Kiri properties

[Willallison]

Does anyone know the technical properties (with regards to sheathed strip planking) of Kiri?

Catmando2 is rather enthusiastic about it ( eg: Questions about wood type, quality and grain? ) but I'd be interested to hear other peoples opinion, and to get some real numbers on the material.

It's sold in Oz by Highpoint Timbers ( http://www.highpointtimber.com.au ) but their site gives no real relevant info other than density - which at 260 - 290 kg/m^3 makes it considerably lighter than the usual material of choice, western red cedar (around 340 kg/m^3). From Dave's comments, it's also substantially cheaper...

[Raggi_Thor]

I don't know exactly it seems to be varying a lot.
I have tried to order a sample from HighPoint Timber without luck.
Now I have a contact in China that will try to look into it.

Since it's so light yoiu can add more glass and have the same weight as cedar+glass, for example.

[waikikin]

Will, I read somewhere an increase in thickness over WRcedar was required in conversion to Kiri, Buy some range of kiri & test it before commitment might be the best bet, nothing beats knowing for sure. Regards from Jeff.

[Willallison]

Jeff, yes I'm fairly certain that it's strength etc is lower that WRC, and testing would be pretty much a given, but some reliable data must be out there somewhere...

Raggi - true you could add more glass, but that would somewhat defeat the purpose (lower cost and weight), though obviously other advnatages would result. I'll be interested to hear how you get on with your Chinese connection...

I've sent emails to a number of suppliers - including Highpoint - as yet no response..... always a nervous sign.....

[Willallison]

I received this reply from an Australian plantation grower this morning:

Hello Will,
>
> thanks for your enquiry. I can give you some basic data on Paulownia
> timber as follows. As for Australian distributors of milled Paulownia
> timber, this is not so easy as the industry is still in it's infancy in
> this country with limited quantities of timber traded.

> PAULOWNIA WOOD:
>
> The Air Dry Density of Paulownia wood is generally between 260-330 kg/m3
> (@10% moisture content: 17.9).
>
> An Analysis:
>
> Specific Gravity: 0.265
>
> Chemical Composition
> Cellulose content: 46-49%
> Hemicellulose Pentosan: 22-25%
> Lignin content: 21-23%
>
> Bending Properties
> Modulus of rupturex10) 5740
> Modulus of elasticity: .84
> Shrinkage Coefficient
> Specific gravity: 0.21 - 0.27
> Radial: 1.1 - 2.0
> Tangential: 2.1 - 3.5
>
> Fibre Characteristics
> Fibre cell length: 0.80 - 1.70mm, average is 1.20
> Fibre cell width: : average is 0.32mm
> Fibre cell length/width ratio: average is 38
>
>
> OTHER CHARACTERISTICS
> Appearance is a pale blonde to a light honey colour with a gradual
> transition from sapwood to heartwood. The fast early growth results in
> large growth rings which rapidly diminish in width as the tree matures.
> The timber has a long straight grain, a silky feel, is slightly sweet or
> relatively odourless and mostly free from knots.
>
> It has a high strength to weight ratio, a low shrinkage coefficient, a low
> air dry density, and does not easily warp, crack or deform.
>
> The wood has excellent working characteristics - easy to plane, cut, and
> carve with little splitting or chipping. The finish is soft and smooth
> like spun silk.
>
> I hope I have been of some assistance. My area is really the propagation
> and sale of the planting stock rather than the timber end of it. If you
> know anyone interested in growing a plantation send them my way.
>
> Cheers,
>
> James Lawrence
> TGG - the paulownia propagation people
> http://paulownia.com.au

Not all the info we require - and lots that we don't - but it's a start!

[Raggi_Thor]

You can of course make it thicker.
That is probably better than adding more glass.
But if Kiri is very soft, maybe you want more glass on larger boats, in case you hit a stone or the boat is going up and down a trialer.

[catmando2]

OK, my experience with Kiri.

I did'nt get much more info than given except that the stuff I got did infact come from China, as Australia did not have any old growth forest as yet.

I had a report from a timber expert in WA who had laid samples of kiri out in termite infested Jarrah log's for month's with the termites not going near it.

I also had an article of coffins in China being dug up after 300 years in wet areas with no visable signs of rot. I have a few stakes in damp areas of the garden, and they have shown no sign of decay over a 3 year period.

