Affordable seaworthy cruiser

After reading this thread, I can only conclude that you are simply not serious, if you choose to take yourself out in rough weather in your poorly constructed and designed coffin, thats your decision. However if you choose to take your wife and children then thats extremely poor form given the excellent design advice you have recieved which has stated the serious shortfalls and gaps in your design skill.

I also really hope this isnt a gorilla glue and steel screw build. We have been down the polyurethane glue path here and its unsuitable for boat construction unless its high quality industrial grade (read same price as epoxy) and your joints and clamping technique is excellent.

 

Tad,

The build method is intended to work as a system. Did a quick calculation for size area of the fore and aft strips and came up with 41 square inches, which is about the same I would think if hefty log, clamp, and stringers were used. I would go ahead and continue building but based upon your observation of my wood quality, that further strengthening fore and aft is necessary.

 

Only satisfactory way I can think of addressing the problem is adding another layer of strip sheathing fore and aft. If this will work and since two layers were already intended would one layer of plywood work as the other layer in between the two strips running fore and aft?

Yesterday, I went out and did the calculations for displacement and waterplane right of the hull, DL is 42.7 - which is too light and was considering lowering hull waterline 1" for more displacement. This is first build, during design period, the vee stern was put there because it can handle changes in weight whether stern is a little above or below. Saying all this, I am not afraid to add more structural weight but do want to keep work and overall costs down, if a total of four layers is needed so be it but, hope three layers as explained above would be enough.

Blocking is the word I was looking for, its purpose is to join the bottom and sides, I put "log" in parenthesis, it was never intended for longitudinal purposes.

 

Went to Reuel's book and pages 3-7 are the descriptions and reasons of frameless construction. The last paragraph says he designed the "terraphin schooners" for using the method. I wonder why he put the other boats in there as examples if that is not the construction method.

I noticed the bulkheads and cleats and thought they were only watertight seperators. Why did he not just incorporated them as he did with chines - frames that would be used for building but remain afterwards? Even if they had to be thicker, it would not have taken away to much space.

 

The screws are "Maze" hot dip galvanized and epoxy glue, although will use deck screws from now on, Reuel say they are protected and good enough. The Maze screws are soft and heads keep stripping. Only the first layer is up and cn go ahead screw more.

 

Direct from hull.

Hull 8756
Vee cutwater 256
Keel 1586n (off plans)
Total displacement 10598
WL 48'
COB .545% aft.
PPI 1317
CP .498 (hull & vee only)
DL 42.7
DL 1" BLW 48
CP 1" BLW .512

Stern is even with current waterline. Center of engine weight is 4' aft of COB. Diesel will be moved fwd to where water storage is drawn, 5" aft of COB. Water will be moved fwd (under galley stove and sink) exactly fwd of COB. This allows batteries at engine area to move to sides and complete unrestricted access to engine (exhaust at port) and almost 5' hdrm other than lowered 2' wide cockpit floor right above the engine.

 

Throwing more material at it in the wrong place is not the answer.

The largest stresses on any hull are longitudinal bending, either from waves or rig load if a sailing hull. An efficient structure concentrates material in areas of highest stress.

Think of your hull as an I-beam viewed end-on. The deck and hull bottom are the heavy flanges and the topsides the light web connecting the flanges. Beam theory tells us that stresses are highest at the edges of our beam, and zero in the middle. Thus we concentrate material (in this case longitudinal wood) in the high-stress deck and bottom. The web in the middle keeps thing together and the water out.

This is the reason for structural members such as keel, chine logs, and clamps....concentrating material at the edges.

 

Your explanation is clear.

Take and 8" high I-beam and add 4" to the web - it greatly increase bending strength, put an 8" hole in the middle of the web and it still retains bending strength because the stresses are located at edges but, they need flange to stiffen them and prevent buckling. So the chine log is the edge reinforcement.

Is this also correct? - This design is square tubular shape and stresses are handled more closely relating to mono structure where long bending forces in hull are are able to transfer to frames rather than all concentrated at edges. The frames then distribute it more evenly upon the whole.

Another analogy which Im not sure is correct - Round tube, like fuselage in an airplane has holes in it for windows that weaken longitudinal strength, building up tube thickness regains it. Can this be applied to square tube that has interior frames with holes at corners?

 

What is the point of this construction method? I can see why one would use flat chined surfaces. Because it is easy to use flat panel materials like plywood. Why on Darwins green earth would you then use strip planking which could almost as easily be applied to a nicer curved hull form? Seems like a very confused building method to me.

