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Author Topic: Sealing Balsa  (Read 5670 times)

rem2007

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Sealing Balsa
« on: October 26, 2010, 10:20:48 PM »

I'm having a go at the PCF SWift 1/24 stand-off free plan in the 25th Anniversary issue of MMI. Going well but never used balsa before, easy to work with, but what should I use to seal the hull, after filling and sanding, also want to protect the interior?
Any suggests, the article rwecommends dope, but I have not used this before?
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sailorboy61

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Re: Sealing Balsa
« Reply #1 on: October 26, 2010, 10:23:25 PM »

Tissue and dope ala flying thingies........ sanding sealer would be my choice, then paint/varnish etc., or maybe even glassfibre and epoxy?
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dougal99

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Re: Sealing Balsa
« Reply #2 on: October 27, 2010, 06:11:41 PM »

As has been said by sailorboy,

sanding sealer, paint and varnish work very well. I have just given my little balsa hulled tug a new coat of paint/varnish after about 4/5 years and she gets used most weeks. Fibre glass tissue and resin are also very good an long lasting if your happy using the stuff.

HTH

Doug
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Circlip

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Re: Sealing Balsa
« Reply #3 on: October 27, 2010, 07:41:34 PM »

This question is constantly being asked and for the benefit of the un-knowing, cos they're too young to know or those who have been entrenched in the plastic wonders, I make no aplogies dragging this thread back. :-

FullLeatherJacket
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  Re: Obtaining a good finish on ply and balsa hulls with simple materials.
« Reply #8 on: December 13, 2007, 11:15:37 PM » 

--------------------------------------------------------------------------------
OK - on the basis that anyone who reads this should take it as A method and not THE method (like I said before), let's have another try, shall we?

Extract from article describing Fairey Swordsman finishing method – Original plan and article published in “Model Boats” May 1999. Reproduced by kind permission of The Editor.


“After final sanding with 180 and 320 Finishing Paper, give the whole model one coat of sanding sealer*, thinned at least 50/50. It should be almost as thin as water i.e. if you can see brush-strokes in it then it's still too thick. Rub down with 320 grit Finishing Paper*. Cover the hull sides, bottom panels and transom with lightweight tissue* as separate panels. Cut the tissue slightly over-sized then lay it onto the model and brush thinned sanding sealer through it. Immediately smooth down the tissue with a folded piece of kitchen roll, mopping up any excess sealer in the process. Allow to dry, then feather off the edges with 320 paper. Apply a further three coats of thinned sealer, allowing to dry between coats. Rub down to a satin finish with 320 Finishing Paper. Don’t cover around the inside corners between the hull sides and the spray rails and rubbing strips, as the sealer has a shrinking action and will result in voids under the tissue; cut the tissue hard up into these corners with a sharp blade instead. The cabin sides and roof are tissue-covered in the same way as the hull. The wood veneer is not covered in tissue but has three coats of thinned sealer.
Mask off the wooden decks and rubbing strip. I personally use and recommend Tamiya masking tapes; they aren’t cheap but give a superb edge and can be bent around quite sharp curves. Also never use newspaper as masking; the ink usually comes off onto the model. I purchased a pad of A1-sized Flip Chart paper some time ago for about a fiver; so far it has served over a dozen models and will probably last me until I retire! Now apply two spray coats of Halfords White Primer (or equivalent car paint); allow to dry for 24 hours, then rub down with 600 grit Wet or Dry* paper, used wet. Rinse off any paint dust; allow to dry naturally; dust off then apply three thin coats of Appliance Gloss White, leaving each coat to dry for about 20 minutes before applying the next coat. Remove the masking as soon as this is touch-dry, but leave it at least 24 hours before proceeding. Re-mask the decks and mask the areas to remain white, then spray the hull below the paint line, the sides of the cabin and the face of frame 25 with Renault Midnight Blue (mine took four thin coats). Finally apply two slightly thinned coats of Ronseal Satin Wood Finish to the deck, cockpit floor and rubbing strip”.

