Hi Duncan, my wife tells me I talk too much, seems like I type too much as well!
Roy

Thank you to everyone for their input. My question has certainly generated a lot of interest and useful discussions about different methods! I will now spend time finishing off the planking and will 'mull over' the different methods and make a choice. Oh and Roy, thank you for all your interactions on this subject - I never felt you had hogged the topic! I welcome
your's and everyone else's input. I'm sure many more modellers have also found this to be an interesting and helpful discussion.😊

I like your thinking LewZ, a model boat spends only a small part of 1% of its time in the water.

A model boat may indeed have more problems from direct sunlight.

There is a previously mentioned point about strength and that involves the other users of the lake. This especially applies to novice sailors, they know where the boat is but not neccesarily where it is going.

This also leads to how powerful a motor is needed. I go for scale speed but have a good reserve of power to stop dead in the water. A bit off thread, sorry but Duncan's thread has been very helpful in making up my mind.

I think I am OK with epoxy resin only as a finish as I make wooden boats. However, the current small yacht I am making requires the lead stabilising weight, which is located in the lower hull to be bonded into the hull to keep it in place. So for this I shall venture out into cloth and resin!

A friend has advised me the cheapest way is epoxy glue, which the local pound shop sells at £1.25, is a good way to go. I did repair a domestic item like this and my second attempt was successful.

I had been using similar principles for years but only for strength internally. That is ladies discarded stockings / tights and ordinary varnish used in much the same way.

Thanks for the advice, I apologise to Duncan for all my posts, did not mean to hog the thread but all been very useful.

You are never too old to learn!
Roy

Regarding whether to use the cloth or not. This is just my preference but I always would as it has lots of pros… It is easy once you get used to it. It helps give a uniform surface. It adds a lot of strength to woods like balsa and other softer types (but if anyone is worried about protection from their boat being hit by another - well it wont really save you from that resultant damage depending on speeds etc). I guess ultimately it is up to yourself. If you are after a beautiful wood finish maybe avoid the cloth as in the right lights and on close inspection you can sometimes still see some weave. Like someone said earlier maybe best to do a test piece and see what you think after that. Best of luck with it whichever route you go 👍🏻

Hi Roy.
I use halfords spray paint (cans) over my glassed hulls also with no problems. I have also used airbrushed Humbrol enamels. No problems with either. I also tend to use the halfords grey primer ( several coats rubbed down with wet and dry) as a base coat regardless of whether I am ultimately finishing with enamel or other halfords colours.

I have never used pigments to colour any epoxy resin I have used so I cannot advise on that one I am afraid. Cheers.

Clarification to my previous post where I mentioned "resin". I meant to say epoxy resin. My experience with sanding polyester resin is on the ugly side. Just using the word "resin" can be misleading.

Another thought on fiberglass is "how long is the boat actually in the water?". Not very often have I seen an rc boat in the water for more then an hour. Given this, unless your boat is a moving target 'glassing' the hull might be considered an over kill.
Lew
Florida ⛱️, USA 🇺🇸

Hi Roy.
I have successfully used Halfords acrylic car paints over the epoxy resins that I have used, I can't vouch for any others but it's unlikely to be a problem with any kind of paint.
I bought my initial supplies of glasscloth and resin from Easy Composites and they do actually sell a range of coloured and metallic pigments that can be used with their resins. I've never thought to try them though.
Rob.
https://www.easycomposites.co.uk/culr-epoxy-pigments-starter-set

Right! Next question:- assuming epoxy is dry can I use any of the usual paints on the surface, i.e. enamel, Halfords acrylic spray or even Plasticote?

Also do you have the option of colouring the epoxy resin before application?

Roy

Thanks for your informative contribution, IanL1.
You were timely and thorough with an excellent practical example.
In your case you certainly couldn't use fiber on the outside and you only used resin, so you had an excellent result from an aesthetic and practical point of view (strengthening the hull, which is never a bad idea).
However you did very well.
Now that I remember, RiverRat also made some great models by coating mahogany with resin.

Also thanks for the feedback on the specific commercial product (because when you have to make a purchase you never know where to start if you are not an expert in the sector).

Hi Roy.
Yes, I always wet & dry sand after each coat of epoxy. On my hulls there are usually at least two coats on top of the base layer with the glasscloth. And I use a progressively finer grade each time.
Rob.

Hi roy, when i rub down the initial coat the first time it is just a very light touch done dry, just to knock any sharp high spots off. Ie where a glass strand may have protruded slightly or whatever . After that when i have put the second coat of resin on , yes I do that wet with a bit of washing up liquid in the water.

