Thread: Ideas for my green island 15....finish, strength or stupidity?

If gluing with epoxy you don't need any permanent screws at all.

Dowels will be way weaker than screws because they don't have heads to hold the ply on.

Satin varnishes are usually meant for interior use so don't have UV filters. You can buy "flattening agent" and add it to a spar varnish (which has good UV filters)

Best wishes
Michael Storer

Epoxy alone needs to be protected from UV or it will eventually chalk up, turn black and be destroyed. It has to be over coated with a clear of some sort. The cheapest is the single part polyurethanes and these are also some of the easiest to apply. Next up the list is oil based varnish, the traditional stuff, which usually costs more then the hardware store variety of polyurethane. The polyurethane will have better UV protection in most cases. Next up the list are the two part polyurethanes and these aren't cheap, but work exceptionally well and are very durable.


You can install "dumb sheaves" in the end of spars, but wood does a fairly good job of this, for a lot less trouble and more importantly less weight aloft (something to be avoided at all costs). I like to use HDPE in these applications, instead of metal. It's lighter, it's self lubricating, it's inert, so it doesn't rust or rot and very easy to machine. In places where a dumb sheave is installed, all most all will benefit from an actual rotating sheave. Again HDPE comes to the rescue and I'll install a sheave (at least 3 times the line diameter, usually much more) on a small axle, that makes very little friction. You're right though, some places all you need is a "fair lead" which is fine.

Flat head screws have more holding power then you realize and are far superior then dowels. Even if you wedged the dowels (drive a wedge in the split top) the screw will easily have better pull out and hold down strength.

You can use a flattening agent or you could just use a high quality gloss clear, building it up several layers thick then very lightly and with 1200 or higher grit wet/dry paper (working wet, with the grain of course) dull the gloss to the desired amount. The nice thing about this method is you can change your mind and buff it back to a high gloss. A flattening agent doesn't give you this option.

Thank you both for the words of wisdom. I have to say that despite your valid points about the dowels i am still tempted use them (i think it comes under the catagory of "You can give a man your best advise but the stubborn ones have to work it out from their own mistakes') I will be epoxying all the joins anyway so Boatmik your point about the screws not being needed is spot on but if i have to fill a temporary screw hole i might as well have a dowel in its place a feature. i'll keep you posted on how good or bad it goes. and post some pics when i get there.

I spoke to the guys at Boatcraft Pacific up here in Brisbane after reading your comments about the epoxy being uv affected and for some reason i thought it was safe to use as a finished surface so thanks for the heads up. I will still try and go for the satin finish but i might put in a bit of r&d to see which method suits me best.

I like your advice and the warning about extra weight up high is much appreciated. I think from memory the end of the boom is the highest point i was considering sleeving. I was thinking about using HDPE or a similar material as a cap for the base of the mast and around the mast shroud.

if you can think of any other points/hints or helpful tips, i'd love to hear them. I am always happy to learn from other ppls experiences and mistakes rather than making them myself(appart from the dowel).

Cheers Andrew

Hi Andrew,

How about a solid technical reason not to use dowels. They add to the structure the possibility of wicking water straight into the structure should the ends be exposed. To avoid this they should be recessed with some epoxy bog over the top. They will have negligible contact with the plywood at all.

If something opens up a potential problem and does not add anything at all positive you should consider whether it is worthwhile using it at all.

Best wishes
Michael

Welcome to the forum, you'd better post pictures of your progress (my idea of )

I'm with Mik and PAR here, dowels aren't a good idea. Look at any mass produced furniture and see where it fails.. the bloody dowels!!!! (Unless it's something made by Ikea with those clever little metal widgets and then they pull out of the crappy timber they use)

In areas where the epoxy fillet can't be used, the screw (or maybe a roved rivet) is the way to go and can look superb.


