Size of wood strips in Cores, pros and cons

[Dtrain]

I recently got a truck load of straight tight grained Sitka spruce boards. All 2x6. Not one knot.

I was thinking of making ski and snowboard cores by planing these, gluing them and Resawing on a local woodmiezer mill.

2 inch strips are larger than most use. Some say more strips equals a stiffer tortional flex. Others say larger strips are better because there is less glue, and the only reason companies use small ones is it is expensive to buy larger pieces without imperfection is the wood.

And some have built one piece cores!

I am looking for people's views.

It seems a shame and a pain in the ass to resaw the 2x6,s of perfect spruce into smaller strips, just to glue them together again?

[skidesmond]

From a purist stand point, glued strips make a more torsionally rigid ski. Today's' glues are very strong. Also from a purist stand point, you want to have the grain to run vertically as much as possible, which is another reason for re-sawing. So look at the end of each board to see how the grain runs. Is it more horizontal, vertical or in between.

No doubt commercial ski manufactures use thin strips for a firmer flexing ski AND it's economical because of imperfections. As a side note I have seen commercial skis that were cut open and the wood strips were not all very pretty. Big companies are not going to pick through every single strip for imperfections, but you can.

I've made a ski from a single piece of ash, it came out excellent.

Any approach will work. Just depends on what you want out of your ski. If you have a truck load of wood, make up 2 cores. One with a glued strips and one natural. See how the flex is different and which one is firmer.

[ben_mtl]

IMO another reason for "bookmatching" and "thinner" strips (mines are 3/4") is that it allows you to "average" the flex and the weight for a pair of cores. If you took 2 raw planks for a pair of skis, chances are the density of the wood is gonna be slightly different to very different between the 2, thus affecting flex and weight on the final cores.
Does it really matter in the real word ? I don't know.. (even though regarding weigth I found out that 2 planks of the same wood can be very different)

[Dtrain]

Thanks for the views guys. I think for skis ill use a table saw and resaw the 2x6 into 3 pieces and then rip into smaller strips.

For snowboards though, I think I am going to go ahead and laminate six 2x6 in a block and resaw on the mill. This will give me six 2'' strips per snowboard core. 10 half inch core blanks hopefully after the kerf of the blade steals some.

I cant stress how perfect the grain pattern is in this wood. Most is close to 90 degrees straight up and down along the 6 inch axis. I will selectively pick the boards for the snowboard core block.

[Dtrain]

. If you have a truck load of wood, make up 2 cores. One with a glued strips and one natural. See how the flex is different and which one is firmer.

I think I will try this though. I will make a one piece ski core from Sitka Spuce and another with >half inch strips of the same wood, and do some flexing and stress tests.

[Richuk]

Stringers average out the effects of the remaining internal defects arising from in-service use. Cracks will grow over time if they have somewhere to go, so stringers stop the growth of the fault along natural (unseen) fault lines - like a firebreak. The issue being managed is the effect on the laminate structural laminate.

Cost is going to be an issue in deteriming the core design and construction ... but what you lose in one area can potentially gained in another.

[Dtrain]

Never thought of it like a "firebreak" for cracking. That is great thinking. And yes, what may be a negative is one aspect, could create a positive in another.

[Dtrain]

Cores are not necessarily hard work. Just a lot of it. When glueing individual cores, you have to find a happy medium between bending the wood and putting stress in the glue up, or spending a lifetime jointing the strips, and trying not to lose half the material. I have found that if you cut the strips wider than what the finished product should be ,you can Joint one edge then cut the other edge parallel on the table saw. This way you can achieve straight strips of proper width. This is a pain in the ass, and time consuming.

[Richuk]

Interesting ... would need to see a photo. Have you checked out Peter's process.

[Dtrain]

I'm not sure. Who is Peter. Does he have a journal. I think I've read every journal dating back to 2010

[vinman]

IMO jointing your stringers is a waste of time. If you are sawing flat sawn lumber(grain running horizontal) into strips you'll likely have a board that has been planed top and bottom. When you rip your lumber you'll be turning each strip 90 deg ( grain in vertical) and gluing the planed surfaces together.

So unless you are buying quarter sawn lumber (expensive) or if you are gluing up your stringers with horizontal grain (weaker than vertical) the added step of jointing is wasteful in material, time and money spent on tools.

[Dtrain]

My 2x6 Sitka is all quarter sawn, so yes, I would be glueing the table saw cuts back together.

[vinman]

Makes more sense then. But still not sure jointing is needed.

[skidesmond]

IMO there's no need to run the strips over the jointer. If your table saw has a 40 or 60 tooth blade and a decent fence then the strips should be ok for glue up w/o jointing. The jointers primary function is to flatten a board and make it smooth. It doesn't necessarily make a board 90 degrees to the adjoining surface, unless you have an expensive parallelogram jointer.

If the 2x6 sitka has a rough surface, run it through a planer. Or run the surface over the jointer, then rip into strips and orient the strips so the end grain is vertical for your glue-up.

[sammer]

Have to agree, jointer isn't needed. Take your time with the table saw, a good sharp blade, and PU glue will fill any minor voids.

sam