RYAN STA 1/18

[Marcin_Matejko]

[Ironwing]

14 hours ago, RLWP said:

I've got a question about your fuselage halves, because apart from playing around with the process I could do with some more learning.

 

Do you make an allowance for the thickness of the material when you form the plugs?

 

And, what happens with the flat bit down the centreline. Will the flat end up level with the bottom surface of the sheet, so you'd have to cut then sand away the excess back to the curved skin. Or will the flat end up level with the top surface of the sheet, so you'd cut off the excess at the bottom, then sand flat

 

I'm not sure I explained that very well. I've had problems with my vacforming where the junction between the moulded part and the scrap sheet ended up as a rather large radius. To get around this, I ended up adding 1/16" to the flat part so I could cut through the scrap above the radius

 

Richard

Hello Richard,

Thank you for looking in. I'm no expert at vacforming but I'll answer best I can. 

This is my first attempt at such a large vacform mold. My vacforming machine is nowhere large enough to handle this job. LSP member Tigger will be doing this on an industrial size machine. 

 

To begin, I had the original drawing increased in size to 1/18nth in order to have a working set. A second copy was made from the working set but reduced by 0.5%. This reduction allowed for material thickness. The fuselage plug was made to the reduced drawing. 

 

IMO, you don't always need to allow for material thickness. In this instance, not allowing for material thickness would have made the fuselage too big. 

 

The flat (.250 plywood)is not part of the fuselage. In this instance, it only provides a surface onto which the formers can be attached and to allow space, such that, when the vacform is pulled, the radius which normally forms at the bottom doesn't become a part of the fuselage. The excess will need to be trimmed away, but as a result, the mating edges of the fuselage halves will be straight. Even when I use my machine, I always build up the bottom to keep the inevitable radius away from the part. 

 

As a suggestion, to eliminate the large radius you mentioned, you might try a couple of fixes.

 

1. Make sure you have no leaks around the edges of your vacform surface. To check this, try sliding a single edge razor blade(or something comparable in thickness) down between the edges of the vacform surface and whatever it's sitting in. It's best to seal it. This can't hurt, even if it seems sealed. 

2. Make sure the plastic has been sufficiently heated. Both of my machines seem to be incapable of sufficient heating. To improve this, I put aluminum foil over the plastic while it's in the heating chamber to trap heat which ordinarily escapes out the sides of the chamber. 

3. I have two machines, a small mattel machine and bigger thing I can remember the name of. The Mattel is a hand pump. The other has an electric vacuum pump. 

In the case of the hand pump, rapid pumping immediately must begin as soon as the plastic is flipped over onto the part. The heated plastic sheds heat very quickly. You can also run some petroleum jelly (vaseline) around the edges of the piston in its cylinder to seal the edges of it to improve suction. 

in the case of the machine with the electric pump, the pump is turn on before the plastic is put over the part so it start pulling the material immediately.

 

In short: Improve heating..improve vacuum..build up the bottom..work very quickly.

 

I hope this has in some way helped. It took a good amount of trial and error (and failures) to come to these conclusions. I'm sure there are many here who can add to this or offer different opinions and fixes to the problems your experiencing.

 

Dont give up!

Best

Geoff

 

[JayW]

Vac forming, or metal forming (like Airscale).  Two skills I ought to delve into.  That way you don't need to buy a sub-par kit in which to base your effort.  Instead literally start from scratch.  Wow!

[Derek B]

Fine work there Geoff - I would be very surprised if john encounters any problems with your fuselage forms when vac forming over them (fingers crossed for some clean pulls).

 

Regards

 

Derek

[RLWP]

4 hours ago, Ironwing said:

Hello Richard,

Thank you for looking in. I'm no expert at vacforming but I'll answer best I can. 

This is my first attempt at such a large vacform mold. My vacforming machine is nowhere large enough to handle this job. LSP member Tigger will be doing this on an industrial size machine. 

 

To begin, I had the original drawing increased in size to 1/18nth in order to have a working set. A second copy was made from the working set but reduced by 0.5%. This reduction allowed for material thickness. The fuselage plug was made to the reduced drawing. 

 

IMO, you don't always need to allow for material thickness. In this instance, not allowing for material thickness would have made the fuselage too big. 

 

The flat (.250 plywood)is not part of the fuselage. In this instance, it only provides a surface onto which the formers can be attached and to allow space, such that, when the vacform is pulled, the radius which normally forms at the bottom doesn't become a part of the fuselage. The excess will need to be trimmed away, but as a result, the mating edges of the fuselage halves will be straight. Even when I use my machine, I always build up the bottom to keep the inevitable radius away from the part. 

 

As a suggestion, to eliminate the large radius you mentioned, you might try a couple of fixes.

 

1. Make sure you have no leaks around the edges of your vacform surface. To check this, try sliding a single edge razor blade(or something comparable in thickness) down between the edges of the vacform surface and whatever it's sitting in. It's best to seal it. This can't hurt, even if it seems sealed. 

2. Make sure the plastic has been sufficiently heated. Both of my machines seem to be incapable of sufficient heating. To improve this, I put aluminum foil over the plastic while it's in the heating chamber to trap heat which ordinarily escapes out the sides of the chamber. 

3. I have two machines, a small mattel machine and bigger thing I can remember the name of. The Mattel is a hand pump. The other has an electric vacuum pump. 