(make sure the slots are aligned though)

You've received advice from two very knowledgable fellas - Boatmik and PAR - who seem to be on some kind of weird 'Pay it back' mission. They seem to enjoy helping out with advice on both the quick, economical, way of doing things... as well as the expensive, excellence at all costs, approach.

hehehe for a laugh, ask for the best way of doing this on the wooden boat forum and watch the posts fly as the traditionalists go head to head with the modern approach

Ooh, and your intention regarding the epoxy coating

Originally Posted by 79andrew

My first idea is to go with a satin finish on the decks, seat tops floors and spars. I am looking at achieving this by applying 3-4 coats of boat-cote epoxy and the sanding the gloss back with 400+ grit paper and then steel wool.

Is sound, in that you will be completely encapsulating the timber and preventing any chance of rot/damage, but may be a case of overkill in one respect, insufficient in another.

Three or four coats of epoxy by itself won't do all that much more than one good coat. Epoxy is quite soft by itself and doesn't do a lot to resisting abrasion, add a suitable cloth to it and now you're talking.

It's still going to decompose in the sun... it can't handle UV. So your going to have to protect it with either paint or some kind of clear finish.

Your best protection wil be a high gloss finish. Satin and matt paints/varnishes etc are all based on high gloss with some form of flattening agent which unfortunately aids in the deterioration of the finish over time. Problem with high gloss is that it requires meticulous preparation to get a quality finish, but it sounds like you're prepared to do that anyway.

Whichever way you go, remember to post some pictures of your progress

Howdy, generally three coats of epoxy are recommended. Some can get by with just a couple if they are careful not to sand through.

Problem is a lot of the first coat is absorbed so means that some areas get dry.

WEST who did most of the serious scientific research on epoxies recommend three coats.

MIK

Originally Posted by Darce

Three or four coats of epoxy by itself won't do all that much more than one good coat. Epoxy is quite soft by itself and doesn't do a lot to resisting abrasion, add a suitable cloth to it and now you're talking.

I used to think this way too ... and it stopped me coating things.
Why?
Because epoxy is not like a paint or a varnish. It doesn't lie down flat or behave in any manner likely to allow one coat to work. If you slather on enough epoxy to coat the timber and to allow for any soakage, you'll wind up with an uneven surface that takes a loooooooot of sanding and wastes a lot of epoxy.

In contrast, the 'three coats, wet on wet' system works because you deliberately put on very thin coats of epoxy by using such tools as scrapers, squeegees and rollers. The first layer soaks in almost completely and you wind up with a matt, rough surface. The second layer goes most of the way to giving a fully sealed surface, the third finishes the process. If you've refined the technique enough, you may be looking for a fourth coat to get that wet look. You put successive coats on with the previous one is tacky so you're getting a chemical bond between the coats.

There are three benefits to putting on very thin layers:
- the first is cost. As an example, the final layer on the rowboat sides (two sides, 15' long, 2' wide) needed only two pumps of West to do the entire two sides, the first coat needed maybe six.
- the second is that you put on only as much epoxy as needed
- third, you get a much flatter finish that is easier to sand effectively

If you put on a thicker layer, as will happen if you don't scrape it out or if you use a brush (even a brush cut back to 1cm long bristles still puts on a lot of epoxy), you wind up with an uneven layer that needs a lot of sanding and you will either waste of lot of the stuff and/or sand through to the timber trying to get it smooth. One, thick coat is not worth the effort you put into it.

Interestingly, the 'one thick layer' is almost certainly where the idea that epoxy coating is soft comes from - you do not need to coat your boat with glass cloth or similar unless working over a very abbrasive surface such as concrete or sharp stones.

Richard

Originally Posted by 79andrew

My first idea is to go with a satin finish on the decks, seat tops floors and spars. I am looking at achieving this by applying 3-4 coats of boat-cote epoxy and the sanding the gloss back with 400+ grit paper and then steel wool. I tried with a rifle stock I was restoring and the affect was silky smooth and very nice. I know it means alot of time on the sand paper but I think the effect is work it.

Note, you're talking about a looooot more sanding than a rifle stock - boats is big brutes

Do your 3-4 coats, but regard these only as a base layer. You're going to need much coarser paper than 400 grit - I've been using 120 on my 15' rowboat and despite using suction on the sander, still needed three sanding discs per side. Mind you, part of that was because I left the things for a week or so and let the epoxy harden fully, if you get to it after a couple of days, it's much easier to sand, still sands smoothly and you don't go broke paying for sanding discs. Leave it from one weekend to another and you'll start to notice why doing the sanding mid week was better

As Darce pointed out earlier, epoxy isn't UV resistant so you'll need to layer on a goodly amount of varnish to protect it.

