted. I certainly doubt they would waste the time, effort and cost on a prototype.
Last edited by Fly Wheel; Jan 04, 2014 at 05:31 PM.
Jan 04, 2014, 07:43 PM
Registered User
Fly Wheel,
The spars may show through the covering, as shadows, but they aren't visible on the surface of the wing because they were internal with the ribs around them.
Most aircraft of this era remained clear doped because of the weight paint added. They were mostly used for competition, setting records, that sort of thing, so weight was the ever present enemy. Add in the pitifully inefficient engines available and every ounce saved mattered. They didn't really start painting them in any quantity until well into WW1.

Charlie,
I thought you were going for some under camber. With a flat bottom wing normal bottom surface spars would have been fine. It's just them showing through the top covering I was concerned about, it just looks wrong to my eye.
When you say 'dowel' spars, you don't mean hardwood dowel, do you? They look pretty chunky in the photo. Far more spar than needed if they are hardwood.
Those horn plates in the aileron need to be laminated to full rib depth so there's something for the covering to attach to around the horn.

Pete
Jan 05, 2014, 09:05 AM
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Quote:
Originally Posted by PETERRAKE
Charlie,
I thought you were going for some under camber. With a flat bottom wing normal bottom surface spars would have been fine. It's just them showing through the top covering I was concerned about, it just looks wrong to my eye.
When you say 'dowel' spars, you don't mean hardwood dowel, do you? They look pretty chunky in the photo. Far more spar than needed if they are hardwood.
Those horn plates in the aileron need to be laminated to full rib depth so there's something for the covering to attach to around the horn.

Pete
Morning Pete,

Well, I don't like the wing much either. What sounded good in theory, and looked good on paper was a disaster when it was assembled. I don't have the proper bits to cleanly drill a stack of soft balsa. I'll have to saw cut the notches in the ribs to receive the spars. Oh...the "spars" are indeed Poplar dowels, and they're too big and clunky, not to mention heavy. No experiment is a failure though....I'm going to build the wing again with rectangular spars, and with a slight bit of under camber. I think I can get the best of both design features. One thing I noticed....the wood I used for the 1/16 ribs was very soft. I could hardly touch one without denting, cracking, or breaking it. I'm thinking that any shrinkable covering, natural or synthetic, might well crush or cripple the rib when tightened. Need to think about that. Also, I added the corner braces at the trailing edge because it "wiggled".

The wing joining tubes looked too small, but that could have been because of the massive spar next to it....Mandelbrot syndrome.

One variant I did like was "bird-beaking" the nose of the ribs to receive the leading edge. I'm going to keep that detail.

So, onward and upward.

It's a good day to build...raining and yucky outside.

More as the day progresses.

C

But the best part about yesterday was that my new scroll saw worked great. The ribs barely needed sanding, and for all intents and purposes, were identical.
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Jan 05, 2014, 09:29 AM
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portablevcb's Avatar
FWIW, I don't drill soft balsa. Get a steel tube and sharpen the edge. Use a twist motion to punch the hole. An old transmitter antenna works well for this when only doing a few. And it has a ton of different sizes to choose from.

When building my SPAD I made up a ply form for the ribs. It was fairly simple to cleanup the edges, notch for the spar with a knife and punch the necessary holes.

Each rib took only a couple of seconds after I got the technique down.

I discovered this after destroying over 100 ribs trying to saw and drill them in a stack.

Soft balsa ribs withstand the covering quite well (just don't use Monokote ). It is the sanding part they don't like

charlie
Jan 05, 2014, 11:22 AM
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builderdude's Avatar
If you can find denser balsa, you'll like it better.
In the absence of dense balsa, you can go thicker to compensate for the balsa's weakness.

Even though you have a lot of monokote, I don't think the shrinking properties of monokote will allow you to undercamber anything. Maybe consider a different material for the undercamber and use monokote everywhere else?
Just a thought.

Maybe you can use your first wing attempt to just throw together a toss glider or something, recycle it somehow.

Can you use stringers on your wing? They might help to strengthen it, in the absence of large spars.
Jan 05, 2014, 12:24 PM
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New airfoil


OK....I "adjusted" the airfoil to include a slight bit of under camber and kept the bird-beak for the leading edge. It's still a 9.5% airfoil with ~ 3.4% camber and a 10" chord.

Once more into the fray !
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Jan 05, 2014, 03:30 PM
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Much Better


Pete,

Better ?

c
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Jan 05, 2014, 08:44 PM
Registered User
Looks fine to me mate.
Had you considered ironing the film onto the lower wing, lightly shrinking it (just to get it even) and then ironing it to the ribs. No more shrinking, but possibly apply a bead of white glue or CA along each rib before covering the top surface.
If it won't do that, I'd start to suspect that it's cheap because it's old. I've yet to find a film that won't do it unless it's past its' best. Not that I've tried that particular film, so I could be wrong.

Pete
Jan 05, 2014, 09:09 PM
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Old_Pilot's Avatar
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Wing 2.0


I'll probably try the "iron-to-each-rib-and-then-a-little-glue" method....on another test frame, before I cover the wing proper !

Guess I got in a hurry with Wing 1.0, but hey, I never was very good at coloring inside the lines.....

Tomorrow is another day !
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Jan 05, 2014, 11:01 PM
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Fly Wheel's Avatar
No failure is a failure unless you fail to learn from it. And you've also told other's who read your thread that this method doesn't work, so in that too it is not a failure.

Just look at how many ways Thomas Edison learned how not to make a light bulb!
Jan 06, 2014, 06:19 AM
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Quote:
Originally Posted by Fly Wheel
No failure is a failure unless you fail to learn from it.
By that measure, I'll be the smartest person in the galaxy by the time I die ! Oh, I did find a bit that will drill balsa......It's used to drill holes for fluted dowels. Extended centering (brad) point, convex relief at the start of the shank. The drill press RPM's need to be at max, and go real slow. Also helped to have a backing board for the balsa to rest on.
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Jan 06, 2014, 08:23 AM
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Thread OP

Learned something else


I've been using a spray adhesive to a hold paper template on a stack of wood blanks....the template doesn't want to come off of bare wood.......so I put a layer of Scotch tape between the template and the wood....came right off !
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