Flowcoating the hull

[cjastbury]

Hi
I'm currently trying to restore a McNulty Huntsman, yes you either love or hate them. Back onto the subject, there are no major damages to the hull, the normal scratches to be expected on a boat of this age. I have sanded out most of the scratches, gel coated a few small holes, areas where the fibreglass shows through. Now I would like to coat the complete hull with something, not shiney and new like, but achieve a neat finish.
We often hear of small repairs to composite hulls, but not the whole hull. After much research on the internet, it seems that floatcoat is the way forward, but I also hear of conflicting stories, thus my question is. Has anyone restored a complete hull using floatcoat or would they recommend something else. If flowcoat is the item to use, is it best painted on with a good brush or rolled on, or both?
Cheers and happy paddling to everyone

[Mikebelluk]

I would recommend as your best option you look for a local spray shop who are prepared to spray the boat with several coats of isocyanate 2 pack paint. It will give a gloss finish straight from the gun and be very hard wearing.

Second option would be to roller several coats of white tinted epoxy resin after sanding the boat to 80grit to key the surface. You would need about 1.5kg of resin. Use West System resin if possible with their own brand rollers, or Harris Varnish rollers. However it will then need a UV filter varnish applied as epoxy pigments do not provide UV filtering.
Pigmented epoxy may be somewhat more UV resistant than unpigmented epoxy, but it should still be covered with a UV resistant coating, either clear coat or paint, to protect it from UV radiation for outdoor applications.

Flowcoat could be rollered on, but you would then have to sand it, fair it, then polish it, and IMO it would be a pig of a job.

[Taran Tyla]

Flowcoat could be rollered on, but you would then have to sand it, fair it, then polish it, and IMO it would be a pig of a job.

I keep shying away from the pig :S

[MikeB]

There's a chap here in Scotland, Roddy McDowell, who runs Kayak Bute, who got his local boatyard to re-gel the hull of his boat. Could be worth asking what / how it was done. http://www.kayakbute.co.uk/

Mike.

[nickcrowhurst]

An electric polisher with the right 3M cutting compounds can produce remarkable transitions on glass hulls. Only once have I been presented with a hull with so many dreadful holes and repairs that it wasn't worth the effort to rebuild it as new. I tidied up the repairs, and rollered on a coat of coloured gelcoat, and then a coat of coloured Topcoat (gelcoat with wax and pigment), the same yellow as the original. It saved a class kayak from the scrap heap, but I would only do it in extremis. The owner then had a lot of wet rubbing down to produce a smooth finish. (The West yellow foam rollers are perfect for getting a good surface)
Nick.

[cjastbury]

Hi

Thanks so far to all that have given me exellent tips on what to do. The hull is actually in quite good condition. I have sanded out all scratches, and gelcoated any large scratches, spider cracks, etc. I used wet and dry to create an pleasing finish, and it now looks very decent. I now would like a uniform colour over the hull so I looked at http://www.paint4boats.co.uk/ yesterday, and called them too. They advised me to use a primer and gloss coat to finish the boat, this could be rolled on and would produce a good finish, but is this strong, etc, or is flow coat the better lonf term solution?
Having all ready done some gel coat work on small areas, I now realise that if I flow coat the whole hull, I've got to be quick in application, in achieving a smooth finish, as I then will maybe face the ardious task of sanding and buffing to create a good finish.
As I was given this boat, I'm attempting to restore it simply with little cost! I went to a car repair specialist, and they quoted me £500 for a paint job on the hull. Please if you have the time, check out the paint 4 boats website, and maybe advise what is now a simple option I,e. primer and gloss coat(s) or flow coat the whole hull!
Thanks again for all your constructive advise.

[branwell]

Is there a danger that flowcoat gelocoat applied ontop of existing gelcoat can flake or chip off? I am sure I read somewhere about wiping the surface to be coated with styrene before hand to get more of a chemical bond.

[nickcrowhurst]

Is there a danger that flowcoat gelocoat applied ontop of existing gelcoat can flake or chip off? I am sure I read somewhere about wiping the surface to be coated with styrene before hand to get more of a chemical bond.