Use your 3 coats of very thin epoxy to provide a stable base for your varnish, then use varnish to give your clear look. Others (PAR I think), have commented on how satin finishes aren't very strong or waterproof and made the suggestion to use gloss varnish for the base layers and then use satin for the final layer - you could scuff a gloss finish too I suppose.

I'd counsell against anything that takes a lot of effort - these methods work on small jobs like rifle butts but boats are really really big. A 15 footer has massive areas that need attention and even work boat finishes such as I specialise in require a lot of effort. If you start with a technique that requires a lot of effort and patience, you can almost guarantee that by the end of it, you won't be doing it properly.

Also remember that boats live in a really hostile enviroment - that fine, beautiful finish will be scarred by the first time you get too close to rock or wall ... and that'll probably happen on the first trip, even just getting her on and off the trailer. By all means make her as beautiful as you feel capable, but make sure you understand that 'maintenace' means fixing up scars ... on a distressingly regular basis (my first six months with Sixpence involved getting out the can of paint for touch ups after every use )

Richard

hey guys

Thanks for your replies. It has certainly made me think through my processes and ideas alot more. I hope i didn't come across as arrogant with my reply about the dowels as i truely appreciate your imput.

Boatmik, your comment...
"If something opens up a potential problem and does not add anything at all positive you should consider whether it is worthwhile using it at all."
makes the most sense to me and with that in mind i will scratch the dowel idea. The only problem i now have is that i really hate the look of exposed stainless screwheads. While the epoxy glue is strong enough in its own right once properly cured, there are areas where i will need to use screws if i am not to use dowels. if anyone has any ideas other than filling over the screw heads with epoxy filler than i'd love to hear them.

As far as epoxy goes, i am using boat-cote for my project. On all the first coats i am planning to use their TPRDA which thins the epoxy and causes it to draw deeper into the timber. If anyone has any experience with using it and can give me any tips on application i'd appreciate it.

After reading all the comment about the satin finish. i have decided i would be better off putting the extra time into surface preperation to get a really nice gloss finish.

My father has accused my of 'over thinking' what should be a fairly simply project but I have been a handmake jeweller for over 12yrs and I cant help but be a perfectionist. I guess i also want to cut my teeth on the green island 15 with the idea of sinking them into something like the 8m trailerable motorlaunch by David Payne later on or a resto job on something similar.

If those of you with more experience can think of any other ideas that will help me along or add to the final finish...i'm all ears

Cheers

Andrew

Originally Posted by 79andrew

As far as epoxy goes, i am using boat-cote for my project. On all the first coats i am planning to use their TPRDA which thins the epoxy and causes it to draw deeper into the timber. If anyone has any experience with using it and can give me any tips on application i'd appreciate it.

DO A SEARCH

Just teasing, especially seeing a search may not turn up the discussions depite this being something that gets discussed a bit on boat forums.

Basically, thinning your epoxy does nothing positive. It does not draw the epoxy further into the timber - the stuff doesn't sink in very far at any time and thinners don't help. What thinners do do however, is evaporate as the epoxy sets to leave wormholes within the epoxy, thus making it no longer waterproof.

You'll find unthinned epoxy easy enough to apply using a roller and/or scraper (I use both). Save the thinners for cleaning stuff ... or better still, buy a bottle of vinegar to clean your hands, use single use brushes/rollers/mixing sticks/etc and save some money on the thinners.

Richard

Hey Richard

I probably should have been more specific about the job of the TPRDA. It is not an evaporative thinner. it's easier if i just post the links

http://boatcraft.com.au/bc_products.html#TPA
http://boatcraft.com.au/Shop/index.p...dex&cPath=1_46

let me know what you think

Cheers

A

There you go, a whole thread devoted to it. Thinning with TPDRA

Richard

HAHA...I can see why you suggested it would be easier if i just did a search! It made for some interesting and informative reading though. Thanks for the link.

Cheers
A