: I think the orientation question can add a lot of confusion. When you apply a
: force to a kayak which way is the stress oriented? I suppose if you
: suspend a kayak from its ends and is in the middle a substantial amount of
: the stress is lengthwise, but the stresses end up getting distributed.
: There is a force trying to collapse the deck and hull together, this is
: counteracted by the sides of the kayak which are put in compression, so
: part of the skin is subjected to transverse stresses. If you make the boat
: too weak either longitudinally or transversely, the boat will break.

: But the supported-by-the-end senario is not likely, it is just one worst
: case. the other worst case, with the boat balanced on a sharp rock is more
: likely. This puts something like a point force on the bottom. The stresses
: can propogate in any direction around 360 degrees. If the bottom is
: significantly stiffer in one direction than the other, that direction will
: load of with the stress first and start distributing the stress along that
: axis of stiffness. Since that is the direction the composite is also
: stronger it is able to handle stresses that might break other
: orientations. Since the forces are not well oriented one way or the other,
: the stress will follow the stiffest orientation.

: There is also the problem that wood strips are much stronger along their
: length than across. This means they don't need as much reinforcement along
: their length as across their width for balanced strength.

: It is a complicated and confusing syste which is hard to analyze.

Here-Here!! All this has given me Excedrin # 99. Time to go take a pill and get to sanding that hull for the final fill coat and preparation to turn it over and work on the inside. Ooouuucchhh!! Might have to forget that mask on this coat, just to clear the head a little. ( But, don't do this yourself... I'm from California )

Actually, I had some of the same concerns last night and wanted to ask about the directional issue as well, but.. as I see it, there's a wide cross-section of information on that and I for one have no clue about all this. But.. do you think that the average kayak ( stripper ) will run into the kind of forces you are talking about, that may sheer it in half. I understand that damage IS a possibility, but with all the layers (weight) we're talking about adding for strength, isn't it also true that adding that weight for strength is also adding that weight to raise the stress and force factors, making the boat JUST as vulnerable.

Another issue I've been wondering about is: With the Stitch and Glue ( plywood ) boats, since there is no grain orientation to speak of, the only points of advantage would be the seams, am I correct. Then if you use a bias cut tape to seam, your glass orientation really doesn't matter. Does it?? Why?

As you can probably tell, I'm no engineer, but just a do it for fun builder. While the information given her means nothing to me( I don't understand most of it ), the final result does, when applied in plain english. Several conversations in the past 3 or 4 years have gone on about this subject and I'm not sure anything has come of it that can be used by the average builder. What I'm saying is, if there actually is some sort of standard that can be derived from this, maybe it should be layed out in some sort of instruction book as a recommendation for all new builders. "Minimums," for size and weight.

Also, is it not correct that the boat, as built for Nick, with certain layers, directions of grain and so on, may be just fine for Nick, but at 250 lbs, that same boat would not, according to some standards, be safe for me, if involved in a collision say, from the side with a pointed rock. ???
My point being that unless all this information is put into some sort of guide showing the variations of force applied, strength in layers and grain direction of materials and so on, it really can be quite misleading for those of us that are not engineers. ???

Man, I'm getting that headache back..... I don't know if any of this has made any sense, but I'm not reading back through it again. I need another Excedrine and some fresh ( garage ) air.

Any ideas on this ( if you can figure out what I just said ) ???? Thanks!!

Rehd