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Old Jun 28, 2015, 10:14 AM
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I can hardly wait. This is going to be good. Version 1 was pretty impressive. And it certainly is an interesting subject.

Best of luck with the build.


Cheers!
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Old Jun 28, 2015, 10:47 AM
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Hi Ken I'll be looking forward to Version 2 as well.
As for electric retracts, have a look at HK's #225000021 10 kgs series, I purchased one more out of curiousity than need, found it to be very robust and powerful for around $30US. You'd still need to adapt struts to the 10mm opening clamp, I didn't consider that any issue for me, and know it won't for you. fwiw Doug B
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Old Jun 28, 2015, 10:50 AM
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Hs129 Aileron hinge detail:
Seemingly a wee bit more complex than a few bits of plastic as hinges.
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Old Jun 28, 2015, 03:18 PM
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Failure is not an option
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Ken - if you have CAD drawings of the parts, I can probably cut alot of them on my laser. Let me know, not a big deal for me to do. I would also be interested in a set of parts and accessories if you are so inclined.
Rob
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Old Jun 28, 2015, 04:40 PM
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Hi Ken, I have been watching this thread from the beginning and I am glad you are going to try again. The original model was magnificent. I hope you intend to provide a stiff spar structure that carries through the fuselage as effective as the one that you provided in the last design to take wing bending loads through the nacelles.

I think that the problem with the last design was that the wing skins were carrying the bending load, whether you intended them to do so or not. If you provide a structure like the wing skin that is stiff enough to pick up load, it will pick up load. The wing was probably carrying most of the bend stresses in the skins and they were capable of taking the loads since the grain of the skins was in the spanwise direction. However at the junction with the fuselage centre section, the wing skins would have passed the loads they were carrying to the fuselage skins/planking where the grain was at right angles, with very little ability to bear the loads in the direction presented (cross-grain in tension).

I know that you had a wooden spar structure that carried through the fuselage but I suspect that it was not very stiff relative to the skins and that it would not have picked up much of the wing bending load being carried in the skins at the wing root. (Think of parallel springs, one soft and one stiff. The stiff spring attracts most of the total load when the springs are deflected together). That is the situation with skins and spars. Unless the spar is very stiff (a carbon tube, say) or you deliberately break the skins, the skins will naturally collect the bending loads since they form the extreme fibers of the structure and their cross sectional area is quite large.

In the last design, you probably went to carbon tubes in the nacelle regions to provide a way of removing the outer wing panels for transport and maybe to help collect landing gear loads, but the structure you came up with was exactly what was required to divert the wing bending moments away from the nacelle structure. If you had carried the carbon tubes across the fuselage continuously, the wing bending moments would have been isolated from the fuselage structure as well. So, I hope that this is the sort of structure you had in mind for for the new design. Best wishes for your renewed effort, John
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Old Jun 28, 2015, 06:57 PM
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I thought the Henschel was lost to a failed aileron (fell off) , not a wing structure failure.
If I remember the video right, both wings where still fully attached all the way down.
Maybe I've lost my mind, too hehe Doug B
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Last edited by Doug Bartley; Jun 28, 2015 at 08:44 PM. Reason: correct spelling
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Old Jun 28, 2015, 08:29 PM
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Quote:
Originally Posted by Doug Bartley View Post
I thought the Henschel was lost to a failed aileron (fell off) , not a wind structure failure.
If I remember the video right, both wing where still fully attached all the way down.
Maybe I've lost my mind, too hehe Doug B
That was how I remembered it too Doug.
Regardless, really looking forward to this next build.

J
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Old Jun 28, 2015, 08:45 PM
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Maybe I haven't totally lost my mind yet, then!!! LOL Doug B
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Old Jun 29, 2015, 01:30 AM
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Hi,

Bare where on earth did you find that! really useful thank you

There will be no CA hinges on this build that's for sure, it was a combination of both I feel, I lost control when the aileron parted and the resulting dive did result in a structural failure

The HS129 has quite a lot of dihedral which makes it difficult to get a continuous tube through the structure but I am solving the problem this time by way of a 2mm thick carbon fibre sheet spar, there will definitely be no failures on this one

I actually think the structure was damaged on the maiden, the model is quite close coupled and I had too much elevator dialled in resulting in a heavy landing due to the difficulty in controlling pitch

Thanks John you are exactly right and I will heed your words, gained a lot in experience over the last couple of years
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Old Jun 29, 2015, 04:39 AM
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...design-build-fly-publish...
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Sorry, but I have to chuck in my two-pennyworth on structure!

I am not happy with a hollow circular shape in bending despite the current vogue for tube wing joiners. It is not easy to find a less inherently stress resistant shape in bending, there being no perpendicular member to hold the top and bottom extremes of the shape in place - so the tube will flatten reducing the beam depth and leading to breakage. A tube is immensely strong in end to end pressure - but that is not how we use it. I assume the fad started when carbon tubes from fishing rods were used by the glider boys for their models and someone thought they could use the bits left over for wing joiners - without thinking it through too well!

A vertical flat strip of carbon will do a better job using half the material.
I have two 12mm x 2mm strips, one in each spar at fuselage centre line, for my 1:10 Stirling. When it stalled and spun in out of sight both outer wing panels broke but the joiners remained intact.

Similarly I do not like the idea of skinning wings and not expecting the skins to 'pay their way'. In order to get a light airframe I prefer to have everything doing it's share of work otherwise it's just excess baggage.

If the wing skins actually needed to be strong in the cross-grain direction as well as with the grain (despite being stiffened and reinforced by the rib members), why not consider artboard with the inner skin stripped off? It gives strength both ways, a card finish that can take painting without any further surfacing material, a finished weight similar to the traditional balsa and costs far less than balsa. (1/3 - 1/4 the cost). Okay it's use may be considered a bit radical - but I have been experimenting with it on my Caribou and have found it quick and easy to use (with the heat gun a vital tool!)

I wish you well with your second 129 Ken.

Robin
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Old Jun 30, 2015, 08:24 AM
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Along those lines, you might look at the Sig wing joiners, as used on the 1/3 scale Fly Baby. Easy to uncouple the wing sections, and strong as the dickens...
;-)
PJ
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Old Jul 02, 2015, 12:28 AM
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Once more unto the 129-breach, dear friends!

The great Ken strikes again! Nice to see you back building another 129 Sir.

My only small bit of advice is build two 129's . . . Not one.
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