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One Stop fill coat for wings and masts

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lightandfrost
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One Stop fill coat for wings and masts

Postby lightandfrost » Mon May 28, 2018 9:36 am

Light and frost has been using the following process to obtain a one-stop fill coat on wing and mast surfaces which requires very little sanding.

This process works on flat, dihedral and anhedral wing shapes and on both sanded plywood and fiberglass. For reference all our wings are made of 2 and 3 cm plywood planform wing shapes. Two thin plywood wings are glued together with epoxy. The wing is then bent, when dried the required bend remains. The wings' shape is obtained thru sanding. Then fiberglass usually 8 to 10 layers is applied to the bottom of the wing only. To the wood top of the wing and to the fiberglass bottom we apply the following mixture

Epoxy 50 grams
Hardener 25 grams
Finely ground silica powder 60 to 70 grams

We then mix thoroughly and apply to the wing surface with a fine varnish brush.

The top of the wing requires two applications. After first application the final wing shape is sanded and then a second coat is the final fill coat before painting.

No carbon fiber, vacuum or mold required and the amount of dihedral/anhedral is only limited to the amount of bend the plywood can adsorb. None of our wings have had structural failure.
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foam-n-fibre
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Re: One Stop fill coat for wings and masts

Postby foam-n-fibre » Thu May 31, 2018 12:02 pm

8 to 10 layers of fiberglass on one side and none on the other? Have you tried putting 4 to 5 on each side and comparing the results? You seem to like to make different things and compare them. I highly recommend you experiment with other layups. The physics tells us that a strong skin on each side is better.

Peter

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Re: One Stop fill coat for wings and masts

Postby plummet » Thu May 31, 2018 1:19 pm

foam-n-fibre wrote:
Thu May 31, 2018 12:02 pm
8 to 10 layers of fiberglass on one side and none on the other? Have you tried putting 4 to 5 on each side and comparing the results? You seem to like to make different things and compare them. I highly recommend you experiment with other layups. The physics tells us that a strong skin on each side is better.

Peter
I agree, The considerable additional stiffness that sandwiching reinforcement layers together gives is well documented. If you are using 10 layers on the bottom and none on the top you could very well get away with 3 layers top and bottom for the same stiffness and also reduce weight at the same time

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Re: One Stop fill coat for wings and masts

Postby BWD » Thu May 31, 2018 3:00 pm

if wing is 2-3cm thick, why not use just 12 oz carbon on bottom for stiffness, or 18oz glass (2-3 layers not 10)?
the floor of your house is 2-3cm thick and a horse could walk on it (not forever, but you get the idea).
Since glass is usually $4-8/yard and carbon $18-40/yard, buy cheapish carbon for the same price as all those glass layers for less work, less weight, more stiffness and ends up cheaper because you only need 25% as much epoxy....


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