Help from the paint experts please
Discussion
I thought that I would post this here because I need advice from the paint experts.
OK here we go. I have just built a strip wood sea kayak which has been fibreglassed with epoxy resin. The weave of the cloth was then filled with more resin until smooth and rubbed down ready for the finish. The fibreglass is completely wetted out during the initial layup which allows the beauty of the wood to show through. The standard practice for the finish is 6 coats of a good quality spar varnish (Epifanes or similar) to give some protection including UV as the resin will degrade without.
There is a builder in the USA who uses 2K clearcoat and I have also found a guy on a canoe forum who has used it too. Both have achieved excellent results that have lasted for several years before any revarnishing is required etc apart, of course, for any major scratches when it was flattened and recoated. One of these guys sprayed on the lacquer in controlled conditions and the other sent his kayak to a body shop. I have also found a guy who rolled it on and then laid it off quickly with a varnish brush. I have literally just carried out the latter and apart from a bit of dust I have to say it went on a treat and is now touch dry and in the process of hardening.
My question is a relatively simple one to you experts. I need to build up several coats and bearing in mind that it was put on with a roller, how long must I leave it before recoating and does it need to be flattened between coats? Is it a bit like the epoxy resin which has a minimum time between recoats in order to get a chemical bond (touch dry, usually 4/5 hours) or if left longer than 24 hours it must be sanded to get a key for the next coat. I guess if it’s too quick the new coat of lacquer may well interact/soften the first one too much and cock it all up.
Help/suggestions greatly appreciated.
OK here we go. I have just built a strip wood sea kayak which has been fibreglassed with epoxy resin. The weave of the cloth was then filled with more resin until smooth and rubbed down ready for the finish. The fibreglass is completely wetted out during the initial layup which allows the beauty of the wood to show through. The standard practice for the finish is 6 coats of a good quality spar varnish (Epifanes or similar) to give some protection including UV as the resin will degrade without.
There is a builder in the USA who uses 2K clearcoat and I have also found a guy on a canoe forum who has used it too. Both have achieved excellent results that have lasted for several years before any revarnishing is required etc apart, of course, for any major scratches when it was flattened and recoated. One of these guys sprayed on the lacquer in controlled conditions and the other sent his kayak to a body shop. I have also found a guy who rolled it on and then laid it off quickly with a varnish brush. I have literally just carried out the latter and apart from a bit of dust I have to say it went on a treat and is now touch dry and in the process of hardening.
My question is a relatively simple one to you experts. I need to build up several coats and bearing in mind that it was put on with a roller, how long must I leave it before recoating and does it need to be flattened between coats? Is it a bit like the epoxy resin which has a minimum time between recoats in order to get a chemical bond (touch dry, usually 4/5 hours) or if left longer than 24 hours it must be sanded to get a key for the next coat. I guess if it’s too quick the new coat of lacquer may well interact/soften the first one too much and cock it all up.
Help/suggestions greatly appreciated.
What does it say in the Technical Data sheets for the material you bought? You got/should have got from the paint supplier.
These give all the things you need.
If you didn't get them then you need to get them ASAP. Have you tried looking for them on the internet?
What exactly did you buy? If you post the details you may find someone who uses it who can give you advice.
These give all the things you need.
If you didn't get them then you need to get them ASAP. Have you tried looking for them on the internet?
What exactly did you buy? If you post the details you may find someone who uses it who can give you advice.
That would be a good starting place to look - Doh! 
Anyway I've now found the info which reads as follows:
AIR DRYING:
At 20°C the film is dust dry after 30 minutes, may be handled with care after 90 minutes and may be re-coated after drying overnight (8 hours).
The only question therefore appears to be - do I need to flatten it before re-coating. Surely there is a time limit or can it be recoated at anytime withought re-keying! In reality I might want/have to wait say 2 or possibly 3 days before re-coating. The only other related info reads:
REWORKING:
After cooling following the above stoving schedules, defects and runs can be removed using P1200 Wet or Dry.
I will be air drying but I have no idea what the equivalent period is to obtain similar hardness or how you tell especially this time of the year when temperatures are a fair bit lower at night. My plan was to apply 2 coats, flattening with 1200 or 1500 then a further 2 coats before flattening and buffing, etc - does this sound about right?
Thanks for your help.
