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  • March 27, 2023, 11:45:08 PM

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Author Topic: Polyspan over open bays only  (Read 513 times)

Offline kevin king

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Polyspan over open bays only
« on: January 25, 2023, 01:26:56 AM »
Has anyone here tried using Polyspan on the open bays only, then covered the rest of the wing with Silkspan?  Ive never tried it so any tips would be appreciated.
Thanks.

Kevin
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Online Jim Hoffman

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Re: Polyspan over open bays only
« Reply #1 on: January 25, 2023, 03:36:11 AM »
I and others first cover entire open bay wing with carbon mat (0.2 lb/ ft2), do not put CF on cap strips. CF makes for a hard sharp edge where the wood ends. Break all CF edges

Then apply Polyspan to the open bay area with above a 1 inch overlap on the Polyspan perimeter.  While filling Polyspan with clear dope add extra material to the Polyspan edge to help blend
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Offline Miotch

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Re: Polyspan over open bays only
« Reply #2 on: January 25, 2023, 08:17:50 AM »
Quote from: Jim Hoffman on January 25, 2023, 03:36:11 AM
I and others first cover entire open bay wing with carbon mat (0.2 lb/ ft2), do not put CF on cap strips. CF makes for a hard sharp edge where the wood ends. Break all CF edges

Then apply Polyspan to the open bay area with above a 1 inch overlap on the Polyspan perimeter.  While filling Polyspan with clear dope add extra material to the Polyspan edge to help blend

Interesting.  But how do you cover an open bay wing with CF and not put it on the capstrips ??  Or do you mean cover the wood on the open-bay wing with CF, but not the capstrips ? I'm thinking that must be what you mean because why would you cover the open bay itself with CF ....
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Offline Dennis Toth

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Re: Polyspan over open bays only
« Reply #3 on: January 25, 2023, 09:36:30 AM »
I think Kevin has it right they use the CF on the leading and trailing edge sheeting then apply the polyspan over it and the rest of the wing. I have read that polyspan works well on "I" beamers that have no sheeting at all. I think you could go straight to covering without the CF and it will be fine. Two tips: make sure you run the grain spanwise and second put the shiny/smooth side up.

Best,    DennisT
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Online Jim Hoffman

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Re: Polyspan over open bays only
« Reply #4 on: January 25, 2023, 02:24:23 PM »
To clarify……. Cover all the sheeting of your open bay wing with CF mat.  Do not cover cap strips with CF.  Then Polyspan

Pure Polyspan on I- beam wings with no balsa sheeting is an excellent option
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Offline Matt Colan

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Re: Polyspan over open bays only
« Reply #5 on: January 25, 2023, 04:15:31 PM »
To illustrate what Jim is describing, here is how I did it on my new classic airplane I’m working on. The only difference is I covered the open bays first and then went over the top with the carbon veil up to the edge of the sheeting. It hides the seam very well after a couple coats of clear and gentle sanding of the veil
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Matt Colan

Offline kevin king

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Re: Polyspan over open bays only
« Reply #6 on: January 27, 2023, 01:20:52 AM »
Thank you for you for sharing everyone. 👍

Kevin
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Offline David Ebers

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Re: Polyspan over open bays only
« Reply #7 on: January 28, 2023, 11:51:29 AM »
 I don't have e enough finishing g skills to fill a sewing thimble. I've covered a profile fuselage with cv and an open frame tail feathers on an rc airplane with polyspan. I'm curious why use carbon veil and polyspan on an open wing (I understand that cv doesn't shrink).
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Online Jim Hoffman

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Re: Polyspan over open bays only
« Reply #8 on: January 28, 2023, 12:19:22 PM »
Quote from: David Ebers on January 28, 2023, 11:51:29 AM
I don't have e enough finishing g skills to fill a sewing thimble. I've covered a profile fuselage with cv and an open frame tail feathers on an rc airplane with polyspan. I'm curious why use carbon veil and polyspan on an open wing (I understand that cv doesn't shrink).

A well finished CL stunt model has the balsa wood grain filled.  An external layer of silkspan or carbon veil adds stiffness to the structure and fills lighter than raw balsa (IMO).  The carbon veil also adds an apparent surface hardness as well.

Polyspan is very puncture proof (silkspan is not) and adds lots of stiffness to an open bay wing.
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