GRP or ply?

[Julian Swindell]

I would really endorse the use of a swinging cradle trailer. It transforms launching and, in particular, recovery. I launch and recover my BayCruiser on my own at Baiter slip on Poole Harbour without any problems (so far...). Launching is easy, just push the bow up and she slides off into 9" of water. Recovery requires getting the boat lined up with the trailer. In a strong cross current or wind it can be a challenge to get it lined up long enough for you to get the tension on the winch. I always put a rope right on the stern of the boat. On my own I will pull it way over the centre line and then run and crank in as the boat swings. If there is anyone around, I just ask them to hold the rope after I have lined her up. Once the winch strap is tight, the rope can be dropped. Generally I only need to get the trailer tyres wet. Anyone who has launched at Baiter will know most people have to unhitch their trailer and push it way way down the very gentle slipway. They look at me with their mouths open when I do the whole thing with the car still hitched and the boat floating in water that isn't much over ankle depth. (Having said all this, I am bound to have a disaster next time I launch.)

[Michael Rogers]

Hallo

Could I pick up on two things which have come up in this thread, about repair and maintenance?

Background - my Storm Petrel has no glass epoxy coating at all (it came in later than 2003-4), and the hull is 4mm ply. So I treat her as a bit of an eggshell, and to date have had no incidents of serious damage to repair. I am about to start a Trouper 12 kit build, and of course she will be proper epoxied ply. She has an 8 mm ply bottom, and otherwise 6 mm below the waterline (I think), so is an inherently tougher little boat

Point 1 - Claus, you mention the BR hull having no glass-hardened panels above the waterline. This surprised me - am I being very naive/ignorant here? Is this to save weight? build costs? both? I haven't got my kit yet (next week!!), but had intended to sheathe the whole hull. Would there be a problem with this (apart from an increase in weight)?

Point 2 - In the context of touching up, repainting etc, I am very UNimpressed with the abrasion resistance, or apparently complete lack of it, of normal one-pot marine paint. I used a very good brand, carefully applied - 6 coats of primer, 3 of undercoat, three of enamel - and in some ways it has lasted extremely well - gloss and colour retention, lack of peeling etc. However it takes almost no contact to mark it, and not much more to scrape it. I may err on the perfectionist side, but I spend a fair amount of time simply 'repairing' scrapes in the paint. (In contrast the Superdec paint on the deck and inside the boat is fantastically resilient: unfortunately it really only binds that well on 'naked' ply rather than epoxy.) I have therefore been giving serious thought to (and quite a bit of reading up on ) using two-pot paint for my second build. It's obviously tricky to apply, probably also for touch-up and repairs; but also very much more abrasion resistant. Does anyone have personal experience? (I'm half expecting a 'don't touch it with the proverbial barge pole' response, I'm not sure why!)

Other people's expertise/experience would be most welcome - thanks in anticipation.

(Storm Petrel) Cadenza

[Andrew Denman]

Hi Micheal,

This has been an interesting thread so far and after reading your post I thought I might contribute. 

On our epoxy/ply/glass boats be they BR's or others we use a good quality two pack paint system with great success.  Although we mostly spray our coatings, you can also achieve a finish as good as a spray job by rolling and tipping off.  The beauty of two pack is that it is hard wearing and repairs are actually quite easy because you can cut and buff the paint once cured.

At our recent wooden boat festival one of the BR20's was rafted up to another boat when sopme young boys decided to mover her without permission.  She was pushed up against a floating tin shed being used as a music platform and the damage to the topsides looked like someone had hit the boat with a ball pein hammer down one side.  Upon inspection, nowhere had the paint been cracked - it was just indented 1-2mm.  It was a simple fix to sand, fill and repaint the area in question.  Once painted the repair was cut back with some wet/dry paper, a cutting polish then buffed to a high shine.  This type of repair is really easy to do at home with a roll/tip method too.  A GRP boat in this instance would probably have ended up with a bunch of stress cracks in the gelcoat which can be a bit of a pain to repair and blend in.

My own boat is a Farrier designed trimaran that was built in 1991.  The boat has spent all of it's life outdoors and although the paint on the topsides is overdue for  new paint( being done now), the areas that have not been exposed to constant UV could easily be buffed back for another few years of use. Not bad for the original paint job! 

You should be able to get at least 5 years out of a good two pack paint job.  Obviously if you sratch the paint through to the underlying substrate you will need to repair it but it is really not that difficult to do. 

