bondwood speedboad under restoration

[jellyhead]

i have a 1970's speedboat,186 inboard, dog cluch, bondwood top and fibreglass bottom. motor is out and rebuilt, new bearers and floor is underway as we speek, i wish to take the top off and replace it using new plywood as the top that is on it is in very bad condition and is epoxyed blue, i wish to give it a woodgrain top as wood looks better by far than paint, then staining mahogany, and marine clear varnish on top, the wooden strip that ties the top deck and sides is badly wrotten and needs to go, how would i go about moulding (bending) this 30mm bullnose strip to follow the curves of the hull.. any help would be great.

[b.o.a.t.]

the wooden strip that ties the top deck and sides is badly wrotten and needs to go, how would i go about moulding (bending) this 30mm bullnose strip to follow the curves of the hull.. any help would be great.

Might be best if you post photos. Can't work out from description whether it's a load-bearing carlin or deckhead or just a decorative moulding.
Also need to know dimensions of the part, & how much bend is needed.
cheers
AJ

[jellyhead]

hi there aj, thanx for your reply....i dont no how to work computers very well, but i do no how to send a pic via e-mail if this helps?...i can tell you that it is decrative strip that runs along side of the boat just like the rubber gunnel on boats, but this one is made of wood. I needs to be bent 4 1/2 ft from the tip of the boat and runs along the side down to the transom. the new timber that i have for it is made of some kind of hardwood. i brought three lengths and used one as a test . we had the use of a heat ellment and soaked the timber in a large water tank for 2 weeks and for the last four days we heated the water up hoping for it to soften the wood to be bent, but no go...and i dont want to cut sections and mould it using a scroll saw, because i would like it to be one length for as you will see this when varnish.

Ash.

[b.o.a.t.]

hi there aj, thanx for your reply....i dont no how to work computers very well, but i do no how to send a pic via e-mail if this helps?...i can tell you that it is decrative strip that runs along side of the boat just like the rubber gunnel on boats, but this one is made of wood.

Ash.

G'day Ash

What dimensions is this gunwale strip ?
Which dimension is giving most grief ?

Suspect it must be a chunky bit of timber to be unable to go around the gunwale of a 16ft (or so) Hartley.

[Boatmik]

Howdy - some comments.

1/ if the deck is blue - it ain't epoxy - or it is unlikely. Epoxy is clear. There are some epoxy paints - but they are quite different.

2/ wetting wood doesn't make a lot of difference to your ability to bend it.

The technology of steaming is a way of heating wood up to quite high temperatures without the timber drying out. It is the heat that works.

But you need to set up a steaming tube that runs at a high enough temperature and get the timber onto the hull quickly. Leave it a few days to dry out then glue in place.

Bending hardwood can be very difficult in this application - generally softwood would be chosen. However if you reduce the thickness of the timber it will bend more easily bent. Halve the thickness and it will be close to 8 times more bendy. Then you can use two pieces to get the full thickness that you need.

Michael Storer

[PAR]

Michael, I've found bending hardwood is easier then soft. There are several technical reasons, but the main one is the tubule structure in hardwoods is much more dense and cellular walls are less prone to collapse in the bending process.

Boiling water will often help convince a piece of stubborn lumber to bend, but the grain needs to be especially straight and clear, plus the bend not very tight.

If it's the piece I suspect on Jellyhead's boat then it's likely a rub strip or an outer face to the sheer clamp/shelf. This typically would be a sacrificial piece of hardwood (teak, oak and mahogany are commonly used), designed to get beat up, but save the boat's sides and deck edge from extra close encounters with docks and such.

Jellyhead, use the "Go Advanced" button at the bottom of the page and you'll be able to upload photos (images) directly from your computer. Once in the "advanced" section, near the bottom of the page is a "Manage Attachments" button which will permit the upload process.

[jellyhead]

hi micheal. thanx for the tips on how to upload, have to wait for the wife to get home to make pics smaller as file is to big...but yes you are right about the rub strip..thanx

[jellyhead]

hi aj....the strip is 30mmx20mm and it is shaped like a D. And its the first sweeping bend just past where you sit up front. We tried it from the front to back as we had more levrage on the timber...And about 100mm before it touch the side it snapped, it was wet rite through too.

