stubborn teen building models

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stubborn teen building models

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2 March 2016 at 17:02 #63709
steven blythe
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@stevenblythe41527
Hi, I am building a model boat for my tech project. I am using a frog diesel engine. (as I said, stubborn) mounted forwards in the hull. I have almost finished building the hull but I have a problem. how is best to seal the hull? and will varnish work. I have done a few test pieces over slightly roughened spray paint and it seems to work. but will it adhere well enough? I will try to add some pictures.

thank you for reading.
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2 March 2016 at 17:02 #2563
steven blythe
Participant
@stevenblythe41527
30 inch cabin cruiser based on vic smeed’s twinkler plan… for A level tech project
2 March 2016 at 18:19 #63710
Dodgy Geezer 1
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@dodgygeezer1
What material is the hull made out of?

Most exterior paints will seal a wood hull adequately if the boat is not left long-term in water – Polyurethane is quite good. If you are using a glow-plug motor you might need to use fuel-proofer, but I think diesel fuel is not so corrosive.

This link may help:

**LINK**
2 March 2016 at 18:51 #63711
ashley needham
Participant
@ashleyneedham69188
Agree with DG. Perhaps a couple of coats of slightly thinned household undercoat (to soak in, assuming the hull is wood/ply), rub down and then and a drop of Dulux on top.

Don't know, but MAY be best to seal interior with a fuel proof coating of some sort to stop fuel soaking through interior to affect the outside surface, not sure what..possibly the undercoat stuff is good enough? Need a fossil fuel man to advise now.

Ashley
2 March 2016 at 19:05 #63712
mark69
Participant
@mark69
Hi Steven you haven't mentioned what you have wood made this out of presumely its balsa ? (Other woods may need another approach) which will need sealing before paint would stick successfully,if your not going to use this boat in the water as its a school project, any DIY wood sealer will work and then maybe a spray paint over that will give you the Finish your after ?? ……mark
3 March 2016 at 17:59 #63728
steven blythe
Participant
@stevenblythe41527
it is balsa, it is quite thick though. about 3mm thick. I used a sand sealer over this which is advertised as "waterproof" but as was the glue I used last year at gcse, so I don't trust it one bit. over this I spray-painted it. I do intend to use this in water. it is something I wanted to build, which just happened to vaguely coincide with one of the exam titles.
3 March 2016 at 18:56 #63729
Dodgy Geezer 1
Participant
@dodgygeezer1
Posted by steven blythe on 03/03/2016 17:59:56:

it is balsa, it is quite thick though. about 3mm thick. I used a sand sealer over this which is advertised as "waterproof" but as was the glue I used last year at gcse, so I don't trust it one bit….

Sanding Sealer is waterproof – but balsa soaks it up. You should put several coats of the sealer on. Note that sanding sealer is designed to be put on wood, and then have 90% of it sanded off – the idea is to achieve a smooth surface before painting…
4 March 2016 at 09:05 #63732
ashley needham
Participant
@ashleyneedham69188
What DG says is of course correct, but after a couple of coats of sealer, rubbed down, apply a final coat (not rubbed down) and then painted with gloss which will do you ok.

Always apply a last waterproofing coat AFTER the last rubdown as a precaution to exposing un-sealed wood to soak up water. This might be undercoat of course, not necessarily more sanding sealer.

The amount of rubbing down depends on the finish you want to achieve , babies bottom or Bruce Willis`s chin.

Ashley
4 March 2016 at 09:37 #63733
Dave Milbourn
Participant
@davemilbourn48782
I would never finish a painted wooden model without some form of covering. I've used Modelspan tissue or lightweight glassfibre cloth with various different sealing and coating products. This will bridge any fine surface imperfections remaining after sealing and provide a smooth and uniform surface for a paint finish. Wood will expand and contract with time and temperature and an uncovered grain will eventually show through. I've seen too many nice models spoiled by a shabby or lazy paint job.

Here's one method I've used **LINK**

There's another in the Twinkler article (last year's Model Boats Spring Special) and yet another in the Huntsman article in Jan/Feb MB this year.

Dave M
4 March 2016 at 12:03 #63734
Phil H1
Participant
@philh196021
Dave,

Your link description includes the use of thinned Ronseal, satin finish for the decks. Is that the water based varnish i.e., thin the varnish with water and do you apply it with a brush or an airbrush?

Phil H
4 March 2016 at 12:22 #63735
Paul T
Participant
@pault84577
For discussion purposes I have to disagree with my good friend Mr Milbourn as I believe that encasing timber in a rigid covering such as glassfibre prevents the timber from breathing.

Timber is a natural product and as Dave correctly pointed out expands and contracts under different conditions of temperature, weather or humidity. Preventing the timber from behaving in a natural way can induce stress loads at critical junctions on the frame.

Not covering the model in glassfibre also makes the model builder take better care during the build and extra special care over the finishing and painting. On the flip side a fibreglass coating allows a more slipshod builder to hide a multitude of errors beneath a glass skin.

Paul

I hasten to add that in no way does Mr Milbourn fall into the slipshod category as his model building skills can only be described as highly professional and as far as the subject of glass coating goes we merely have a difference of opinion.
4 March 2016 at 12:54 #63738
Dave Milbourn
Participant
@davemilbourn48782
Phil

At the time of writing that article you could buy "proper" Ronseal i.e. solvent-based varnish. I've only ever used the water-based stuff for boat stands. These days the choice of solvent-based polyurethanes has been reduced to just a handful. I have used Rustin's Satin Outdoor Polyurethane, thinned down about 10% and applied with a fine brush. My most recent model uses Rustin's Plastic Coating, which is a two-pack product and sets very hard indeed. It is gloss but you can flatten it down with fine steel wool or a red Scotchbright pad. It can also be applied with a soft, flat brush as it's thin enough straight out of the mixing pot.

Paul

My small models are made predominantly from kiln-dried and heat-pressed liteply of relatively thin sections (3mm maximum), whereas yours are about three or four times as big and made of "real" wood. I've never heard any of mine creaking or groaning under stress, and there's no sign of structural cracks anywhere. Bear in mind that you approach your modelling with a structural engineering background, whereas I'm just an untutored old balsa-basher. We must agree to differ. Thanks for your kind words about my finishing skills anyway.

Dave M
13 March 2016 at 15:14 #63866
steven blythe
Participant
@stevenblythe41527
ok, thank you very much, you have given me a lot to think about. I will experiment with different coverings and such, most imperfections I have filled using wood filler but I may try glassfibre or another such material to add to my folder if nothing else.
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