finished the profiler this afternoon and ran a trial core of scrap pine though. I had a couple issues with the core staying in place. Probably because there was varnish on the bottom and it did not grip the tape well. I also had an issue with the outfeed platform staying put. I'll anchor this in place when it comes time for the real deal.
I think I'll wax the outfeed tables and platform as well as the base of the profiler so it will slide though the blades better since I had to put a little pressure on the end to make sure if fed nicely.
My mock up came out a bit too thin in the center. I was off by 1.4mm. I was shooting of 11 and it came out 9.6. Not sure if this was due to the slippage I had on I'm just off on my measurements.
My center width and end widths are both 9 mm different. As I'm shooting for 2-11-2. I might have to run a second trial and then adjust from there.
I'm now looking at lumber for cores. Does anyone have any info on quarter sawn/rift sawn or flat sawn lumber and their applications as far as core design, flex/torsion patterns etc...?
First off.... That's a first rate shop you have! The planer crib need tweaking, thats all. Could be slippage....
As for lumber, the best is to have the grain running vertically no matter the type of wood. For hardness of wood look up Young's Modulus on the internet. There's plenty of references out there.
Even if a board is flat sawn (most likely the grain is running more horizontal) it can be cut so the grain runs vertical. Grain direction is one of those details that can get overlooked. Does it make a huge difference? Not huge, but should make a stronger ski.
Thanks on the shop comment. I'm pretty proud of how it has come out. Adding gutters that I got for free this weekend. I can't have the dirt splashing up on my nice siding.
After researching the differences in flat/ 1/4 /rift sawn boards it seems that rift and 1/4 sawn are more expensive and less likely to shrink and warp. They could also be stronger. But for now I'll go with what is cheapest. I'll worry about dinking around with grain patterns when I can build a decent ski.
As for the crib, I'll plane down the center section to blocks a bit and see what I get. I've got to some something with dust control on my planer. the attachment I have is too narrow and jams with planer shreds easily.
I'm also going to hopefully start building a mold this weekend or next week if things go well. I still have a ways to go before putting a ski together but things are rolling nicely now.
so then ideally 1/4 or rift sawn would increase stiffness without increasing weight. or perhaps decreased wt. with a thinner core in comparison to flat sawn laminate pieces?
Yes. Now how much I don't know? There's another thread here some where that talks about this topic. You can do a simple experiment, take a piece of flat sawn wood and another piece that's has vertical grain, both having the same dimension. Then try to bend them and see which one is stronger. The one with vertical grain s/b stronger.
Vinman wrote:so then ideally 1/4 or rift sawn would increase stiffness without increasing weight. or perhaps decreased wt. with a thinner core in comparison to flat sawn laminate pieces?
Yes.
Most commercial lumber such as poplar from Home Depot is flat sawn, that's why we have to rip it into strips, rotate each strip 90 degrees, then glue it back together to make ski cores. I stopped messing with this once I started using vertically laminated bamboo flooring planks.
Has anyone considered the posibility of the timber core "shearing"? When I was a kid and had to split fire wood.... the wood split much eaiser between the growth rings.
So... if you have a quarter or rift sawn core (growth ring vertical) the layers of early and late wood (summer/winter growth) vertically link the reinforecment. If the core is flat or crown sawn the early/late wood layers are arranged in such a manner that the reinforcement are only bonded to the outer layers.
So if a ski/board has a flat sawn core the layers of the core are more likley to seperate (or break down slightly) causing the ski/board to lose it's pop or worse still partially delaminate. So vertical growth rings are stiffer and stronger!
Has anyone made any samples and tested?
Chris
carnold wrote:Has anyone considered the posibility of the timber core "shearing"? When I was a kid and had to split fire wood.... the wood split much eaiser between the growth rings.
So... if you have a quarter or rift sawn core (growth ring vertical) the layers of early and late wood (summer/winter growth) vertically link the reinforecment. If the core is flat or crown sawn the early/late wood layers are arranged in such a manner that the reinforcement are only bonded to the outer layers.
So if a ski/board has a flat sawn core the layers of the core are more likley to seperate (or break down slightly) causing the ski/board to lose it's pop or worse still partially delaminate. So vertical growth rings are stiffer and stronger!
Has anyone made any samples and tested?
Chris
Not that I'm ware of.... Unless the wood is extremely soft/punky I don't think it would break in that way. Wood splits much easier when it's freshly cut as opposed to seasoned/dry wood. Wood used for skis has to be very dry, low moisture content. The bond is still pretty strong even when flat sawn.
