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  #11  
Old 06-30-2005
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Marine Grade Plywood?

Well Jeff... I suspect that I shall do the final design work myself, but that the design will be closely based on an existing boat. I don''t think I have anywhere near the expertise to redesign the wheel, just tweak it a bit to suit my uninformed ideas about sailing.

And yes, actually I do appreciate all the advice. I remember some sailing things from "days of old" as it were, and am picking up many bits of information from all the advice provided. I''ve picked up alot of the terminology and still have much to go... one in particular is "skeg hung rudder", which I haven''t gotten around to researching yet.

A couple of other considerations for me... I''m not totally clueless... just somewhat. ;-) I currently have a 14'' sailfish and know some basic sailing technique. I also currently have a 12 foot dinghy under construction in my garage. It''ll serve as an excellent training project and trial run for some of the contruction techniques that I''ll use on the larger boat.

Also, finally... am I in over my head with the idea of building a 20-25 foot boat? Most likely! (But that''s half the fun now, isn''t it!) ;-) Also, I''d like to note that most activities, like wiring, mechanics, wood construction, pouring cement, metal working, etc. are scary to contemplate when you don''t know what you''re doing, but none of it''s really all that difficult once you get into it. That is why I''m not really afraid of building a boat. It''s basic wood construction and some resin work (I''ll be relying on tried/true/and safe designs)

A catboat style boat could easily go up and down rivers, couldn''t it?... provided they''re not too tiny and shallow. Here in Michigan, I''m nowhere near the sea... so lakes and rivers will likely do it for me for at least a few years to come.
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  #12  
Old 06-30-2005
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Marine Grade Plywood?

"A catboat style boat could easily go up and down rivers, couldn''t it?..."

Like many of your questions that is a less than simple one. In a general sense, a well designed catboat could work reasonably well on a large-ish lake or wide river. I have added the modifiers because in a general sense, catboats do not go upwind very well and generally do not do all that well in light air. When you add the additional drag of heavy displacement and a full length keel, I would suggest that a catboat would be a poor choice. Here''s why I say that:

River and lake sailing tends to involve a lot of upwind work, because the wind tends to bend down the long axis of a lake or river. Lake and river sailing tends to involve a lot of light air sailing, punctuated by bits of very heavy stuff often in very confined quarters.

Because a catboat is stuck with a single sail, and because it is a tricky design expercise to design that sail so that it can be easy to reef and still maintain a balanced helm, it is harder to design a catboat that has enough sail area for light air and yet is not overpowered in a breeze. A boat that does not have good light air ability will miss a lot of otherwise pleasant sailing days which given the short sailing season in Michigan could be a real problem. At the other end of the wind range, because of the confined nature of most river sailing, being able to control the boat in a breeze becomes especially important.

In that regard, a more moderate design, with a sloop rig and a lighter displacement to improve your ability to sail in lighter air and upwind probably will work better for you than a catboat.

"Also, finally... am I in over my head with the idea of building a 20-25 foot boat? "

I don''t think that it is for any of us to say whether you are in over your head. I have been involved with a lot of boat building and boat restoring projects over the years and frankly it is never easy to predict who will succeed and who will not, especially without having met the person.

I am not sure that this is the proper forum for this kind of discussion. Please feel free to email me directly if you would prefer.

Regards,

Jeff
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  #13  
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Marine Grade Plywood?

No Worries! The "in over my head" comment was more in a rhetorical nature. Of course I''m in over my head, but I don''t really care. Building things is fun!

I''ll have to spend some time looking at various small boat designs to settle on one. Mainly, I''m trying to go for versatile. I want to be able to sail Lake Michigan and perhaps the other great lakes... but I want to be able to come into shore too. As such, I''ll spend some time comparing designs until I think I''ve got the right one.

Thanks for all the help! ;-)
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Marine Grade Plywood?

