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Miyot

Ocracoke 24

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Finished stem and keel, although I still need to bevel it and round the inside corners. I'll mark it and then hog off the majority of the bevel, leaving some until after setup. Especially the area where the keel meets the stem (the gripe) as this spot can be tricky. I did a little experiment, cutting off some of the keel as I made it long. After I had glued up one side of the keel (mine is made from Douglas Fir) I read that Douglas Fir can have problems gluing with epoxy. The article said that after planning doug fir it should be sanded with 60-80 grit to open the pours of the wood as planning can cause case hardening. I knew you should sand hardwoods before gluing with epoxy but didn't consider it with doug fir, so I didn't sand the first side I glued up. After reading the article I did sand the remaining side with 80 grit. I think the sanding did help the wood absorb the epoxy a little better.

Anyhow I cut off some of the extra length and clamped it in a vise and cranked until I achieved failure. (The two outside pieces were several inches longer than the middle one, allowing me to test the strength of the glue up) The joint failed in the wood and not the glue lines. I felt better. Here are some pics.

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Hmmm . . . never heard about doug fir not liking epoxy, but rumor sez white oak is a bugger to glue and should be sanded and wiped with acetone prior to a glue-up. I prefer a sanded surface to give some separation of the parts when glued. Hint: An FAA build inspection of a wood airplane requires epoxy glue lines of a "pencil line" width. A skinny joint fails because the FAA considers it weaker, and a fat joint fails because it adds unnecessary weight, and airplanes dislike extra weight.

That stem curve is very attractive - gonna be one pretty boat.

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Fir glues fine, as do most softwoods. The only one I've tested that failed was a pressure treated pine sample, but that was a 5/4 deck board that it turns out had been treated with a water repellent waxy coating.

As for sanding, it sounds counter intuitive, but a planed surface is better. Storer has a good explanation, which is similar to what I've seen on US Forest Service literature.

http://www.storerboatplans.com/Faq/Sandingforglue.html

Sanding crushes and closes the cells......think of these as a bundle of drinking straws.......a sharp planed edge opens them up to allow deeper penetration of the epoxy. If you really want it to hold, you can brush on a coat of un-thickened epoxy on both surfaces before a layer of thickened goop.....especially so when working with end grain joints. I also add a bit of 30:100 grit walnut shell to act as a spacer to prevent excessive clamping pressure from too thin of a joint. It has the additional benefit of locking the pieces in place to prevent them from sliding around.

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Thanks Howard - makes me feel better about all the stringers that went straight from the surface planer to the glue pot because I was too lazy to sand them :-)

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www.gurit.com/files/documents/Bonding Guide.pdf This is where I got my info. Although I think if your blades are sharp, glue up with epoxy will be fine. I had no problems, as you can see. Both glue lines were stronger than the wood itself. One was planed and the other sanded with 80 grit. Getting solid info from the internet is not always easy. I had almost always gone from the planer straight to glue up and have never had any failures in any of my past projects. The above sight also recommended whipeing down doug fir with some kind of solution because it is so resinous. I did apply unthickend epoxy to both surfaces before using the microfibers. Interesting discussion. To sand or not to sand, that is the question. I think I'll sand, but not spend much time on it. And I always wet out both sides before applying the thickened epoxy. Standard operating procedure.

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I've read that before. The section in there that I found curious was this one:

Abrasion

The best bond can be obtained from wood where the bonding surfaces have been roughened. If surfaces have been planed beforehand there is a danger of the ‘case-hardening’ effect giving an insecure bond. This can happen whatever glue is used for bonding. To ensure that this does not happen roughen all planed timber by sanding 30° to the grain direction using 40 - 60 grit aluminium oxide paper.

The reference to "case hardening" was what caught my eye. I was of the opinion that related to problems associated with drying wood at different rates, with dry exteriors and high moisture interiors and different rates of shrinking, etc. leading to twists, warping, etc. Not sure how planing affects that.

Another reference is found on the Forest Service site:

http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p

Rather than downloading the entire 500 page document, I'd suggest you go for Chapters 3, 8 and 10, the later relates to adhesives. Put that by your bed side reading table and you can forget the sleeping pills!

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Hogged off some of the bevel on the keel & stem. My form for laminating the transom. I didn't want any screw holes in the transom. So I rigged some clamps and some culls to spread the load across the transom. It seemed to work well. post-2660-0-19875400-1354671624_thumb.jpgpost-2660-0-91272500-1354671643_thumb.jpgpost-2660-0-26885200-1354671663_thumb.jpg

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With the exception of one or two pieces, my Belhaven was all Douglas fir, #1 select. It always soaked up plenty of straight epoxy before the thickened glue went on. On the other hand the cypress I have been using for my 28 will never quite soaking epoxy into the grain. I have wetted out some joints two and three times before adding the thickened glue. When we glassed my cypress hull we wetted out the wood very heavy, then laid the glass. We had to keep putting the epoxy to the glass to keep it wet, until the first epoxy coat started to kick. I was telling Graham that the epoxy must have been absorbed better than an 1/8 inch into the planks.