I'm not sure what products you get in the UK but most of the big paint companies have two packs specifically designed for rolling and tipping.  If you have any specific questions about methods etc try the companies tech lines first and if you haveno joy send me an email and I'll try to help out.

regards,

AD

[Craic]

...
Point 1 - Claus, you mention the BR hull having no glass-hardened panels above the waterline. This surprised me - am I being very naive/ignorant here? Is this to save weight? build costs? both? I haven't got my kit yet (next week!!), but had intended to sheathe the whole hull. Would there be a problem with this (apart from an increase in weight)? ...

(Storm Petrel) Cadenza

Hi Michael,
I can speak from own experience only for my plywood SeaRaider, but Andrews comment above suggests that also the plywood BayRaider has no glass hardening above the waterline. For the SeaRaider, the only reason for this I can see is weight. The SeaRaider is 22 ft., has a fully glassed tank underneath the double floor, and still only weighs 300 kgs. Which is extremely good.
But if you build your own boat yourself, and have the skill, I would recommend you harden the hull sides a bit.

Andrew,
I would not know how much force it takes to stresscrack a GRP hull, I never knowingly had such a damage in 30 years of sailing GRP boats, but in 5 years of owning and sailing one plywood boat I already had two cases of a cracked plywood hull. From that, and completely unscientifically I would suspect GRP hulls are A LOT more robust against the accidental impact of the unwanted but unavoidable sort.

[Julian Swindell]

There used to be a common form of surface cracking on GRP called spider cracking (I think) which resulted from a hard bang on a small area. A very typical example would be on decks where an anchor had been dropped. The cracks would spread out very slowly like a spider web from the point of impact. They are superficial but a real pain to deal with. I had a lot of them on my old Drascombe Dabber and a couple on my Winkle Brig. I think modern GRP is much more resistant to them.

I get the impression that fibreglass sheathing above the water line is not common on most ply construction because it is considered not necessary. Fibreglass below the waterline is mainly for abrasion resistance more than impact protection. Ian Oughtred recommends only to use Dynel fabric rather than fibreglass for bottom sheathing as it fits his lapstrake designs much more closely than glass cloth. I would suspect, but have no evidence (the best basis for a suspicion) that bottom sheathing is more important on a heavy boat than a light one, to protect it from grinding on rocks, sand etc.

Regarding painting, I am a philistine. I have a dark green top coat on a dark grey primer. Most scratches are almost impossible to see against that! When I repainted this winter, I found all sorts of scratches and surface marks that I hadn't even noticed on the water. I am shamed by the description of painting in an earlier message. 6 coats of primer! I don't have that many coats of paint in total, let alone as a primer. I would have said that that was actually too much primer and could be counter productive. Primer is there as a bonding layer between the substrate and the paint system. 6 layers could actually weaken the system. The real thickness should be in the undercoats.

[Clem Freeman]

I'm hoping to pick up my S 17 kit next week as well so not ready to paint yet. What are the 2 pack paints like for spraying? I've completely resprayed my lotus elan +2 in celulose which is quite forgiving if you make any mistakes, you can just let runs dry and then rub them down after. Also what are the fumes of 2 packs like, do you need to wear masks with an air feed? As far as gel coat cracks are concerned certainly on a car bodyshell the main cause is a sharp impact from something like a stone from the inside or outside. The gelcoat is important to keep in good order as it keeps the water out of the uderlying fibres which can be pourous.

[Jeremy]

I used the International two pack PU for the topsides of my old boat many years ago.  I applied it under cover with a foam roller (you have to be quick, as it makes the foam go a bit soggy after a while!) and was amazed at the finish.  It was incredibly hard and seemed to flow to a very smooth and shiny finish with very little work.  After 5 years or so of weathering it still looked like new (it may well have lasted longer, but I sold the boat with it still looking like new).

I have also sprayed 2K PU paint but it is a bit of a palaver.  You need an clean air fed mask, ideally a Tyvek suit and gloves.  The stuff is really quite nasty to spray, with all sorts of dire warnings about isocynate poisoning etc.  I used an HVLP spray set up and found that it was exceptionally easy to apply, much easier for my negligible level of spray painting skill than a conventional high pressure spray system (and much less over-spray).  Applying it with a roller avoids much of this hazard (except the skin contact one) as it does not fill the air with all the nasty stuff.

