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Author Topic: Silkspan and sharp edges.  (Read 583 times)

Offline Tim Wescott

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Silkspan and sharp edges.
« on: February 18, 2023, 03:10:32 PM »
I've got a hatch with nice sharp edges, and I'm contemplating what will happen when I attempt to apply silkspan.  I'm pretty sure that if I leave it knife-sharp as it is now, I'm going to have a mess when I try to apply silkspan around it.

What's the best way to handle this?  If I knock the edges down a bit, how far should I go?

As a separate question, how much room should I allow for finish in the gap?  Right now it's a pretty consistent 1/32" gap all around.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online kevin king

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Re: Silkspan and sharp edges.
« Reply #1 on: February 18, 2023, 11:02:15 PM »
1/32" gap now seems a little tight. Add to that the thickness of the silkspan on the edges of both the hatch and hatch cover, plus the
thickness of the paint. Might be better to make the hatch cover a little more undersized. You could always add extra
clear paint to reduce the gap if your looking for the high tolerance fit look 😁
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Offline Tim Wescott

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Re: Silkspan and sharp edges.
« Reply #2 on: February 18, 2023, 11:05:53 PM »
Quote from: kevin king on February 18, 2023, 11:02:15 PM
Add to that the thickness of the silkspan on the edges of both the hatch and hatch cover, plus the
thickness of the paint.

Those thicknesses are the dimensions I don't know!
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online kevin king

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Re: Silkspan and sharp edges.
« Reply #3 on: February 18, 2023, 11:12:36 PM »
Quote from: Tim Wescott on February 18, 2023, 11:05:53 PM
Those thicknesses are the dimensions I don't know!
Tim, A 1/16" wide gap should do. And for the sharp edges, 2 swipes with 600 sandpaper 'just to break the edges' on the cover.
Kevin
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Online doug coursey

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Re: Silkspan and sharp edges.
« Reply #4 on: February 19, 2023, 05:28:32 AM »
is it necessary to wrap the silkspan around the edge....just trim it at the edge and dope it and you can still adjust the gap if you need to...and keep the sharp edge
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Offline Dennis Nunes

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Re: Silkspan and sharp edges.
« Reply #5 on: February 19, 2023, 08:31:33 AM »
Quote from: Tim Wescott on February 18, 2023, 11:05:53 PM
Those thicknesses are the dimensions I don't know!
Hi Tim,

Not that I build 20 point stunt ships, but I try to set all my gaps for hatches with 1/32 plywood which is a little over .003" thick. Then I paper/polyspan over the top while hatch cover is in place. After several coats of dope I will cut down the middle of the gap with a surgical knife and remove the hatch cover. This will leave an edge on the inside of the opening and the outside of the hatch cover. Using a very fine emery board or sandpaper, I ease off the edges. Then proceed to finish as normal with the hatches removed. So far this has worked for me. But again, I don't build 20 point airplanes!

Hope this makes sense.

Dennis
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Offline Tim Wescott

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Re: Silkspan and sharp edges.
« Reply #6 on: February 19, 2023, 09:41:21 AM »
Quote from: Dennis Nunes on February 19, 2023, 08:31:33 AM
Not that I build 20 point stunt ships ...

So far the worst you've brought to Roseburg have been better than the best that I have.  So just go ahead -- be all modest.  And tell me your secrets so I can get a few more points!

(I did the same thing as you, except that the edges were all bunged up so I used the lid of a plastic food tub, then worked Super Fil into the gaps.  I probably should have waxed the plastic, but everything came apart with minimal damage.  Then I sanded it all flat with the hatch in.)
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Ken Culbertson

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Re: Silkspan and sharp edges.
« Reply #7 on: February 19, 2023, 12:28:15 PM »
I use two strips of 1/32 bass with a double layer of wax paper between them.  I glue the ones to the hatch then press fit the outside one into the fuselage with the wax paper between them so that they are snug but not tight.  Tack glue the fuselage strip in with thin carefully aimed CA then lift out the hatch and permanently glue in the fuselage strip.  I do the same with cowls and fuselage bottom hatches.  My current plane has hatches from the firewall to the flaps on the bottom.  This was the only way I could get all of it to fit.  Bass is easier to sand than plywood and so far has not caused any problems.  1/32 plywood would be better but nobody seems to have any, bass I can get at Hobby Lobby.  I am going to monokote this one so the wax paper gap will be fine but if you are going to finish the interior that nobody will see then perhaps 3 strips of wax paper?

Well I guess I spoke too soon!  1/64 from Midwest is back on Amazon!  This is MUCH better than Bass and you can do curves!

Ken
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