Restoration Advice - 10ft GRP Tender (pics inside)

Hi All,

My girlfriend and I have just purchased this modest little twin-skin GRP boat:



We're hoping to spend a few weeks giving her some TLC (the boat) and then plan to get her in the water with a small outboard on the back as a fun little run-around for the summer.

Whilst I am realistic about what can be achieved, I would definitely like to re-paint both the deck and topsides and re-antifoul the hull (the boat will be left in the water in the River Yealm (Devon, UK) for several months, and sometimes on a drying / mud berth, so I think that antifouling will be essential).

My initial plan is to:

Somehow strip back the paint on the deck and topsides to a point at which I can apply some new primer and paint system (the simpler the better - I want it to look nice, but I'm not really prepared to spend too much money, or too much time filling and fairing).

To remove the old paint, I was thinking of sanding back with 150-200 grit paper, using a DA polishing machine. I did a quick test on a spot on the transom and as per these pics I am pretty sure I went too far and got down to the laminate:





So, I am wondering if I should sand carefully until I'm fairly sure I'm at the original gel-coat all over, then give it a final pass with a much finer paper (maybe by hand / with a board?) to give it a relatively smooth surface for the primer to sit on.

The deck has some nice contoured features where I think a non-skid pattern has been moulded in:




I was hoping I can scrape along the edges of these to clean them up a bit along with the general sanding.

For the underside of the hull, I intend to record the position of the waterline and then scrape off the old antifoul with a Tungsten Carbide scraper. I will then re-tape the waterline and apply a couple of coats of new antifoul.

Does this all sound like a sensible approach? I would really welcome any advice / ideas / suggestions...

There is a full gallery of pics here: http://imgur.com/a/fYABJ#6

Thanks in advance and I will keep this thread up-to-date with my progress.

Cheers, Rupert

 

Welcome to the Forum

A small project but it could work out well if tackled from the right perspective. Are you sure you removed paint? not the gelcoat?. I would assume any GRP/Frp is gelcoat finished rather than painted unless post painted to 'hide' unsightly crazing...
If the layup is sound, yoi only need to replace the gelcoat, if there is damage - cracking or flaking in the layup (sand off) and a little roving of fine CSM would be needed first.

My personal approach would be to isolate the cracked areas and sand them down quite locally and re gelcoat them. Plug any through holes into the internal buoyancy tank etc with epoxy, and gel those holes too. You will need gelcoat, white polyester pigment or a matching white gelcoat - there are hundreds of whites. The best pure white (in the UK) is the Scott Bader 337 Super white, but you will likely need a few other colours to mix the correct 'white' if you want a really neat job. Do not use the plastic padding stuff - it's rubbish an yellows a lot over time. Try Blugee and East Coast FG Supplies they might have a match, but a hell of a lot of 'whites' are not perfect from the pigment.

You will also need Styrene Monomer (Wax) and catalyst both normally added at 2% proportions, to add to the gelcoat. As you may find, at least 10 deg + temp will be needed to get this stuff to set. 15+ is better and dry. Read up about applying external gelcoat but it is not too hard, but requires a fair bit of sanding level, working through the grits (wet and dry) until final buffing.

Check with any suppliers to see if the 'wax' has been added to the gelcoat prior to using. Some do some don't. You can bond to new gelcoat once the 'wax' surface has been thoroughly sanded back. Do not leave on, as it won't bond on to it, it effectively forms a skin which is a release agent for any top coating.

I'm surprised she has anti foul, it's not visible in the pics though I am suspicious of the blue showing on the bow photo...
She does not really need this and will be a fraction faster/easier to row/outboard with a smooth bottom which is cleaned on a moderately regular basis.

Perfectly possible to gt it back to as new condition. Good luck with her.

 

Be aware, you can't get rid of spider webs by sanding over them. You have to dig them out (Vee them out) using, for example, a shaped tool, and fill the crack with an epoxy putty.
As far as removal of old anti-fouling, a scraper is too brutal and will result in many scrapes and gouges. Use a paint remover or wet sand with 80 grit wet/dry paper.

