ID of aircraft part, please

[Jemiba]

I've got a number of scans of an aircraft under construction, a kind of ultra-light, actually built,
not a project. For improving my old cut away, I would like to know, what's the shown part for.
Judging shape and curvarture, I assume, it was a kind of stringer for elevator or ailerons.
Somebody of you, who knows for sure ?

 

[Jemiba]

Sorry for bothering with this question again, but maybe it rings a bell for someone here.
To be more precise, it's a part of the MS.660 very light, single seat aircraft, intended to be
built by amateurs. I still think, it's a part of the ailerons or elevator, as written below.
AFAIK both were plywood covered. As I know, that some people experienced in building
aircraft are member of this forum, perhaps one of them can tell me, if such stringers (or
what the are called) would be needed for giving shape to completely wooden parts ?
Building them, which would include bending them to the final shape wouldn't be a problem,
I think ? They would look like shown below, maybe a tedious task, but probably possible ?
And a more general question, as I've no experience in building an aircraft at all: How thick
is standard plywood used for planking elevators or rudders ?

 

[Bill Walker]

At a guess, these are moving control surfaces, ready to be fabric covered. With that curvature seen from the side I suspect they are ailerons. The curve is a continuation of the airfoil cross section. Plywood is rarely used to cover control surfaces on small aircraft, because of weight. You are trying to get the centre of gravity as close to the hinge as possible. Even the B-17 used fabric over metal for movable control surfaces, for this reason. If they do use plywood, it will be very thin, 1/32 inch, or 0,8 mm.

 

[Stargazer]

At a guess, these are moving control surfaces, ready to be fabric covered. With that curvature seen from the side I suspect they are ailerons. The curve is a continuation of the airfoil cross section. Plywood is rarely used to cover control surfaces on small aircraft, because of weight. You are trying to get the centre of gravity as close to the hinge as possible. Even the B-17 used fabric over metal for movable control surfaces, for this reason. If they do use plywood, it will be very thin, 1/32 inch, or 0,8 mm.

Precisely. That's why I find it surprising that the MS.660's ailerons are described as being plywood-covered. Doesn't make much sense in terms of weight if the wing was fabric-covered... especially with such an elaborate (and necessarily heavy) structure within them...

 

[Bill Walker]

And a quick note on terminology: a span-wise structural member will be a spar, a chord-wise structural member will be a rib.

 

[Jemiba]

First let me thank you for your efforts !
The ailerons are described in Janes 1947 as plywood covered, too, and at least the sketch about
the construction from "Les Ailes" suggests, that it actually was a wooden part. My idea here was,
that maybe thin plywood would need supporting structure, too ?
I've attached a cut-out of one of those photos, the only one showing the wing with its alleron, but
I don't know, if there's a clue, which material is used for covering it.

 

[Bill Walker]

Very interesting Jemiba. Perhaps the pieces in the original photo are portions of the upper wing skin. Their small size fits with the idea that the whole airplane could be built on a 2m X 1m table, piece by piece.

 

[Jemiba]

Bill, that could be a very good idea indeed !
-On the attached cut-out something like half ribs, reaching just to the front spar is visible.
-The sketch of the components is (intentionally) incomplete and shows the leading edge still
uncovered, so it would be no wonder, that those parts aren't visible.
- A very rough calculation, using the hand in the photo as a scale, gives the length of each of those
"cooking spoons" as about 27 cm, the front spar was about 30 cm behind the leading edge.
- The large number, too much for ailerons or elevator, probably would fit for the whole leading edge.

Seems to be the most plausible solution still yet and if we exclude the impossible, the rest has
to be the truth !
Elementary, my dear Walker !

 

[cluttonfred]

Sorry, Jens. I do admire the spirit of the MS.660: imagine a major aviation company today offering kits for amateur construction on the kitchen table? I have no idea what those parts are for and they don't appear consistent with the construction technique in the images already posted. :-\

 

[Grey Havoc]

Just a thought; rather than be of alloy, could those pieces be made of a wood such as Sitka spruce, but resin impregnated?

 

[Jemiba]

Just a thought; rather than be of alloy, could those pieces be made of a wood such as Sitka spruce, but resin impregnated?

Judging the construction and what it was intended to be, I'm pretty sure, that it was made from wood.
Would an impregnation with resin have been feasible for an amateur constructor back then ?
Another photo shows a guy bending a sheet of material, that may have been used for covering the wing.
Seems to be relatively soft, so stiffening it may not have been a bad idea ?
Brought me to the idea, that those ribs and half ribs visible on the leading edge probably doesn't
represent the ribs itself, but perhaps are covering the fixtures of the planking to those ribs. Glue and nails
are mentioned in Janes 1947 for the fuselage, would it be plausible for the wing, too ?

..I do admire the spirit of the MS.660: imagine a major aviation company today offering kits for amateur construction on the kitchen table?

The idea of building an aircraft on a kitchen table, was somehow politically influenced, I think, as the basic
idea behind this aircraft probably was similar to that of the "concours de l'aéronef de grande vulgarisation"
(competition for an aircraft of wide propagation) somewhat later. Flying should become a hobby for
common people, so that in the event of an national emergency a big cadre of trained pilots would have
been available.

 

[Bill Walker]

Glues and nails would be used wherever the structure is plywood. Very small nails are used to hold the curved wood into place until the glue sets. The bending in that last picture is possible with very thin plywood. As for "resin impregnation", that is how you make plywood. Some manufacturers (think de Havilland Mosquito and Anson Mk. V) laid thin layers of wood into or onto molds and then lathered the wood up with resin, and added the next layer. You had to have some way of holding the wood against the mold until the glue set, like another mold. The end result is a very strong piece of plywood premolded to the shape you desire. This is probably not practical for the home builder, the molds are big, and very expensive to make. It is worth your time and effort to make the mold if you then make hundreds or thousands of parts in it, but not one airplane. And probably not on your kitchen table.

 

[Jemiba]

Sorry for bothering you again and again with this theme ! :-\

I'm still trying ti integrate those "cooking spoons" into the structure and still considering all
other photos and drawings. I've just added (provisionally and not fully to scale) those parts
to the leading edge, where it certainly was plywood covered.
- As pointed out, the sketch about the construction shows the wing not fully finished, so it's no
contradiction, that those parts aren't visible.
- Length of those stringers is about the same, as distance from spar to leading edge. The curvature
could match the profile of the upper leading edge.
- Judging the photos, those parts were longer, than the distance between two ribs. The photos
show at some points "full" and at other only "half" ribs. Maybe the joints of two such parts were
covered with strips of, say fabric, in the same was as the joints between the ribs and the covering ?
How is plywood covering attached to (wooden) ribs ? Are such stringers necessary for plywood
covered parts at all ?