I MENT TO THANK PAR FOR THE PIC UPLOAD,,,,AND MICHEAL FOR HIS ADVICE

[PAR]

Jellyhead, you'll find wet wood isn't the same as soaked wood. dig a shallow trench (the wife will love you for it, especially in the front yard). Line it with a plastic painter's drop cloth, then fill it with water. Drop your lumber in it and weigh it down so it completely covered. Leave it for a few days. On the day you're going to try the bend, remove the water and replace it with water directly from the water heater, which typically will be around 50 C. Soak the lumber in this for an hour then try your bend with hot wet wood (just how you like your women). Start at the front and work fast, but not quickly (what!). By this I mean get the wood bent around in a few minutes, but don't make sudden jerky movements, particularly along the tightest radius areas, which will probably be about 25% back from the bow.

The wood has to be straight grained, knot free and preferably quarter sawn. If it's flat sawn you'll get grain run out and this is the place it'll break. You can help prevent this with a metal strip backing up the outside edge, or another piece of wood, though wood makes the bend more work. Also don't round over the edge until you're bent on.

[m2c1Iw]

Also don't round over the edge until you're bent on.

Excuse my ignorance but why, a couple of bits I've bent I have rounded first thinking that a rounded edge would be less susceptable to splitting. I am certainly not argueing the point as I don't have enough experience just pondering the science of it.

Cheers
Mike

[Daddles]

Excuse my ignorance but why, a couple of bits I've bent I have rounded first thinking that a rounded edge would be less susceptable to splitting. I am certainly not argueing the point as I don't have enough experience just pondering the science of it.

Cheers
Mike

Imagine this scenario. You're fitting a coaming to a boat ... oh, hang on, we'll be doing that saturday

Okay, poor example, try a gunwale or an inwale. You glue it to the boat. Did it line up perfectly? Not on your nelly, it'll need some shaping to follow the sheerline of the boat. That mucks up your carefully rounded corners. Maybe you're a bit ropey with the clamps and knocked the timber around a bit - leaving it unshaped, that damage will probably disappear as you shape it.

Shaping the timber ON the boat is easier, quicker and only needs to be done once. That's why I do it that way.

There may, of course, be merit in what you're saying about split edges but every failure I've had has been catestrophic, not the sort of thing I'd expect to be affected by the edges being rounded and really, if a lump of wood is that close to going 'bang', I'd rather it did so before the glue set.

Just my thinking anyway.

Look at this picture of Sixpence



There's a gunwale, a rubbing strip, an inwale and a strip running across the top of the gunwale, inwale and plank - all of these were fitted cold, simply by carefully and gently easing the planks into place. I wanted to avoid steaming ... so now have made a steamer for the coamings duh

The inwale is around the 30x20 that jellyhead is working with and is oregon. The others are a bit smaller in cross section but are kapur. The capping strip was fun as it's quite wide and carrying a hell of a horizontal curve.



The curves on the gunwales on Redback are very tight and the timbers are up around that 30x20 mark. I just couldn't get solid timbers to go, even after stuffing around with a lot of boiling water and towels (Welsford's 'advice'). I wound up making them out of plywood, cutting the vertical curve and bending for the horizontal curve.

How much hassle would I have saved myself if I'd built a steamer back when building Redback? HEAPS. But I can understand why people avoid the things. I think you can put steamers into the 'borrow when needed' category - borrow one until the borrowing process annoys you enough to make your own. And on that basis, any Adelaide members will be welcome to borrow my steam box ... but you'll have to negotiate elsewhere for the boiler because I'm borrowing that myself

Back to the topic. Jellyhead, Sixpence shows what can be done. Choose the grain of the timber carefully. Take it quietly. But Redback cost me far too much in broken oregon (it's expensive, especially as I didn't have the tools to machine it myself in those days and was paying the lumber yard to do it). Going to steam is a big and scary step, but look at the number of bits you're going to have to bend and maybe it's not such a silly step ... maybe it is. I got this far without having to resort to steam, I'm not sad I waited this long, but life would have been a lot easier if I'd given in back in the days of building Redback.

Richard

[m2c1Iw]

Daddles,
Your right of course, I was thinking about the resistance to splitting aspects of rounding first but take the point about shaping after fitting.

