Sealing wood boats prior to assembly

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David Santistevan

Well-Known Member
Joined
Aug 5, 2011
Messages
1,368
I am working on a new boat an decided to take a different approach. To minimize the amount of epoxy sealer in the boat I decided to actually seal the wood parts before I assembled them. Anyone else done this ? Are there any drawbacks ?

Thanks,

D
 
I would think it would adversely effect the strength of each joint. As once a part is "sealed" it can no longer wick the epoxy into the part.
 
I have to agree with Rodney on this one. That being said, what you COULD do is tape off the areas where wood is epoxied together and spread a thin coating over the rest. Now you would have the majority of the material covered and still have bare wood for the epoxy to soak in to so strength wouldn't be compromised. This would, obviously, require more work and time prepping for the seal coat but it would also give you the results you are looking for
 
I would think it would adversely effect the strength of each joint. As once a part is "sealed" it can no longer wick the epoxy into the part.
Bingo!!!!!!!!!!!! David, what I've done is tack with thin CA it wicks into the bare wood better than the thicker stuff. Buy a couple cheap "bondo spreaders" wherever they sell automotive paint and body work supplies and cut them into various size strips. Mix whatever epoxy you are using and brush a little onto the areas you want to seal and spread it thin with the cut down spreaders. If you do slobber a bit onto the tops of stringers or bulkheads just wipe it off and sand with some 180 grit when it dries. Tower hobbies makes some thin masking tape also.
 
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I thought about that but consider, the epoxy I used to seal already penetrated the wood. In the end it is the expoxy itself that creates the bond. So properly prepped epoxy when glued should ahere as well as any.
 
What Im saying is, I would think a joint that was allowed to absorb the epoxy into the substrate at the time of gluing would be a stronger bond then just epoxy to epoxy.
 
I seal both sides of the plywood sheeting with West Systems and sand the sheeting before gluing to foam or frames. I use epoxy for construction. I could be wrong, but I don't think epoxy wicks very much, if at all.

JD
 
I thought about that but consider, the epoxy I used to seal already penetrated the wood. In the end it is the expoxy itself that creates the bond. So properly prepped epoxy when glued should ahere as well as any.
Not so, Read Tim's post and note the words "textured surface". I learned my lesson on my Sport 40. I epoxied a pair of hardwood blocks to the floor of the hull to keep the radio box from moving fore and aft and attached hooks for rubber bands to the blocks to hold it down. I did not think to roughen up or sand the spots on the hull bottom- just washed them off with iso Alky. One of the blocks popped loose while the boat was sitting in the pits!!!! Can you imagine what would have happened if the boat was at full song with the box going back and forth and up and down? The epoxy bonded well to the bare wood but not a bit of it bonded to the smooth hull.
 
I don't think epoxy wicks into the wood either.. That is why I use CA.. could be wrong,. but it works for me..
 
The thinner the CA the more wicking you will see. Same with the Epoxy,. Epoxy does not tend to penetrate the wood grain as thin CA will. CA bond will tend to be less tolerant of vibration than Epoxy, less flexible when cured. Choose your weakness,..

Anthony Marquart

Global Process Leader for Adhesives Applications

EMA
 
What is interesting here is that I am using a very thin finishing resin that I let soak into the wood for some time. It gets a very good penetration as I can see it on the cross sections. As far as adhesion I decided to take a long look at this for my own curiosity and as long as it is clean and not perfectly smooth it appears it does not weaken the bond.

Thanks for the info guys.

D
 
I use Zpozy finishing resin for sealing,. It flows real well when you put a heat gun or hot blow dryer to it. The penetration is really a function of the viscosity of the adhesives. if it's thin like water it will penetrate, but also take many coats to build up,.. if that is what your looking for. There can be some chemical interactions that aid or hinder penetration as well. The surface energy of the substrate dictates the wetting characteristics,.
 
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I used to thin my epoxy for sealing with alcohol which gave me wonderful penetration, however after some discussion on here I did some reading and thinning the epoxy will dramatically take away from it's ability to resist water. I have used Z Poxy but like you said it is still pretty thick for sealing. My current approach is to use a finishing epoxy that is fairly thin without thinning. I generously coat my parts and let them set for about 30 minutes. I then take paper towels and wipe all the excess epoxy off the parts. This allows me to get it out of places it should be and get the thinnest coat possible. Then with a simple scraping with a single edge blade they are smooth as glass and fully sealed with as little epoxy as possible. I have built a couple of boat this way and they are very light and very sealed. This is the first time I have sealed the part prior to assembly.

As a follow up I have done a lot of reading about epoxy mechanics and chemistry and there is no difference in strength of the bond gluing plain wood and epoxy sealed wood so I may do more of this.

D
 
Bruce, funny your should mention Systems Three because that is the very stuff I am using for this project and so far I really like it.

D
 
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