Making jump rails - trim first or air dry first?

[LCDR]

I am making a dozen new jump rails. My usual technique is to start with pressure treated 4x4x10’s or 4x4x12’s. I set a circular saw to cut off all four corners to produce an octagon, by setting the saw at 45 degrees with the edge guide set at 1-1/16 inches. In fact, I have a saw with a blade for cutting wet pressure treated wood that I use only for this, so it is always set up and ready to go. I can produce nice almost perfectly octagonal rails this way. Now for the question.

I usually cut the rails into octagons when they are fresh from the lumber yard and then lay them out flat with an air space under them to dry to about 11% moisture content before painting. Some always rack or twist, the center cut 4x4’s being the worst, and are unusable. Quarter sawn 4x4’s deform much less, but they are about as rare as hen’s teeth. I am wondering about trying air drying first, and then cutting later. Any one have experience with this or have a way to reduce warping that works for you?

[goodhors]

Perhaps weighting the drying poles could aid in keeping them straighter as they dry down. We stack green boards in layers with spacer (all the same thickness) pieces to separate the layers slightly. There are a number of spacers the length of boards. Not sure if they are quarter or center cut at the sawmill. Not treated wood, just trees we took down, too big and nice to waste as firewood.

Not sure if leaving them as 4x4s to dry would aid in staying straighter when stacked and weighted during drying would help. There is more wood fiber surface to keep them rigid as squares than as octagons, with weight above holding them in place. I would probably buy more than 8 or10, to try with drying in a stack with my spacers and weights holding things in place. You gain the wood weight of extras in the stack, dry more at a time to use when needed. You will end up using them all eventually, just more expense at the start than buying only a few.

[B_and_B]

You are using 4x4s that are already pressure treated? I think they are going to twist no matter what you do. Some won’t, they are the ones that happen to be correctly cut from a tree that didn’t grow too fast.
If you are starting with air dried wood, stacking and weighting may help. There is a funny thing with air dried wood that is not plantation grown, if you can stack and weight it, and Leave it, chances are it will be dimensionally stable. But that takes time and space. Kiln dried wood can do some really weird things as it reacts to the atmosphere. In the right setting, it will settle back down. (I had some doors the other year 14’ high by 8’ wide sliders) that warped almost two inches of bow in the center every time it rained, they are since back to dead straight even in rain but they were built right and it took a year…)
Unfortunately, a 4x4 that is loose is never going to settle down, it will warp. Fast grown, cheap plantation wood will warp more than anything else.

[clanter]

use western cedar? these would be lighter and would not needed to be treated as the western cedar is naturally rot resistant

[LCDR]

I do usually fbuy lumber in larger quantities and stick and stack it to dry. But there are always a few pieces that outsmart me and warp sideways. Almost like they are trying to escape from the weighted stack.

I do use western red cedar for most of my jump standards. I learned the hard way that they will rot within a few years if they touch the ground at the bottom, though, so now I build with the butt of the cedar 4x4 off the ground when I put on pressure treated pine feet.

Using cedar for rails is something I have not considered before, simply since I cannot find 4x4 cedar any longer than 8 feet anywhere around my location in SC.

I think I am going to try stacking this latest small bunch of 12 pressure treated with sticks in between into a 3 by 4 rectangle and use pipe clamps side to side and all my 16 tractor suitcase weights on top and letting them air dry.

[B_and_B]

That might work. An interesting experiment!

[Greys]

Have you considered “laminating” poles? Rip 3 good quality straight 2 x 4s to matching dimensions with square edges, glue up with waterproof glue into a beam, then proceed to cut the corners off as you have.

I’ve not done that for outdoor jump poles, but I do use that technique to build up posts for basic cabinetry, work tables, and the like.

greys

[NaturallyHappy]

Someone did ghat for me with jump poles nearly 30 years ago!!! I’d forgotten. Some of those poles are still in very good shape.

[LCDR]

Change of plans. I decided to go ahead and trim them to octagons while they were still wet because they were nice and straight at that point, which make trimming easier. Now they are stacked to dry.

BTW, I had always worked on the premise that a 4x4 really measured 3-1/2 x 3-1/2. Well these name brand poles are all 3-11/16 square. The first one I trimmed didn’t look quite a perfect octagon, so then I measured and made the necessary saw corrections. Note to self - actually measure the dimensions of each batch of lumber.

[Southernboy]

Treated yellow pine 4x4s will warp no matter what. As wood dries, it contracts. If you could clamp them down with enough force, they would start splitting. The treatment does not go all the way through the wood. Think of it as an eggshell. Once you cut the edges, cut the ends, nail, or drill, you will need to paint or reseal where you broke that seal. The 4x4s were initially dried to 25% or less moisture content. The pressure treatment will add to that and will also increase the size until they dry back down. If they ever get to 11%, they’ll look more like cork screws and will be smaller.

Grey’s idea of laminating 2x4s will give you a better product.

[LCDR]

Thanks. Maybe some readers don’t have our knowledge levels about woodworking. Been doing it myself for sixty years and still still being schooled.

[clanter]

@Southernboy

Grey’s idea of laminating 2x4s will give you a better product.

if so use wooden wooden dowel pins to hold the laminated pole together so that you use a saw to round the squared product

[LCDR]

Laminating? Wouldn’t I still need to dry the pressure treated lumber first? And if it warps then I’ d have to try to run the 12 foot boards through my bench top jointer and planer before gluing.

Or is there an adhesive/glue that would be effective laminating wet pressure treated lumber?

[Greys]

I don’t think I would try that on fresh/wet pt lumber.

I think I’d try some good quality kiln dried pine, or Douglas fir if you’d like a workout, and then use marine grade paint to protect it. I haven’t done this myself (although now I think I’m going to), so it’s theory rather than practice, of course.

Clanter’s idea of using a dowel for alignment seems like a good one to me too. Cut flush, sand, and seal the end grains well.

greys

[Southernboy]

Some retail yards will carry KDAT, kiln dried after treatment. The lumber is pressure treated, then put into a dry kiln where the moisture content is brought back down to its original MC before it was treated. Lumber will be dry to the touch and the warping and shrinkage will be much less going forward.

Or you could stack the pressure treated lumber on sticks for 30-45 days during the summer and do the same thing.

Look up laminated, pressure treated timbers. These can be used structurally as beams so I’m sure they’ll hold up for jump rails.

[Rackonteur]

I have no knowledge whatsoever of woodworking and I am finding this thread fascinating and educational.
I’m glad y’all are posting! The cool things we learn on COTH.

Good luck with the new rails!

[clanter]

I would look around for 12 ft 4by4 western cedar , these are readily available in my area (Home Depot says they have 844 available locally)

https://www.homedepot.com/p/4-in-x-4-in-x-12-ft-Rough-Green-Western-Red-Cedar-Lumber-0530112/313533429