Thread: looking at building a timber strip kayak, just a few questions

cheers for that

i will see if i can hunt down a piece of paulownia nearby and match it to the same size as my spanish cedar and see what the weight difference feels like - the cedar i have, i can pick up the entire pack by myself under 1 arm

or can anyone put a 1metre x50x50 onto a set of scales and tell me how much it weighs?
cheers

The cubic weight of Paulownia is about 290 kg. That is a fact. Your method of weight comparision is not going to supply enough information for you to make a realistic assessment. Given that the samples may be RS or dressed, the error factor in kitchen scales and the fact that I don't have a short piece of 50 x 50 to waste I don't want to go there.
I do have short scrap pieces of othere sizes of RS Paulownia in 25mm and would be prepared to weigh a specified amount - for what it would achieve.
Why not weigh some other timbers you have that have a similar weight differential and compare the result. It chould give you a reasonable basis for comparision.

I

I just weighed a couple of pieces of Paulownia left over from my last kayak.
3.58 metres x 50mm x 19mm=0.0034
My kitchen scales say 965 grams

That works out to 283.8 per cubic metre which is remarkable close to the figure John quoted.

So if you do the maths, a 1 metre length of 50x50 would weigh about 700 grams.

The same amount of your Spanish Cedar should weigh about 1kg.

WRC should weigh 950 grams

Individual pieces of any of those timbers of course could be a bit denser or lighter, but that is what my pieces of Paulownia weigh.

Chikoroll,
This is an unashamed advertisement for Whitewood.

I have purchased some Paulownia for boat building and a more obliging supplier you will not find.

Contact John he will steer you in the right direction.

Regards
Mike

good idea, i will take a cut of all that i have and cut it to the same sizes- probably a 40x40 x200 (make it up to that if the boards are too small)

btw, does this test help at all (i don't think it would, but it shows the buoyancy)- i put a piece of 100x100x100 into water, when it settled 5mm's was underwater 95mm's above water

whitewood, if it's alright by you, i'll go for a drive down there in a few weeks on a weekend and do a true comparison between the 2- weight, strength, how interesting it is, buoyancy, etc...

Chikoroll,

My web site states visitors are welcome. I trade any days of the week so weekends are usually not a problem. For contact details email me [email protected] to get directions and to make sure I am available.

Howdy Chikoroll, You can do the same test more accurately by..

Weighing the wood in grams = WEIGHT

Then measuring the block in centimetres - length and width and thickness - multiply them together to get the VOLUME

Then Divide the WEIGHT by the VOLUME and that gives you the DENSITY

If you multiply that by 100 you will find out how much of a percentagewill be underwater. The remaining percentage will be above (ie BUOYANCY)

Also different woods have different strengths more or less according to their DENSITY. So if a timber is twice as DENSE then it will roughly have twice the strength, twice the resistance to denting etc.

Best wishes
Michael

If you are interested in the appearance, then you probably want to know what it looks like with a covering of glass and epoxy.

I'm not sure if John has such samples available, but this photo might give you an idea.

I reckon it looks a lot like Tasmanian Oak both before and after coating with epoxy.

Did I put the link to the whole building process of a Paulownia canoe.



through to



I have written about all the steps on this photo series. All these paulownia strip planked canoe taken at the Duckflat Spring school over 10days - they did come back about two weeks later for two days more work.

About 70 photos with reasonably detailed comments

Best wishes
Michael

that's a nice looking kayak anewhouse, is that aussie red cedar and paulownia?

thanks for the link mik, that will come in very handy

Only the small diamonds in the strip up the middle of the deck are Australian red cedar.

The dark sheer strip is a fairly pale piece of American Redwood and the dark strips on the deck are darker pieces of the same timber. They were old, free skirting boards.

for the trimming in mine, i will probably use veneered jarrah, walnut burl and quartercut american oak (1mm thick cuts)

i will add in a marquetry scene also (will think of the theme when i build it)

using kayak foundry, anyone feel like posting up there opinions and any tips on designing a better kayak

what i am looking for is-
i weigh 80kilo's
roll-over stability,
able to carry about 15 kilo's (fishing rod, tackle box, water and food),
decent to paddle (i don't mind a bit of resistance)
handle choppy water

300mm feet
550mm lower leg to kneecap
600mm kneecap to seat
1100mm from heel to seat
260mm minimum kneecap and foot width
440mm wide butt



just had a play with kayak foundry, and this is my results, anyone feel like altering it to make it better?
http://www.fileden.com/files/2007/2/20/797870/no001.yak

how much space should i allow for entry/exit, and seating+feet supports?

I don't know how to input the file you posted into KF so can't comment on your design, would it be possible for you to post a file like the ones in the attachments on the Blue Heron Forum? http://www.blueheronkayaks.com/phpBB...1f76c99f155520

A few questions about what you desire, I'm guessing you can't do an eskimo roll, do you intend to learn?

This determines whether you want a kayak you sit in or a kayak you wear. Assuming you won't be rolling and also assuming you wish to access the fishing gear while on the water I would recommend a large open cockpit in a flattish hull around 60-68 cm wide, 4-5m long with some flare above the waterline to give a dryer ride in chop. The wide flat hull will give increased stability and turning at the expense of speed. Flat hulls also tend to pound in large swells but I don't expect you will be using it in those conditions.

The amount of rocker determines maneuverability/tracking and this is very much a personal preference with the type of use also being a determining factor. Probably a medium amount of rocker would suit your needs. The shape of the keel line also determines the centre of lateral resistance which determines weather cocking/lee cocking. How strong are the winds you will paddle in? Most sea kayaks have the centre of lateral resistance slightly forward so that the kayak will tend to weathercock as the wind increases ie: turn into the wind. If you are not planning to paddle in strong winds and not planning on rolling you may wish to have a fairly high deck height to give a dryer ride.

Have you read John Winters articles on the shape of the canoe? http://www.greenval.com/jwinters.html
He is a naval architect and these short articles give a lot of information that is also applicable to kayaks.

Hope this helps.
Kelvin