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Blown 1975 Hallett Jet
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Discussion Starter · #1 ·
I know this has been asked a thousand times, however I have yet to see anything like what I’m looking for.

I need to replace the stringers in my 96 21 Daytona because the balsa has delaminated and that fix obviously goes underneath the stringers. They have a lot of repair holes plugged already and the glass was not adhered to the wood at all. This is turning into a can of worms as this was supposed to be a turn key rig and now it’s unraveling bad. (it’s “reasonable doubt” purple and white with the blown gas motor)

It has Douglass Fir currently and I’ve been reading about LVL, and coosa composite etc…. I’ve also been thinking about some more exotic stuff to highlight the rest of the boat. Snakewood, tigerwood, zebrawood, Philippine mahogany, Peruvian walnut etc. all of the hardnesses range on the Janka scale from 600-2300. Fir is on the low side of hardness but the lightest per cubic foot. Zebra and mahogany are heavier but harder. I like the looks and thoughts of an exotic wood that is light and strong but I don’t want something that is too stiff or brittle. I feel like a stiffer harder stringer will start cracking other parts of the hull potentially.

There is inlaid carbon floor next to balsa on the tunnels. I am going to put new balsa down (recommendations on that? Brand? type? Cross cut?). I want this to be unique but also don’t want to do something that might cause issues later. If I need the flex, the harder wood or LVL might be a bad idea let alone be 30-40 lbs heavier in total…

This is in a 1400 hp jet and I don’t want to make any mistakes at this point but also want to be different.

Can anyone please shed some light on this subject? I know it’s all been discussed, but I’m on the odd side of the bubble and need some help. Thank you very much
 

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Village Idiot
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3,605 Posts
I am an LVL fan. I have used in in a couple circle boats that take a pretty good beating and have to flex a little. I put carbon under them to try and stiffen up the boat a little without adding too much weight. Also, do to the strength and lack of grain issues, you can run a thinner stringer as well. No need for monster 2” thick stringers. Also, so much easier to get and the cost is much better than exotic woods. Anyway, that is my two cents.

Paul
 

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Blown 1975 Hallett Jet
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Discussion Starter · #3 ·
How is the epoxy absorption when using epoxy resin for the glass? I read the glue they use and the hardness/coating on the lvl’s makes it hard for saturation of the resin. I’m sure it can be stained as well if I’m still trying to keep some good looks. I like the fact they’re dead straight, won’t warp or dry rot and are very strong. Due to the fact this setup is higher horsepower, I feel like I want the stout aspect but I don’t want it to jack the rest of the hull/keel up because of rigidity. We are planning on going 24-32 oz (in staggered 4 oz layers) aft of the rear seat, and 16-24 oz from there forward over the stringers in glass
 

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Village Idiot
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I always ruff up the stingers with a good 120 grit and I use vinyl-ester resins. I have not had any issues. I know others have wrapped theirs with glass, but I always finish with carbon as it has its own cool look.
Paul
 

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From a structural standpoint, the core material used in the stringers is not where the strength comes from. The outer fiberglass/carbon fiber gives most of the strength. The core material's main goal is to prevent the outer glass layers from collapsing when bending stress is applied, so the core can be made of 5 to 10 pounds or more per cubic foot foam or most anything that is similar or greater in compressive strength.

Some people think of stringers like they are iron I-beams for structural strength with fiberglass applied over the outside for water proofing and decorative reasons, but that is not a proper engineering viewpoint.

The greatest stringer strength is obtained by increasing the 3-dimentional cross profile. Think about height and width to increase the strength.

De-lamination of the outer glass layers from the core material does affect the ultimate strength. With foam core, small shallow holes can increase the surface area to improve adhesion. Other core materials need rough surfaces to increase the surface topography so that the resin can bond better to the surface.

If wood is used for the core material, be sure that it's moisture content is as low as possible. Some woods have resin/sap that must be eliminated as much as possible because it can weaken the bonding strength to the surface of the wood.

Sharp corners, inside corners and outside corners, need to have as large a radius as possible so that the fiberglass can properly transfer and distribute the stress/loads from one surface to the adjacent surface.
 

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Blown 1975 Hallett Jet
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Discussion Starter · #6 ·
That is all very very good information. I appreciate the help. I’ve been between, coosa, LVL, zebra wood and clear vertical grain #1 or better kiln dried Douglass Fir. Matter of fact, Mr. Skagen recommend doug fir and I’ve been sort of considering setting with something that is tried and true/proven, not to mention its fairly light when it comes to lbs per cubic foot. It’s only about 6-700 on the hardness scale…. Makes me worry about the whole “squishing” effect of bolts and nuts. Especially over time
 

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Check out Grioux Boats. Pete makes beautiful stringers by running a router down the center of the stringers (say 1/2 inch wide, 1/2 inch deep) and inlays your choice of contrasting woods. Or go wild and inlay Plastic, Metal or fill with tinted resin to match the gel coat or paint. sand the top to contour and glass them in. Just my 2 cents worth.
Enjoy Skidder
Wood Road surface Rectangle Flooring Hardwood
 
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