Ski Builders Forum

The winter is coming and it is time to make some good cores. We did not find any poplar lumber in good condition for reasonable price locally.

So we just bought 10 poplar trees. They are in the sawmill at the moment

We picked them up right from the forest. There were a lot of different trees - younger and older, different sizes.

We took young trees 22-25 cm in diameter, 5.4 meters length with less branches.

The question is:

What is better - young or old tree?

What about the moisture in the wood? What is its perfect value - 8%, 12%...?

We suppose to dry it in a kiln. Is it necessary or we could dry the planks in the shop?

No idea on age....Poplar can hold a lot of moisture. Get it kiln dried and ask the guy there. I'd say single digits for moisture content.

If you let it air dry it will take at least a year to dry out. You want the moisture content to be around 6-10%. (I also build furniture on the side and this is what I shoot for) I say your only option is to get it kiln dried.

Generally older trees are usually better. Depending on how the tree is milled you'll get straighter grain. But since you're going to be cutting it into strips it may not make that much of a difference. Definitely get it kiln dried.

For sure there is difference in the mechanical properties of young and old trees. When we buy so raw material, it is good to know what to take exactly. Next time we will get some older trees in order to find out what is better.

Thanks for the answers. We found very cheap kiln nearby - the price for drying is about 35 euro per cubic meter. Hopefully they will do the job well.

You might find these guys helpful ... maybe they will have a conversation: http://woodcores.wordpress.com/. There is some technical detail available on the webiste.

I would speak to your epoxy supplier and find out what they know about maximum moisture content, usually the answer is 'too much moisture is bad'.
Conducting tests based on small samples is advisable.

Older trees are better. As far as moisture. If you mill 1x6 and air dry, you will be able to use them next year if kept indoors to dry. We use wood that has a 10-12 percent moisture content. Living in a wetter area of the world, achieving dryer is hard unless you use a dehumidifier or let it sit for years. We use air dryed wood most of the time now. Sitka spruce and yellow cedar.

Surprise.. Nobody wants to dry our poplar decks, because they are too wet. The kilns we found are suitable for 40-50 cubic meters lumber. We have just 1

We will keep the wood in our house for the next season.

What do you think about fir? We found kiln dried fir for reasonable price. Fir is listed in "how to" skibuilder`s section. Does somebody make cores with this wood?

Good quality fir without knots is a great wood for skis.

I have used fir in most of my skis as I got quite a few strips of clear vertical grain for free. However, I am careful as to where I use it in the ski. I find it doesn't hold screws that well so I don't put it under the binding holes. I also don't use it on the outside stringers that I shape with my router before putting on the sidewalls. It tends to not cut that cleanly and can rip apart even with a sharp router bit.

What grows locally and survives harsh winter conditions. Is the species being 'farmed', if so, can you use the 'thinnings'.

I've used fir also. Makes for a lighter ski. Follow Dr. Delams advice.

Back to the original poplar Q - Is it better to use the green heartwood? or the white sapwood?
My plan is to re-saw veneers, and flip them, concentrating mostly toward QS ("Vertical grade") grain.

As opposed to gluing up a stack of toothpicks edge to edge as one would do with poorer quality starting material.

Veneer top and bottom over a profiled center section of probably maple? to hold screws.

Since this "core" between veneers is the total vertical shape of the actual core before the veneers meet at each end, Is soft maple ok? Is hard maple better? Or ash? These are the easy options here, but i can use harder lumber if those are not ideal.

Thanks!
smt

I would use a hard veneer to cover the poplar for binding screw retention. How thick is your veneer? Cutting the poplar so the grain is more vertical will help strengthen the wood core.

Actually I did this a long time ago... I used a thick ash veneer about 1.6mm thick on the top and bottom of the poplar wood core. I didn't use any fiber glass. It was an all wood ski aside from the ptex base and edges. The ski was super stiff and the wood core was thicker than it needed to be. I think I still have the skis in the corner of my basement.