first broken board

So, did they work, and how were they? Show everyone proof that your ride was a success (or even a complete failure)!

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doughboyshredder
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Joined: Mon Sep 17, 2007 7:37 pm

first broken board

Post by doughboyshredder »

This was a 162 that I built for someone quite a bit smaller than me, but of course I had to ride it. Super fun board. I'll have to look and see what the core profile was. It was pretty thin though. Probably 6.25, maybe 6.5 all basswood with 18 oz biax. No carbon fiber. I started the taper right under the bindings and the tip ended up being super soft. I tried to do a little nose blunt last time I was out on it, and it just folded over. The combination of the rocker and the flex sent me right to my shoulder. Didn't think anything of it, and then this morning I looked at the board, and it's broken right in front of the front binding. Just the wood. Not the glass layer. You can see it when you flex it. I think this is the downside of doing a long graduated taper. The weak spot is moved to right where it shouldn't be, right at your binding. Is this one of the reasons that most major produced boards have a short taper well outside of the bindings? Maybe? I also think that the glass is too light and not having anything in the 45 / -45 also contributed to it. I guess it would have been fine under the feet of a 145lber but just couldn't take 235lbs cranking it. I'll look at my notes and see exactly what the core thickness was if anyones interested.
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Brazen
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Post by Brazen »

I would love to know. I just finished a bunch of cores for a 162cm with about that same thickness. I'm using a 19oz triax and carbonfiber though...but still. Thanks DBS
"86% of the time it works 100% of the time".
doughboyshredder
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Joined: Mon Sep 17, 2007 7:37 pm

Post by doughboyshredder »

I just looked and it was actually either 6.75 or 7mm basswood. I went back and forth, and can't remember which I went with at the end. I will check my core stock tomorrow and see if I can figure it out.

It broke where the core was about 6.5mm.

I think my early core taper and the biax glass were they main culprits.

That, and I shouldn't be riding a board like that. Way over the weight limit.
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Brazen
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Post by Brazen »

Yeah, these cores I've just finished for the 162cm are 4.5mm in the center, 6mm underfoot tapering to 1.9mm at the tips, they have the effective edge of a 167cm. I'm using maple center stringers with poplar, and I made them this light since I'm using biaxial carbon fiber top and bottom, with triaxial fg and that aramid simile. You've scared me now though dammit, we weigh the same...I might have to pass these on to lighter friends.
doughboyshredder
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Post by doughboyshredder »

4.5 is soooo thin. But, with the extra carbon and what not, it may be o.k.???? Hard to say.
strangesnowboarding
Posts: 133
Joined: Sat Nov 06, 2010 2:26 pm

Post by strangesnowboarding »

doughboy
noseblunts will do that to all but the strongest boards, sadly all the boards i built with a biax are broken now (most in front or behind the bindings, some in the middle from jumping onto rails), however i always had the glass fail before the wood core (with binding thickness ranging from 7 down to 5.5)

we did a couple with 5mm in the center, 6mm at inserts and down to 1.something i dont remember at the tip and tail. carbon stringers helped the integrity of the center but when overflexed the carbon (uni) "pops" and will shear in a straight line. this failure actually changed the camber/rocker of the boards permanently. kinda funny how similar carbon is to steel!

i will be using triax from now on and just working with core profiles to get the right flex pattern.
im riding a 6mm core now with triax and it is fun, flexible, and rips at high speed.

have fun breaking boards! its why we do this!
carlito
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Joined: Fri Dec 24, 2010 1:53 pm

Autopsy

Post by carlito »

Time to do an autopsy!

First, are the bindings leaving marks in the topsheet. especially at the "corners". cut the upper facing along the broken part of the core with a razor knife or a sharp chisel. really look for signs of areas where the core did not bond to the facing material. Look for crushed wood in the area of the bindings. It can be difficult to tell if what you are looking at caused the problems, or is the result.

My two cents. If you don't have quality issues, ie. dry spots/lack of bond or inserts that are too tall (watch this one!) my guess is that you are punching through the top facing and damaging the core enough to cause a delamination to begin. What to do? this is a tougher question.

Your first approach/suggestion centers around core thickness/profiling. This can help alleviate the problem (breaking) but comes at the cost of changing the flex pattern. Assuming you like the flex pattern you might not want to do this. You can always make it stronger by making it stiffer, but eventually it doesn't ride so nice. I would look at adding facing material. Either something with more than 9 oz in the zero axis (same problem as thickening up the core-it's gonna get stiffer). Or add a layer of materials around the binding areas . What you are looking for here is something that will add some dent resistance without really affecting the flex pattern. Again, there are some problems. This added material needs to be tapered (diamond shaped, "v" shaped or something) so it does not cause another stress riser, and it will cause thickness issues. That is, you might end up with voids where the thicknesses change. You might need to rebate/router a hole into the core to fit this layer.

There is no easy answer to this, but a lot of possible ones. Depends on what you can live with.

I think what this raises is the more interesting question: What is reasonable? How big a flip/crash/tomahawk should you be able to survive without breaking ski/board?

My first guess is that you want the stuff you build to be at least as good (tough) as what you used to buy. Fair nuff. But sometimes you have to ask yourself "would this have broken any board that I actually want to ride"? I think its pretty easy to make an indestructable board/ski. One that is indestructable and fun, not so easy. Ending up happy, somewhere in the middle of these two positions, can keep me up at night.

Currently, I'm really happy on the durability front. Using wood topsheets is an issue cosmetically, though you can refinish and end up nearly new. I am getting great longevity, most of the stuff I have works for over 200 days before people just want something newer (rocker, early rise etc.). But every once in a while someone eats shit and the questions start to keep me up at night. Should that have broken? Would a store bought have broken? What, if anything, should I do? God knows i've broken stuff, but when you take out the QC F@#$ups most of the crashes were heinous. Straightlining glacier bowl in Whistler, and hitting a bar fridge sized avalanche cookie, just under the surface of the beautiful, flat powder. Binding shattered, snowboard nose exploded. Maybe stuff breaking saved my leg. A buddy found himself on the wrong traverse line in the fog in whistler bowl. About 35 feet above where he should have been. He went around a corner and fell the distance to the proper traverse line. He landed on the tails of the skis on the traverse. Ski exploded behind the binding heel and he thought he broke his leg. He lay around moaning for a few minutes and tried to get up, eventually he managed to put the skis back on and limp/ski home. Couldn't walk for a few days. He figures anything would have broken. maybe if it didn't his leg would have.

I don't know, what do others think? What is reasonable here?

Fog, and confidence together are trouble. Carlito
artski
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Location: Boyne country, Mich.

Post by artski »

I'm no expert on wood but I have basswood trees on my property along with maple beech and ash and the basswood trees break. They just don't have the elasticity the the other trees have.
I've seen them break 15 feet up in a wind storm, ( a 14 inch tree! ).
just my 2 cents.
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