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Dec 26, 2015, 10:12 AM
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Knoll53's Avatar
Quote:
Originally Posted by Hussle
Not much work done for the moment, just the first of the joiner boxes made for the 15mm main spar. The anti-rotation spar will be 10mm. How long should the rotation spar be?
Hussle
I can see that you are playing "hard to get" on your blog, not any info. on you.........but from your avatar, I'm guessing that you have built a scale plane. I see that you're not afraid sand a groove in a block of balsa. I don't think that I've ever tried that. Looks tricky.

Your anti-rotation spar ( or alignment pin for me ) can be short if it is just that. But if you locate it at a sub spar (just forward of the elevons) and build a sub spar similar to main spar, you could justify making the pin long enough to transfer some bending strength.

If you can manage to scan and post a sketch, we'll have a better idea of what you're thinking.

Kent
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Dec 26, 2015, 03:05 PM
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Quote:
Originally Posted by Hussle
Also, thinking about laying up the spars again, it seems that everyone sands a shallow trench and lays the carbon tow face down in the slot. Has anyone tried cutting a thin, deep slit and laying the tow in edge up. This seems like it would obviate the need for a shear web or for relying on the foam to act as the shear web.

You could even cut the slit and then lay carbon face down above your vertically oriented tow, forming a "T" shaped spar, which might even help with torsional loads.

Seems like this could significantly strengthen the wing, or is added strength in this direction unnecessary?

Hussle
The spar caps are where the primary load path is, which is why CF is placed there and in that fashion. I suppose you could try to slide some tow into a slot to form a shear web - but it wouldn't necessarily be the optimal use.

-Dave
Dec 26, 2015, 03:32 PM
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Hussle's Avatar
Quote:
Originally Posted by Knoll53
... you have built a scale plane.
I'm afraid that's just a parkzone Ka-8, lovely flyer, but hardly a build.

Quote:
Originally Posted by Knoll53
I see that you're not afraid sand a groove in a block of balsa. I don't think that I've ever tried that. Looks tricky.
It actually worked quite easily, and would probably be even easier with an appropriate diameter round file.

Quote:
Originally Posted by Knoll53
Your anti-rotation spar ( or alignment pin for me ) can be short if it is just that. But if you locate it at a sub spar (just forward of the elevons) and build a sub spar similar to main spar, you could justify making the pin long enough to transfer some bending strength.

Kent
I was intending to make 4 tow spars in two sets (front abd back), paired top and bottom so that the end of the joiner box would be sandwiched between them. Thanks for the advice, I'll probably now extend the rear joiner (10mm Carbon) and join it to the rear tow spars in a similar fashion to the main joiner.

Hussle
Dec 26, 2015, 03:38 PM
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Hussle's Avatar
Quote:
Originally Posted by Cap_n_Dave
The spar caps are where the primary load path is, which is why CF is placed there and in that fashion. I suppose you could try to slide some tow into a slot to form a shear web - but it wouldn't necessarily be the optimal use.

-Dave
Thanks Dave, but would vertically oriented tow not reduce any tendency to flex up and down along its length? (The combat wing guys do something similar by inserting strips of carbon)

Thanks,
Hussle
Dec 26, 2015, 04:36 PM
You know nothing....
Stuart A's Avatar
Check out this,slightly bigger than yours,same carbon tow system-
https://www.rcgroups.com/forums/show....php?t=1562220
Dec 26, 2015, 05:28 PM
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Hussle's Avatar
Quote:
Originally Posted by Knoll53
If you can manage to scan and post a sketch, we'll have a better idea of what you're thinking.

Kent
Okay, here's what I'm planning now:
Main joiner is bonded to the forward tow spars which are top and bottom, same deal with the secondary joiner.

Also, does it look like these flaps should be fairly pitch neutral? How do you tell?

Hussle
Last edited by Hussle; Dec 26, 2015 at 07:16 PM.
Dec 26, 2015, 06:11 PM
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EdSoars's Avatar
You can gain some torsional stiffness by making that rear spar run from just ahead of the flap hinge line at the root, to overlap the forward spar at the tip.

