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Ballerina - Material list


kc
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You don't. The quick and easy way is this. Take some normal A$ writing paper and cut a stril wide enough to go into the holes about 1 1/2" time. Wrap this round a dowle or pencil, slide it up the holes, release it and then glue it where it tuches the wing ribs, quick and easy.

Sorry kc. I just went from the email to this . Oh well, written it now

By the way, this idea was passed on to me by someone but can't remember who now

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Actually I had forgotten the important part of the trick, as Peter said it's rolling it around a dowel or pencil that makes it work. The other important thing is to do it before joining the wings, otherwise there is probably no way to get it in.

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For those of us in Europe the balsa and ply is sold in metric sizes. Here are the equivalents I use:

1/32" = 0.8mm (Plywood)
I can buy 0.8 mm ply but I would also be happy to 1mm. If weight was critical one can always cut some lightening holes.

1/16" = 1.6mm (Balsa)
You could use 1.5mm but it is very flimsy and quite difficult to work. I always use 2mm where 1/16" is specified. It just gives a better sanding margin and just that little bit easier to work. By the time everything is nice and smooth you are probably back to 1/16" anyway.

3/32" = 2.38mm (Balsa)
This is very close to 2.5mm so no real problem here.

1/8" = 3.175mm (Ply or Balsa)
If the shape is simple and not much finishing required I will use 3mm. If there is a lot of shaping to do I might use 4mm on the basis that it is easier to take more off than put it back on.

1/4" = 6.35mm (Ply or Balsa)
The nearest equivalent is of course 6mm but don't forget that if you are mixing things up, a 6mm spar will be sloppy in a 1/4" slot.

As the sizes go up the differences become less important.

To make thicker pieces, two thinner sections can be used and they don't have to be equal so there are many variations. The sections can also be glued together with the grain (balsa) at right angles or 45 degrees which makes a very strong yet light homemade ply.

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Levanter3: I just wish we would drag ourselves into the 20th century, never mind the 21st, and scrap Imperial units altogether. I always work in mm anyway instead of all those peculiar fractions my Dad used to use. It wouldn't be so bad if they used decimal inches. I'm 76 in a couple of weeks btw so it's not as though I just left school I have both 3mm and 1/8" balsa sheet in stock because I've bought up stock recently from people giving up building. That gets confusing.

Just a point - dowel is often metric these days so make sure the hole in F2 (if you're cutting your own) is the same as your dowel. If you have the CNC cut F2 make sure your dowel is the same as the hole.

Geoff

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Re balsa strippers .As supplied most of them have a No 11 fine point blade. Looks nice but is rather too flexible to keep an accurate cut . Especially in thicker or harder wood. Put in one of the convex curved blades which has more meat closer to the tip .Better yet use one of the chisel shaped blades some of which have an angle edge. These are stiffer and keep the cut straight and not wander into the grain.

John

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On Balsa strippers,

Stripping 1/16" sheet for capstrips. The wood tends to rise up the blade, especially if using a Master aorscrew type. Just slade a small scrap of 3/16" balsa up the blade and it will hold the sheet down.

The only sheet joint on the wings is the centre section to leading edge sheet. and that is roughly at the highest point. Not a lot you can do about that.

I use map pins because they are short and the head can go right down to the wood and hld it in place firmly. Only snag is that some map pin heads come off and leave the pin just sticking out of the wood.

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Posted by kc on 27/11/2015 19:18:09:

After a quick look at the plan this evening I have drawn up my estimate of the main materials needed. Obviously this is unproven and just an estimate. You should check for yourself before placing an order for balsa!

Balsa all 36 inch long
1/16 by 3 1 sheet webbing.

1/16 by 4 5 sheets wing sheeting + fus underside


3/32 by 4 3 sheets fus sides & turtle deck
3/32 by 3 3 sheets wing ribs
1/8 by 4 2 sheets formers, fus under & Leading edge
1/4 by 4 2 sheets fin tailplane rudder & aileron spar
1/2 by 4 half sheet (18 inch) cowl
1/4 sq hard 6 strips main spar & aileron spar
3/8 by 1/8 2 strips Trailing edge stock
1/2 triangular 1 strip

Ply and spruce.
1/8 sq spruce 6 pcs 36 inch
1/32 birch ply 18 inch by 12
1/8 birch ply 8 inch by 10 inch
1/4 birch piece 3.5 by 4.5 inch
1/8 Liteply piece 9 inch by 12 inch
1/4 dia dowel piece 1.5 inch

Edited By kc on 27/11/2015 19:48:14

kc, thanks for doing the counting for us lazy guys! However, I am missing the grade (soft, medium, hard) for the balsa. Or have I missed something?

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Well I just stated the main use of each size so each builder can decide for himself!

I don't think the grade is specified on the plan or article except for the 3/8 by 1/8 Trailing edge stock which should be hard. . Usually Peter says " rock hard " for wing spars so I mentioned hard for the 1/4 sq. Personally I might use spruce for spars if my stock is not really hard enough.

I would say medium for most other parts except tailplane & fin etc where I would want lightweight stuff but firm.. And the 1/2 for cowl could be soft to carve easily. The wing sheeting and turtle deck needs balsa that curves easily. ( or else it will need wetting on one side and holding to shape whilst it dries )

Perhaps Peter will give some more guidance on what to order.

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As KC says. Medium for most of it, soft for the tail and cowl, easily bent stuff for the turtle deck but not too soft of you get the starved horse look and it can crush as you pick it up.

Spars are ALWAYS rock hard They have to survive the greatest loads. As mentioned elsewhere 24.8G measured!!! Although unlikely with Ballerina...Oh, I don't know put a bigber engine in it and who knows.

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I made a little spreadsheet that may help sort a mixed stack of balsa sheet into hard/med/soft. I found it usefull sorting through my stuff and relabeling it. You can find it on http://www.modellflynytt.no/attachment.php?attachmentid=84024&d=1450279319

Save this to a file and open it in Excel.

 

Edited By Lucas Hofman on 16/12/2015 15:30:09

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  • 4 months later...

You do seem to be right - 7 lengths of 36inch to produce the 13 bits 18 inch long. Sorry if I mislead you - but I did say check for yourself. Nobody else noticed!

If you are short of 1 length I suggest making one of the middle pieces from hard balsa. i made half from hard balsa on my model.

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