replacing timber beams with FG

Going back to the designer is the best approach.

The problem here is that it is not just the strength that you are changing by replacing the beams, but the stiffness. These beams are relatively flexible, and allow the hulls to move relative to one another and to not impart high loads because the beams are flexing and spreading the loads over a number of beams. Increasing the stiffness of the beams could result in much higher loads being imparted to the hulls where the beams attach and that could be a disaster.

Unless the solution is properly engineered you are just asking for trouble. New beams could be designed using fiberglass, aluminum or any number of other materials, but to work properly they need to have the same stiffness as the existing beams, and be at least as strong as the beams being replaced.

 

Sure Wayne, you found me out. In the meantime, it's irresponsible of you to blather answers when you have no knowledge.

 

Bump,

Raf pali, would love to know what you have done (or did) with your TM beams. I was about to order hoop pine for mine but would love a more durable solution. Ideas?
Thanks

 

Why not use Ironbark ( eucalyptus ) Very strong and durable and available most any where now that they farm it all over south and central america. I love the stuff.

 

Its a weight issue really, although 12m long, it should displace only a few ton total. Camphor laurel is an option as well. Needs to be 4 or 500kg cm ithink. Thanks!

 

...Why not use Ironbark?... rasorinc, Ironbark is very durable but way too heavy and way too difficult to work with.

triskrd: ...Camphor laurel is an option as well... No triskrd, camphor laurel is not an option at all, you'll never find any planks long and straight grain to be of any value to build beams. The best bet to source the right timber now, is to contact demolition companies and ask for old Oregon beams.
Cheers

 

We've been getting some nice Oregon/Doug' fir clears from Harper timber for laminated spar work, oregon has good strength to weight, also got some comparable pricing from Simply oregon in Vic. Oregon is way more durable than hoop. It's gunna cost some but then it's a boat- bring on another thou.... or ten.

Jeff.

 

Raf pali, i have a source actually. I can get cl, hoop, silver ash or even red cedar. Thanks anyway.

Jeff, I was thinking of doing that as well. Maybe even birdsmouthing spotted gum or thicker Oregon

As this thread explains, the engineering is complex. Although I think building the beams like masts is comparable in expected loads?

 

Thanks Jeff!

 

I might have posted a pic.... not sure I'm on a mac

lam'ned about 300x300 x 12m cost about 7-8k with glue & clamps plus sundry items, plenty of labour outside that as tapered & rounded etc.
J

 

Scary work!!! Did you spread the glue on all the boards at once? How many rings can you count on the end grain?
I have a few sticks of 50 y old Oregon/Douglas fir and counted 40 rings in 25mm/1''. It is a rare A1-quality timber that now a day is not available any more. That's the type of timber I'd like to use for vital parts as cat beams.
Using fat timber is recipe for rot soon.

 

Spotted Gum is heavy and "greasy", doesn't glue well.

 

Hi Raf Pali,

not so scary as good professional labour resources, we did the first two laminations-single glue line plus scarfs with back up blocks on scarfs first day with three up to form a stable straight base & next day kept cutting scarfs & did the glue up with around 8-9 with dedicated mix team of two, the rest applying & one on clamp set up, got it under some squeeze in prolly 45 minutes. set up the stack dry & just lift & turn in order. There's about 25-30 kgs epoxy went in. The steel shs clamps are terrific, very little spring or crush & turn the nuts for good ooze factor, we shot some dowels(these got cut out with tapering) in as the stack went so everything stayed aligned because it's bad when layers slip. took five days from start to finish painted & gear fitted & back fitted on ship was next day.
Not sure on the grain count but pretty tight, only one small knot in the lot, ordered overs by about 30% to cut scarfs, stagger & pick boards.

Jeff.

 

Impressive!!! My hat off to you. When you bought the timber, did you go personally to see it and select what you wanted or you did order the lot on good faith? Just to know if I can trust the merchant. I live in north QLD, it's a long way to Melbourne.
Thanks.

 

Hi,
the timber in pic came from Harper timber in western sydney, didn't see it before but had an industry recommendation from a similar job & also a very very very tight timeline to replace that spar so the vessel could meet commitments. Pretty much sorted availability, got a price, got them paid so it could be thicknessed/faced & had one of our contract workers head there that afternoon to pick up material for next morning early start, he headed back for another load whilst one of my guys & I started cutting scarfs, unfortunatly every lam layer had two sets of scarfs but pretty hard at the length to get around & at 12:1 & staggered around just some extra work really. Prolly got 2/3rds the scarfs cut on the first day & didn't chase fit up on the scarfs past about 1.5-2mm, epoxy glued pretty ideal.
Got some straight forward info from Simply Oregon & pricing similar but for that job I was in a hurry so couldn't wait, kinda got lucky with Harper as had been doing material research for a small topmast when this other effort popped up.
Have also got some good stuff from Barrenjoey timber in past, another reliable source recommended supply from Wooden Boat shop Melbourne but didn't follow up on pricing etc from them.
I can see the issue with remote supply, you really need to talk to supplier about what they have on offer & if it will suit your purpose, in my case with the pictured spar blank there was an imperitave to meet... I'm very careful with my employers dough but again if the spar was not the best we could go again later...... at leisure....... as it turned out it was better than the last one that it replaced.

Jeff