Dinghy timber

[AlanChap]

G'day,

I am a new member about to embark on a dinghy building exercise.

The dinghy is of a geodesic design, ie stringers and frames and covered with 2 layers of shrunk on Dacron. This makes for a very light craft, the one I have ordered the plans for is 8ft and will only weigh 13kg.

The notes that will come with the plans call for timbers "that local houses are made from", something that doesn't sit too well with me.

Can anyone tell me if they have used any local (Australian) timbers for boats and where did they source it?

I can get to Mathews Timber in Melbourne as they normally carry a reasonable range of timber and they are the only company I know.

The timber strips for the stringers and frames may have to be steam bent, so that will have to be taken into consideration.

Hoping someone can help out.

Cheers,

Chappy

[PAR]

Welcome to the forum.

Which design are you building? "Local house" lumber is fine, assuming it's well suited for the role it'll play. The frame in SOF designs, carry a lot of longitudinal loading, so need to be stiff, but also light. Building material lumber can work and often is employed, possibly sized differently, to address stiffness issues, compaired to say hardwoods. If you do use construction grade lumber, do some research on the species and its physical properties, so you can match up what's available to what you need (this assumes changes over the BOM). Additionally, if you need say a 20x40 (mm) section, don't buy this, but mill it from a bigger piece. I routinely cut 2x12's down to 1x2's on the table saw. I buy 16' long 2x12's and mill stock from these. The reason is pretty simple, a 16' long, 12" wide board has to come from a big, older tree. The grain will be tighter, straighter and fewer defects will be seen, over smaller stock, which can be cut from smaller, younger trees. I commonly sort through stacks of 2x12's at the local big box store and select 4 or 5 pretty ones. On a single pallet of 2x12's, I'll find a few perfect, dead straight grained, no knot pieces. They cost the same as the knot riddled, pitch filled stuff, usually found, but they'll be much more stable and stronger.

[labr@]

Welcome to the forum Chappy. I well understand your concern - I suspect that using house framing timbers would result in a difficult build and an inferior boat.

I have built a skin on frame kayak and used paulownia for the stringers. While not exactly the same type of construction there are similarities and I would make paulownia my first choice if building a geodesic. Second choice would be western red cedar.

I bought my paulownia from a Qld supplier but there is also this one in Vic:
Contact Us (http://www.paulowniatimber.com.au/contact.php)

Good luck with it and remember to post some photos along the way.

[AlanChap]

Thanks Bob,

I know of Paulownia but did not consider it as I had it in my head that I had to use hardwood for the stringers and frames.

I suppose with each part I would cover with epoxy anyway so it wouldn't matter if it was not hardwood.

Thanks for that Bob, got me thinking now.

[ian]

I am a new member about to embark on a dinghy building exercise.

The dinghy is of a geodesic design, ie stringers and frames and covered with 2 layers of shrunk on Dacron. This makes for a very light craft, the one I have ordered the plans for is 8ft and will only weigh 13kg.

The notes that will come with the plans call for timbers "that local houses are made from",

The timber strips for the stringers and frames may have to be steam bent, so that will have to be taken into consideration.
hi Chappy, and welcome to the forums

what the US and Canada call "construction lumber" should be fine if as PAR suggests it's bought in large sizes and ripped down to what you need. In Australia, construction lumber is most likely to be radiata pine.

steam bending is likely to be you biggest issue -- most Aussie hardwoods are sold kiln dried. Unfortunately, kiln drying sets the lignun and makes the wood unsuitable for steam bending.

[AlanChap]

Thanks Ian and PAR,

I'm still waiting on the plans, should be here next week, before I go ahead with purchase of materials.

I may be able to get Mountain Ash from a local sawmill before it goes into the kiln but not too confident of that and it may be a bit heavy. I'm leaning towards Pawlonia as it is very light and the supply is 200km away which is not that far in Australian rural terms.

Thanks and regards,

Chappy

[Pagie]

The last boat I steam bent ribs for I used blackwood.

[AlanChap]

Thanks Pagie, I will consider that, should be able to get that at Mathews.

[Nanigai]

Welcome to the forums AlanChap hope you enjoy them.
Just noticed your comment "I know of Paulownia but did not consider it as I had it in my head that I had to use hardwood for the stringers and frames."
I just did a quick search as I believed paulownia was a hardwood and found this:- Paulownia is by far the fastest growing hardwood tree in the world, allowing ... Paulownia wood is a third of the weight of Oak and half the weight of Pine.

From what I have read about it it is an amazing wood and very strong longitudinally and resistant to rot and termites etc but as light as balsa.
If you are looking to make a light dingy this would be a great place to start.

Just my 2c.
Cheers, Ian

[Sumbloak]

Unfortunately, kiln drying sets the lignun and makes the wood unsuitable for steam bending.
You can still steam bend kiln-dried timber. It just may, or may not, be less flexible. Only way to find out is try a bit and see if it does what you want. It if doesn't, use thinner strips.

[Sumbloak]

Welcome to the forums AlanChap hope you enjoy them.
Just noticed your comment "I know of Paulownia but did not consider it as I had it in my head that I had to use hardwood for the stringers and frames."
I just did a quick search as I believed paulownia was a hardwood and found this:- Paulownia is by far the fastest growing hardwood tree in the world, allowing ..

From what I have read about it it is an amazing wood and very strong longitudinally and resistant to rot and termites etc but as light as balsa.
Balsa is also a hardwood. In botanical terms, as far as trees go, softwoods are conifers. Hardwoods are everything else. Or if you want to get techy, gymnosperms and angiospserms. Impress your friends with sciency stuff.

And paulownia isn't really as light as balsa. More like 60% denser, AFAIK. Which still makes it one of the lightest timbers around.

[AlanChap]

Thanks Sumbloak

[labr@]

Alan, in an earlier post PAR asked what design you are making - I'm interested to know too.

Have you seen the "Canoes and Lampshades" website? Peter Ingram-Jones has a number of boat types shown there including skin on frame kayaks and geodesic dinghies. He is based in Tas and uses various timbers including huon pine for his frames. You may be able to get some specific local knowledge based advice from him. He is making boats in the sub 10kg range so the denser timber obviously isn't preventing him making a light hull. Looking at the photos on his site the frame members seem very small in section and this may have some bearing on timber choice as well.

[AlanChap]

Hi Bob,

I'm planning to build a Westport 8ft dinghy as a yacht tender.