If you were resining without cloth, I am guessing it would be similar and you could go for wet sanding after a couple of coats of resin…

Hi to all contributors, very interesting and useful. The mention of using several coats of epoxy resin only, do you sand wet and dry after each coat?

Roy

Hi Duncan, I have just about completed a 1/10 scale model of a Venice water taxi and I used the West system epoxys throughout. As the full size boats are generally varnished mahogany I gave the outside of it about 6 coats of just resin and finish sanded with 2000 grit wet and dry, then brasso and finally car polish and I am very pleased with the result. The epoxy fully seals the timber and I am amazed as to how strong it has become. West system can also be used with various micro balloons to turn it into a glue or filler. I used mahogany sanding dust to make the glue so the joints blended in with the timber it was joining. I have attached a couple of photos for your info but I certainly recommend using this product and I honestly don't believe you need to cover with glass. Check out the interent on West system especially Dan Lee as he uses West system. He is on Youtube and in the UK I think. I hope this helps. Cheers Ian

Duncan, there is so much about this on the internet so I'm not going to cut and paste it here like some others do.

I'll just answer your basic question based on my personal experience: "I'm building a plank on frame motor sailor (Mantua Bruma) and I'm wondering whether to fibreglass over the hull to waterproof."

I believe your model is 32 inches long, correct? If the planking is double or if it is single with a good thickness (per Roy's thoughts) as long as it is not a sort wood like balsa, l would not glass it. What I did on a similar model of this size is sand and I used several coats of spar varnish inside and outside, sanding each coat when dry. You could use resin instead of varnish. The varnish soaked into the wood quite well and was hard.

If you are sailing with boats that run fast and crazy, you might want to armor the hull with fiberglass and resin.

Lew
Florida 😎, USA 🇺🇸

Hi Duncan, your questions have received very informative answers.

Thanks to you I have read very interesting comments, real vademecums like the one by Trident73 and Flaxbybuck (who really knows his stuff with resins and I recommend you to see his works).
I hope that when I need it I will be able to easily find this topic (even after months or years) on this WEB site.
In this regard I always invite everyone (please) to put more keywords in the title, in order to facilitate the search (in fact the search is currently only possible on the title and not in the text).

I am not an expert in resin but I still want to give you my opinion. Just consider that it is the point of view of a neophyte in terms of resin.

In my opinion:
- Resin for RC naval models (not those for static display) is always an advantage.
- The resin coating will make the hull waterproof (if it wasn't already), or at least improve the waterproofing (if the hull was already waterproof), but above all it will make the hull much much more resistant (mechanically resistant in the face of a relatively insignificant increase in weight).
- I don't know (I have no experience) the effects of the resin's behavior after long periods of time (20, 30, 40 years), but I think that since it isn't permanently in the water like real boats it won't have any problems (osmosis bubbles, swelling, deformations, etc. etc.), or at least I hope so.

You can do the resin coating in different ways depending on your needs and your skill, your manual ability and personal experience.

1. You can also resin the hull without using fiber (I mean the specific synthetic fabric to support the resin). In this case, in the absence of such fiber, the wooden planking will act as a support for the resin coating. The resin, by impregnating the wooden planking, will create a very compact shell even without the use of the support fiber. Of course, using the fiber will give you an even more resistant and solid structure, but I assure you that the resin on the wood already guarantees an excellent result. Don't think that using only the resin directly on the wood is useless.

2. You can resin only the inside of the hull. If you want to show the planking, by resining only the inside you will get the desired result but you will still have a very solid structure. For those who are not very experienced, it is easier to use paint rather than resin on the outside of the hull. On the inside, however, any imperfections will not be seen and will not have negative aesthetic consequences.

3. You can resin the outside and the inside. If the hull will be completely painted and you are not interested in showing the planking and, above all, if you are very good, you can resin inside and out using the fiber (as Trident73 and Flaxbybuck did).
If you feel like it you can do like Trident73 and Flaxbybuck (but he is very experienced, I would say professional, I would be afraid to do the outside with fiber) but be careful with the curves and follow his advice carefully. If instead you still don't feel confident but still want to resin the outside too, don't use fiber, just use resin (a little and be careful with the drips that are very ugly and difficult to eliminate).

In my case I preferred to resin only the inside because I wanted to show the planking and I wasn't (and I'm not) an expert. The internal resining has however greatly increased the solidity and waterproofing of the hull.
In your case you could resin the inside with fiber and resin and the outside only with resin, you decide.

I can't recommend products that are easily available in the UK because I don't know them.