It's going to be SO interesting to see the CO5 in the air and get your impressions; I'm glad you tackled the project!

ed
Dec 26, 2015, 09:32 PM
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Hussle's Avatar
Quote:
Originally Posted by EdSoars
You can gain some torsional stiffness by making that rear spar run from just ahead of the flap hinge line at the root, to overlap the forward spar at the tip.

It's going to be SO interesting to see the CO5 in the air and get your impressions; I'm glad you tackled the project!

ed
Sounds good, something like this? Or have a rear spar in addition?
Dec 27, 2015, 12:12 AM
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Hussle's Avatar
Joiner boxes fully shaped. I'm planning on wrapping some tow around them to hold the two halves together.

Fins cut out and need to be glassesd.

Hussle
Dec 27, 2015, 03:18 AM
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EdSoars's Avatar
The first spar layout would provide twist resistance for the wing as a whole. You would still want a subspar at the elevon hinge to provide stiffness there for both the main panel and the control surface.
Dec 27, 2015, 03:58 AM
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Hussle's Avatar
Quote:
Originally Posted by EdSoars
The first spar layout would provide twist resistance for the wing as a whole. You would still want a subspar at the elevon hinge to provide stiffness there for both the main panel and the control surface.
Thanks Ed
Dec 27, 2015, 09:28 AM
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Knoll53's Avatar
I would suggest that torsional strength is secondary to bending strength and rigidity.

I like your sketch. The connections will be the hard part. You'll need a good skin as well.

If you have 2 long joiners, they must be exactly parallel to each other, or else you will not be able to slide them on. It takes a jig.

You could simplify this build greatly by building a one piece wing.


Keep those pictures coming !
Last edited by Knoll53; Dec 27, 2015 at 09:36 AM.
Dec 27, 2015, 09:34 AM
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Knoll53's Avatar
Quote:
Originally Posted by Hussle
Also, does it look like these flaps should be fairly pitch neutral?
Hussle
Not at all. They will act as an elevators. When the flaps go down, the nose goes up. I believe that this part of the design goal of the CO5. You can easily mix in some elevon to make them pitch neutral. If you ran the flaps out to the elevons, then they would be close to pitch neutral.

There are lots of discussions about moment neutral flaps on this forum.
Dec 27, 2015, 01:36 PM
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Hussle's Avatar
Quote:
Originally Posted by Knoll53
I like your sketch. The connections will be the hard part. You'll need a good skin as well.
Excellent!

Quote:
Originally Posted by Knoll53
You could simplify this build greatly by building a one piece wing.
Unfortunately not an option as I can't transport such a large wing. Also, the joiner is a hollow 15 mm tube, not solid.

Quote:
Originally Posted by Knoll53
Not at all. They will act as an elevators. When the flaps go down, the nose goes up. I believe that this part of the design goal of the CO5. You can easily mix in some elevon to make them pitch neutral. If you ran the flaps out to the elevons, then they would be close to pitch neutral.
Surely for a thermal wing pitch neutral flaps would be optimal? (Camber changes and all that)
Edit: Found stuff on neutral flaps here and here
So pitch positive flaps could reduce workload in a thermal. I have a dx9 radio, however, and could easily set up trims for multiple flight modes and mix elevator to flaps. If extending the flaps would still make them slightly pitch positive, then I could do the rest with my radio. Would a longer flap surface be preferable assuming I can make all the compensation in my radio?

Hussle
Last edited by Hussle; Dec 27, 2015 at 01:56 PM.
Dec 27, 2015, 01:56 PM
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Knoll53's Avatar
Quote:
Originally Posted by Hussle
Surely for a thermal wing pitch neutral flaps would be optimal? (Camber changes and all that)
Hussle
Here's my theory. Adding camber to a wing will create good lift at a slower speed, thus allowing tighter thermal turns..............it's a good thing.

With full span elevons and flaps the entire wing can be cambered. Here's how. Make the flap as long as possible while maintaining a pitch positive effect. The remainder of the wing is elevon. Compensate for the pitch positive flap with elevon deflection, which would be a downward deflection, thus providing a fully cambered wing.

Kent


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