In the case of the hand pump, rapid pumping immediately must begin as soon as the plastic is flipped over onto the part. The heated plastic sheds heat very quickly. You can also run some petroleum jelly (vaseline) around the edges of the piston in its cylinder to seal the edges of it to improve suction. 

in the case of the machine with the electric pump, the pump is turn on before the plastic is put over the part so it start pulling the material immediately.

 

In short: Improve heating..improve vacuum..build up the bottom..work very quickly.

 

I hope this has in some way helped. It took a good amount of trial and error (and failures) to come to these conclusions. I'm sure there are many here who can add to this or offer different opinions and fixes to the problems your experiencing.

 

Dont give up!

Best

Geoff

 

 

Thank you for that Geoff - and I'm not giving up! I'd just like to get better results

 

I think my particular problem is in the heating of the styrene. I'll also have a look at sealing my vacuum plate around the edges. Food for thought - which is exactly what I was after

 

Richard

[Ironwing]

21 hours ago, JayW said:

Vac forming, or metal forming (like Airscale).  Two skills I ought to delve into.  That way you don't need to buy a sub-par kit in which to base your effort.  Instead literally start from scratch.  Wow!

Jay

For sure!! The stuff you've been doing proves your more than capable of scratch building. It has its ups and downs but but I know you have the skill to pull it off. Go for it!

Ive started on the Ryan wing. All was progressing well until I realized that the wing section as depicted doesn't match the drawing. Irritating but a part of scratch building. 

You can do it!

Glad you looked in...

Best

Geoff

 

 

[Ironwing]

21 hours ago, Derek B said:

Fine work there Geoff - I would be very surprised if john encounters any problems with your fuselage forms when vac forming over them (fingers crossed for some clean pulls).

 

Regards

 

Derek

Thanks Derek..I hope for the same. I'm glad you've been looking in...

Thanks Bud

Best

Geoff

[Ironwing]

Greetings All

 

Ive begun sorting out the wing. I cut the wing drawing from a copy of the plan and laminated it to a piece .030 card using a glue stick. 

The two are then peeled apart. For some reason, part of the drawing image transfered to the card and that is fortuitous for sure.

 

[Ironwing]

The current plan is to run spars of appropriate height at specific points to mimic cord depth the length of each wing panel but stopping short of the tip. The tips, I hope to vacform as a single piece. I hope be able to vacform the leading edges as well. Since my vacform machine isnt big enough, it would have to be done in sections and then joined on the wing panel. Once the leading edges are attached, the plan is to cover the rest of the wing with .020 card bent over the spars.

The spars pictured are of different heights but its hard to tell. They dont vary by much.

Still a bunch of head building to do but thats just part of the fun. Im also open to suggestions if anyone has some.

 

Hope everyone is well..

 

Best

Geoff

[RLWP]

Have you tried the Harry Woodman method of making wings - a balsa core wrapped in styrene? I've made several wings that way, it's quick and pretty easy

 

Richard

[Buster99]

Very interesting build of a beautiful airplane that I have just become aware of, thank you!

 

Regarding using the drawings, would it not be necessary to take the wing dihedral into account? I may be terribly of track, but should the wing not be slightly larger to compensate for that dihedral (hypothenuse). That is if the drawing actually represents a top view of the wing?

 

Marc

 

 

[Ironwing]

2 hours ago, RLWP said:

Have you tried the Harry Woodman method of making wings - a balsa core wrapped in styrene? I've made several wings that way, it's quick and pretty easy

 

Richard

Hello Richard

A balsa core is in the running as a possibility. I haven't yet settled on a method. 

If you would..what adhesive did you use to attach the styrene to the balsa core?

Best

Geoff

[Ironwing]

1 hour ago, Buster99 said:

Very interesting build of a beautiful airplane that I have just become aware of, thank you!

 

Regarding using the drawings, would it not be necessary to take the wing dihedral into account? I may be terribly of track, but should the wing not be slightly larger to compensate for that dihedral (hypothenuse). That is if the drawing actually represents a top view of the wing?

 

Marc

 

 

Hello Marc,

I too find the ST-A quite attractive. 

The span overall all takes the dihedral into account. When you say shouldn't the wing be slightly larger..do you mean greater in span?

 

Geoff

[RLWP]

10 hours ago, Ironwing said:

Hello Richard

A balsa core is in the running as a possibility. I haven't yet settled on a method. 

If you would..what adhesive did you use to attach the styrene to the balsa core?

Best

Geoff

 

Double sided tape. Have you got Harry Woodman's book? 

 

Richard

 

MORE: I don't seem to have taken any pictures during wing construction, this is my Morane Saulnier Parasol wing:

 

 

EVEN MORE: Ahh, yes I did, in my Cirrus Moth build:

 

 

Edited April 22, 2021 by RLWP

[Buster99]

On 4/21/2021 at 11:10 PM, Ironwing said:

Hello Marc,

I too find the ST-A quite attractive. 

The span overall all takes the dihedral into account. When you say shouldn't the wing be slightly larger..do you mean greater in span?

 

Geoff

Hello Geoff, indeed a beautiful plane!

And yes, the span would have to be slightly increased in order to have the same span as drawn when viewing from the top. Looking from the front the dihedral forms the hypothenuse of a right angle triangle. The drawing forms the horizontal leg of the triangle and the distance that the wingtip is lifted from the horizontal forms the vertical leg of the triangle (Pythagorean theorem). As the hypothenuse will be slightly longer it will so correct the length in relation to the top view.

HTH, Marc

Edited April 23, 2021 by Buster99