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1/ When applying first layer of ply to framing after fairing...is ply stuck to frames as well as sheers? or are sheers faired so they leave a clearance between them and frames? or faired to down to frame?
2/ When I build model planes the more sheers along the length of the wing the better...Is it advantageous to do same for the boat? As in adding an extra one or two between the ones on the plans?
3/ I understand Limber cuts for drainage....but what about limber cuts on sheers up the side of the boat? Wouldn't water sit on them and create rot?
Thanks in advance......I am getting really excited about starting She'z Amaz'n Riviera.....Getting good contacts at work for timber cutters and suppliers....Merry Christmas to All and have a Safe and Happy New Year!!

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The Bitterness of Poor Quality, Remains Long After The Sweetness of Cut Price is Forgotten...Thanks Dad R.I.P.

No questions are stupid. If you were stupid you could not have thot up the question.

Don't fasten ply to frames. Only to longditudinale members. No point in putting in extra, unless you want it to be heavy. The designers specified what is needed for what the boat is designed for.

I don't think you need limbers on the sides.

Some pros might take exception to my comments. That's OK. Then I can learn too!

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Ches

Thanks don't mind it being heavier (using it in probably rougher water (open sea) not lakes or rivers as in Stateside)....I was thinking extra sheers/longitudinals would give a better curve to boat...

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The Bitterness of Poor Quality, Remains Long After The Sweetness of Cut Price is Forgotten...Thanks Dad R.I.P.

Good questions that you ask. I hope I can contribute to the good answers.

For the 1st part, as Ches said, do not fasten to the frames. If you do it creates "hard" points that will telegraph through the fair curve as angle lines lying perpendicular to - across - the direction of the curve. What you want is a fair, smooth curve. Almost always this is one with a constantly changing radius. It is that, after all, which creates the fair lines that we perceive as "sweet". Touch-points caused by contact with the frames interrupt the fair curve and make it into a series of shorter curves separated by angles. It will sorely dissatisfy you.

For the 2nd part, installing more "sheers" as you call them (actually these are "battens" when located between longitudinals of sheer, chine, keel, etc.) will disturb the flatness of the plywood plank that is across the direction of its curve. It will probably try to set a convex or concave shape across the direction of curve. It can be done to an extent. When you accomplish that, you have crossed into the unholy region of "stressed plywood" construction. Some aircraft designs have used this construction, called "monocoque" because of its great strength to weight ratio. You can eliminate most of the frames and battens with this structure, it's so strong.

I'll try to explain that better.
A flat sheet of plywood bends willingly (unstressed) in one plane, only. Plywood in this mode is actually a section of a cone in any cross-section. Think about it. A cone made of a flat sheet of paper is curved in only one direction, right? At any point on the curve, a line that is perpendicular to the curve, that is, from the top of the cone to the bottom, is totally flat - a plane. The same with plywood in your boat. You can lay a long straight-edge across the curve of the panel and, unless it is forced into a slight compound curve (two directions or more) the straight-edge will contact across the entire panel.

Therefore, unless the additional battens you install are in precisely the correct plane, perpendicular to the curve, longitudinal angles, concavity or convexity will result. It will appear not fair - in the boat building sense of that term. The best plan is to stick to the designer's plan. Don't worry about strength. In fact, additional members, hence weight, do not always yield greater strength. Wood is already incredibly strong. Made into an engineered product like plywood enhances even that.

I hope this helps. It is somewhat abstract and hard for me to explain it well.

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Paul Miller in Memphis, TN
"Yeah, I had lunch with him last week at the Cracker Barrel out on I-40."

Thanks V-Driver....I understand your answer....I was thinking if the distance between Battens the ply would have its normal curve but if hitting wave or such wouldn't the ply try to flatten itself in that area? thats was my thinking if I put in extra it would help hold its shape better?

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The Bitterness of Poor Quality, Remains Long After The Sweetness of Cut Price is Forgotten...Thanks Dad R.I.P.

I'll be getting to this point some day, so let me ask this. I understand you do not want to put fasteners through ply into frames, but do you glue the ply to your frames ?

Tom. Simple answer....no!
Also keep in mind that the ply,especially good marine ply, is exceptionally strong when curved in to that conical form.

Doug