I abrade the gelcoat surface with a nylon flapper wheel, wipe down with acetone on a rag to remove the dust, and then apply the Topcoat. (Gelcoat + catalyst + pigment + wax.)

Nick.

[Graham T]

In the situation described I would have sanded wet/dry used wet down to perhaps a 400 grit and used a two part paint system. The application of the paint should be relatively straight forwards and without issues.
Can somebody point out for me the benefits of using a flow coat instead please ? Is it that you get either a tougher finish or simply a thicker heavier one in one coat but at the expense of extra work to flat/polish this afterwards ?
Extra thickness will add weight
In either case once scratched the old surface will show remember this when choosing a color

[Jim]

I will jump in here - Nick already knows I think his beaatiful restorations are a waste of time (although I do like them) and I find equal satisfaction in a good repair that doesn't pretend not to be.

If you are going to paint the boat, you are probably being recommended an etch primer - this will eat into the existing gelcoat a little to provide a good mechanical key for the paint, which will be part of the same system so should cover well and look good. Paint has a small DFT (dry film thickness), it is relatively easy to scratch it off under fairly normal sea kayaking use. Larger boats remain looking fine because they don't necessarily get dragged up and down beaches the way kayaks do, painted kayaks to me start to look patchy quite quickly if used (if restored for looking at it's no problem).

Gel coat serves several purposes, firstly it goes against the mould to make sure you get a shiny flat outer surface that doesn't have the texture of the reinforcement (when applied too thinly or used with a too coarse a reinforcement you may still get some texture), secondly you can pigment it to make the boat look pretty and thirdly it acts as a slightly less permeable barrier than plain resin with ends of fibres potentially forming pathways for water to be soaked in (Polyester is semi-permeable anyway, in that water can be drawn through it by osmosis). If the gel coat is too thick it will tend to break off in chips when you take a knock, a lot of old boats have too thick gelcoat for a number of reasons - it is difficult to paint on the right thickness, and it is convenient to fill tight corners with gel and not worry about how to get the glass reinforcement and resin in there. What you do may depend on how sound the existing gel coat seems to be, it if will continue to flake or chip away then covering it up just means it will take your new finish with it, in which case you may want to peel the boat first. If it has rampant osmosis (very rare in kayaks because they are out of the water and dry most of the time) you may want to peel it and let it dry out before continuing.

You can flow coat over the gel or after peeling it. Flow coat resin should be less thixotropic and thus easier to apply than gelcoat, but also make sure you get liquid catalyst in a measuring dispenser. Weigh out your resin (old or cheap kitchen scale is fine) and calculate the right percentage of catalyst to use for the ambient temperature, then measure this much out and mix in in thouroughly and quickly with minimum handling of the pot (don't want to add extra heat from your body) - a plastic potty with a handle is preferred in some places. As soon as you are happy with the mix pour it into a roller tray, thus increasing the surface area for heat loss. Polyester is exothermic, it generates heat as it cures, the hotter it gets the faster it cures, so long as you have the right quantity of catalyst you can extend your working time by not dirctly handling the pot and maximising the surface area - also mix small batches frequently so you can use it all within it's pot life (it will stay wet on the boat where it is rolled out thin with lots of surface area for a couple of hours). Working in a greenhouse in mid summer is obviously a bad idea - I once fitted an oval hatch rim to an Anas Acuta in my mate's greenhouse because of rain showers, fortunately I was working as a laminator at the time and was able to work quickly and ditch any excess resin batches before they started to become unuseable, but it was a horrible horrible place to work! A cooler working environment will help your pot life.
Flow coat is much thicker so you will scratch it, not scratch it off, unless the underlying substrate flakes off anyway.

Now, an alternative to the paint you have discussed or flowcoating, if you decide to peel (sounds like you don't need to) is to use one of the products for osmosis repair, which is basically a 2 part epoxy based paint which will adhere well to a peeled and dried hull and is thick enough to level out to a degree. The reason it is used on yachts etc. for osmosis treatment is that epoxy is much less permeable than polyester so it forms a better barrier and should prevent recurrence of the blistering, I used to find it easier to apply than flow coat but perhaps not as easy to get smooth? Also being epoxy there are tight recoat times and once fully cured the waxy finish means you will need to mechanically abrade it if you ever need to stick something to it, like a future repair.