BTW hows that assignment coming along don't want you all stressed out while trying to steam or totally steamed while trying to steam or something like that.

Mike

[PAR]

Bending wood is a crap shoot at best. I've bent a lot of it over the years and have a feel for it, which increases my success rate.

Some general observations for the novice wood butcher.

Kiln dried stock is usually too dry to steam with reasonable success, typically managing close to a 40% breakage rate, which will off the most noble among us, especially at several dollars a board foot. You can increase your odds with kiln dried by soaking it, not wetting it, complete soaking. The wood will only soak up so much in a given amount of time so 24 to 48 hours is usual enough to lower the breakage rate into the low 20% bracket.

Air dried, well seasoned stock bends better, but still can benefit from a good soak, say maybe a half a day. I find alcohol works better on naturally seasoned stuff. Boiling alcohol even better, but not something I'd recommend the novice try as you can loose eye brows easily. Air dried stock will break around 15% of the time.

Freshly cut stock is the best bending stuff going. It still thinks it's a tree and willing accepts a hurricane coming through and bending it over. This stuff will give up 10 to 15% of the time.

Flat sawn lumber will lift it's grain around a radius. This is the beginning of a crack, which will follow the grain lines or along an internal flaw, then snap, if asked too much. Often you haven't much choice and must use it, so, bend it with another piece or my favorite is a strap of metal. The metal or extra piece of wood will prevent the grain from lifting as you work through the radius. Once the wood sits in it's new position, the internal heat will help it remember this and the piece will become more stable. This doesn't mean it will not break, as it might, but you odds are better.

Vertical grain and quarter sawn lumber bends best. In some applications it's not the best grain orientation, such as on a rub rail, where flat grain would wear better, but it's safer to bend.

Grain run out is a big issue when bending stock. This is when the grain line leave the edge of the plank at an angle. This happens when the tree has a bend in it, but the saw didn't. You can rest assured this is the place the piece will snap, so located these areas in the least amount of bend on the piece or on the inside of the radus, which will increase you success rate. An example would be a steamed rib. Place the run out near the top of the rib where it's almost straight.

Grain density and straightness are also key players. The tighter the grain, the less likely it'll get prissy about you bending it. Of course the stock should be as straight grained as you can find, which should go without saying.

It's not a sin to bend two pieces at the same time to make up one boat element. Split frames and laminated parts are very common and perfectly acceptable. If you break a buch of sticks, then decrease their size and use two.

May folks think you can over cook the stock in the box and it'll be more limber. Nope, you'll make it less limber. Each species is different and requires a feel for it, but as a fair rule an hour for each inch of thickness in the shortest dimension. I have a sliding scale I use, per species. I use 45 pounds per cubic foot as the base line. Stock heavier then this gets proportionately more time, lighter, less. This is an hour in the box, with a full head of steam running. When I place stock in the box, I don't start the timer for 5 to 10 minutes, so the box can get a full head of seam going inside again. Every time you open the box, you lose most of the steam in a few seconds.

You don't trim you stock for the reasons stated above, but also because machining crushes the ends of the tubules in the wood, restricting steam entry. This coupled with the guaranty you're going to have some raised grain, means any machined wood will need to be remachined anyway, so why bother.

[m2c1Iw]

PAR,
Thanks for that, now tucked away for future reference.

Mike

[b.o.a.t.]

hi aj....the strip is 30mmx20mm and it is shaped like a D. And its the first sweeping bend just past where you sit up front. We tried it from the front to back as we had more levrage on the timber...And about 100mm before it touch the side it snapped, it was wet rite through too.

I MENT TO THANK PAR FOR THE PIC UPLOAD,,,,AND MICHEAL FOR HIS ADVICE

Probably too late now - the planks are cut to finished size & shape, yes ?
You've probably also noticed that thin bits of wood bend easier than thick ones, yes?

My Teal gunwale is 30 x 19. Most of the curve is in the 30mm direction rather than the 19mm direction. To get a 30mm wide gunwale, I laid 2 courses of 12mm x 19mm & capped it with some 10mm x 20mm hardwood moulding from Bunnings. easy-peasy. No breakages, no dramas, no steaming.

cheers
AJ