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I am planning to build a small clinker dinghy and wondered if anybody has used leatherwood timber for the structural parts of it. I do have a quantity of air dried leatherwood.
I am considering paulownia for the planking and would also be interested in hearing from people who have used it.
Thanks
I used to grow, mill and sell Paulownia. Much of my sales were for building boats, Kayaks and wooden surfboards/paddle boards. The boats were from small sailing dingys, Runabouts with large outboards and even a 36' sailing boat. The timber is soft so has to be protected with fibre glass. The overall weight saving is great and the timber is easy to work with. I'm sure if you go to the boat building section of the forum you will find all the ideas you need to help make a decision.
Whitewood
Thank you for your information and the suggestion to look at the boat building section of the forum too.
I found this website which had some details on the properties of leatherwood, including durability - which was my reservation about using it:
https://www.woodsolutions.com.au/woo...es/leatherwood
I didn't know that paulownia was so soft that it needed fibreglass to protect it, so I'll probably go with marine ply despite the saving in weight.
As you'll realise I am a fan of Paulownia. The difference in weight between ply and paulownia is huge. Well worth it when rowing or handling the boat. Paulownia only needs a very thin coat of glass and resin to do the job especially for a small dingy. I'm sure there are designs for paulownia boats that will give you professional specifications.
As far as durability is concerned I don't know where to get 'professional' results but from personal experience I gave a friend a few imperfect mill offcuts and he laid them down, unsealed in his vegie patch between rows. They are still there on the ground, intact after 10 years or so and the area gets 70" of rain each year.
Whitewood
I have used Paulownia for over a dozen of the kayaks and canoes I have built. I used to buy from Whitewood until he retired.
My sea kayaks have one layer of 125 gsm glass inside and out and the racing canoes and kayaks and have one layer of 85 gsm.
The sea kayak use strips 5mm thick and the racing canoes 4mm while the racing kayak uses 3.5 mm thick strips.That one of 5.2 metres long and weighs 8.3 kg.
Obviously a dinghy is a bit different from a kayak and the clinker construction creates a problem for glassing.
I have found the Paulownia is between 10% and 20% lighter than WRC and is only slightly softer. It is about the same to saw, bend, plane and sand as WRC.
Thank you for your useful comments. I first heard of Paulownia when we lived in Qld 15 years ago when I learnt about them being planted, but it seemed to drop off my radar after that. My interest in Paulonia was rekindled by finding the website of what I presume is your former business, and I've seen the demo videos. I was impressed by the flexibility and lightness of the timber, which could make planking easier. However after learning from you how soft it is, and due to my long experience with fibreglass, I'm not a fan of working with 'spiky plastic', no matter how thin!
I'm not in a hurry so I'll keep looking and researching.
Yes, your observations about clinker and fibreglass are valid. Your comparison between WRC and Paulownia is helpful. I'm using an American design that specifies cedar for the planking but I suspect that it's one of the more dense varieties that are available there.
Hi Black Dog
I know I'm pushing Paulownia but I really believe it is a great timber for what you intend building. As Allen Newhouse said it is only slightly softer than WRC. If you are planning to use WRC you will have to, at the very least, seal the timber to prevent it absorbing moisture. I assume your plans provide specifications for the timber size for the planking. Port Phillip Plantation Shutters gets it supplies of Paulownia from a grower and sawmiller in the Coffs Harbour area and I'm confident this sawmill would be a be able to provide paulownia in the sizes required in the plans and then you would not have to fibre glass the timber but end up with a dinghy that was about 20% lighter than one made of WRC.
Keep researching as you only get 1 go and if it is not right for you it is too late once you have bought the timber and started the build.
OK. I'll pop over to Mordialloc and get a sample. The cedar specified was Eastern White which would probably be too expensive in Australia but I haven't checked that out yet, and anyway I'd prefer to use a locally sourced timber. I may also be able to get some English elm.
just 'cause I've time on my hands (info from the Wood database)
Northern or Eastern White Cedar
Average Dried Weight: 22 lbs/ft3 (350 kg/m3)
Specific Gravity (Basic, 12% MC): .29, .35
Janka Hardness: 320 lbf (1,420 N)
Modulus of Rupture: 6,500 lbf/in2 (44.8 MPa)
Elastic Modulus: 800,000 lbf/in2 (5.52 GPa)
Crushing Strength: 3,960 lbf/in2 (27.3 MPa)
Shrinkage: Radial: 2.2%, Tangential: 4.9%, Volumetric: 7.2%, T/R Ratio: 2.2
Western Red Cedar
Average Dried Weight: 23 lbs/ft3 (370 kg/m3)
Specific Gravity (Basic, 12% MC): .31, .37
Janka Hardness: 350 lbf (1,560 N)
Modulus of Rupture: 7,500 lbf/in2 (51.7 MPa)
Elastic Modulus: 1,110,000 lbf/in2 (7.66 GPa)
Crushing Strength: 4,560 lbf/in2 (31.4 MPa)
Shrinkage: Radial: 2.4%, Tangential: 5.0%, Volumetric: 6.8%, T/R Ratio: 2.1
Paulownia
Average Dried Weight: 18 lbs/ft3 (280 kg/m3)
Specific Gravity (Basic, 12% MC): .25, .28
Janka Hardness: 300 lbf (1,330 N)
Modulus of Rupture: 5,480 lbf/in2 (37.8 MPa)
Elastic Modulus: 635,000 lbf/in2 (4.38 GPa)
Crushing Strength: 3,010 lbf/in2 (20.7 MPa)
Shrinkage: Radial: 2.4%, Tangential: 3.9%, Volumetric: 6.4%, T/R Ratio: 1.6
The three species look pretty interchangeable to me. Though you might want to consider using something a little tougher for those planks that will run on the sand when you beach the boat. That or rubbing strakes (I think that is the correct term)
Thanks for the info and the link to wood-database.com Ian.
My interest in boatbuilding is as much about the building process and acquiring the ancillary knowledge, as using the finished boat. Clinker/lapstrake using solid timber is probably not the best path for making a boat that will spend much of its life on land, but it's a more interesting path for me. I enjoy the challenge of reclaiming the trade knowledge and skills lost through technical innovation and changing fashion.