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Gentle Curves - Lucas his Skywriter


Lucas Hofman
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Experiment with laminating the wingtips: I made a template from 9mm MDF board that is 6mm smaller in radius than the finished shape will be:

img_3513 (small).jpg

The strips (I used 3 times 2mm medium balsa) have been soaking in warm water for an hour or so. After that the strips were layed up together with white PVA glue while flat on a table. The "package" was thereafter wrapped around the template:

img_3515 (small).jpg

Quite a bit of force was still needed. Probably better to use 1.6mm balsa (1/16). It looks good, but tonight we will find out if and how much it will spring back.

Lucas

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Hi Lucas,

I never tried myself (of course), so this is just a 'projected' thought.

Wouldn't it be easier to bend one strip at the time and pin it at he extremities to the jig?

If you make the first one a bit longer than needed you can pin it down and making the second one a little shorter allows you to pin it at the extremities as well while leaving the first pins in place.

Same procedure for the third one and when done than pin the 'pack' over the total length. I believe it would require less force to bend them individually and the remaining final 'tension' should then be less or even nonexistent.

Just my 'two euro cent'.

Cheers

Chris

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Hi Chris,

Nice to see somebody is still reading my scribblings!

I started that way, but found that all glue then runs down, since the wood is saturated with water. Keeping the glue surface horizontal kept the glue between the strips. I fixed the bundle in the middle and then slowly bended them over, setting pins every few centimeters.

Somebody wrote about this in the Ballerina build blogs. I do not remember who should have the credit but it looks like a very nice way to get the fiber oriented correctly around the whole curve.

Lucas

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Hey again, Lucas.

Yes, still reading. In fact, I've subscribed to your "scribblings". wink

Remember, young man. Reading too many build blogs is totally hazardous...

I remember reading it too (Martyn or Chris Barlow?) but not so sure anymore. Any way, I also remember he was squeezing the excess of water out of the wood between his fingers.

Another method seems to bend the strips wet against the jig but without any glue. Leave it to dry completely overnight, then 'unpin', apply some glue between the strips & re-pin in position.

It seems that we both like to 'experiment' a little... yes

Cheers

Chris

 

Edited By McG 6969 on 21/12/2016 15:15:51

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Posted by McG 6969 on 21/12/2016 15:14:27:

Another method seems to bend the strips wet against the jig but without any glue. Leave it to dry completely overnight, then 'unpin', apply some glue between the strips & re-pin in position.

I did this for my Woodys Pusher turtle deck and it worked real well.

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More then one way to skin a cat here! the first wingtip came out nice. Next to none "spring back":

img_3516 (small).jpg

The strips for the 2nd had been under water for 24 hours and went on easier. Or maybe it is just the second one that goes easier. This saves (on the Skywriter) nearly a whole sheet of balsa and one ends up with a more solid tip in addition!

Will do the leading edge of the horizontal stabilizing the same way.

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Lower wing drawing complete now:

lower wing.jpg

Changes compared to Lindsay's design:

  • laminated tip using 3x2 mm balsa strip (6mm wide)
  • different way of fittting struts, which makes it possible to cover the wing and glue in the attachment points afterwards.
  • more open structure
  • slightly smaller ailerons, creating a more "inset" look.
  • moved the bolt to a stronger area.

Construction method is described in the building article for the Ballerina. (pm. me if you need a copy).

The dowel construction is Lindsay's, but drawn here (missing on the RCME plan).

Construction will begin in the new year!

Regards, Lucas

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The first 2 formers are cut and one (F3A) is sanded! Always nice to transition from the computer screen to actually cutting wood. I cut up the drawing (actually a copy) and glue the paper templates on the light ply. Black lines on white paper are easier to see when cutting:

img_3566 (small).jpg

I modified the formers slightly (more/bigger lightening holes and no cutouts for the 6x6 strips). But I kept them all in ligth-ply, allowing the cutouts for all the stringers to be made:

img_3567 (small).jpg

The plan is to make a complete kit first (well, maybe the fuselage only) and then assemble it.

Cheers, Lucas

Edited By Lucas Hofman on 03/01/2017 07:54:44

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I feared I was going to be the only runner....

The aluminium comes from a local building supermarket (Bauhaus). They only had 15x2mm, so I have to adjust the mounting points in the upper wing 5 mm closer to each other. (I choose to leave the formers in the fuselage in place, which limits the spacing of the cabanes).

Happy new year to you too!

Lucas

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Last night good progress on cutting out the formers. Probably well knows but I would like to share some of the home made sanding tools that make life easier:

img_3568 (small).jpg

Paint stirrers and solid coffee stirring sticks. The sanding paper is attached with double side tape that is normally used when laying carpet. I cut the sanding paper oversize, glue it and trim with razor blades. That is the last thing you do with the blades! (they start their life cutting covering material, then do wood and end with sandpaper).

Lucas

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Continued with the ply and balsa bits during the weekend:

img_3573 (small).jpg

It give a some satisfaction laying it all out out on the drawing. A little bit like completing a jig-saw puzzle.

This is all the preparation for the fuselage I think. For some reason I have always made the tail surfaces first. Maybe because you get a part finished very quickly. See if we can make a start tonight.

Lucas

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Posted by Lucas Hofman on 08/01/2017 14:42:59:

Peter, what will the 1/64'' ply do when used as inner layer? Add compression strength (like doublers on a fuselage)?

Lucas

It helps stop the kinking at the pins if you have internal pins it also addds some strength but isn't really essential I justblike it if Ihave some spare 1/64"ply.

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