Engineered wood in boats

What are your thoughts and experiences with using engineered wood products in boats? I've seen some references to using LVL as stringers. I worry about dimensional stability but I see that people are using it. Who has used it? Anyone use I-joists?

 

There have been many failures of engineered wood due to humidity. I would not go near the stuff.

 

I always thought wooden boats were engineered wood........

 

Lots of uses for "engineered" wood products, for many decades. Plywood is the most common example. This category is called structural composite lumber (SCL), including laminated veneer lumber (LVL), parallel strand lumber (PSL), laminated strand lumber (LSL) and oriented strand lumber (OSL). This are specifically aimed at the construction market and typically use moisture resistant, not waterproof glues. This is their basic problem, though WBP adhesive can be had, it's often a custom order. If electing to use these SCL products, check with the manufacture to see what adhesive is used.

In terms of stability, all of the SCL products are very stable, much more so than solid wood elements of the same dimensions.

 

There are products that are rated for direct ground contact and have a 30 year warranty. That is better than any non-engineered wood. Paralam is one of those. I suppose other companies have comparable products.

 

All LVL that I have seen was made with PF adhesive, so no worries there. But the product is sold for interior use. The ability to get clean, straight 60' boards is pretty cool.

I haven't done anything with strand lumber.

The I joists I've seen, if LVL flanged, used WBP adhesive as well. My concern is the OSB webbing. The osb is sheathing rated, though.

And yeah, a stick-frame house could be called "engineered wood." Plywood does call itself an engineered panel, but it's all visual graded veneer with no strength QC testing during production. LVL starts with strength-graded veneer and the product is sampled and tested to show that it meets published strength values.

 

Here in New Zealand there is a lot of LVl essentially plywood for want of a name . There is a lot downgraded for face defects So they say its not structural But when you are looking at 50mm ply for 10mm price Cant see it would make much difference .Where you might use it presents a problem ! I wouldn't use it for stringers or planking (30-50mm) probably has potential for ring frames, gussets.bulkheads and floors. Interesting what others might think it would be useful for

 

Make sure you know the reason it's non-struct. There are a lot of processing issues that can result it that designation. I'd worry about the ones that can result in a poor glue bond.

 

All LVL material in the north America are considered structural. There are some variations to these products, some with facings and others, all belonging to the same category of SCL (Structural Composite Lumber). Adhesives can vary, but most are at least type 2 WBP, with some type 1 WBP. Though it might look like plywood, it's not and considerably stiffer and stronger than plywood.

 

They say in the adverts here. That to be certified for framing there are to be no defects on surface faces For example 8 by 2 will sawn from a sheet of ply
typically 3020mm by 1220mm giving 6 planks .PAR is correct in saying its superior to plywood just the shear amount of laminations gives you a clue So there is quite a lot downgraded because of face defects available at 75% of the price of standard lumber and 30% of the price of clears. So you start thinking where can you might use it

 

No Par, it isn't. There is off-grade, rejected LVL sold as non-structural. Much like off grade plywood is sold as "shop," "blows," or "dunnage." To be fair, non-struct LVL isn't available to the general public.

As I said,
"There are a lot of processing issues that can result it that designation. I'd worry about the ones that can result in a poor glue bond."

Not that it's the wrong type of glue. It's possible to use epoxy and get a poor bond. Think of it like that.

 

Had a quick look at prices for LVL even structurally certified is 10% cheaper
than stress tested standard framing timber here in NZ probably holds true in
USA Canada if you can find a willing wholesaler. Ok what about finger jointed timber as a material for stringers ,Any thoughts? I have noticed the premium for clear timber is increasing year on year due to export demands in NZ. So boatbuilding timber is getting scarce unless you are on good terms with a sawmiller

 

If you're willing to buy a rejected product, you get what you pay for. No one makes a perfect product, so some discounted stuff is available, but if built to standard, LVL has its place. All LVL stock is constructed the same, with specific defect rates, per veneer, just like plywood and other "engineered" products. I've never seen a marine LVL, though I'll bet you can special order one, I'd be inclined to use something else (like a truss), if I needed a single timber the typical dimensions seen in LVL's. What's good about LVL are its dimensional stability and stiffness, but in the sizes it's used, there are better choices from an engineering standpoint.

 

LVL uses strength-graded veneer, plywood doesn't. The visual grade requirements on LVL are lower than in marine plywood.

I've also wondered about finger jointed timber for stringers. I like LVL for strength and consistency but feel that solid is better in a high-moisture environment, although I don't have solid experience to back that up.

 

In a marine environment you would be epoxy encapsulating just like you do with solid stock, at least with modern wood construction methods , so I don't see a problem with using LVL in place of solid stock. There are many materials that we commonly use that you simply would not use without epoxy sealing, okoume marine plywood being one.