I can remember as a teenager in the boatyard, after a good night out, mid summer (hot) laying on back under a 23 foot canal boat that had been peeled and dried out, rolling on the epoxy paint, overalls on, paper hood, gloves and goggles to protect me from splashes, severely hung over with paint fumes not clearing (windless day). That coat of paint took me forever, part of the problem seemed to be that I had to keep scrambling out from under the boat, de-kitting and rushing to the lavvy to be violently ill into it.... To be honest whatever solution you use, beware the fumes and hangovers!

[Graham T]

Good description Jim. I once painted several 505 Dinghies the front bulkhead under the deck the hull and hog and the backside of the rear bulkhead took about an hour with paint containing isocyanates prior to the company having an air fed mask = bloody stupid thing to have done and yes it did make you feel bl..dy quere.

Good to know the flow coats are as expected but not tried perhaps a cross in consistency between paint and gel coat .......good info

[cjastbury]

Wow, this is brilliant information :)

I'm over whelmed with such excellent information.
Now I am confused as either to use flow coat or paint, but it looks more favourable to use flowcoat as its seems the longer lasting and stronger. I'll post some pics of her soon, if I can figure how to do this.
I have also took out the right hand chimp pump, sealed this area just behind the seat, and fitted a day hatch cover. I've also got the old henderson hatches, so I think I may change those if not too costly. I fitted some adjustable foot rests in place of the fixed rail. One day I may tackle fitting a skeg, I have a skeg and wire, just need to make a slider and box section :(

Thanks, and any more tips welcome.

[MikeB]

I'll post some pics of her soon, if I can figure how to do this.

http://www.ukseakayakguidebook.co.uk/po ... _links.htm

I've also got the old henderson hatches, so I think I may change those if not too costly.

Valley hatches are, I believe, a direct replacement.

Mike.

[Daker]

You can flow coat over the gel or after peeling it - -

Am I right in thinking you mean to peel off the entire gelcoat layer ?
Forgive me if this has been covered elsewhere but could you briefly explain how this is done ?

[Jim]

You can flow coat over the gel or after peeling it - -

Am I right in thinking you mean to peel off the entire gelcoat layer ?
Forgive me if this has been covered elsewhere but could you briefly explain how this is done ?

On a big boat you would get someone in to peel it with a machine. I never saw that part, I was actually at Uni by the time we started doing osmosis repair and missed the stripping, I was back later in the summer when the boats were dried out to be painted. I think the people we used to use used a waterjet of some kind, possibly with a blasting media, or not. It's amazing what can be done with high pressure water lances these days!

If your gel coat is already bad you would be surprised how much just pings off working away with a stanley knife and/or chisel, I would think if a kayak is bad enough to need peeling it could be done manually with such tools.

[mick m]

what if you gave it a good going over with sand paper to remoove eny parts not atached properly befor filling and flowcoting ?

[cjastbury]

Hi Guys

After much thought, I did some sanding and polishing tests on the McNulty Hull. I was actually quite suprised as to how good the hull was, so with wet and dry, rubbing compound, and orbital polisher I have now brought the hull up to a lovelly shine, in some parts mirror like finish, I guess this needs to be waxed?
I do have a tin of flowcoat in white to which I will apply on as much of the insides as possible, this will give the boat extra strength, and improve the appearance. I've also got some black flowcoat, and as I have scrapped/sanded off most of the water line, I'll simply apply this to create a nice neat black band. Then if funds are open, I'll invest in some keelEasy from Chill cheater.
If I've missed anything out, I am sure that you'll let me know. But thanks for all your tips and advice. Pics coming soon.

[Mikebelluk]

If you add the flowcoat on the inside it will add extra smoothness and weight but not strength.
Strength comes from the matrix of resin and glass combined.