Thread: Australian timber for steam bending or laminating

The ribs in my 50' cruiser from 1937 are Spotted Gum. They were about 1 1/2" square - but on closer examination had been split up the middle except for the last 6" or so. We replaced or sistered 13 ribs in one hit a few years back.

We used fresh milled Spotted Gum that we steamed and nailed using the original holes in the planks. We had cut off the original nails and punched them out.

Not too difficult. I used to have photos of the process up before that miserable mob of snots (Sony) pulled Imagestation.

Do you have any photos of the damaged frames?

I've really only just ripped out all the loose clutter from the boat. Tomorrow I'll be doing acloser inspection and will take some photos. I'll post them. Some have been reinforced with metal straps - I'm pretty sure that's not original. I'm also pretty sure some have snapped in the tight spots where you'd expect problems. It's actually in these spots that I'm considering laminating up frames from thin strips, but no decisions yet. I'll send photos soon! Rick

Good steaming wood should be the density you desire (for strength and flexural requirements), preferably have an interlocking grain (helps prevent checks, splits, etc.) and most importantly have wide growth rings, rather then the more tightly packed ones we're constantly looking for. Of course this assumes you select good looking stock, with straight grain and minimal run out, particularly in areas with tight bends.

Lamination can solve the wood quality issue, though it's usually more work to laminate frames then to bend them. Steaming isn't hard. If you select a good bending species (some just bend better then others), keep and eye on grain run out and work efficiently, it's a fairly enjoyable experience.

Originally Posted by RFNK

II'd appreciate any opinions on the best Aust. timber to use for either bending the frames into place (they're about 40mm square) or laminating with thin strips and epoxy.

That makes two of us, as I'll be doing the same once the heat of summer is over. A local shipwright did say that good old Tassie Oak will do the job. He recommended ripping it into strips and laminating - something I can do while it's still on the water and still sail in the meantime. He's all about maximising time on the water and minimising time in the shed - reckons you can be a either sailor or a shipwright but rarely both (unless you have a fleet).

RFNK and Darce

There are Forestry NSW booklets on Aussie timber for boatbuilding and on bending Aussie timber.

If you (or anyone else) would like copies, please PM me with your e-mail address and I will send you pdfs.

I should have also mentioned, I'll be laminating up some Spotted Gum ribs in the next week or two (although getting the diff back into my car after the wife ripped it out is taking priority - and that involves a bit of metal laminating....)

I've got some 40mm x about 3mm maybe 4mm dried Spotted Gum strips. We think we can get it into the Payne Yellowtail without steaming it - I've tested one bit and it did snap, but it should make the fairly gentle curves we need to do. I'll update when I get to that stage....

Ian

As promised, here are some pictures of the tighter spot in Windrose where the timbers are obviously overstressed. As this area, along with many other parts of the boat, is likely to need fairly substantial refastening, I think I'll laminate new timbers (frames) for this area. I know it's pretty typical to find the timbers cracked in these tight areas - I just have the opinion that if the years have shown that the timbers as designed are not really up to the task, then an opportunity to reinforce the intended design should be taken. You might also notice the split stern post where the propellor shaft is. That'll need to be repaired too but I'll start worrying about that and other tasks once the hull shape has been stabilised through refastening and some reframing. Rick

Those engine beds are mighty short. I take it they are steel? They may have contributed significantly to that cracking.

Rick, do you intend replacing the frames completely or will you use sister frames? You're about two months ahead of me, so I look forward to following your progress. It would be cool if I can follow your thought processes with each decision.

I've started a blog about 'Genie' and will be updating it whenever I complete a project, or learn something new (probably every day in that case )

The engine bed isn't really short - the photo angle is a bit deceptive. However, I will probably replace it later anyway so if it's necessary to change it at all, I'll do that. I'll certainly look at how the engine load is spread and see if it can be eased a bit more.

darce, I'll be heading back to Vietnam (where I work these days) for much of 2009 so it could be quite a while before I'll actually be replacing frames. The order is like this:
1. Build a shelter right over the boat to keep water off.
2. Remove `decking' to see how much deck needs to be replaced. I'll probably have to remove the side decks anyway due to the extent of the damage done by the `decking' (thousands of screws run through the deck toi secure teack strips - can you believe it? )
3. Remove deck in all suspect areas
4. Remove the cockpit sole and sides (they're all shot)
5. Reframing, I think mainly by laminating, and refastening, in all suspect areas
6. Replace deck
7. Once the hull is tight, I'll have to decide whether to sheath it. I don't want to do this, I'd rather keep it original but it's possible that sheathing with glass or `cold molding' may be necessary.
8. Sheath the deckwith glass
9. Remove the ballst and repair timber keel, improve ballast etc.
10. Extend floors around the mast area - cut a curve into the floors and laminate wings to extend up the sides (to spread compression loading more evenly)
11. Replace the engine and all relevant fittings
12. Rebuild the cockpit
13. Put everything back together!

