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Author Topic: Help, sanding sealer question  (Read 4703 times)

andygh

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Help, sanding sealer question
« on: May 21, 2008, 12:02:05 PM »

Something that's been bugging me for some time, can one of the experts tell me whether cellulose sanding sealer/dope is waterproof, water resistant or do I HAVE to finish with a top coat of something else?

Cheers, Andy
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FullLeatherJacket

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Re: Help, sanding sealer question
« Reply #1 on: May 21, 2008, 12:19:16 PM »

Andy
Sanding sealer is the same as dope but with an added filler - something like French Chalk - to bulk it up so you can sand it back. As such it's probably a bit porous. Dope, on the other hand, is waterproof. If you don't want the bother of applying a coloured top coat then I'd advise several thin coats of sanding sealer, rubbed down between coats, followed by a couple of thinned coats of dope. I do mean thinned, by the way - at the very least 50% thinners.
It's worked for me for longer than I care to remember!
FLJ
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andygh

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Re: Help, sanding sealer question
« Reply #2 on: May 21, 2008, 01:09:19 PM »

Thanks FLJ, it's always nice when the answer is just what I wanted to hear, it don't happen very often  O0

Cheers, Andy
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andrewh

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Re: Help, sanding sealer question
« Reply #3 on: May 21, 2008, 01:50:43 PM »

andygh

IMHO its even better than that! 
All that FLJ sez is true, and my experience is that SS is completely waterproof, and if it matters diesel fuel-proof!
The material added to sanding sealer is, I believe completely surrounded in the dope, so it is fully sealed in a layer of dope.

Also later coats of all the cellulose products soften all the coats below them - which is why they build to such beautiful finishes.

So take your pick - dope on top or not, as you like; no wrong answers

What are you sealing btw?

andrew
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andygh

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Re: Help, sanding sealer question
« Reply #4 on: May 21, 2008, 01:59:23 PM »

I've been using it to waterproof all internal timberwork, underside of decks, wheelhouses, planking, you name it really, I much prefer it to using varnish because of fast turn around.
I thought it was OK but it's good to have it confirmed by you helpful chaps
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roversean

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Re: Help, sanding sealer question
« Reply #5 on: January 01, 2009, 03:50:09 PM »

Hi i have just finished coating my ply and balsa hull in 3 coats of sanding sealer it gives a nice finish ,my question, though,is i am going to cover the hull in tissue which will be applied using shrinking cellouse dope to give a good waterproof seal and to cove all the joins in the hull.
  Has any one any advice how best to use the cellouse dope ref dilution and applying it and the tissue.             
                 Many thanks Sean
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dougal99

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Re: Help, sanding sealer question
« Reply #6 on: January 01, 2009, 04:38:04 PM »

Hi there Sean

I normally thin the dope 60/40 to 50/50 and paint it on over the tissue and then use thicker dope as a second coat. However, I have never applied tissue and dope to sand sealed surface so you may like to experiment a little on a scrap piece before attempting your boat.

HTH

Doug
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FullLeatherJacket

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Re: Help, sanding sealer question
« Reply #7 on: January 01, 2009, 06:11:48 PM »

Skim down the first few posts of this thread and you'll find a method which I've used for a long time. It seems to have a few fans out there.

http://www.modelboatmayhem.co.uk/forum/index.php?topic=7710.0

FLJ
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wallace

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Re: Help, sanding sealer question
« Reply #8 on: January 20, 2009, 09:58:08 AM »

I always use car body filler its great for sanding down and great for hiding joins etc
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Martin13

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Re: Help, sanding sealer question
« Reply #9 on: January 23, 2009, 11:21:45 PM »

I'm building a model of HMS Brave Borderer and the forward superstructure is made and carved from Block Balsa. Whilst working on various sections of the model, the balsa tends to get small dents in it when knocked.

Question:- Will sanding sealer help prevent these dents from happening (toughen/harden the surface) or is there another product/procedure available.

Currently, I have filled some areas with P38 and sanded back to obtain correct profile and the structure will eventually be primed and painted.

Martin
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tigertiger

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Re: Help, sanding sealer question
« Reply #10 on: January 24, 2009, 03:21:38 AM »

I'm building a model of HMS Brave Borderer and the forward superstructure is made and carved from Block Balsa. Whilst working on various sections of the model, the balsa tends to get small dents in it when knocked.

Question:- Will sanding sealer help prevent these dents from happening (toughen/harden the surface) or is there another product/procedure available.

Currently, I have filled some areas with P38 and sanded back to obtain correct profile and the structure will eventually be primed and painted.

Martin

I know that soaking balsa in thin CA will increase its strength 3 fold.
Try this on a piece of scrap.
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Colin Bishop

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Re: Help, sanding sealer question
« Reply #11 on: January 24, 2009, 10:40:44 AM »

Using CA sounds a bit expensive! Sanding sealer or dope will strengthen the surface and it's still sandable without any problems. However, when you have got the hull the way you want it it is always best to "armour" it with something harder, GRP tissue and resin is a common method but if you have already used sanding sealer then aircraft tissue and dope works pretty well too. I used to use polyester resin and nappy liner tissue which holds together as well as GRP tissue but is a lot easier to sand down.

Colin
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Martin13

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Re: Help, sanding sealer question
« Reply #12 on: January 24, 2009, 12:12:38 PM »

Using CA sounds a bit expensive! Sanding sealer or dope will strengthen the surface and it's still sandable without any problems. However, when you have got the hull the way you want it it is always best to "armour" it with something harder, GRP tissue and resin is a common method but if you have already used sanding sealer then aircraft tissue and dope works pretty well too. I used to use polyester resin and nappy liner tissue which holds together as well as GRP tissue but is a lot easier to sand down.

Colin

Colin,

I'm thinking of just using the sanding/sealer on my Balsa Superstructure of Brave Borderer. Sounds like it will harden the balsa and that has to be better than in it's raw state.

Martin
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Colin Bishop

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Re: Help, sanding sealer question
« Reply #13 on: January 24, 2009, 01:24:48 PM »

If it isn't likely to get knocked then it should be OK. After all, that's how everybody did it back in the 60's! Sanding sealer takes a good paint finish. I was using it myself last night to seal the surface of some davit supports I've made for my steam yacht kit. I made them out of ply as the white metal ones supplied looked too flimsy and sticking plasticard ones onto the side of the hull where they might get knocked didn't seem a good idea either.

Colin
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