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Old May 30, 2009, 04:49 PM
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DH 87B Hornet Moth

I'm in the process of drawing up the plans to a DH87B Hornet Moth. I just found out that the original has the RAF 15 aerofoil. Any thoughts about using this section on the model? Has anyone used it on any of theirs?

Ian
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Old May 30, 2009, 07:24 PM
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Hi Ian,
The RAF 15 is fine as a model section but you will have to use functional rigging. It's too thin for cantilever construction.

Martin
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Old May 30, 2009, 08:52 PM
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Hi Ian,
Agreed, I've used it on a couple of biplanes and it's fine. Finding good coordinates for the RAF 15 is another thing! I have coordinates from a couple of sources and they are somewhat different.

Rich
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Old May 31, 2009, 06:22 PM
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I used it on a 1/5 scale, IC powered, Hornet Moth and it worked fine...
Only problem I had with the Model was trying to keep it tracking straight on take off and upon landing. I believe problem was the scale location of landing gear, which is way forward of the CG.
Discussion with ED Clark, owner of airplane I modeled, warned me of problem. Said, real one was a bear to take-off and land.

Lloyd
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Old Jun 01, 2009, 12:12 AM
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Thanks for the input guys.

Loyd, that's a good looking MOth you have there.

Rich, The profili programme has RAF15 but from the sounds of it maybe I should check a couple of sources.
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Old Jun 01, 2009, 05:58 AM
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Ian,
Try this page for coordinates of the RAF 15 and RAF 15 mod. I think DH used the RAF 15 mod- read that somewhere I suspect but can't really remember. It always seemed to me that the RAF 15 was just a cambered fairing drawn around couple of conveniently arranged spars...
Rich
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Old Jun 01, 2009, 06:18 AM
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Hi Jan, absolutely agree with Martin Irvine, used RAF 15 on my SE 5 1/4 scale ( sorry at the time wet engine), 6 times Italian Scale Champ, a couple of World Champs, lovely performer with scale section, but true scale functional rigging.

Carlo
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Old Jun 01, 2009, 06:58 AM
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Ian,

Lloyd's Moth was built from my plans, its 20 odd years ago that we did this for the Shuttleworth Trophy, but as far as I remember it was the scale section. As others have said, the wing needs to be functionally braced for stiffness although we cheated a little, using wire wing dowels rather than the pure braced folding arrangement.

Mike
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Old Jun 01, 2009, 08:01 AM
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Ian,
Here are the RAF 15mod coordinates from the site I linked to above, adjusted for a datum through the LE and TE rather than at the lowest point on the lower surface.
I did this so I could create a coordinate file in Compufoil. Maybe it will be handy for Profili users as well. Compufoil can overlay airfoils for comparison but I haven't had time to adjust the coordinates and compare RAF 15s from different sources.
Rich
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Old Jun 01, 2009, 12:31 PM
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Quote:
Originally Posted by Mike Smart
Ian,

Lloyd's Moth was built from my plans, its 20 odd years ago that we did this for the Shuttleworth Trophy, but as far as I remember it was the scale section. As others have said, the wing needs to be functionally braced for stiffness although we cheated a little, using wire wing dowels rather than the pure braced folding arrangement.

Mike
Mike,
I modified your plans of the DH87B to provide the folding wing feature, which changed the structure of the fuselage as well as the wing. The rigging therefore was functional. I have copies of the factory drawings from de Havilland which were used to get the details right.
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Old Jun 01, 2009, 03:21 PM
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I really appreciate the input guys, especially the fore-warning about bracing the wings. Having seen my Black Magic fold it'd wings a couple of weeks ago I wouldn't want to see the same thing happen here.

Loyd, You wouldn't happen to have the factory drawings in a computer file would you?
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Old Jun 01, 2009, 07:43 PM
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Sorry Ian, They are the plain old kind, and copies at that.
However, Since you are located in Riverside, and I'm living in Hemet, just 30 miles from Riverside...perhaps we could get together and make copies of what I have. I got mine from ED Clark the owner of the DH87B I modeled.
I also have a lot of photos of his airplane, which were a big help with the details.

Lloyd
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Old Jan 22, 2015, 09:33 AM
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Quote:
Originally Posted by Ian Easton View Post
I'm in the process of drawing up the plans to a DH87B Hornet Moth. I just found out that the original has the RAF 15 aerofoil. Any thoughts about using this section on the model? Has anyone used it on any of theirs?

Ian
I have just got the plans from Traplet as I was hoping to build as free flight version. All wing rigging angles are shown as zero, zero but in the D H Listing it shows them as +4 lower wing +2 top wing any ides ? The RAF 32 would be about right also
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Old Jan 22, 2015, 11:48 PM
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Jack, If your going to build it for FF I would increase the angles of the wings, leave the tail at 0 and increase the dihedral.
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Old Jan 23, 2015, 01:01 AM
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Jack, I got to thinking after I posted my reply that I had drawn the original plan with the +4 and +2 as you mentioned as I would have had no reason to change the original geometry set out by Dehavilland. I dug out my original drawing and it does show the different incidence in the wings. The lower being a little more than the top so that the lower will stall first. When you build it just make sure it is that way and definitely increase dihedral as the there's not much on my model - hence the ailerons.
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