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Old Mar 15, 2013, 03:01 PM
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Knoll53's Avatar
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The flaps look good. Nice and big. I trust that the "optional' spoilers would be centered in front of the flaps in hopes that their deployment would also be pitch neutral. I may try test flying it without spoilers. I can always add them later inasmuch as they will be located right over the existing servo wire hole. Also at my 2 favorite flying sites, landing a little short is a good workable option for a glider with a very flat glide. Just come in 3m low and fly into the side of the mountain....works every time !

Based on limitations of foam cutting and the need for straight hinge lines, a simplistic approach to panel breaks is shown in the sketch. I don't suppose that this lends itself too well to wing twist. Panel breaks COULD occur within a control surface and still maintain a straight hinge line.

I understand that this is a wood wing project and that I may have to make some less-than-attractive-choices in order to transform it to a foam wing. Currently I predict a minimum of 5 panels per half span for the foam version.

Kent
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Old Mar 15, 2013, 03:35 PM
Herk
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Just curious - have never tried it.

What do you think about the possibility of bagging the Horten twist profile into a single panel layup ????
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Old Mar 15, 2013, 04:43 PM
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I'm not sure I'm following you Herk.
A single panel foam core?

That would be linear twist from the root to the tip?

Sure, but it would lack BSLD. IIRC I tried this on my first flying wing, shown as Flying Wing Prototype at the bottom of my blog. It was a E205 airfoil and the wing twist was provided by the up elevon, derived from flight testing. It flew....it turned....just not very well.

My Horten 9-V1 is 2 panel as far as wing twist goes. Slight better.

If it's a bagging question...sure no problem. If the mylars will not suck down to the curvy wing under full vacuum, you can just slice them up until they do. Then tape them together and you'll have "seams" between the mylars. I did this at the root joint of the Plank 2.5.

Currently I'm planning on bagging this wing with a single mylar. My guess is that since it is designed for speed, it will not have much twist in it. We'll see.

Kent
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Old Mar 15, 2013, 05:30 PM
Herk
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Quote:
Originally Posted by Knoll53 View Post
I'm not sure I'm following you Herk.
A single panel foam core?

That would be linear twist from the root to the tip?
Kent
Well no - not linear.

Usually when one bags a wing panel, they use the bed to support it and keep it straight while it cures. If the bed was supported by a thin plywood base that had the Horten twist supporting the bed, it seems to me that the BSLD twist could be built into the bagging process.
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Old Mar 15, 2013, 05:49 PM
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I think that you are still a step ahead of me.

So cut a wing without twist, then, as usual, place it on the beds , THEN place that assembly on top of a special warped building board that approximates the BSLD twist, or any desired twist, add weight and apply vacuum........Very clever! You would need a left and a right warped building board. The warped building board could be as simple as 1/4" plywood screwed down to a heavy sheet of MDF with blocks at the screws to set the twist.

It would be much quicker than cutting 5 panels and the twist might be accurate. You would still have to cut separate foam panels for the airfoil variations. 3 to 4 different airfoils are not unusual for a Horten.

The number of new variables scares me, so I won't try it but could very well be THE way to build a foam Horten......Any takers?

Kent
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Old Mar 15, 2013, 06:14 PM
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This IS an interesting idea.Not for me I'm afraid,I have no intention of getting into vacuum bagging.I have doubts about the foam holding the twist,wouldn't it be stressing the skin?
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Old Mar 15, 2013, 08:09 PM
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I have doubts about the foam holding the twist
I don't...

It's not so much the foam, but the composite action of the continuous FRP skin completely supported by the foam. Stressed skin construction is amazing rigid. The only weakness is at the hinge line where the top and bottom skins are not actually connected...which I may remedy with an added strip of FRP.

Stuart, did you know that you can do a vacuum bag process using only an aquarium pump? Real magic happens when you compress your FRP lay up.

