spruce vs pine

[Charly]

Hey guys, I am getting ready to build my crossbeams for my Kurt Hughes 36 Beachcat.

The plans specify 3/8 fir ply with the corner/joins made up of two laminated pieces of 3/4 x 2-1/4 x 22' spruce.

Sitka prices are killing me. I am thinking about using southern yellow or longleaf pine instead. Pine is plentiful here in the southern US, so I should be able to find some affordable and excellent quality stock. I understand that pine is heavier and stronger than spruce.

Questions: When is the pine too "sappy"? Is there an issue with proper bonding epoxy to the resinous pine? Should extra measures be taken to prep this wood for bonding with epoxy?

Any other advice as to wood choices?

Thanks!

[BATAAN]

Go on the WEST systems website and I'm sure they have advice for LLYP gluing.

[CatBuilder]

Also, I am looking feverishly for my source for sitka spruce. It was a very small family mill out of WA state and it prices were about half of everyone else for spar/aircraft grade. Hope I can find it... They were more of a "telephone" type company, so it doesn't appear to be in my email.

[hoytedow]

Cut your boards from large boards. Bigger boards will have been cut from bigger trees, so knots will be less an issue. possibly totally clear of knots. Be selective.

[Charly]

I didnt find anything specific to pine at gougeons site. Just the ususal wipe down with acetone, free of dust and contaminants, etc. I was mainly wondering about the chemistry going on there with the pine resin and the epoxy resin.

It seems the tighter the grain, the more strength, more weight, and more resin in the wood. So I am thinking I want good balance of straight grain, clear, but not with too much resin. Pine resin is also quite brittle when dried.

I made up the stringers by picking through the spruce stock at the lumber yards. It is a hassle, but I was able to get what I wanted by ripping down two- by stock into 7/8 or smaller strips and then ripping those to get what I needed for laminating up the stringers. I may do that again, but these pieces have to be 2-1/4" wide, by 3/4 thick. It is harder to find long knot- free sections for that dimension, and more difficult to get an accurate rip when cutting the two-by stock on edge

Cat, I may still have that number you gave me a year or so back, I will check on it. I did call them, an told them what I was doing. They said they would call me back, but never did. I got the impression they didn't want to fool with such a small order.

[PAR]

SYP is over twice as heavy as the spruce. It's not difficult to glue.

[thudpucker]

Cedar? Locust?

[PAR]

The thing about many of the spruces is the compression tolerance and strength for weight ratio. It's had to match in other species.

[rberrey]

I would look at fir before I went with the pine , if you know for sure your getting long leaf maybe, but you could end up with loblolly. Last year I bought 2x4 studs from Lowes that were some sort of fir, one did,nt have any knots at all. They had 2x6,s as well,worth looking into. Rick

[Boston]

Pine and Douglas have wildly variable characteristics even within the same board let alone the same tree. I do a lot of woodwork and avoid both unless the customer specifically insists on it. Some of the spruces are really nice tho, Sitka ( small island off the NW coast ) grows some of the nicest and most consistent.

I don't use epoxy all that often but gluing properties include stuff like moisture content and how porous the wood is. Some woods like Cedar soak up a ton of glue and end up heavy so how porous the wood is makes a big difference. There is a few interesting bits and pieces in here about encapsulation of laminates that you might find interesting, I've never tried it but I plan on it for my own build once I get the shop cleared of the present project.

best of luck
B

[CatBuilder]

Yes, that was the place, Charly (you PM'd me). Sorry they weren't interested in the smaller order, but they were $4 bdft. For aircraft/spar grade sitka spruce, that's a good price.

Look at it this way: These beams you are about to build are what hold your two hulls together, that you've spent countless hours and a truck full of money on. These are the most important part of a catamaran. This is the one place I wouldn't skimp on materials or craftsmanship. As Kurt says in the plans: "These need to be perfect."

Reconsider the spruce and just see if you can get that company in WA to do the order. They were very difficult for me as well, as I was putting together a possible spruce order before changing to a corecell/glass boat. They are just kind of lazy is all, but they have good stuff, cheap.

The spruce is lighter per unit strength, you have exact scantlings for it (you have to modify scantlings for substitutions), it's more uniform and performs much better. Just as Boston is saying, this is one place (the cross beams) that you don't want any variation. Imagine those two hulls trying to go in different directions and a big old pine knot in the middle of the beam. Yikes!

[Boston]

can one of you guys send me that number and whats there minimum order ( most are in the 1000 ft range ) $4 a foot isn't bad at all and it'd be nice to have those guys on file. I still schlep wood from time to time and the more contacts the better.

Thanks
B

[CatBuilder]

Here's part of that PM. These guys should get a plug for their good pricing anyway:
-----------------------------------------
Hey Charly,

I just found some mast/spar grade Sitka Spruce from a reputable place in WA state (closer to where it's from) for $4/ft!!

They are Fred Tebb & Sons, Inc., Phone: (253)272-4107.

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[nwahs]

greetings

its probably best to go by the book and let cost end up what they are, hopefully in the big picture compaired to your time not that big a deal.

however that said, if your thinking alt woods there are huge amounts out there- as mentioned eariler spruce has a great ballance to strength ratio. and with its grade (should be defect free)
to be honest my exp, has found wood varies hugely form the particular board to board,
read the grain no matter what grade someone says it is! beside the knot deal- you want very strait grain, and circle grown rings that indicate older growth far from the center of tree- lots of internal stresses there to due with shrinkage, not to mention rapid growth of first seasons. (its the biggest proublems with todays lumber they dont let it grow, well maybe besides hurry and get it out even if its too wet). i like quarter sawed pieces myself even thought your dementions listed above should not have cupping issues
when you cut your wood make sure the kerf dose not exspand, or feel for a binding on the blade both i feel indicate stress being releived- but a peice under forces not good.

if you go to other woods reseach them, (pocket ref thomas j glover) is a good starting guide you will quicky see over a hundred wood compaired quick and dirty your see many are stronger than spruce all be it maybe not at the optium weight ratio.
you can weight them look up there densities or weight them out find a desired ballance.

final note- your find moisture a huge factor in wood strenth aprox 1/5 to 1/4 stronger section when at its best moisture content, making a well cured board of slightly sub spec off speicies way better than the spec speices at poor moistuer content.
(better strenght and less weight- you really can have it all- lifes good)

dont over look recycled wood, often its proven stable- well curred- and came from best selections of old growth we just dont have today.

shawn




i prefer quarter sawn to prevent cupping stresses

[rasorinc]

I'm using Cypress in my build. http://www.connectedlines.com/wood/wood22.htm Paying $ 2.60 BF + delivery
for #1 select KD and I have to mill it to size. http://www.cypressusa.com/products2.htm