Douglas fir would never give me second thoughts about the strength of the joint, if wetted out first or not before the glue went on. When wetting out Douglas fir I have noticed that the smooth hard grain stops absorbing epoxy pretty quick compared to the rest of the grain, but still absorbs to a point it will never fail.

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Excellent build, good job. Good information on epoxy/joint application. I've talked to the West guys alot and the information in these posts are spot on. I've had to wet out joint faces more than once many times. The joint stress to failure test sums it up. Never heard of the walnut shell thickener/filler trick before....very interesting. I'm checking these Ocracokes out. I'll build one when I can.

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On the walnut shell, these photos show a couple glue lines on 1/4" (6mm) okoume plywood. Samples on the right were epoxy coated and clamped. Sample on the left had a small amount of 30/100 walnut shell mixed into the same mix, then clamped. Resulting glue line widened to about .5 mm. This always comes out about the same thickness no matter how much clamping pressure you use, meaning for something like a curved lamination, it works pretty well to maintain the thicker glue line you want when using epoxy. Keeps you from having a thin, glue starved joint that may fly apart on you (don't ask why I know).

I can't recall exactly, but the thicker glue line between the two samples may be from using the 20/30 grit walnut shell. That leaves almost a full 1 mm glue line. If that is what you are shooting for, it would work. Again, walnut shell also has sharp, fragmented edges, so they tend to dig in and bite, which helps prevent the pieces from sliding around when the clamping pressure goes up.

Something similar to the 30/100 walnut shell is the plastic granules System 3 sells as a non-skid paint additive. Gives about the same response and thickness of glue line, and does not have the dark brown color you get from walnut shell.

Both the walnut shell and the S3 non-skid glued pieces can be worked with edge tools, although the combination of epoxy and walnut shell it going to be rough on them. You could do the same thing with various grit sizes of sand, but don't plan on working the finished piece with wood working tools unless you want a damaged tool.

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Just was reading this and wanted to interject as a long time wood worker-

 

The "case hardening" that is referred to is for material that has been planed, then stored for a while, as in lumber yard stuff. Exposure to air for a period of time is what does it.

 

Freshly planed wood is NOT casehardened- hasn't had time to do so. That's one method of getting RID of any case hardening.

 

Also- I've built many boats and masts, rudders, dagger boards, etc, including all stringers on a 35 foot trimaran, using Doug Fir- good stuff, but pick the wood so it's clear.

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Makes sense Tehani. I looked up case hardened wood and it said something along the lines I think Howard had mentioned. The outside had become drier than the inside and forms a sort of shell. The article also said you should plane both sides of a case hardened board or it is liable to cup and or twist. Scarfed up my side stringers, chine and intermediate sheer. Ten 27ft boards. I made them a little long, just in case. You need some room to work with these. Now to plane them to final dimension and round the inside corners.

Were in for some weather here and I have to set the planer in the door and work outside because of their length. Supposed to blow a gale, which will hold me up a few days. All well, back to work on the basement.

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Set up underway. Now I'm worried. Things are really going well. I couldn't be more pleased. The marks on the keel and stem are lining up just right with the frames as lined off on the jig. Square and plumb. I should complete setup in the next few days and start bending battens around and cutting notches. I'm really enjoying this build. Here are some pics.post-2660-0-24108600-1356577079_thumb.jpgpost-2660-0-67325700-1356577109_thumb.jpgpost-2660-0-18321000-1356577130_thumb.jpgpost-2660-0-95173300-1356577157_thumb.jpg

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All stations on except for transom. Now some adjustments and a bunch of protective tape so I don't glue things that shouldn't be. I have to stiffen up some of the stations with some timber. Lots of work. Getting the transom just right may be a little tricky. Moving on.post-2660-0-02997800-1356665863_thumb.jpgpost-2660-0-53685600-1356665881_thumb.jpg

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Began fairing, among some other things. Kind of intimidating, I didn't know where to begin. So I started at the transom and will move forward. I'm finding a few small problems with my setup, but nothing to far out of whack. Now this is really fun and I can hardly pull myself away from it. I'm finally building the boat.

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Still some humps and dips, but the bottom is getting close to fair. I have finished installing the vertical stiffeners in the bottom and have the longitudinal s left to do. After they are done I will install the chine batten and then finish fairing the bottom. Here are some pics of progress.post-2660-0-90984600-1358736329_thumb.jpgpost-2660-0-64954700-1358736359_thumb.jpgpost-2660-0-91717400-1358736387_thumb.jpgpost-2660-0-15703500-1358736432_thumb.jpgpost-2660-0-42373300-1358736508_thumb.jpg

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