mustangermatt

Don't go cheap on the wood. For my CS 17 the cost of plywood is about 20% of the total cost. If you save 10% on the wood, you are only knocking about 2% off the total price of materials. Woo Hoo :-) It is not worth the risk of a delaminated boat or worse. When you start bending the bow pieces as you go 3-d you'll be glad you spent the extra 2%. One void someplace in the bow will ruin your whole day when it breaks while your bending it. On the other hand if your working with good materials this stage is one of the most enjoyable. Also remember that the plywood is the primary structural member of this boat, not just a skin.

From what I have read glued lapstrake like welsfords boats is no more difficult than the stitch and glue I did on my coresound. In fact my next boat will definitely be glued lap because I like doing the wood work a whole lot better than the glass work :-)

I actually didn't use clamps for the inwales, I used sheet rock screws. Starting at the stern I drilled a pilot hole, put in a screw, drilled a couple more, put in screws, all the way to the bow. Then I pulled all the screws, glued the inwale and the ply, started at the stern and screwed it back in. I did it by myself and had no problems, but I might just be lucky :-) A helper would certainly make life easier and give you someone to talk to while you work as a bonus.

Actually, I did exactly the same thing. And I used two pieces. Looking at the structure I figured that you don't get the strength from the keel batten itself since a flat sawn 1x4 laid flat in the bilge is not exactly rigid in and of itself. But it will hold the V form in the bottom in the area where it is shallow, and the V form in the bottom IS very rigid. This will prevent the "oil can" effect on the reletively flat run aft. The aft bulkhead does the same thing at the keel batten joint. I originally planned on installing a knee on both sides of the bulkhead on the batten, but could not induce any flex in the bottom before they were installed so I dropped that idea as overkill. I have already added extra framing and weight in my boat. Of course this is just my opinion and I am sure Graham will have the input that really matters :-)

I did see a Bolger design (I think it was Bolger anyway) with a trolling motor lower unit built/faired into the trailing edge of the rudder. The advantage is it would require less sophisticated modifications than your "trap door" idea. The disadvantage is that your dragging the prop around while sailing. Both are very innovative solutions. Independant thought like yours is what keeps the building process interesting. My personal reason for not doing either is my enjoyment of this boat depends on it's simplicity.

I layed glass on each side and JUST around the edges so they had twice as many layers as the sides. The best way I found to do this was stretch an oversize piece of glass cloth (6 oz in my case) over and around the wetted side and then cut off the extra with a razor knife after it had partially cured. This of course means you can only do about one layer per day.

Centerboard trunk and all its framing are done. And I got the spruce for masts and booms today! I used 6 oz glass for the bilges, and am applying the final epoxy on the interior today. I will start priming and painting the interior this week, and then on to the decks :-) [attachment over 4 years old deleted by admin]

A bit off topic, but in coming up with my foam board I did some failure testing with glassed wood. I found in the cases of soft woods that were fiberglassed the wood is more elastic so would bend further before failing than fiberglass under tension. Bending two pieces of fir the same amount, you eventually hear a pop on the glassed one. This is the epoxy cracking. Keep bending and the glass fibers fail and the wood fails spectacularly. The wood by itself is much less impressive when the outside fibers start to tear causing that familiar splitting tearing sound. But the bare wood also bends further with considerably less force. I didn't learn a whole lot new but had a lot of fun :-)

My centerboard is made of foam and fiberglass although I took a little heat when I did this. Too bouyant, not strong enough, etc :-). For comparison the 1.6" thick foam cored board I built with 1/16" skins has an inertia moment (I) of .886 to the 4th power. A 1" solid fiberglass board would have an I of .167 to the 4th power. If you think of the I as how much leverage the fibers have to resist tension, that is a huge difference. In your case the solid 1" cedar board would have an I of .167 to the 4th power again. If you put 1/16" skins on the board (3 layers of 8oz. glass?) I would equal .237 to the 4th power. A significant increase in strength, but enough to equal douglas fir? Maybe... but I will warn you that putting that much glass on and coming out with something decent was a hell of a lot of work. From my experience I would recommend sticking with Grahams recommendation unless you have some specific reason not to. I was shooting for a 10% - 12% chord ratio which would have been very difficult to fabricate in solid wood.

Yes, I put the bunks at each bulkhead, the center bunk being at the temp bulkhead. I used the bulkheads as a pattern for the bunks so they are a snug fit. The center bunk is dropped down to allow for the run of the keel. I don't remember exactly how much. I found the measurement in an old thread that Graham had posted.

I have been working for three weeks to get everything finished on the centerboard and trunk. There were a number of modifications to accomadate the increase in sail area on the mizzen and thicker chord of the centerboard. The trunk is 3 1/2" aft of where Graham originally put it, and about 1/2" wider (the centerboard is 1.6 inches for a 10% chord ratio). It was pretty nerve racking to cut the slot in the bottom. When my teenage daughter first saw it her reaction was "OH M'gosh, whose idea was that?" :-) I of course immediately pointed the finger at Graham. In another thread there was discussion about plywood movement after cutting the slot. I found that the outboard edge certainly did want to drop down, but in my case it was nicely contained by the center bunk in my cradle. I highly recommend three supports along the bottom while building. That center support has saved more headaches :-) Everything is all glued up now, very exciting (for me anyway). I will post pictures this evening.