I can tell you that I used this product:
POXILAM 125 Epoxy Resin (see attached photo)
I don't think you'll be able to find it but I'll give you three pieces of advice (if I'm wrong, please correct me):

1. Don't use fiberglass but epoxy resin (the first is cheaper and easier to find but the second is much better, in my opinion).

2. Be careful with the doses. As you've already been told, you have to be very precise. Above all, don't confuse the proportions between the two components (resin and hardener). If the proportions are expressed in weight, you have to weigh them; if they are expressed in volume, you have to measure them in volume.
It may seem trivial but many people make mistakes in this and end up with either too fast hardening reactions or permanently soft resins. As you've already been told, it's preferable to let the reaction take place at the temperatures indicated by the product, so usually quite hot and dry.

3. Pay attention to the specific instructions of the product you will buy. There are various types of epoxy resins. There are, for example, those for stratification and those for filling. In our case we need the stratification ones logically, but these could have a problem. The Poxilam 125 (the one I used), not being a filling, had a critical mass. Above a certain mass a terrible chemical reaction is triggered and the temperature rises to dangerous levels (I speak from personal experience and I also had an argument with the shopkeeper who had not informed me). In short, if you spread it nothing happens but if you put it in a jar (as I did with the leftovers) a very harmful reaction is triggered.
A lot of resin was deposited in the hold (be careful: filling) but not enough to trigger the harmful reaction, fortunately.

sorry I'm re-editing due to translation issues

All of the suggestions so far are perfectly suitable 👍
In answer to Roy's comment about my own method here's an extract from the build blog of my SLEC pilot boat regarding the fibreglassing of the wooden hull...

"My preferred method is to apply a coat of resin over the hull and then gently lay the cloth into the resin and then lightly brushing from the centre of the cloth outwards without applying any additional resin, this ensures that the cloth settles into the resin and any creases or bumps are easily brushed out.

I applied the glassfibre cloth in five stages starting with one side of the bottom of the hull and when set continuing with the other four faces of the hull the last being the transom. This process usually takes a few days but the resulting cloth and resin surface is free from ripples and bubbles and I can then give the whole hull a light sanding to flatten the surfaces.

Previously I have used additional coats of the EasyComposites resin but on this occasion I used Z-Poxy Finishing Resin because the cure time is about four hours which means that I was able to apply a second coat of resin over the entire hull, again in five stages over the course of a single day. I have found the Z-Poxy finishing resin far less susceptible to producing streaks and ‘fish eye’ blemishes in the surface, but I still clean over the entire area with fast evaporating ‘panel wipe’ to remove any last traces of silicones or oils from my hands and fingers.

After leaving the resin to cure completely overnight I was able to sand the entire hull with a 480 grit ‘wet & dry’ abrasive paper used wet to flatten the epoxy to a fine finish".

Hi. I do a lot of glass fibre covering on both boats and planes. I would use 0.6 oz or 1oz per sq yard weight cloth. Take a look at my blog of my occre ulises as it shows how i do it.

In a nutshell:
I use bucks composites resin or finishing resin from Zap./pacer
Once mixed i personally add a bit of meths to thin it.

Be precise with the mix ratios as the instructions specify. This is critical. I mix by weight and use a digital scale that i got off ebay.

Once I have mixed it I tend to let it sit for a few minutes, maybe 5, before I start to work with it.

Personally I lay the cloth on dry, having first made sure the surface of the wood is smooth and blemish free

I dab the mixed epoxy resin on with a bit of torn sponge. With fine cloths, if you use a brush you can snag and wrinkle it, hence the sponge and dabbing technique. You can also use an old credit card to scrape the resin around on the cloth if you are careful.

Once it is saturated i keep dabbing to remove as much excess resin as poss. You only need enough to get it to stick at this stage. Too much anf you will have a lot more rubbing down to do which should really be unnecessary. Looking along the wet cloth, if it is a sort of ‘satin’ finish then it is about right, if it is glossy in places there is a bit too much resin there and you can dab that off with toilet tissue (see below).

You may need to make small snips in the cloth in places where the curves are severe, but it is pretty good with compound curves.

I then use toilet tissue wadded up to dab any additional excess resin away. It will not stick to the epoxy in its pre-cured state.

The epoxy mix will be workable for about 30 mins. The warmer the environment the faster it will go off.

Let it dry overnight. I sometimes put my covered components in the airing cupboard where the HW tank is if it is a cold day.

Once dry and no longer tacky….

