wooden compression post: laminated or solid teak

[granche1]

Hi all,


I think that I need to replace the compression post in my Pacific Seacraft 37. The original is 5"x5" laminated white oak. I am in the Philippines and have the option to use solid teak or some other very hard wood. Is there an advantage to laminating that I should be aware of or is it better to go with a solid defect free piece of teak?


Thanks,


Grant

s/v Viandante

[tkeithlu]

Will the oil in teak create a problem for you? Will a solid piece instead of a laminate risk a split under compression?

[Compass790]

Laminated wooden beams are much stronger than single piece beams IF GLUED PROPERLY

[Wotname]

If the compression post stays in column, I don't think it would matter but I'm not a structural engineer!
Me, I'd use SS pipe unless the wood was way cheaper.

[Pete7]

Originally Posted by Wotname

Me, I'd use SS pipe unless the wood was way cheaper.

Me, I'd use mild steel pipe unless the S/S was way cheaper

Actually we do, ours is a normal piece of steel and covered in a hardwood veneer, now 31 years old.

Pete

[David1033]

I don't yet have much experience, but I have a little bit (dangerous thing!) of engineering insight, and I was about to suggest steel pipe, coated in glass and epoxy (against rust) then the glassed-in pipe encased in a teak (or other, suitably protected wood) lamination.

It might be a bit over the top, but I'm a belt, braces (suspenders in USA) and a bit of string person. That post isn't called 'compression post' for nothing, and I'm prone to a bit of over-building.

[stormalong]

I do not have an engineering background either but teak is not a hardwood and is not as strong as oak.

Teak is called a hardwood but actually it is quite soft. For such a structurally important component I would consult someone more qualified than the opinions on a sailing discussion board.

No insult intended to the participants of this forum.

[David1033]

Agreed that teak is not a hardwood. My suggestion of encasing a steel pipe in teak was mostly for cosmetics. On reflection, choosing a wood to match the interior would make more sense, and if the original compression post is Oak, then it would make sense to cover the pipe with oak laminations.

[Cheechako]

You don't need anything heavy. Build a box beam of lightweight wood. Or a box beam of whatever you have available. It's in compression. There's a reason lightweight Spruce is used for wooden masts and bowsprits a lot. Oak is a terrible marine wood unless it's white oak. It blackens and rots fast.

[barnakiel]

Beams are laminated but posts are often solid. You can calculate the data with online calculators - use your original post material as the starting point.


If you cannot find a matching wood, you can use other wood then use glued on veneers of matching material.


A SS pipe is also 100% viable but not cheap if you look up prices for large diameter long piece.


In our boat we used solid Iroko. Sailed then the boat across the pond twice. No issues.



b.

[roverhi]

Had a 3' x 6' teak compression post on our Westsail 32 that we built in 1974. Still there and doing fine after 3 voyages to SoPac. It hasn't rotted at the base like the mahogany post base on our current boat.

A laminated beam would be less prone to warping but not really an issue if you have a straight piece of air dried lumber to start with. A laminated piece could be subject to delamination especially if water gets in the end grain.

Steel works fine if there is no water intrusion. Hey it's a boat, water will get in and steel will rust. Ask Cal 40 sailors about their steel mast supports. It's not only steel that has corrosion issues. The aluminum base plate of my current post is looking very iffy from corrosion and it hasn't been sitting in water.

[SwellGuy]

Originally Posted by stormalong

Teak is called a hardwood but actually it is quite soft. For such a structurally important component I would consult someone more qualified than the opinions on a sailing discussion board.

My years of personal experience with teak would disagree - I think it's an incredibly hard wood. While I'll believe there are significant variations based on exact species and environment in which it was grown, I can't imagine finding teak that was "quite soft." Drilling, scraping, routing, all these activities have left me with the impression that teak is one of the harder woods I've come across.

Regarding qualifications, I'd have to agree with you. Replacing my compression posts were a matter of identifying the load they were designed to take and sizing a steel pipe that would not experience buckling failure at that load. Not a lot of room for forum opinions, its a pretty cut and dry engineering calculation.

To the OP, note that the loads are significant and have little to do with the weight of the mast itself. When the mast and standing rigging are working to lean the boat over, there are 10s of thousands of pounds of compression possible on a heavy old 40 foot yacht.

[sailormed]

Concrete is cheap and on top of the compression resistance materials. Just sayin

[peter loveridge]

on my 31 foot boat, the compression post is 3x4 larch. Never given me a problem

[Jim Cate]

Grant, if galvanizing is done in your area of the Philippines, then a mild steel pipe with welded plates on each end would be inexpensive, hugely strong and wouldn't be a corrosion problem. And if there is an industrial scrap yard around, scrap stainless pipe wouldn't be too dear.

Jim