Double covering fabric covered wings

On Thu, 06 May 2004 15:04:54 GMT, Richard Lamb
wrote:

The Poly Fiber manual specifically recommends NOT to do this because
Poly Tack, when dry, it too hard to stand up to the flexing of the
fabric.

That would mean using Poly Brush to attach the second layer - and how
now do we shrink the second layer???


Richard Lamb

I dunno. The second layer of fabric might be applied with polybrush
and not polytac. I'm not familiar enough with the process to state
accurately. I'll find out.

As to shrinking the second layer, that's done with the iron calibrated
for 250 degrees. I've seen the results and even without any anything
applied to the fabric to seal it yet, it looks very nice.

Corky Scott

wrote:

On Thu, 06 May 2004 15:04:54 GMT, Richard Lamb
wrote:

The Poly Fiber manual specifically recommends NOT to do this because
Poly Tack, when dry, it too hard to stand up to the flexing of the
fabric.

That would mean using Poly Brush to attach the second layer - and how
now do we shrink the second layer???


Richard Lamb

I dunno. The second layer of fabric might be applied with polybrush
and not polytac. I'm not familiar enough with the process to state
accurately. I'll find out.

As to shrinking the second layer, that's done with the iron calibrated
for 250 degrees. I've seen the results and even without any anything
applied to the fabric to seal it yet, it looks very nice.

Corky Scott

250 degrees is only the _starting_ point.

Last pass is at 350 degrees!

If the first layer has been coated with Poly Brush, the heat from the
iron will quickly soften the coating. PB starts melting at 200 degrees.

By the time the iron is up to full temp, it would be hard not to melt
into the previous PB layer - possibly causing fabric pulls and gouges.

Maybe the outter thin fabric doesn't have to be tightened that much?

As long as the first layer is strong enough, the second might only need
to be snug enough to pull out the wrinkles. Call it non-structural?
Second pass at 250 on light fabric _might_ do it?

Bottom line, Corky, I don't really know much, I've never tried it.
It seems like there may be some potential pitfalls in the doing part,
but it sure did look pretty on that Pacer.


Richard Lamb

On Thu, 06 May 2004 19:57:24 GMT, Richard Lamb
wrote:

250 degrees is only the _starting_ point.

Last pass is at 350 degrees!

If the first layer has been coated with Poly Brush, the heat from the
iron will quickly soften the coating. PB starts melting at 200 degrees.

By the time the iron is up to full temp, it would be hard not to melt
into the previous PB layer - possibly causing fabric pulls and gouges.

Maybe the outter thin fabric doesn't have to be tightened that much?

As long as the first layer is strong enough, the second might only need
to be snug enough to pull out the wrinkles. Call it non-structural?
Second pass at 250 on light fabric _might_ do it?

Bottom line, Corky, I don't really know much, I've never tried it.
It seems like there may be some potential pitfalls in the doing part,
but it sure did look pretty on that Pacer.

Right, 350 is the final pass for the first layer. But the way this
was explained to me, you definately do not want to go to 350 on this
outer layer.

I don't know whether you iron the pinked tapes or not, but if you do,
do you go to the full 350 degrees? I thought not but I haven't
actually covered a wing myself, I've just helped out here and there.

Corky Scott

wrote:

On Thu, 06 May 2004 19:57:24 GMT, Richard Lamb
wrote:

250 degrees is only the _starting_ point.

Last pass is at 350 degrees!

If the first layer has been coated with Poly Brush, the heat from the
iron will quickly soften the coating. PB starts melting at 200 degrees.

By the time the iron is up to full temp, it would be hard not to melt
into the previous PB layer - possibly causing fabric pulls and gouges.

Maybe the outter thin fabric doesn't have to be tightened that much?

As long as the first layer is strong enough, the second might only need
to be snug enough to pull out the wrinkles. Call it non-structural?
Second pass at 250 on light fabric _might_ do it?

Bottom line, Corky, I don't really know much, I've never tried it.
It seems like there may be some potential pitfalls in the doing part,
but it sure did look pretty on that Pacer.

Right, 350 is the final pass for the first layer. But the way this
was explained to me, you definately do not want to go to 350 on this
outer layer.

I don't know whether you iron the pinked tapes or not, but if you do,
do you go to the full 350 degrees? I thought not but I haven't
actually covered a wing myself, I've just helped out here and there.

Corky Scott


I pre-shrunk my tapes at 225 - 250.
Otherwise, the warm Texas sun could shrink them - after the fact...
and it would probably show after a while - big time.

Once in place (with PB), I did iron the _edges_ of the tapes to get
them down super flat. But it was generally a short quick swipe at 250.

If the tapes have not been pre-shrunk, they will shrink some at 250 -
usually unevenly - depending on how hot it gets where. Makes for
wiggly tape lines - not considered a Good Thing(tm).

If that happens, you _may_ be able to straighten the edges out by
adding 25 degrees (at a time) and ironing only the unshrunk areas.

Another tip is that slick backing paper from self adhesive sanding
disks, and such. With the slick glossy side down, I found I could
work a small model iron at 250+ and not make gouges - IF - I let the
surface cool down before trying to remove the paper.


Since my wing design doesn't allow rib stitching (foam ribs) I taped
every rib with 2" medium weight pinked tape (false ribe too).

Besides local reinforcement over the rib contact areas, they also should
act as a rip stop for puncture/rip type skin failures.

It's a little extra weight, but it makes me feel much mo betta.

Richard Lamb


http://home.earthlink.net/~n6228l/happy.htm

Corky ad Richard,

I have experience with this double covering method. I have done it a few
times. It does not match the polyfiber manual but it worked very well on high
power and acro airplanes. Feel free to email me directly if you would like
more info on how it is done. If you look at the cover of the new June Issue
of Kitplanes, 2 of the 4 model 12s on the cover are finished in this method.

Kevin Kimball

KJKimball wrote:

Corky ad Richard,

I have experience with this double covering method. I have done it a few
times. It does not match the polyfiber manual but it worked very well on high
power and acro airplanes. Feel free to email me directly if you would like
more info on how it is done. If you look at the cover of the new June Issue
of Kitplanes, 2 of the 4 model 12s on the cover are finished in this method.

Kevin Kimball


Thanks Kevin.

Were we even close?


Richard

Any idea of what the weight penalty would be in dope and fabric vs. reduced
drag? And is this method more or less expensive than pinked tape?

Just wondering,
Harry

Shellac dope would have added 76 lbs. to the weight of a Wright 1902 glider,
and almost 155lbs. to the 1903 "Flyer." ...Based on tests made with my 1899
kite, August 2001