Presaturating a wooden hull

[Roly]

I am about to glass my strip planker with triaxial.
Several publications recommend several coats to fully seal the hull,de-blush, abraid and then glass.
My gut feel is to heat the hull,and to apply a wet coat and then prewet the
glass on a table,rolling the wet glass onto a pvc tube and then onto the wet hull. Excess resin air can be removed with squeegee/roller.
Saves a step and a mechanical bond to the prvious surface.
Am I barking up the wrong tree here?

[nero]

If you think about it enough, you can find even a more complicated and difficult way to fiberglass something. smile

And what about the dry method. Lay the glass on the wood. Mix up the epoxy. Pour it on, then spread it. Then squeege the excess.

You need to do test samples on the same wood as your hull. Afterwords, try to pull off the glass. This will tell you if you what method works best, given the epoxy/glass/wood you have.



I

[gonzo]

Ideally you should laminate in only one operation. If you can't do it all at once, it is better to do as large a section as possible. Secondary bonds are not as good and it adds a lot of work to dewax.

[frosh]

It is best to bond the glass directly to the wood subtrate than over a few coats of resin. However many resins being viscous will not penetrate the wood sufficiently. You can buy epoxy ( I assume that you want the highest quality result, so use epoxy) resin thinners that also have the ability to act as a wood preservative. I have sheathed wood in glass many times and usually use the wet method. First I paint the resin mixed with thinner/preservative onto the wood fairly sparingly, then immediately lay the glass over the top. Next using full strength resin continue wetting out the glass until nearly fully covering the weave. Do the whole boat in one operation ideally. When this layer is partly cured, trim excess glass off the edges with a box knife, and immediately apply another layer of resin to now fill the weave completely. The next step depends on whether you are aiming for a clear or painted finish. There are plenty of books on the subject of finishing. Hope that this helps.

[Roly]

Thanks guys. Pretty much what I had in mind bar the thinning. I will probably heat the batch that goes on the hull first, so it is thinner and penetrates better. Also will have the hull cooling so will suck a bit of resin in hopefully. I will crank the fan heaters up the night before and turn them off progressively
section by section. I have access to a wetout machine, but sounds like a lot of cleaning. We will probably wet out on a plastic covered table so will use a bit extra resin. Rather that than a dry interface. 810gm triaxial is reasonably
thick so I don't want any dry areas. Boat has been restrip planked to above the WL, 34' loa. Getting quite excited with this step!

PS I hate the smell of xylene and are a bit solvent intolerant. I have used a bit of epoxy diluted with xylene & toluene + preservative for the old keelson.
May just dose that area as all the rest is tiptop.
Cheers!

[DanishBagger]

Roly, FWIW, I have begun a similar project to yours, and from what I can tell (from all the reading and so forth), it won't soak in better because the hull is cold.
No, what will happen is, that when the (warm) epoxy hits the cold wood it will be cooled down immediately. The Gougeon brothers (and others), recommend heating both. And that seems to make sense (to me, anyways).

There is no extra capilary action from having a cold hull and warm epoxy. If anything, having them at different temperatures will make it harder to work with, as the epoxy will have different temperatures over an area (some places, the hull will be able to soak up more heat than other places).

If both are warm, on the other hand (same temperature if possible) you will have a consistent consistency (so to speak), and a consistent hardening time. And if anything, since the epoxy and wood is warm, it's more likely to soak in better.

[frosh]

Heating resin will dramatically shorten usable working time with the catalysed resin. This will put you under pressure to work really quick, probably having it gel while you have plenty left in your working pot, and you will likely have to compromise your workmanship. Is this really what you want to do? You have mentioned Xylene and Toluene solvents; are you refering to polyester resin? I use an epoxy resin called Bote Cote made in Australia and they have a non volatile, non- solvent user friendly thinner/wood preserver. You might be able to get something similar in your part of the world. You can check out the following web site to read about it. www.boatcraft.com.au/bc_products.html

[Roly]

My last post was somewhat scambled.
What I planned to do was put three fan heaters in the hull,aft,amidships & forward the evening before we glass.
I will have all my resin at 25deg C with electric heaters.
Just before we wet the hull at 1st panel section, I will switch off that heater
thus that section will slowly start to cool and will stop out-gassing, rather the air in the wood will be contracting, hopefully increasing the resin uptake.
I am glassing across the hull with the 0deg at 90deg to the strip plank.
as a section is complete I will turn off the next heater. Make sense? Or do you see potential problems?

Any links to pics of your project?

I will update the rough faired hull pics of "Pukka" this weekend.
http://www.imagestation.com/album/in...?id=2120245606

[DanishBagger]

h, like that - seems like a good idea. Remember to get someone to help you with the cloth. Slippery son of a ...


I don't have any real pictures yet (I'm not that that far yet), but I like yours, though

Personally, I won't be using cloth over my nice mahogany, I have asked around here, and gotten loads of help, and it turns out that it is not needed on my small dinghy, which (and here comes something utterly unrelated) has a centerboard I have calculated will weigh around 250kgs if it's 32mm thick. Ouch!


Andre

Edit:West Epoxy recommends working with their gooey stuff at temperatures between 16 and 21 degrees centigrade, so maybe 25 degrees is a tad high?

[Roly]

Gidday frosh,
I am using West systems with slow hardner.
I have heard good things about Bote-cote, not available here . We used to have a product called Everdure, but they have pulled the preservative in it. It has been around for years and many people use to swear by it. You also have CPES which is a great product used correctly.Also not available here.
I am confident we will get the pot life right---thanks for the warning.

My main question was that of precoat to cure of the hull and the secondary bond thing. Seems a lot of experienced epoxy laminators are shy of thinner,dilutants, such as xylene, toluol, phenol etc.

http://www.seqair.com/skunkworks/Glu.../Thinning.html

[Roly]

Thanks for that Andre, I will turn down the heat.

[yokebutt]

Roly,

Epoxy resin with solvents is garbage, heat the substrate and resin instead.

For laminating overhead you want to use 6 or 10 ounce cloth, many layers if neccessary, with those fabrics you can wet the surface and stick the glass on without it falling down on your head. (I recommend using three people, fast hardener and a mexican radio station)

Yoke.

[Roly]

(I recommend using three people, fast hardener and a mexican radio station)Love it!
I've got 4 and the hull is turned over.
Fast hardner?

[frosh]

There is a world of difference in using volatile solvents to thin resin and non-volatile specific purpose designed thinners. It is a definite no no to use resin thinned with volatile solvent such as acetone directly onto timber. If you dont care about penetration of the resin into the timber then forget all about it.
Regarding heating the resin, this is a very delicate balancing act. One winter I built a cardboard box with 2 compartments, one for the resin and the other containing a 25 watt globe which was constantly on. The temperature of the resin was always about right so had the right viscosity. Any more heat than this will shorten your pot life a lot!! Just trying to be helpful here.

[Roly]

And it is appreciated! I currently have the (20L pails) wrapped in an electric blanket, but the temp is too hard to control. I gonna make a box with a light as you suggested. Ta,
Roly