Bad Scarf Joints

COK, So I'm building my first boat, a Wood Duck 12 from plans only.

My scarf joints have come out embarrasingly aweful. Looking for options to hide them. One of my ideas involves paint.  Please, Looking for other suggestions because I was originally planning to do a full boat wood varnish finish. 

If I fill gaps with wood flour epoxy and spread that thin like a dry waller would spackle over a tape joint,... would that help?

Does the Glass stage make it blend in?

 

 

 


13 replies:

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RE: Bad Scarf Joints

Yakaroo,

Anyone who's read any of my posts knows I'm a big fan of one-part polyurethane paint. As my puzzle joints were executed early in my project, they were not the best examples of my work. I ended up using a marine "bondo" (my build partner restores old cars) under the glass cloth. One cannot see them on the finished boat. The key issue is using a reasonably sized sanding block/board to keep things fair. Another point is that epoxy is an excellent primer for Interlux Brightsides, so you can pass on the PreKote if you don't need its high-build properties.

Cheers,

Dick

RE: Bad Scarf Joints

Aaah, Marine Bondo,  now that sounds like a good idea.   Thanks Dick  

So with partially painted boats, what is the order of application.

Is this right;  Bondo, Paint, Glass/Epoxy,  and then do you varnish back over the painted areas?

Thanks again

Yak

 

RE: Bad Scarf Joints

   and I'm going for the Glossy paint look. So do I need to use high gloss paint, or will the epoxy create that glossy look for me?

 

RE: Bad Scarf Joints

Ummm... unless all my prior experience at building things is wrong, the proper way to complete an assembled project is wood (mostly plywood for CLC kits) then epoxy+ fiberglass reinforcement, then marine Bondo (if necessary) followed by varnish OR paint. The last two shouldn't both be used, it's either/or.

And epoxy over either/or isn't a good idea at all.

 

RE: Bad Scarf Joints

 

Have the pieces that were joined already been shaped into the finished dimensions? If not, then just cut out the bad scarf and start over. If you have already cut the shapes to final dimensions I would still cut out the scarf and but then add a new piece in between the previiously cut scarf, sort of like an oversized "dutchman". If you are working from themplates this should be straightforward. Even if you lofted the shapes you should still be able to insert a new section fairly easily.

I know people use it but Bondo is not the best idea. It's not designed for immersion in water and since it's made of polyester, it might not  be compatible with your epoxy and may not bond well. A well executed scarf is not only a mark of craftmanship but is stronger than a poorly executed one.  

 

RE: Bad Scarf Joints

   I built the CH17 from a kit. After I glassed the interior and turned the hull over it had gaps in the seams. I filled the seams again with epoxy and wood flower, then the real small holes I used wood putty.Then the nail holes looked bad so I filled over them with wood putty, . Sanding down smooth. Then I stained it with Water based stain, then sanded with a block sander using straight lines and no swirl's in the wood.  Then the glass work began, it was a perfect finish. No putty or wood flower could be seen under the glass. Now the tops of those nasty nails that are visable I mixed up one pump of Epoxy and added black pigment and painted over every nail making a perfect circle. Then the varnish work began, it looks great.

RE: Bad Scarf Joints

   And yes bondo should never be used in water based toys or boats, one person I meet used bondo on the boat he has and it peeled off on his first run, he learned the hard way.

RE: Bad Scarf Joints

Folks, I said marine bondo. I don't remember the brand, but it's not called Bondo and is formulated for marine use. It's also under glass and epoxy. In the 2 years my boat's been used, there have been no issues.

RE: Bad Scarf Joints

You can make your own from phenolic microballoons and epoxy/hardener. That lets you vary the texture from a runny slurry to a very stiff frosting.

Microballoon mixes are very strong in compression but weaker in shear than other fillers. That means that they are good for filling the weave and fairing, but should not be used for structural purposes, like joint adhesives. Once cured, they are very easy to sand.

Good luck,

Laszlo

RE: Bad Scarf Joints

   Here is some advise on the use of Bondo and wood in the woodenboat forum. Not a wise choice to use. Even Marine Bondo. Besides, bondo won't work on raw wood. I'm done here, do as you wish.

 

http://forum.woodenboat.com/showthread.php?95312-Big-Bad-Bondo

 

RE: Bad Scarf Joints

   Just to be clear, Bondo is the brand name of a readily available auto body filler. I suppose the name has been genericized to a certain extent but this product should not be used in a marine environment. Whenever I hear builders say they using Bondo on their boats I cringe. We should strive to use correct names lest strife, turmoil and darkness prevail.

RE: Bad Scarf Joints

Hi all,

Apparently boatbuilding has a lot in common with politics and religion. We all have our opinions and we're passionate about them.

Perhaps I should not have used the term "Bondo". I too have seen horrendous Bondo patch and fill jobs on cars. What I was talking about was using a fairing compound, not filling major gaps and holes. CLC recommends priming with Intelux PreKote high-build primer (which you can hear suck water out of the air). If you understand its limitations, it works beautifully under Interlux Brightsides.

I was talking about the next order in fairing compounds. The stuff I was given by a knowledgeable friend was developed for fairing hulls on fiberglass boats. That's why I used the term "marine". It adhered beautifully to the plywood. In no place was it even 1/32 inches thick. After curing, it sanded and feathered perfectly and was then covered by glass, epoxy resin, and polyurethane paint. So far, it has endured 2 seasons of heavy use on saltwater with absolutely no signs of failure and still cannot be seen on the boat. To know where it is I have to dig out a photo taken before priming and painting.

As to the WoodenBoat link, if one reads the whole thread, it contains posts of successful professional use of the same kind of compound I used. Not everything is black and white and details matter. By the way, Lazlo's recommendation of epoxy resin and microballons, works great too. That's what I uses on the same puzzle joint on the inside of the boat (because it was not going to be covered with glass).

Cheers,

Dick

RE: Bad Scarf Joints

Hi guys, Im back   

My WD12 is coming together, Ill be ready to glass soon.

Through this thread, it seems we have a difference of opinion, and Im still not sure I have a diffinative answer.  So does paint go on under glass? If it goes on last, wouldnt it scratch off when you rub a rock or tree?

And Dick, did you ever recall that product name?

Thanks Again

Yak

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