30' plywood sharpie

I got back to my roots this morning for breakfast: I made corn meal mush with butter, brown sugar and light cream. I also fried up some spicy pork sausage, and crumbled that into it.

 

Could you stack two deck beams, then shave the ends so the middle is taller? Hope you feel better. Chip.

 

I'm not sure what you mean. If you mean stack them on top of each other, I don't think I need that much extra on any of them, no matter what I do. Just laminating a thin strip on top would do it. I always wind up fairing deck beams one way or another anyway, unless I loft each and every one of them individually. And even then they always need a little fudging. Maybe I'm just not a professional boat deck builder.

Yes, I'm feeling better. Not good yet, but better. I'm strong enough to start getting grouchy again...

Been about 15 years or so since I went down sick like this; usually I just keep plugging away while everyone else catches whatever is going around.

 

If I understand you correctly, the deck is dished because the tops beams are too low? If this is so, you can use two beams, one atop the other to make them taller.
Also, could it be that the sheer is too high? It'd be interresting to measure the sheer on your model, then convert it to the sheer of the full size boat.
I have bought plans for Ruel Parker's 22 foot Cedar Keys sharpie to build as a 'warm up' for the real thing.
Chip.

 

OK. We're on the same page. But I don't need enough extra meat to stack entire beams. I can just laminate a thin layer on top of the low ones and reshape them, if I decide to go that route.

Yes, I have a strong sheer--as you can see from the pictures. But it's no stronger than on the original working sharpies. However, I did make the crown quite a bit higher than the originals had. Chapelle shows a crown of 2 1/2" for a beam of 7' 2" on a racing sharpie; mine is laid out as 6" for a 7-4" beam. That's partly to give more headroom in the V-berth; every inch helps. And since the cockpit is actually just a shallow foot well with the deck itself being the seating, the crown makes for a more comfortable seat angle.

 

how about if you just give it enough camber to not be dished or maybe find a balance by adjusting the sheer line
seems like a dished deck would not be to ascetically pleasing anyway

PS
what no grits
sacrilege

 

Troy; You can save a bunch of lofting and grief in laying out your deck beams or other side to side cambered things like arc bottoms. If I was smart enough I would include a sketch of a simple tool that you can make. Failing that ability, I will attempt to describe it.

Find two straight sticks, each a little longer than the maximum span of the deck. Bevel one end of each stick about 8 or 10 degrees. Join the beveled ends of the sticks so that they are firmly attached. Use a plywood scab or whatever plate you choose. You now have a wide vee shaped thing that resembles the top of a roof truss. Cut a small notch on the underside of the vee apex. The notch will position a pencil.

Temporarily fit and clamp into place, the uncut planks that will be the deck beams. You can notch and bevel the ends of the beams just as though you were going to install them permanently. The sheer ends will stick up an amount that will equal or excede the height of the crown. Use the vee thingy by sliding it from side to side while pressed against the deck beam. The pencil, that is held in the notch will make geometrically perfect marks. Procede to the next stations and repeat. Make all the marks on the side of the beams that are nearest the middle of the boat.

Cut the beams to the marks, re-install them. A careful bit of planing forward of the previously penciled sides of the planks will yield a nicely faired set of deck beams. No hollows, no problems.

The angle of the vee thing can be fiddled up so as to create any amount of camber that you choose. We can calculate the camber with trig but it is easier to experiment to find a curve that you like. Begin with a slope of the roof truss at about one and three quarters on twelve. That'll give a camber of about 3/4 inch per twelve inches of span.. The steeper the angle the more camber and visa versa.

 

Not touching the !@#$ sheer line! I went to a whole lot of trouble getting it right....

I'm still not sure we're communicating here. The whole deck does have crown, (or camber or whatever you want to call it), from side to side. But fore and aft the centerline of the deck somewhat follows the sheer, instead of being a straight line. That's absolutely fine for looks and strength; trust me.

The problem is that combined with the crown athwartships, it makes the surface of the deck a compound curve, which is hard to sheath with solid plywood. That's not a disaster. If I want to use sheet plywood anyway, I can torture it a little--maybe by using thin sheets, and laminating a double layer. Or I can fudge the shape of each beam, so that the centerline of the deck fore and aft is a straight line from cabin to bow, and from cabin to stern, which will remove the compound curve.

It isn't a major conundrum; I didn't mean to spend a page and a half on it. It's just something to deal with, one way or another....

 

I got you Im just saying that a large enough sheer makes getting a comfortable camber a bit difficult
either you have a huge crown up buy the bow or you alter the sheer
sounds like that sheer is going no where

just string line from stem to stern and set the crown that way
put a toe rail on it and be done
if you dont like it rip it offf and do it again

that or you could recess the line of the deck below the line of the sheer rather than aim for a flush deck

 

Allow me to repeat myself. The sheer is quite appropriate for the boat; not touching it. It's actually fairly modest for this type of vessel, especially compared to something like Munroe's Egret. The old sharpies solved the deck problem by simply getting rid of most of the crown, and letting the deck follow the sheer. What modest crown they did have was no problem with a planked deck. I want more crown than they had, so I'll deal with it.

Stringing the deck from stem to stern would give me a ski-slope deck, everywhere but at the ends. But the cabin is a long one and almost full width, with just a few inches of deck on either side. So stringing from cabin to bow, and from cabin to stern, would work. That's what I was contemplating, with all the talk about shimming the top of the beams. But combined with the straight run of the bottom in the forward and after thirds, it might give the boat kind of a clunky, boxy look in profile.







edit: the model is down a bit at the bow, in that profile shot. It should be higher than the stern. One of the hazards of balancing it on the nearest handy surface for a quick snapshot....

 

flat decks just look bad
go with the crown and a straight top line stem to stern
cheers
B

 

A straight line stem to stern would give me a crown of over a foot for a seven-foot beam, at the bridge deck. Thanks, but no thanks....

It isn't going to have a flat deck. If I do decide to string it bow to cabin, and cabin to stern, the deck beams at each end of the cabin will have an appropriate crown to them. So will the transom.

 

There are time when compromises must be made for that material used. I think what compromise is best is the test . here is a straight cabin of ply.

I dont see that the deck cannot be designed to use ply. the question is how.
I would experiment with thin model ply and try for a visual approximation .
I hope I did not offend by jumping in .

 

No offense here. If I didn't want people talking about the subject, I wouldn't be posting.

 

`I think Par nailed it when he suggested the diagonal ply strip method
you could also do a basic for and aft planking but it would not be as strong or as waterproof