Another question for the crew.
What are the pros and cons of running the balsa lengthwise as opposed to diagonally for the bottom and/or deck skins? I really like the look of the diagonal layups.
Dave_D
take a piece of wood like a balsa strip
bend it lengthwise along the grain and watch how easily it bends
now try and bend the same strip across the grain
notice how it doesn’t want to bend
now think of how the strips are aligned on the top and bottom
the ones running fore and aft
and the ones running diagonally
remember the little experiment above and that’ll tell a little of what’s happening but…
look at where bert’s placing them hmmm
kelly’s board the diagonals are in the tail on the bottom
wonder why?
Silliy made his across the whole bottom hmmm
Haven’t seen diagonals on a deck yet but I’m sure someone’s done it…
What side of the board do you stand on
what side faces the water
what side are the fins attached to
where at the fins attached
this will give you some idea why they are doing what they are doing but more importantly…
The second component to notice is whether the wood wraps over the rails or not cause this has alot of impact on the flex capability of the substrate it’s covering…
one way is soft absorbing flex and the otehr is snap back flex there are two types both with desired results…
Alot of folk subscribe to flexing tails because like some one said once it’s the last 18 inches that do most of the work…
Bottomline though if you wrap over the rail it won’t matter but I’d like to see someone wrap over a rail cross grain using diaginals without snapping the wood…
Found out about this more trying to wrap hardwood over a jewelry curved box top than doing my balsa lams… bending balsa is easy compared to ebony, koa or other stiff hardwoods.
markyv, danb & silly (and others have done diagonally bottoms and say it increases the flex (reduces stiffness).
down side, depending on how you mate your skins/rails is making the connection. I.e. wrapping the diagonals over the rails has been said to be troublesom. I’m going to do diagonal on the bottom and lengthwise on the deck. I’m only wrapping the top skin over the rails, but not the bottom so I don’t think the mating will be an issue.
do a search on silly no5, and danb 9 foot 12 lbs you can see pictures.
Quote:
Haven’t seen diagonals on a deck yet but I’m sure someone’s done it…
Done in fact, in 1995. . . . here’s Slim with the 7 of Hearts, a flexible 4 layer balsa sandwich board with diagonal deck.
Four layers of 9.5mm balsa.
I did two more 7’10"s like this with diagonal deck (also 1995), one is in the USA, the other in Australia
Plus a 7 footer with a diagonal bottom, now in Raglan. The diagonal deck definitely increased flexibility
yah
and youll notice problems at the ends of the board on the deckside
thats why i glue my sheets up
cuz they pull apart at the end of the board ( when vacced down)
and also cuz its end grain
i did diagonal on the deck and it was a pain
also its imprtant to trim your deck sheet pretty close to the right size
or you may get breakages and splits