 

Hi Guys,

Thanks for the welcome and quick responses:

- Yes, she definitely is painted on top of the original gelcoat. I went down through at least two layers of paint.
- I think there is some spider cracking in the gelcoat, and I am aware that these cant be sanded out. I would be up for doing some simple filling as part of the surface preparation for painting if it doesn't become a huge job
- It definitely is antifouled (burgundy colour - check out the gallery of photos). The reason I want to re-antifoul it is that the boat will be kept in the water all over the summer, sometimes on a drying mooring. I believe the marine growth is quite severe where we are, so I think it would be worth a coat or two?
- Thanks for the tip re: scraping antifoul. I was hoping scraping would be preferable to sanding more from a health-risk perspective, but I do have a good dust mask so will sand instead if that's the better option.

Thanks again for the tips and detailed advice.

 

Sanding the hull with wet/dry paper means zero dust----- all the particulate is suspended in water. No mask necessary. A stick sanding pole (as used for drywall) makes it easy to get at most areas. Just be careful to capture the run-off using a tarp

 

Unless you have need for the two holes in the transom corners, I'd reglass them in. TBH I don't know what they are for, but they signicantly weaken the moulding on the corners, hence the cracking gelcoat. Looks like the rowlock holes are already filled in.....

Worth checking the condition of the outboard external (transom outer) pad. It looks glassed in but could be lot of rotten (saturated) ply. It is possible this requires replacing. I assume you'll be using a 2 - 4Hp motor, so it might be worth a protective aluminum sheet to face the inside ply and protect it from the clamps.

The small multitool sanders don't raise much dust and are capable of rmoving the bulk of the anti foul, followed by hand sanding. I concur with Alan's wise advice. Pity it's painted, a PITA to remove especially textured stuff. If repainting I'd go with a quality One Pack Polyurethane. One way to prepare the textured area is to 'sand' with degreased wire wool (say 00 or 000 grade) or the grey Scotchbrite pads. If you can get the crevices to go matt and clean it with Acetone, or alchohol new paint should stick.

 

Hi, the holes in the corners seem to have been used to fix the lines holding the fenders around the topsides. I can see how they are obviously a bad idea re: stress concentration, but I would like to keep some kind of fender solution as the place we're going to leave the boat is quite crowded with other dinghys - is there an alternative? Deck fittings perhaps??

Wet sanding sounds like the best solution for me as I am quite worried about the dust. What do you think would be the minimum sequence in terms of grit for the topsides? I was hoping to use a maximum of three grades, maybe 80, 200, 800 on a rubber sanding block and/or the sanding pole that Alan suggested.

Engine wise I was looking for a 2 stroke in the range 4-10 hp as the Yealm is very tidal. I have been told that there isn't a huge weight penalty between the larger and smaller engines in this range, but I need to verify this. I suspect that 10 would be perceived as too big for this boat?

I will check out the one pack polyurethanes - sounds like a straightforward solution. Presumably these will come with a recommended primer.

The transom reinforcement is definitely worth checking - how would you suggest I do this? Sand down or bore a hole through it perhaps? If it does need replacing how big of a job is that? I can imagine that it would involve sourcing some new wood reinforcement, removing the old and re-glassing...

The general principle I'm aiming for with this project is to get as much done as possible in the most efficient way in order to get it in the water for April.

Thanks for all the advice!

 

One part urethane is fine. Formulations designed for porches and decks are available at your local box store. They contains enough urethane to protect like marine enamel at a much lower cost than the marine version.
Check the transom both high and low by drilling if you don't have access to a moisture meter and see how dry the core is. All transoms are suspect no matter how good the rest of the hull is. Typically, drain plugs and bolt holes are where to look for problems. Are the original holes sealed to prevent absorption into the core? Now's the time to prevent future problems. Make sure to fill the drill holes with epoxy.
Topsides, prep for paint with 320, or 220 grit if priming/re-sanding.

 

I suspect that 4Hp will be plenty, even a 2.5 may be enough especially if you intend to carry the engine any distance. The small 2 - 4 Hp 2 strokes are light enough wheraas the 4 Hp 4 strokes are quite a bit heavier and realistically need a trolley if you want to move them more than say 10-20 meters singlehanded.
Do not forget the extra motor weight (of a large engine) on the transom will sink it and put the boat out of trim. It would take a 4 Hp 4 stroke for weight by the look of it, but not much more. The small Honda 2.5s' (4 stroke) are fairly light for example.

