Mahogany planking preparation/finishing

[Edward Matthews]

Hi guys,

I'm building a model that has a mahogany planked deck, this is my
first model to have a planked wooden deck, and I was wondering about
preparation/finishing techniques etc.

The deck has to be varnished with a clear satin finish, and I'd be
grateful for any help with preparation etc to get the best possible
finish - Can anyone help with a detailed description please?

The sort of info I'm after is:

1. should the mahogany be given a coat of sanding sealer first?
2. I'm having difficulty finding spray on satin varnish, can I get a
GOOD finish using brush on products? I'm in the UK, so no American
only products please.
3. How many coats of sealer/varnish would you recommend?
4. What about rubbing down between coats. What grit paper is
recommended? And should I sand it wet or dry?
5. Should the varnish be thinned or used straight from the can?
6. Any other hints and tips?

Many thanks
Eddy

[Stuart Badger]

Hi Eddy

For what it's worth here's my technique for wooden decks. Mahogony is an
unusual wood for ship's decks - they were usually teak, elm or oak. The best
wood for simulating this on a model is either lime, oak or maple. This is
because after a period of exposure to the sun and the action of generations
of matelots scrubbing the deck virtually all the colour of the wood was
bleached out!

I start by working out the scale width of each plank and then gluing the
planks to either deck beams or a sheet of 1/16th ply formed to the profile
of the deck. If the planks have to be joined then remember that there should
be no coincident join lines across the deck for a minimum of 4 deck planks
apart. Between each plank I glue a strip of thin black mounting paper 'edge
on'. If the deck has a cover board around its outside edge then the planks
are trimmed and the cover board cut to fit the deck planks (I can mail you a
drawing of the standard full size method of construction if you like) Ships
with a concrete waterway around the outside of the deck generally did not
have cover boards after about 1920.

The whole deck is then sanded using progressively finer grades of sandpaper
to remove the excess black paper 'caulking' and to achieve a smooth finish.
The final sanding should be done with 320 or 400 grit wet and dry paper -
USED DRY!!!

The deck is then given a brushed coat of spirit based sanding sealer. I use
'Liberon' sanding sealer, available at most good timber/cabinet makers
suppliers. Then the deck is sanded using first 400 then 600 wet and dry used
dry. Sandpaper, I find is useless at this stage because of its gritty
nature - it leaves miniscule scratches.

Once the sanding is complete apply another coat of sanding sealer as thinly
as you can but without thinning the product. Once dry sand again with 600
wet and dry used slightly damp. When this final coat is completely dry after
the damp sanding use a tack rag to remove any dust.

For a final finish I use liberon clear satin varnish. One coat is sufficiant
but if you require a more durable finish then give a second coat after using
steel wool to rub down the first.

The Liberon varnish is water based but is waterproof enough for a model - in
fact it is a good standard, non yellowing varnish - it just isn't quite hard
enough to qualify for the 'exterior' title! The problem with polyurethane
exterior varnishes is that they are very hard and tend to chip. Also I find
that they yellow with age. Liberon's address (if you have trouble finding a
stockist) is :

New Romney
Kent TN28 8XU

Telephone 01797 361136

hope this helps

Stuart Badger

[Paulrjordan]

Hi Eddy:

I'm writing this between loads..STILL MOVING HOUSE!

Now this is how we used to do competition racing boats (real ones)
with varnised mahogany decks.

We never used Sandind Sealer on the real ones because of salt water..
but used 10 coats of Spar Varnish instead. However on a model,
sanding sealer is a MUST on Mahogany or youll spend ages trying to
fill the grain. FIRST THING...Take a sample of your mahog and wet it
to see what colour its going to end up. Sometimes a tiny bit of
stain can help mahogany along. If the grain is a little "bland" it
sometimes needs a bit of helping along by giving it a black wash
which saturates the soft grain but doesnt soak into the raised hard
grain..so when you sand it the soft grain is darker (trick we used to
use on antique mahogany furniture restoration).

If you are using boxwood caulking strips between planks (a la Chris
Craft), don't stain the mahog unless you are using white plastic.

I got a really good cellulose sanding sealer from a Hobby Shop in
Worthing while I was in the UK. Dries in five mins and really easy
to sand.

The can says "Made in England by H. Marcel Guest Ltd M/CR England.
Tel 0161 205 7631. You put on enough probably Max 3 coats so you can
barely see the grain contours when you hold the surface of your model
obliquely to the light. Too much build up of sanding sealer (while
its great for filling grain) can make the surface brittle. Sanding
between sealer coats is done with 220 trimite paper (its dry and and
a grey colour used for furniture) Standard sandpaper is too
scratchy. Make sure you NEVER sand back to the wood or you'll mess
up your colour if you stained the mahog. I dont need to say this but,
always sand WITH the grain and never across it)

Try to use a soft sanding block ( thick felt pad you buy) so you're
not "finger sanding" i.e. leaving impressions from pressure by
individual fingers (dips). Take your time sanding making sure your
strokes are light and even pressured.

I suggest two to three coats of the Sanding dealer...and place it in
a pan of hot water to warm it up before applying it. Flows a little
better.

Then start with your varnish. The age old standby "SPAR" is still
most often used although I have had lots of success with the spray
bombs of urethane..but you MUST EXPERIMENT first tiull you find one
you like...coz some are 'orrible. Remember, Spar varnish takes a
good 24 hours to dry and that's quite time in which to pick up
ariborne dust and grit.

Get hold of a tack cloth and always WIPE surface clean before you
apply a coat of varnish. Also get a plastic "tent" to place over the
model while its drying to prevent dust settling on it. Dust and
airborne grit is the worst enemy of a good finish.

ALWAYS sand between varnish coats (don't EVER be tempted to skip and
lay two coats together). Use trimite (dry) 220 for first coats
until grain is filled and no more grain contour is visible..this is
the time you sand out any runs or imperfections. When you have the
entire surface smooth start with thinned coats (75 varnish/25 thinner)
and sand wet (Black paper) 400 then 600 but just enough to take out
dust particles. Essential to use "tack cloth" immediately before
applying each coat from now on. Next two coats Wet sanding only 600
and 1200. Finish coat cut 25 percent thinner and wrmed in pan of hot
water. Make sure surface and completely DUST FREE. When it's dry
you then polish with a high quality car (NON SILICONIZED) car or
furniture wax.

Little tips. Always apply thin coats...with varnish warmed in hot
water first. Use CLEAN brushes if you're not using spray bombs. Work
must be done in entirely dust free area. Wet the workshop floor
first. Use "tack cloths between coats". Watch for runs on the SIDES
of the hull..I have sometimes propped up the hull so the side lays
flat and just varnish one side of the hull to the keel first. This
will prevent runs on the side and if any occurs it wil be on the
bottom of the boat and easier to deal with. Don't forget the "tent"

Hope some of this makes sense..gotta go and move some more
furniture. Computer will be down for a couple of days tomorrow, and
it will be at least a month before I can get back to modeling.

PJ