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Author Topic: Strengthening Miss Canada Senior Wings  (Read 177 times)
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a23smith
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« on: December 18, 2020, 11:43:47 PM »

Hello Everyone,

I’m building a second Miss Canada Senior in an attempt to make it better than the first time (I don’t have much experience in this hobby). Actually I’m making a third wing because the first one buckled on a test glide, and I built a second wing to go with the first fuselage. I think one of the reasons the first wing broke is that I got the tissue that came with the Easy Built kit mixed up with some that wasn’t made for model airplanes, but I have also read online that the wings on this model are prone to buckling. When the wing broke I stripped the weak tissue and replaced it with the kit tissue, as well as built the second wing. Later I discovered that the copy of the plan I had used for both the first and the second wing (which was a photocopy of the plan that came in the kit) was not full size (the half-wing was 17 1/2” long, instead of 18”). Consequently I assembled the framework for a third wing and the rest of the plane, then put it aside (partly because I didn’t have any more tissue). Now I’m back to where I stopped, with new tissue being shipped, but I’ve been reading more and thinking about it more, and I’ve become doubtful about the method I used to strengthen the wing. When I built it the second time and constructed the framework for the third wing I added two more 3/32” square spars, one on top at the high point and the other directly below it. This probably added significant weight and it kept the tissue from sagging as much as before, which I think is not a good thing (I’ve read that thinner airfoils are generally better and I’ve been told that the reduced sag probably decreased the efficiency of the wing). A person in another forum wrote about strengthening the wing of his Miss Canada Senior by making the top spar much deeper at the root and tapering it toward the tip, plus using much harder balsa. I have also read recently about other methods of strengthening the wing. One person coats the spars near the root with CA on his fragile wings, Another puts the ribs closer together toward the root and gradually increases the spacing toward the tip. Another adds carbon fiber caps to the front of some of the ribs, and another adds caps to just the part near the TE. I don’t know what weight balsa I used for the parts of the first or second wing, but I used light wood for the ribs and TE of the third wing. I also assume that just using heavier balsa probably wouldn’t make the wing strong enough, since apparently many people have had failures with wings built according to the plan. So, what do you think would be the best method of making the wing for this model reasonably strong while keeping the added weight to a minimum (not including such changes as going to sliced ribs with geodetic bracing because that would be quite a bit harder to do)?

PS: I plan to add a Mylar substrate to the covering this time, which is supposed to add some strength while adding little or no extra weight.

Alan
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gossie
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« Reply #1 on: December 19, 2020, 04:44:56 PM »

Too hard to read.
Please use spacing and commas and stops.
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a23smith
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« Reply #2 on: December 19, 2020, 05:10:14 PM »

Hello Everyone,

I’m building a second Miss Canada Senior in an attempt to make it better than the first time (I don’t have much experience in this hobby). Actually, I’m making a third wing because the first one buckled on a test glide and I built a second wing to go with the first fuselage. I think one of the reasons the first wing broke is that I got the tissue that came with the Easy Built kit mixed up with some that wasn’t made for model airplanes, but I have also read online that the wings on this model are prone to buckling. I am starting this thread to get advice on the best way to strengthen the wing with minimal added weight, reduced wing efficiency, or significantly more difficult construction.

When the wing broke I stripped the weak tissue and replaced it with the kit tissue, as well as built the second wing. Later I discovered that the copy of the plan I had used for both the first and the second wing (which was a photocopy of the plan that came in the kit) was not full size (the half-wing was 17 1/2” long, instead of 18”). Consequently I assembled the framework for a third wing and the rest of the plane, then put it aside (partly because I didn’t have any more tissue). Now I’m back to where I stopped, with new tissue being shipped, but I’ve been reading more and thinking about it more, and I’ve become doubtful about the method I used to strengthen the wing.

When I built the second wing and constructed the framework for the third wing I added two more 3/32” square spars, one on top at the high point of the ribs and the other directly below it. This probably added significant weight and it kept the tissue from sagging as much as before, which I think is not a good thing (I’ve read that thinner airfoils are generally better and I’ve been told that the reduced sag probably decreased the efficiency of the wing). A person in another forum wrote about strengthening the wing of his Miss Canada Senior by making the top spar much deeper at the root, tapering it toward the tip, and using much harder balsa.

I’ve also read recently about other methods of strengthening the wing. One person coats the spars near the root with CA on fragile wings. Another puts the ribs closer together toward the root and gradually increases the spacing toward the tip. Another adds carbon fiber caps to the front of some of the ribs, and another adds carbon fiber caps to just the part near the TE.

I don’t know what weight balsa I used for the parts of the first or second wing, but I used light wood for the ribs and TE of the third wing. I assume that just using heavier balsa wouldn’t make the wing strong enough, since many people have had failures with wings built according to the plan.

So, what do you think would be the best method of making the wing for this model reasonably strong while keeping the added weight to a minimum, not reducing it’s efficiency or making it significantly harder to construct?