Anyway I've now found the info which reads as follows: AIR DRYING:
At 20°C the film is dust dry after 30 minutes, may be handled with care after 90 minutes and may be re-coated after drying overnight (8 hours).
The only question therefore appears to be - do I need to flatten it before re-coating. Surely there is a time limit or can it be recoated at anytime withought re-keying! In reality I might want/have to wait say 2 or possibly 3 days before re-coating. The only other related info reads:
REWORKING:
After cooling following the above stoving schedules, defects and runs can be removed using P1200 Wet or Dry.
I will be air drying but I have no idea what the equivalent period is to obtain similar hardness or how you tell especially this time of the year when temperatures are a fair bit lower at night. My plan was to apply 2 coats, flattening with 1200 or 1500 then a further 2 coats before flattening and buffing, etc - does this sound about right?
Thanks for your help.
Can only really tell you what I've done.
I use a 2k clearcoat with a very fast hardener - 10 mins at 60 degrees - for SMART repair, mainly on car & caravan body repair over solvent & waterbase base coats.
I HAVE used it on marine ply on the seat bases of my own boat. These then have the seat foam & covers stapled over them so not visible when seats down.
I flatted the bare wood then spray applied 2 full wet coats of clearcoat. Infra-red lamp baked for 20 mins.
Finish very rough - most of the first coat soaked straight into the wood.
Sanded with 1000 grade (coarser would be OK, I just didn't have any to hand & it's only about 3'x2'!) wet& dry used dry then 2 further full wet coats.
Further baked & then it was as good as I needed for the job. Some texture, but not rough.
If I wanted a super smooth finish I would be looking at flatting those then applying further coats.
I use a 2k clearcoat with a very fast hardener - 10 mins at 60 degrees - for SMART repair, mainly on car & caravan body repair over solvent & waterbase base coats.
I HAVE used it on marine ply on the seat bases of my own boat. These then have the seat foam & covers stapled over them so not visible when seats down.
I flatted the bare wood then spray applied 2 full wet coats of clearcoat. Infra-red lamp baked for 20 mins.
Finish very rough - most of the first coat soaked straight into the wood.
Sanded with 1000 grade (coarser would be OK, I just didn't have any to hand & it's only about 3'x2'!) wet& dry used dry then 2 further full wet coats.
Further baked & then it was as good as I needed for the job. Some texture, but not rough.
If I wanted a super smooth finish I would be looking at flatting those then applying further coats.
Edited by paintman on Sunday 20th November 21:57
If you go the varnish route then be sure to get a proper marine varnish, not the B&Q type 'yacht varnish' - that doesn't last long on garden furniture never mind in a salt water environment.
Many marine varnishes recommend flatting after every second coat.
Few are suitable for use under the waterline.
Often recommended to sand a varnished finish & then apply a couple of coats of varnish on top each year to prevent peeling of the old varnish.
Many marine varnishes recommend flatting after every second coat.
Few are suitable for use under the waterline.
Often recommended to sand a varnished finish & then apply a couple of coats of varnish on top each year to prevent peeling of the old varnish.
Edited by paintman on Tuesday 22 November 17:44
Like I said, several have tried 2k clearcoat with success. All say it's harder, wears well and needs less maintenance. In the main, most use a marine varnish like Epifanes (£26/litre and about 1.5/2 litres needed along with six coats deck and hull. Now by my reckoning that's 12 days and I have to wait until its at least 18 degrees because my shed is not heated, so that's May time I reckon. None of the varnishes are for below the waterline but all builders are aware and have had no problems and let's face it the Kayak will only be in the water for a few hours at a time. Dust is clearly a problem so I've thought about building a poly tent over the kayak to help stop it falling from the ceiling and stirring up from around the workshop which is a bit tight. Can stick a fanheater inside the kayak to warm the shell, switch it off while applying the material and on when finished.
Anyway, the link below which you will probably have to paste in your browser, shows the kayak prior to rubbing down the epoxy.
https://picasaweb.google.com/105345728000840541913...
Another point is UV protection for the epoxy which evidently degrades if not protected.
Anyway, the link below which you will probably have to paste in your browser, shows the kayak prior to rubbing down the epoxy.
https://picasaweb.google.com/105345728000840541913...
Another point is UV protection for the epoxy which evidently degrades if not protected.
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