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Using Sanding Sealer Question

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Peter Miller14/04/2020 08:24:10
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The finish that I used to use was as follows

Dope and talc to fill the grain, THen doped on tissue folowed by coats sanding sealer to get a perfect finish which was rubbed down with fine wet and dry paper and then crocus paper followed by sprayed on paint also rubbed down with crocus paper and then burnished to a high gloss with metal polish.

You get a pretty good finish that way

NOTEthat you have to leave each coat to dry for a long time or eventually it will sink to reveal any blemishes

Edited By Peter Miller on 14/04/2020 08:25:37

Barrie Lever14/04/2020 08:48:41
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Well I have always used this approach when using cellulose finishes.

If covering with tissue, sand the surface smooth and apply 1 coat of thinned dope, allow to dry and then de nib with fine abrasive paper, now apply tissue using thinned dope around edges.

Some people wet the tissue before applying.

I would now spray a light mist of water to dampen the tissue and get the water shrink, once the water is dry then apply thinned dope to shrink and seal the surface.

No sanding sealer used by me when covering with tissue.

I use sanding sealer only when going over solid surfaces that are not getting covered with tissue.

What are reasons that support this approach?

Well the density of sanding sealer will be higher than dope due to the fillers which will be something like unperfumed talc being made from chalk with an average density of 2.0 versus a cellulose dope of less than 1 (it floats to the surface if poured on water).

So with not using sanding sealer the grain is filled with dope and then bridged by the tissue, if you use sanding sealer to fill the grain, the filling is somewhat heavier than cellulose and then you cover across it with the tissue.

Over time with both techniques there is unavoidable shrinkage into the grain..

Just my thoughts and I tend to build light !!

B.

Mike T14/04/2020 12:35:52
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What I'm getting from this is that there is no 'golden rule' and that people get acceptable results from varying approaches.

FWIW (I last used tissue about 30 years ago...) I tended to use Peter's sequence on larger models and Barrie's on smaller...

Peter Miller14/04/2020 13:37:37
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Posted by Mike T on 14/04/2020 12:35:52:

What I'm getting from this is that there is no 'golden rule' and that people get acceptable results from varying approaches.

FWIW (I last used tissue about 30 years ago...) I tended to use Peter's sequence on larger models and Barrie's on smaller...

I should have mentioned that my sequence is for solid sheet, not tissue covered frames. Things like fuselages and solid sheet covered wings etc.

Barrie Lever14/04/2020 15:56:46
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Yes many good points raised in this thread and shows the multitude of techniques to get to the end point.

I think I last film covered a model about 30 years ago, I put too much work into my models to let them be film covered!!

B.

David Hazell 102/07/2020 16:28:49
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What do folks use under film to strengthen/prep their sheeted airframes? I'm going to be using HK film that has just arrived in three colours and I want to toughen up the soft wood a bit... Do people use thinned shrinking dope? or thinned non-shrinking dope? Sanding sealer or no sanding sealer? I'll be prepping for a leccy, so no fuel proofing required. It will just be about getting her pretty and pretty-tough!

Phil Curtis 103/07/2020 08:56:52
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I use 1/3 paint thinner “gun wash” 1/3 non shrinking dope and 1/3 talcum powder, brings up a very nice smooth finish to then apply your finishing material.

David Hazell 103/07/2020 09:23:16
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Thanks Phil. Does it give you that bit of "ding protection" and does the film go on ok afterwards? I spent an hour watching that solarfilm tutorial DVD on youtube and that gave some absolutely invaluable tips, but nothing on what to do to make the squishiest of balsa a bit tougher from hanger rash dings...

Bob Cotsford03/07/2020 09:24:12
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Posted by Barrie Lever on 14/04/2020 15:56:46:

Yes many good points raised in this thread and shows the multitude of techniques to get to the end point.

I think I last film covered a model about 30 years ago, I put too much work into my models to let them be film covered!!

B.

Oddly enough these days I have the reverse philosophy, I put too much work into my models to go near them with paintbrush or spraygun! Wasn't always so blush

Phil Curtis 103/07/2020 10:10:39
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My previous advice was given to me by an expert builder in our club, he builds a lot with tissue on flat balsa. To get a harder finish over tissue he uses 50-50 non shrinking v shrinking dope. I have used the HK film from Rapid RC it’s very good, have not had to use a coating of any sort over my previous flat balsa build the HK covering gave me a good protective finish. Another option for ding protection is coating with Poly C, agin from RC. I am currently covering a Cambara Spit using 1/3 mix as an undercoat and then applying tissue on the smooth finish and then polyC to give a harder finish, I then spray. Good luck.

Phil Curtis 103/07/2020 11:14:56
4 forum posts

Apologies Poly C is supplied by RC World.co.uk

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