Just to throw out some ideas for consideration. Given that you are lake and river sailing you might take a look at the work of Antonio Dias. Tony is an old friend and a really wonderful designer. For some reason his website is not up at the moment but he has designed some wonderful small and traditional cruisers that offer a nice mix of seaworthiness and performance. I have sailed on a number of his designs and they have proven to be very good boats.


Another thought would be to look at Dudley Dix''s design for the marconi rigged Cape Henry 21. http://www.dixdesign.com/ch21.htm

This is a very clever 21 footer designed for plywood construction.

If you were interested in a more modern interpretation of a small cruiser, this one has a daggerboard with a bulb for greater seaworthiness, you might look at Dudley Dix''s Didi 26 design. http://www.dixdesign.com/26didi.htm

Jeff

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Marine Grade Plywood?

That Cape Henry is a cute little boat!

I have to agree with Vasbinder (and Jeff_H) here. As stated before, I am only a "tinkerer" at this stage - replacing bulkheads, redoing decks, repairing wooden mast, etc. on a 28ft sloop. BUT I completely sympathize with the joy derived from these exercises and would love to build a small boat myself someday. I frequently get dock mates who gaze in on me when I''m working on the boat who clearly don''t "get it." There''s sort of a grudging admiration, but if sailing meant working on a boat, they would have no interest. Whatever Vastbinder decides, best of luck to him. BUT, he SHOULD spend the extra money for marine-grade ply!
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Marine Grade Plywood?

Actually, just thinking more about this: Since you seem to now be leaning toward a boat for gunkholing around lakes and rivers, you''ll want to find a way to make her bottom bullet-proof (hey, no laughing). From my days canoeing the rivers of the Midwest, I can attest that you will encounter any number of deadheads, rocks and other obstructions which will prove damaging or deadly to a plywood boat. Maybe there''s a way of sheathing in aluminum?? Something to think about anyway.
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Marine Grade Plywood?

neuman has a good point. That said, it might be stronger, cheaper and easier to simply vaccuum bag a couple layers of kevlar over the bottom. Just a thought.

Jeff
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Old 07-01-2005
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Marine Grade Plywood?

Jeff, I''ll look at the dix boats shortly...

Wish I could afford the marine grade plywood, but not likely to happen for me.

Now, some thoughts...

Sounds like I could retain my double hull idea and perhaps reduce the weight if I went to 2 layers of ply for the outer hull and a single layer for the inside layer.

I had considered the problem of running up on a snag/rock, whatever... I suppose I could sheath the bottom in light gauge steel... maybe 18 gauge. Seeing as the boat would come out of the water after each use, touching up the bottom paint to keep the steel safe from the water would be no big deal and the steel would also toughen up the lower hull mitigating the reduction of the outer hull to 1/2 inch total ply.

I''m guessing the steel would go on the outside of the resin layer to protect everything under it. The steel layer would only add a couple hundred pounds at most as 18 gauge is pretty light stuff, but likely more than enough to repel minor collision punctures.
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Marine Grade Plywood?

Again if you can''t afford the marine grade plywood, you can''t afford to build this boat. If you assume that in your current configuration the boat will have 24 sheets of 1/4" plywood, the cost difference between using marine plywood and exterior plywood of equal species and thickness would be roughly $200 for the whole boat. Frankly, you cannot afford NOT to use marine plywood.

The 18 gauge steel idea makes absolutely no sense at all. 18 gauge steel would add cost, would add a lot of weight, would be next to imposible to bond without creating a whole bunch of colateral issues and would not really help with impact at all. I think from an impact resitance, durability, construction time, and cost standpoint that you would be far and away ahead of the game looking at a vinylester- directional fiberglass or even a kevlar sheathing solution.

Respectfully,
Jeff
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Old 07-01-2005
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Marine Grade Plywood?

Having made fairly extensive use of sheet metal for other things, I can say that the cost and weight issues would be insignificant. However, if the protection offered would be so slight, seems like it''d not be worth the bother.

Easy to do, low in cost, low in weight... but if of no real protective value, then no point worrying about it.
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