PS: I plan to add a Mylar substrate to the covering this time, which is supposed to add some strength while adding little or no extra weight.

Alan
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« Reply #3 on: December 19, 2020, 05:21:28 PM »

The 'weight bearing' stresses on a wing are lowest at the wingtips and highest at the fuselage. Concentrate on strengthening the inner section of the wing. Use 3/32 x 1/4 " bottom spar in the inner section of the wing, and leave the rest of the structure as is. It should be fine.
YMMV
ian
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a23smith
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« Reply #4 on: December 19, 2020, 05:27:53 PM »

Ian,

Thanks for the advice.

The bottom spar is near the TE (maybe at 2/3 of the chord). Why do you advise to strengthen that one, rather than the top spar, which is near the LE?

Alan
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randoloid
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« Reply #5 on: December 19, 2020, 06:28:55 PM »

I had no issues with my Ms Canada Wing.  I did make laminated tips and strengthened my dihedral joints with a layer of ladies nylons and epoxy.  Don't laugh too hard, it really works. 

Like you I don't have a ton of experience building, and it took me a second build to get a good flyer but when you get it together right it's an awesome flying plane. I lost mine last year and will be building another one day.

In my opinion, the biggest improvement you can make is to take that white plastic prop that comes with the kit and throw it in the garbage.  If you don't feel confident making a balsa prop from scratch order a blank from volareproducts.com.

Best of luck.
randy
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a23smith
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« Reply #6 on: December 19, 2020, 07:05:14 PM »

Randy,

Thanks for the advice.

My enjoyment is primarily in the learning process for building and trimming the plane. I doubt that I will ever enter a competition.

When I built the plane the first time I carved a folding prop and used an aluminum hinge plate (the kind that is attached to the rear of the hub) that I bought. I had some trouble because I cut the blades from the hub before gluing the hinge wires to them, and I plan to make a wire hub this time. I’ve read that contest rules have been changed to prohibit wire hubs, so maybe most people have switched to plywood hubs, but if I understand correctly a plywood hub usually won’t allow using compound folding angles, which is supposed to be more proper.

Good luck with your next Miss Canada Senior.

Alan
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« Reply #7 on: December 19, 2020, 07:16:08 PM »

If you're going to compete in the FAC, you need to make sure the prop DOESN'T fold in the air. It's ok if it folds when it hits the ground. If you're talking about SAM, it may be another story.
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a23smith
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« Reply #8 on: December 19, 2020, 07:20:11 PM »

Lincoln,

Thanks for the clarification. I was referring to something John Baker wrote in another thread here. If I remember correctly he was referring to FAI rules.

Alan
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PB_guy
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« Reply #9 on: December 19, 2020, 07:21:34 PM »

Looking at the bones on Easybuilt, the top spar seems to be meant for support of the tissue. I would leave that one there, and add a top spar at the apex of the rib, with a bottom spar directly beneath it, and eliminate the rearward bottom spar, but only on the inner wing sections. However, I am no designer, and if you are entering it in a contest, they might insist on 'as the plan was designed originally'.
YMMV
ian
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Re: Strengthening Miss Canada Senior Wings
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a23smith
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« Reply #10 on: December 19, 2020, 07:35:55 PM »

Ian,

Thanks for the revised advice. When I built the second wing and the framework for the third I did it the way you advised in your second post, except I didn’t eliminate the original bottom spar. If I eliminated it the weight increase (by adding the top spar) would be half as much, but I’ve been told that the reduced tissue sag would reduce the efficiency of the wing. If that’s true, would you still add the top spar rather than beefing up the bottom one?

Alan
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a23smith
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« Reply #11 on: December 19, 2020, 07:40:08 PM »

Ian,

Another thought occurred to me. The airfoil has under-camber, so wouldn’t eliminating the original bottom spar cause a problem keeping the tissue adhered to the bottom of the wing?

Alan
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« Reply #12 on: December 19, 2020, 07:44:47 PM »

Download the plan for the Senator from the Plan Gallery and take a look at the layout of the wing spars. They also have undercamber. It seems to work quite well. You might just adapt the spar layout from it to your model. I wouldn't worry too much about increased weight, when your primary concern seems to be strength.
YMMV
ian
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a23smith
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« Reply #13 on: December 19, 2020, 07:46:03 PM »

Ian,

What about just adding a 3/32 X 1/4 bottom spar in the inner panels? Thanks for your additional advice.

Alan
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« Reply #14 on: December 19, 2020, 10:59:27 PM »

Sounds OK to me. Anything to add some stiffness to those panels would help.
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a23smith
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« Reply #15 on: December 19, 2020, 11:11:58 PM »

Ian,

Thanks for the response. I don’t know if adding the bottom spar to the inner panels would be the best solution, but it seems to fit my criteria best, assuming it adds enough strength.

Alan
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