On the topic of paint, does anyone know anything about this flexible stuff: http://www.plastidip.co.uk/eStore/index.cfm?type=Domestic_Solutions/HCF&stage=1

I have a need for a flexible paint coating for a project and am thinking of using this stuff, rather than very expensive Hypalon paint.

Jeremy

[Michael Rogers]

Jeremy

Is the Plastidip for your 'Cordless' project (Readers of Water Craft and/or the HBBR-UK forum will know what that's about)? One of the testimonials (presumably unsolicited - ?) on the website for which you gave a link refers to use to cover canoes.

(SP Cadenza)

[Jeremy]

It is indeed, Michael.  I'm looking for a flexible coating for the Aerowherry (the design of which will appear, with luck, in Watercraft's July/August edition), my entry in the Cordless Challenge, a competition for boats powered by cordless tools that's taking place at the Beale Park show this summer.

If the logistics permit, I may well have both my electric Winsome and the Aerowherry at Beale Park, ready for an adventure down the Thames to Hampton Court.

Jeremy

[Michael Rogers]

Thanks for the useful comments, folks, much appreciated.

Can I complicate the discussion still further, and ask if anyone has experience/comments about using Dynel fabric rather than, or as well as, fibreglass for sheathing? Apparently Ian Oughtred recommends it for his boats. I have no idea of relative costs etc.

(SP Cadenza)

[Anthony Huggett]

From my reading, spraying 2 pack PU definitely requires an air fed hood.

I'm hoping to pick up my S 17 kit next week as well so not ready to paint yet. What are the 2 pack paints like for spraying? I've completely resprayed my lotus elan +2 in celulose which is quite forgiving if you make any mistakes, you can just let runs dry and then rub them down after. Also what are the fumes of 2 packs like, do you need to wear masks with an air feed? As far as gel coat cracks are concerned certainly on a car bodyshell the main cause is a sharp impact from something like a stone from the inside or outside. The gelcoat is important to keep in good order as it keeps the water out of the uderlying fibres which can be pourous.

[Brian Pearson]

I'm not sure what products you get in the UK but most of the big paint companies have two packs specifically designed for rolling and tipping.  If you have any specific questions about methods etc try the companies tech lines first and if you haveno joy send me an email and I'll try to help out.

regards,AD

I have had lots of problems with trying to paint two pack paints. Very difficult to tip off and also the paint seems to slump before it goes off and looks terrible when you come back to it.
I have had good success with Epifanes two pack varnish, so have been thinking of trying their two pack paints.
Which make do you use for hand painting? Thanks, Brian

[Andrew Denman]

Hi Brian,

Most two pack paints are designed for spray application and the thinners used are very fast drying so the poor old spray painter can lay the paint on without runs/curtains.  When rolling/brushing, a slower retarding thinner is required so the rollerr/brush marks flow out. 

When I roll and tip two pack, the consistency of the paint is like milk and a number of thinner coats are required to build up film thickness 0 at least on vertical surfaces.  I use a high density foam roller and then a foam brush to tip off. 

For a spray like finish, onbce you have completed painting and the paint has fully cured - about 7 days, give the paint a wet rub back with some 1500 grit wet and dry then using a machine polisher, cut the paint with a good marine cut and polish and finally some 3M Finesse it for that real wet look.

International make a product called Perfection which may suit.  I haven't used it  ( I use Altex paint for this) but it sounds similar.

regards,

Andrew

[Michael Rogers]

When I fetched my Trouper 12 kit from Cardigan recently, Matt showed me the finish they got with 'roll and tip' on a (not quite completed) Trouper: I must say it was brilliant, in more senses than one. Apparently they don't spray two-pack because of the palaver (protective kit etc) involved.

Someone on the UK-HBBR forum wrote approvingly of Jotun paints. Looking into the options, Jotun impressed me for two reasons - 1) they seem to do a wider range of colours than most; 2) they have comprehensive no-nonsense technical information right there on their website (getting that sort of info out of some makes, who shall be nameless, is a blood/stone scenario). I wonder what  their customer advice service is like: I haven't tried that out yet. Apparently they have a very good special primer to go over epoxy.

Thanks, everyone, and especially Andrew, for all the helpful comments. If anyone has a go with two-pack and could let us all know how they get on, that would be great. I'm still rather a long way (6 - 9 months?) from that potentially scary moment when the lid comes off the new paint tin for the first time.

[Lorenzo Wynn]

Can anyone tell me what iss the best soul set up for dps?