Kent
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Old Mar 16, 2013, 02:11 AM
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Herk,

the problem with cutting the foam in one piece is that the wing section varies in span, as Kent mentioned. To be precise, there are 19 different non-linear interpolated airfoil sections per half span at the moment . I will try to reduce the amount of foam pieces to a minimum without affecting too much the design. But before we decide on the number of pieces, the design needs to be finished...

@Kent: The max twist is 4.6° at the moment. That's not much and comparable to the 5° of the small Schapel.

Cheers
Andrés
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Old Mar 16, 2013, 02:26 AM
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I've looked into vac.bagging,I'd thought about one of those food saver set ups.I think I'll stick with a press/ weights/clamps method.After seeing first hand the results Richard(shed) obtains it'll do for me.
I still like the idea though;it should be possible to cut a set of "ribs"to set the twist between a steel reinforced bed plate and a ply plate.Four would have to be made,but that's no big deal
Thinking about it,would a carbon tow spar system similar to the one I've just used,pressed in before the skins are added lock the twist before skinning? Hmm.............
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Old Mar 16, 2013, 02:47 AM
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Quote:
Originally Posted by andrecillo76 View Post
Herk,

the problem with cutting the foam in one piece is that the wing section varies in span, as Kent mentioned. To be precise, there are 19 different non-linear interpolated airfoil sections per half span at the moment . I will try to reduce the amount of foam pieces to a minimum without affecting too much the design. But before we decide on the number of pieces, the design needs to be finished...

@Kent: The max twist is 4.6° at the moment. That's not much and comparable to the 5° of the small Schapel.

Cheers
Andrés
It's not going to work for this bird then,but has possibilities.Going back to something like Verns Colibri,where,iirc he only used a root and tip foil.Would cutting that in one piece work,with the transition between the foils taking place along the span?If that was ok,a "tuned" twist could be built in.
Im way out of my comfort zone
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Old Mar 16, 2013, 10:09 AM
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While Andres is busy designing, thought I start the "Guess the CG" ball rolling.

Kent
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Old Mar 16, 2013, 10:50 AM
KlonWarz
Joined Dec 2012
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Quote:
Originally Posted by Knoll53 View Post

I understand that this is a wood wing project and that I may have to make some less-than-attractive-choices in order to transform it to a foam wing. Currently I predict a minimum of 5 panels per half span for the foam version.

Kent
Are you going to make a mold off this wing?
Or have you already posted sectional rib templates for a wing carver to use with a hotwire?

Sry Kent... there's so darn much information here on RCG and I've been bouncing around looking at SO many interesting planes!!!

I've gotten myself confuzed.

Must learn to focus.

rustycase
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Old Mar 16, 2013, 11:14 AM
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Are you going to make a mold off this wing?
No, not me.
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Old Mar 16, 2013, 11:48 AM
KlonWarz
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...wouldn't really take much...

wax it up, polish it, spray it with pva, lay some glass over it and embed some scrap sticks...
make a top and bottom...

Your wing is beautiful ! It could be forever! :-)
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Old Mar 17, 2013, 09:41 AM
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Quote:
Originally Posted by Knoll53 View Post
I think that you are still a step ahead of me.

So cut a wing without twist, then, as usual, place it on the beds , THEN place that assembly on top of a special warped building board that approximates the BSLD twist, or any desired twist, add weight and apply vacuum........Very clever! You would need a left and a right warped building board. The warped building board could be as simple as 1/4" plywood screwed down to a heavy sheet of MDF with blocks at the screws to set the twist.

Kent
Kent

I built a wing for a Dh 108 that way. I had a stiff flat board and fixed a more flexible board to it and fitted wedges to obtain the twist. The wing was then built on the twisted board without needing sub ribs. When I made the second wing I just lifted the flexible board and flipped it over and fitted the wedges to get the right twist for the second wing. The plane flew really well and was much better than a commercial version I bought later. The wing section was MH 60. The wing was covered with thin epoxy sheet and was immensely strong.

John
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