Might be worth trying to borrow one just to check trim and balance and perhaps weight in the hand? Tidal does not equate to very strong current especially at the edge of the river. Although I don't know the Yealm well enough, the Thames and quite a few rivers on the East Coast are no real problem to row even an inflatable out to a mooring. Tide on the river Ore (for example) is pretty strong....

The boats displacement speed is very roughly 3.5 Kn so bear this in mind. Any more power input than this speed achievement is largely just wasting fuel. For any distance trips you should plan your route to use the tide to advantage as much as possible.

Alan's advice regarding the transom is spot on, I would check the 'through mount' holes first as often they are not sealed properly. If you glass on a new core, remember to seal the timber/ply itself prior to glassing on and fully seal any new mount holes if required.

 

Ok, thanks guys I now have a clear plan of action and have started sourcing various bits and pieces... One immediate question:

Filling in the holes in the rail at the corner and bow - I think these have all been drilled straight through the laminate. They are approx 15mm diameter. As has already been pointed out, these are obviously causing stress concentration and weakness in the laminate.

I would like to fill these holes (and whilst I'm at it, to re-install the rowlocks, which are badly fitted). Crucially though, I would then like to install some deck fittings to take my lines. Could you give me some advice on the simplest way to do this?

I was wondering if an epoxy filler would work, but not sure how to approach the job (presumably you need to create a temporary surface on one side of the hole). Also, if I want to install hardware subsequently then presumably I would need to look at glassing in some kind of reinforcement e.g. wooden block under the rail? A simple explanation of what is required would be invaluable.

Thanks in advance guys, Rupert

 

The way I would approach glassing the large holes is to cut a large chamfer from above ie bevel the edges. Although technically you should use a 1:7 for a perfect no strength loss joint, you'll get away with about a 1:4 bevel. Glass in with either polyester or epoxy, using something like 200gsm roving on the underside face and the top face. Inside could be fine CSM or thicker 280/300 gsm roving, I'm guessing not much more than 6mm thick total. Cut a load of round pieces ready to go and build up the thickness. If you want a smooth undersurface a piece of scrap timber (shaped to suit) with polythene sheet on it will clamp in position and release easily afterwards. Even stretching polythene sheet with tape works but tends to sag. Sometimes a piece cut from say an ice cream tub lid or box can be shaped to fit and taped. This works well. PP (polypropylene) is just as good, just look on the containers and use either but NOT anything marked PS which is Polystyrene and will just dissolve....

Cut this down after curing so it is sub flush by a mm or so then seal with one coat of resin (either) abrade after setting then gelcoat. You can then redrill smaller holes through this for mounting stuff although if you want anything substatial say a lifting handle then a bonded in 'pad' of timber underneath is useful. If you want say a hole of 10mm diameter to run a line through you should be fine. One sort of rule of thumb is, if the outer part beyond the hole is three times the hole diameter there is no loss of strength sideways. This would apply to lateral loads ie running a string of fenders, not lifting.

If you stayed all polyester, and you have reasonable temperature, you easily could do the whole thing in less than a day. That allows for some hours curing etc. Epoxy takes quite a bit longer for cure cycle. Again personal, but for most of the glass work, I'd probably stay polyester, it's enough for this type of craft. Strong enough if you work cleanly, and fast.

The rowlock holes can be filled with epoxy and microfibres or similar filler, even balloons or lighweight filler and rebored. If they are nylon, and closed ends you could even seat them in the epoxy mix, removing squeeze out carefully. Good practice to seal the glass with neat (mixed) resin prior to adding the filler, easily done using the same mix. For example mix resin, correct ratio, allow to degass and settle, apply to raw edges, then with same batch of resin add the filler and fill hole. Do not assume epoxy and polyester will take the same fillers, they often don't. However both resins will bond roving and CSM OK, though you need to check the CSM is suitable for epoxy. Some very fine tissue and very light CSM has a binder that is only compatible with polyester.

 

Hi - thank you very much for that! All makes sense. I'm going to make a start on the sanding of the deck and topsides, and will follow your suggestions for filling the holes before flipping it to work on the hull. Thanks again, really appreciate the advice. R