what wood for daggerboard?

[sigurd]

wet feet, I was hoping to get less induced drag for an AR of 5 with a 10% thickness. I think I will put taper to reduce root bending. something like (in cm) root:20 tip 10 length: 75

[sigurd]

Here is the answer to what i was asking earlier, strain to failure, it is called.

Sounds ok so far, except there's something we've left out: strain to failure. For e-glass it's 14.3, but for balsa it's only 4.4 . This means that at the load where the balsa lets go, you've only used about 1/3 of the strength of the e-glass.

http://www.djaerotech.com/dj_askjd/d...ions/fuse.html

So, to ensure that the wood does not break before the carbon, the wood should have a bit higher strain to failure than the carbon. Right?

[peter radclyffe]

Originally Posted by sigurd

Here is the answer to what i was asking earlier, strain to failure, it is called.


http://www.djaerotech.com/dj_askjd/d...ions/fuse.html

So, to ensure that the wood does not break before the carbon, the wood should have a bit higher strain to failure than the carbon. Right?

use teak or lignum vitae or ekki, greenheart, jarrah

[peter radclyffe]

if spruce breaks, build a wider slot, spruce is supreme in so many applications, so if it breaks you must redesign the board

[Boston]

my old Grand dad used to do exactly what Al White said in one of the first posts but with White Oak
was heavy but the stuff doesnt swell and its strong as doug fir without the splitting problems or the rotting problems

although that last from Peter is great
Sitka spruce is the bomb for lightweight and strength
White oak is one of the denser of the hardwoods
Hickory isnt all that water resistant and although its a good strong wood it has the same problem doug fir does with splitting

best
B

[PAR]

The original poster on this threads wants a light, very strong daggerboard. He has carbon tow on hand and would like to incorporate it into the build.

For his application increasing the chord, on his high aspect foil is likely not wise and probably out of the application's effective performance envelop.

Sitka's only real attribute is it's compressive strength to weight ratio, which makes it well suited to spars, not foils.

White oak is twice as strong as Douglas fir and nearly twice as heavy, live oak is stronger and heavier, but is less prone to checking and splitting. Both of these oaks will swell like a pregnant woman compared to the typical softwoods used in appendage applications.

Hardwoods in a sandwich laminate isn't a wise idea and is self defeating. The idea of these laminates is light weight, which negates the use of oaks or other particularly dense woods.

Douglas fir is a reasonable choice, but is farther down the list then other species, such as white spruce or red western cedar.

It's very likely the builder will use a foam or honeycomb core, some of his carbon tow and directional fabrics, which will produce the lightest, strongest bang for his buck.

It's important we speak what we know, not what we think we know.

[peter radclyffe]

Originally Posted by PAR

The original poster on this threads wants a light, very strong daggerboard. He has carbon tow on hand and would like to incorporate it into the build.

For his application increasing the chord, on his high aspect foil is likely not wise and probably out of the application's effective performance envelop.

Sitka's only real attribute is it's compressive strength to weight ratio, which makes it well suited to spars, not foils.

White oak is twice as strong as Douglas fir and nearly twice as heavy, live oak is stronger and heavier, but is less prone to checking and splitting. Both of these oaks will swell like a pregnant woman compared to the typical softwoods used in appendage applications.

Hardwoods in a sandwich laminate isn't a wise idea and is self defeating. The idea of these laminates is light weight, which negates the use of oaks or other particularly dense woods.

Douglas fir is a reasonable choice, but is farther down the list then other species, such as white spruce or red western cedar.

It's very likely the builder will use a foam or honeycomb core, some of his carbon tow and directional fabrics, which will produce the lightest, strongest bang for his buck.

It's important we speak what we know, not what we think we know.

how about 25 mm bruynzeel ply, with several guitar neck tie rods, vertically to tie plate strip washers,full length of board, top & bottom, would this counteract the lateral breakage