It is actually a little disturbing to me to see somebody go to this great a length trying to fill that empty hole inside himself. A very impressive piece of engineering, too bad it is basically useless.

I noticed everyone seems to be smiling :-) That is a very nice looking boat.

I finally got around to posting a picture. This is after the last coat of epoxy , but no paint yet. I did another strength test today, I put the board on the edge of a bench and had my tenage daughter stand on one side while I stood on the other (had to offset it just a little :-) In short it held a little over three hundred pounds without flexing. I am pretty comfortable that it won't break :-) I will be using the same technique for the rudder. I am going to test sail the boat before I decide whether or not to add weight. [attachment over 4 years old deleted by admin]

Got the last layer of glass on the skins. Standing in the middle of the board (190lbs) I got virtually no deflection. VERY tough :-) It is not as light as I originally thought it would be. It has three layers of six ounce glass each side and four on the leading and trailing edges. I think this thing is going to work out well.

And at this point my paint of choice is going to be the oil based enamel I am familiar with, the type that has never left a sticky gooey mess on my boat. Didn't dry on the stick either.

I don't have much shallow water around here. And when it does come up it does it fast. Big ugly rocks and all :shock: But that is another point in favor of the weight.

I agree that humidity wasn't the problem. We had a high pressure front which around here means dry air and sunshine. I had sanded the surface with 180 then 400 so I don't think blush was a problem. I am using System three and have never found ANY blush yet. I thought I might have put it on too thick, but when I scraped it off tonight I ruled that out. I could see through to the epoxy in places, still gooey four days later. I guess it is possible I got a bad batch, but I'm sure not going to try another can! I have painted a lot of boats and never saw anything like this. I have mostly used interlux products in the past, enamel and interthane two part. The most frustrating part is having to clean up the mess :-)

The bouyancy is minimal, somewhere in the neighborhood of 8 lbs, there isn't that much foam in there :-) I did toy with the idea of weighting it but decided that would affect beaching etc. If the bouyancy is noticable I will probably cut a hole and glass a slug of lead in there. None of the one designs I read about using foam core carbon fiber boards mentioned any problems, but... The one "structural" member isn't supposed to keep the board from breaking. The only load it is intended to take is the crushing load right at the hull where the board meets the edge of the trunk. The fiberglass skins are the actual structural members the same way your hollow aluminium mast uses the wall as structure. The foam and wood simply keeps the skins/wall in position to bear the compression loads as the board tries to bend. I have seen masts constructed this way (foam cored fiberglass) with a two inch cross section support a 180lb man standing on it. The mast deflected about twenty degrees and could have bent a lot further without breaking. The biggest broblem I see structurally will be too "soft" a board that might spill water the way the unstayed masts spill air in a gust. But then again I could be wrong and the board may break. Then I will build one the Graham says to do it in the first place ;-) Joe Nelson is building a core sound 20 about twenty miles north of me I think. I am hoping to compare my boats performance to his and get an idea if this was worth it. It has been a lot of extra work :-) I got the first layer of 6 Oz glass on tonight, sorry but I am too tired to go back out to take pictures :-(

Ok, maybe not such a good idea. I bought two quarts of the stuff and tried some on the the centerboard trunk. I painted inside the shop at 75 degrees, and three days later it hasn't cured. I took it back to Fisheries supply where I got it and they said the humidity might have been too high. I live in the Pacific Northwest, of course the humidity is high :x Why sell a paint to people who live near large masses of water when the paint won't dry in a humid environment? Doesn't seem like much of a marine paint to me. At least I got my money back, but now I have to clean this mess off the centerboard trunk. I think I will stick with the interlux enamel we always painted the tugs with, at least I know that will dry in a humid environment, and stick to anything to boot.

Just an idea. If you run a tape measure snugly around the outside of the sheer on both sides you will be able to tell if one is in fact longer than the other which would force it out. If they are the same it may just be on side is stiffer than the other.

In order to achieve the foil section I wanted in the centerboard, I am building it 1.4" thick instead of 1". This gives me a NACA 0010 foil which is right in the middle of what is recommended for slow moving foils (like sail boats). I have also altered the construction considerably. I am using foam cored fiberglass with one strongback running through the widest part of the board. This will insure that the localized compression where the board rides against the trunk can't crush the structure, not provide any real stiffness laterally. That is the job of the fiberglass and core. I have the wood parts done and the foam shaped and in place. After work tomorrow I will start laying up the glass skins. Hopefully I will also get some pictures up tomorrow. At this point I am hoping this is worth the extra work :-)

Great, I think it's what I will use. Thanks

Does anyone have experience (good or bad) with Pettit easypoxy paint? Thanks

Wow! Your rudder and dagger board are absolutely beautiful!