Glueing oak and teak

[Runhammar]

Hello
I am building two mast supports to be screwed to the main bulkhead of my 29ft fiberglass sailboat. They are plain horizontal beams, 6x8 cm in dimension and some 1,80 meters high. Teak is nice but expensive. I’m planning to build a core of oak, say 5x7 cm thick, and then glue 1cm planks of teak to dress them. I use epoxy glue. Naturally, the pressure on tje beams will be horizontal compression only.
Question one: these woods are known to be hard to glue because of acids in the oak and oil in the teak. Is it a bad idea? Can the acid and teak issues be overcome by buffing with lots of acetone?
Question two: given that it is ok to glue these woods, will the inner core of oak be weakened if I glue up planks to reach the length? (I do not have 1,8meter lumber) I would of course use a 12-1 tapered glue joint.

kindly
Per

 

[Rumars]

Oak and teak are overrated woods. Yes you could glue them with careful preparation and a suitable epoxy like G-Flex, or by using resorcinol. Veneering the beam will only require max. 3mm thick planks, 10mm is a waste and highly unstable, it moves to much. You can scarf the individual laminations, just make sure the joints are not all in the same place.
Instead of using oak and teak you could use iroko (kambala), sipo (utile), bilinga, black locust (robinia) etc. wich all glue well, and some even look good. For the amounts you need you can even buy the wood from a flooring store.

 

[fallguy]

scarfing to achieve 1.8M seems like one too many skimps...but perhaps okay...the loads here are a bit unknown?

Another approach you might consider is bonding with 600/225 glass in between. This will help maintain consistent bond dimensions and if the wood sucks resin; there is plenty in wetted glass to spare.

I tend to agree with Rumars, a full cm lamination is a bit big; I'd go for about 6mm.. Bonding the wood requires precoating and the glass tape method is actually eaiser than troweling thickened resins. I found it rather difficult to get thickened resin bent laminations consistent thicknesses. Pinning them can help a bit. No bends helps some. The issue is it is really hard to uniformly clamp across a couple meters.

 

[Runhammar]

Thank you!
Will definately consider glass in between.
The thing is: I have the lumber already. And I use solid teak for the whole new interior, that I alfeady have. I was going to use solid teak for the beams but came up with the oak idea to save some teak for later. That is why I wanted to know if the two woods go together well.
As for veneering: I didnt think of it as veneering, more like replacing the innermost few planks with oak. The reason why I wanted 1cm thickness is I thought I could run the whole beams through the thicknesser as a final touch up, and also add 8-10 mm roundovers. But now you have given me food for thought...
The original was just two thick planks of teak glued. And they seemed not to move at all...

 

[Will Gilmore]

Are you using white oak? 'Cause red oak is not as rot resistant.

Dido to good surface prep and everything Rumars wrote.

 

[Rumars]

The originals were glued with resorcinol in a hot press, that's why they were able to use thicker wood, and teak also moves much less than oak.
Run the beams trough the thicknesser before veneering, and if you want to add roundovers router a groove in the corner and glue in a small piece of teak then veneer over the whole beam and cut the round. You can cut the veneer yourself or buy commercially cut 2,5mm one. This is sufficient for you to sand smooth and varnish or oil.
Even if you have the oak, you should consider switching to another wood. If it's going to be veneerd anyway, ash is a good cheap and ready available option.
If you must use oak, use G-Flex or a similar epoxy designed for difficult woods. Don't plane the wood before glueing, straight off the saw is best. Don't go overboard with the clamping pressure and you don't need any glass, just epoxy with microfibers and silica applied with a toothed spreader.

 

[Runhammar]

Thank you!
I do not insist on oak. Just thought it was the toughest of them all. Here in Sweden it has a strong reputation for durability. I have access to ash, although more expensive here than over in the US.
Good advice on roundovers!
Thanks again

 

[Rumars]

The toughest and most durable wood that grows in Europe is robinia (black locust) and luckily for us it glues better then oak, and is usually cheaper, altough it has increased in price in the last year. It has become a commercially important wood, so availability is good, even if straight lumber in big dimensions is a little hard to find, so it's best used for laminations and steam bent or grown pieces. It is also the second most ecologically sustainable european wood (first beeing paulownia), if that is important.

For your application durability is not a requirement, the wood will be encapsulated in epoxy, so ash is a good fit, it can be tougher than oak. Price should be significantly less then oak. Plain cut boards are ok, no need to pay extra for vertical grain or bigger sizes, just remember to alternate the grain direction when you glue the beam.

Do a test piece to determine how thick the strip that takes the rounding needs to be, no need to use more material then necessary, and you can use all your offcuts from building the interior.

 

[Will Gilmore]

Is yellow pine availible? Great strength and working qualities as well as durability and rot resistance. Slash pine, Long Leaf pine, Short Leaf pine or Loblolly pine all make great structural beams. They typically have the same specific gravity as maple. The softer white pines are strong, but not nearly as dense.

-Will (Dragonfly)

 

[fallguy]

Sounds like Rumars knows the part well and he offerred lots of good advice.

I made two ash laminated timbers about a year ago to glue onto the beaching keels. This is pretty thick laminations of about 9-10mm, but not much concern about them as they are sacrificial. And these had butt joins in the stack; not structural. But I chose ash over oak and had both options and both red and white oak on hand. These get glassed as well.

good luck

 

[Runhammar]

Thanks for all good advice. I will probably go for ash, and buy the length needed.
/Runhammar