*Further notes:
Finishing paper (which is also sometimes called Production Paper) is a pale grey colour. It’s manufactured from aluminium oxide and can be obtained in the UK from Wickes Do-It-All under their own brand, or from other DIY stores under the 3M or Scotch brand names. Grades vary from 60 grit, which is far too coarse for all but the crudest shaping, to 320. I use a selection of 120, 180, 240 and 320 for finishing wooden models.
Sanding Sealer is a mixture of clear cellulose dope and a filler powder. Humbrol is probably the best-known brand but I also have acquired assorted tins from H Marcel-Guest and J Perkins. If you can’t obtain any then you can make your own by adding talcum powder to clear dope. It should not be used “thick” – I thin down the commercial stuff 50/50 and apply it with a flat, soft brush. Ripmax used to do a fantastic little range of very soft dope brushes called “Flatties” – these are just the right tool for this job, but I don’t know if they’re still available. If not, a wide, flat squirrel-hair brush is nearly as good. Best advice is to visit an artists’ supply shop.
Modelling tissue is available from most model shops and is commonly used to cover the open rib-and-spar structures of small model aircraft.
Wet or Dry Paper is available from practically any shop which sells car paints – Halfords being the most obvious. I use several grades from 600 to 1200 for finishing paintwork; the former for flatting down primer and the finer grades for later coats. Wetting the paper helps it “stick” to the paint and eases removal of the paint surface, while rubbing wetted 1000 or 1200 paper onto a block of ordinary soap will give a very fine abrasive suitable for flatting down final gloss coats prior to lacquering, burnishing or polishing.

When sanding a timber hull smooth prior to painting, ALWAYS wrap the paper around a flat block – never use a fold of paper in the hand (you’ll just dig grooves in the surface where your fingers are). Sand with a circular motion and let the paper do the work; don’t press on too hard. Once the paper clogs, replace it.

Don’t just rely on a good blow to remove dust; use a clean paint-brush on uncoated wood to brush away the dust, then go over the whole thing with the domestic vacuum cleaner, using that little round dusting brush attachment. Wash down the sanded primer and gloss coats with clean water and allow to dry naturally.
Never spray in a cold or damp atmosphere; aim for a minimum 15 degrees C. Any colder and you risk the paint crazing at a later stage; ask me how I know….. 
Always wear a face-mask when spraying (Machine Mart do an excellent one with replaceable filters for about £15).

THE TWO BIGGEST ENEMIES OF A DECENT PAINT-JOB ARE DUST AND IMPATIENCE.

There is no agreed “best practice” here. This is just the way I did it – there are numerous variations on the same theme. Suit yourselves; works for me.

FLJ



 
 
« Last Edit: December 13, 2007, 11:17:57 PM by FullLeatherJacket »   Logged 
 
 This is too good to loose in the archives, read, save and take note from a master of the method.

  Regards  Ian.
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rem2007

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Re: Sealing Balsa
« Reply #4 on: October 27, 2010, 08:49:43 PM »

Thanks.
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tobyker

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Re: Sealing Balsa
« Reply #5 on: October 28, 2010, 10:17:11 PM »

I've just finished planking the stepped hydroplane in balsa - sloshed a couple of coats of Z-poxy finishing epoxy over it and will wet & dry it tomorrow. Have used a bit of fg tissue to reinforce shaft exit from hull. Hull now feels very solid and strong. I'm sure you can get better finishes with a zillion coats of superthin other stuff but, hey, works for me.
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soldier151

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Re: Sealing Balsa
« Reply #6 on: October 28, 2010, 11:26:51 PM »

Hi Rem
Balsa great to work with.  I use cellulose dope 50/50 with thinners and cheap J Cloths.  These are used to cover the whole hull.  Dope mix is stippled through the J Cloths.  By using these you can see where you have covered.  sand down with very fine sandpaper between coats.
Hope this helps
Soldier151 <*< O0 :-))
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