320 grit glasspaper to cut the excess off that overhangs the edges


A REALLY light sanding with 320 grit all over to remove any roughness. Not too much as you don’t want to sand off the cloth.


Mix some more epoxy resin up and paint it on or dab it on with another bit of torn sponge. This fills what is left of the weave.


Wet and dry sanding to give a glass like finish for painting


H&S: do wear a mask for sanding. You dont want epoxy and glass dust in your lungs!

Lots of youtube videos out there showing methods similar to described above.

Oh, one more tip. Get a box of nitrile gloves from amazon or somewhere. You will go through a lot of them. Use meths to clean up scissors and other tools.

Hi Duncan...I use .75 or 1.0 oz cloth, with Z-Poxy finishing resin. I brush an even coat on and lay down the cloth and brush evenly downwards from keel to rail. But, when in doubt set aside or a sheet of balsa and plank it (maybe around 6" square) and use it as a test bed. I always do test shots. I'm a bit obsessive about such things.
😂😉

Hi Duncan
I have a number of wooden boats and have had to make time consuming repairs to them after optically challenged sailors have crashed into them. (sharp pointed bows travelling at speed into the flank of a plywood hull can do a whole lot of damage) The hulls I have clad with fibreglass have survived intact. Initially I questioned whether all the extra effort in doing this was worth it, but in retrospect I would say yes.
I have used glassfibre tissue (sorry I do not recall the weight, but tissue is very light.) I found this on-line. The polyester resin I have bought from Halfords.
My method has been to cut out pieces a little oversize that will be needed to do the whole hull. The tissue will move, ie. it will 'stretch', so compound curves should not be a problem to achieve. Apply the resin to the hull first (it doesn't have to be over the whole hull, just the panel area(s) you are about to do .) Carefully lay the tissue into place. Now comes the tricky bit. DO NOT TRY TO MOVE IT once it is in place otherwise it will disintegrate and you will be left with bits on your brush plus unwanted ridges and bumps in the tissue. Use your brush with a stippling action, but do not try to stroke it (as you would when applying paint or resin) . Stipple the surface until resin shows through the tissue. Add more resin where needed by using the brush, again with a stippling action.
When the resin has set you have two options. You can sand it smooth, or you can use car body filler to achieve a smooth uniform surface (or a combination of the two) Rubbing down resin is a tedious and time consuming job. Rubbing down filler is satisfyingly quick. My chosen method is to use wet and dry paper or cloth, wet. ie. wet the paper and keep cleaning it in water. I use two cork blocks, one being a regular decorators block, the other I have sanded to create convex surfaces. When you are happy with the surface you can begin painting, but be prepared to have to fill dips and holes before getting an acceptable finish.
Don't be afraid to lay on just one piece of tissue and stippling it before moving onto the next piece. Resin will set quickly according to the quantity of hardener used so be prepared for this to happen whilst you are working on it. As soon as you feel it going off you should stop the task and throw away any remaining resin. So after mixing your resin you should brush it on quickly to the whole area you plan doing, then get the tissue on quickly, stipple it, add any further resin needed, stipple that and finish as quickly as you can.
I wish you good luck 😉

Hi Duncan I know the feeling! I often have trouble keeping the spring clamps we use open.

Robbob is an expert! How about it?

Regards
Roy

Thanks for your input Roy. Because I'm having trouble applying pressure with my hands these days the planking isn't as tight together as I would have liked. I managed to do a very tight job on the planks on my Riva but especially with the curvature on the stern I have found this to be more difficult. Filler wasn't really an option when building the mahogany varnished hull of the Aquarama! I've got some Holts Knifing putty for car body repairs that some one had recommended.

Hi Duncan I am a novice here and interested. I have spent time on preparation of the wood for all my models and they have lasted well some at close on 50 years now.
I wonder whether they need to be as strong with the glass fibre coating?

I have seen some beautiful finishes which look better than the prototype, which I would question. However, if the glass fibre is the strength of the hull fair enough but Bruma has 2 layers of planking and I am expecting that to be enough when I eventually get round to starting my one.
I have a 40 inch long yacht with double planking and it is very strong and was enjoyable to do.

I have been diverted from Bruma to building a Wild Duck yacht and there is a build video available which has a glass fibre coating. Overkill I thought and only average in finish. My approach from experience is that 1/32nd ply is not a good material for hull sides as it flexes too much when rubbing down and as soon as you go to 1mm or 1/16th ply then you have all the strength you need.

Sorry if I have diverted from the original thread, but only because I wonder where the advantage lies. But I do look forward to an experienced response so I can re-assess my own thoughts.
Regards
Roy