Of course this list isn't complete, and the order will change, but it's a long-term project. especially as I'll be back and forth to Vietnam and possibly other places.

I'm very happy to share ideas and all ideas etc. are VERY welcome! This will be very much an exercise in learning by doing! Rick

Hey Darce, i just had a look at your Genie page - I told you already you're a showoff! The page is great!! And Genie's beautiful! We have the same mushroom vents on the Twister (Windrose). I'm going to take one to Vietnam and get a foundry to make up a couple more for our Folkboat. Rick

RFNK, in the top image (second set) all the frames have tension cracks/breaks. In the second image, I count 11 or 12 that I can see for sure have the same kind of breaks.

I'd recommend you release her of the burden of ballast casting(s) first, after blocking. This will take a lot of strain off the floors. I'd also try to jack or wedge some of those seams closed, rather then try to "suck" them down with fasteners. This way you restore her shape before any frames go in, which will just serve to lock any distortions present in place. Then move onto decking repairs. I typically fix deadwoods and keels (which can address hogging and drooping, plus damage) first, then wedge, jack and intimidate planks back into position (addresses bilge turn sag and frame spreading), then firm things up with frame and floor repairs (which fixes her shape again), before moving on to other elements of the project. Then again that's just me.

Thanks PAR, always good to hear the voice of experience. I'll take some more pictures of the boat over the next day or two and post them. I'll take shots of the seams that have opened and other sections inside. The hull is splined, by the way. Several planks are rotten but throughout the boat, the breaks in frames, opening of seams etc. all seems very even. I consulted with a marine surveyor (ex-boatbuilding teacher) who believes the fundamental problem with the boat at present is slack fastening. I'll post these additional photos to see what you think, and I'll also do some more precise measuring, but I don't think there's really any distortion at this point. As far as the cracked frames go, every boat I've seen of this age with this very tight turn to the bilge has series of cracked frames. It just seems to me (please correct me if I'm wrong) that this is because too much has been expected of these timbers, i.e., the bend is just too tight for them. I'm hoping that we can build up stronger frames (either full frames or intermediate frames) by laminating thin strips with epoxy. Rick

The cracks and breaks you're seeing are very likely what we call "tension" breaks. These occur as the boat wet/dry cycles and the frames are stretched and relaxed repeatedly, until they just break, usually while in tension. The break is characterized by looking quite uniform and squarely perpendicular to the grain, plus nearly always where a fastener penetrates the frame (the weakest point).

It's possible the fasteners have worked loose and have "egged" out their holes, but this generally doesn't break frames. Honestly, it's often a combination of several things that lead to these types of repairs, loose fasteners, leading to working planks, which spit out or split their spines, tight bilge turns, light framing scantlings or spacing, cyclic loading, impact damage, etc., etc., etc. Whatever the cause is really unimportant now.

I blew up the image and did see a slight droop of the bow, but this also could be the angle of the shot too. The midship section seem slightly raised too, which is what happens when the bilge turn sags. In short, if there are planking gaps, particularly on a splined hull, it's distorted some. A little bit here, a little bit there and it all adds up.

Here's the way I usually handle those old CCA war horses. I carefully block it up, with the intention of immediately removing the ballast. With the ballast gone, I level the boat in both directions and remove the garboards a plank or two at the bilge turn and one or two just below the sheer strake, unless the sheer strake is in obvious need of replacement, then I remove it too. This opens up the boat so I can see the places where issue like to hide. Through the gap where the garboard used to live, I can see the keel, keelson, hood ends of the frames, cheek pieces (forward), outboard ends of the floors, plugged up limbers, etc. I can also reach through and chain things down if necessary or just to slap a wrench or hammer on something I'm at. The hole along the bilge turn will reveal the majority of the tension cracks and is a handy place to feed in small sister repairs in the bilge. The missing plank(s) along the sheer permit a whole frame to be slid down the inside of the planking. You also have access to the clamp, shelf, knees, underside of the decks, etc. from this location.

Your boat looks solid enough to tolerate this partial plank removal without additional bracing. I've had to truss up many a rebuild in fear she'd fall apart after removing this much planking (which really isn't that much). I remember one I trailered about 300 miles with a 1/4" plywood skin (cut into 6" wide strips) drywall screwed to her planking, just to insure she'd be pretty much the same shape after 300 hard road miles. I removed the strips as necessary gain access, until she was "firmed up" enough to repair properly.

Use your eye and sight down the sheer and a fairly stiff batten to sight her bilges, looking for hollows, bulges and any other humps and bumps you may not desire. Another clue it trying to picture how a frame would have looked if it wasn't broken and how much this would lift the turn of the bilge or tuck in the hollow of the garboards.

I love those style boats. They're sea kindly, comfortable and if sailed well, fast and weatherly. They don't have the internal volume of a modern yacht, but they also don't bounce around like a cork in a bath tub either or try as best as they can to broach on you in a steep sea. These are the type of yacht that will "take care of you" and look good doing it. You're in for some work, but a real treat when you're done.