 

In the picture above, at the first frame, the top row of planking, is a butt join on the frame. That doesn't seem like a good a way to do that, but moving on down to rows 5 and 9, there seem to be butt joints in between framing. Is there something to back them up, such as butt blocks?

Also, looking at the photo, I can imagine an awful lot of twisting of the hull in waves. In general, what strengthens against that? I had an open plywood jonboat that did that so I put two bulkheads in it, but they hardly helped at all. My next attempt was going to be a coaming around the top edge, but the boat was traded before that happened. It seems that would have helped. I guess maybe once a sturdy deck is put on Goodwill's boat, that would resist twisting.

It looks like it is not too late to let in some actual chine logs and stringers into Goodwill's boat if he wanted to do that, although the bottom members of the frames are too small to be notched. Stringers/keelsons could be surface mounted on the bottom of the frames and the spaces filled in solidly with blocking though.

On the sides, if the framing members are big enough, a few rows of planking could be removed, the frames notched 3/4" deep and 2x4s substituted, coming out flush with the planking already installed. The same at the gunnel, so then there would be a chine log, a few evenly spaced side 'stringers' and then a sheer clamp or 'gunnel log' or whatever it is called.

Then maybe a layer or two of plywood, some glass and then some angle iron screwed to the chines to give some wear ability to them.

 

Greetings,

Strips serve as longs, and additional layers of either ply or diagonal strips will tie butt joints. The idea of an angle iron was considered before the build but wouldnt work as a result of the side-bottom angle not being 90 degree, even now that sharp corner would eventually cause problems.

There are about 15 frames total, four are major bulkheads, frame 14'-6" and frame 42'-5" are six inches wide, the rest are at least 12" wide because of use as interior built ins. Thinking of notching chine 2"x5" and adding uninterupted chine log, probably will have to laminate, originally thought the strips would avoid this step until Tad mentioned the problem. Sheer clamp to be exterior.

 

The angle of the angle iron does not have to be exact. If it is close or is beaten close, bedding will take up the slack. Two flat steel straps could be held in place and tack welded, then taken down and welded more thoroughly. The angle iron wouldn't be for longitudinal or any other strength, but just as a wearing surface for that sharp chine corner which will be very vulnerable to wear.

 

The problem is that you tied a very loose idea that just occurred to you to your scripture. I'm sure if you were not trying to defend the positively foolish ideas about how stability works with scripture that far less attention would be paid to it.

No, the frames will not suffice for the purposes of a chine log. while they do help to spread the loads up the sides of the boat they don't do anything for the real killer (that beam theory would point to) which is the stress in between those frames. And no, three layers of strips will not do.

You seem to be under the impression that the fact that you've curved the surfaces in one plane will help you, and to an extent that is true. Unfortunately someone got the foolish idea to make it impractically long and shallow, which gives the forces extra leverage and increases the importance of a strong chine log. This is the sort of problem that you run into when you design a boat backwards.

You could normally just notch the frames at the chine and fit a chine log in. Unfortunately you made the bottom member of the frames super thin. No doubt this was intended as a way to get the headroom that you wanted without increasing the height of the boat; I feel like the explanation for this would be redundant.

Follow samsam's advice on retrofitting in a chine log. Since you get the benefit of multiple layer lamination I would take advantage of it, putting a rabbit on the corner so it buts flat against stripping layer 1, striping layer 2 fills the rabbit and comes even with the surface, and stripping layer 3 covers over the chine log, or alternatively have another rabbit so it covers another strip of it. That would help you tie the chine log more tightly to your laminated surface.

People are complaining about the butt joints, but if you plan to go ahead and add two more layers of wood, well glued down, I wouldn't worry too much about that. I do agree with the others that your wood is of inferior quality (I suspect that you are not being as selective as you could be at the lumber yard, if you aren't spending the money you should it means spending a lot more time), but honestly I think that you will experience failure at other points from the bizarre design long before the quality of the wood catches up with you. Spend extra time filling those voids before you try to add an extra layer.

 

goodwilltoall, i have not read this entire thread, but from what i have read i would seriously question if there is any sense to what you are building, i know nothing of boat design but i know enough to know that you dont just come up with a safe design like pulling a rabbit out of a hat, boat designers are people with university education in the engineering principles involved and years of experience, if you are one of those then please accept my apologies, however if as i suspect you are just an ordinary joe like myself who knows little or nothing of the principles involved then you really should have regard for the safety of those that might sail with you if not for your own, remember your god will not save you from the forces of nature or deficiencies of design, he has remained silent and inactive through famine and war and injustice so i wouldnt just expect him to turn up to save the day especially for you, also having had an uncle in the rnli who lost his life at sea along with one of his colleagues i find your comments about the coastguard most offensive

 

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