I found Kiri to be easier to work with than WRC and more uniform in its grain, and any dodgy bits were easily detected as a discolouration or a sap hole.

Out of enough planks to do a 50 ft cat, I may have had 40 reject planks, which had the bad section cut out and the planks re-scarfed to length.

The planks for me were supplied in 6 metre lenths, so much less scarfing than WRC.

I suffered no allergic reaction, I get one now from WRC.

The timber was marginaly softer than WRC, not enough to really notice, certainly not as soft as Balsa or foam.

It behaved in some ways like foam during drop testing as it seemed to absorb a hit with less damage,spreding the shock through the panel.

WRC had a more explosive failure, Kiri seemed more gradual.

All the info I had on Kiri I obtained from Highpoint timber in WA, though I did my usual destruction test's(deflection and drop ) till failure.

Nothing overly scientific, 16mm thick x 42mm wide glued into a 150mm wide plank 1200 long with 600GSM double Bias in epoxy either side in a cedar and Kiri sample.

Set both up between tressles and hang 10, 20, 30 +++ litre water containers from the middle measuring deflection every 30 minutes then adding more weight until destruction.

The Kiri won hands down, infact the kiri had about half the deflection, took a lot more weight, and lasted about 3 hours longer until slowly folding in half.

It still had the glass skins intact where as the cedar had gone bang much earler and had ruptured the glass skin.

Same with a 1000x1000planked and glassed panel clamped around the edges to a frame and dropping a 15kg rounded end lead shot weight down a tube from various heights until failure.

Again the Kiri was a winner absorbing the hit much better than the cedar.

The kiri dinted and eventualy blew a side out leaving a glass skin intact.

The cedar stood up well, but failed earler with an explosive jagged hole rupturing both inner and outer skins,

That was my observation, and on that, and the fact that it was a good weight saving on my project and as I got in early(guinea pig like) I saved about 50% on the cost of WRC, which allowed me to justify a 50 footer over a 40 footer, same accomadation, just bigger hulls.

Hope this helps

Dave


All information and testing was for my own benefit and project.
Any one else should still perform "Due Dilligence" ensuring the product suits their individual circumstances

[waikikin]

Nice post Dave, interesting to hear that the deflection was less on the kiri at the same thickness as cedar, maybe the advice on increasing the thickness for Kiri is just caution on a "new/unfamiliar" material, dont remember where I read it though. Also I enquired from a distributor on supplying some for a 20' open launch but never got the prices or samples/info from them, might have slipped through the gaps & should give em another go as it sounds like good material. All the best from Jeff

[Willallison]

Well, I have a little more info and things look more interesting all the time!

Comparing Kiri (correctly called Paulownia) with Western Red Cedar, which is probably the 'standard' material of choice here in Oz for strip plank construction....


KIRI PROPERTIES
Density 0.27 psi
Mod of Rupture 5740-6060 psi
Mod Elasticity 1 million psi
Compressive Strength 3500 psi


WRC PROPERTIES
Density 0.32 psi
Mod of Rupture 5200 - 7500 psi
Mod Elasticity 1 million psi
Compressive Strength 2700 - 4500 psi


WRC figures are taken from Gougeon Bros, Kiri from my quoted source above plus another.

This would suggest that there's little difference between the two, backing up Dave's observations.....

[Raggi_Thor]

This is getting better and better. I will definitely try it! Thanks all.

[waikikin]

Will, I suppose its up to the source of the figures, but it appears that the Kiri is kinda more predictable in its properties which is good from an engineering veiw & is in the case of WRcedar easily seen on the rack at hardware in the diversity of colour & weights of sticks "on the shelf". Keen to get my hands on some Kiri to see for myself. All the best from Jeff. PS: saw a "lifestyle show" the other night that featured Paulownia as a cool garden tree!

[rwatson]

Very impressed with the timber myself. I have had a small untreated piece in the shower for over a year (alternate dry/wet/cold/hot) and despite small discoloring on underside, still totally sound. I come from Tasmania (Australia) that has (had? - hard to get now) some of the finest timbers in the world, and this stuff compares really well to Huon Pine and Celery Top Pine for ease of working, longevity and weight V strength. I am really pleased it is relatively fast growing so I dont get the guilts about building from it.
I am just finishing a small boat in Western red cedar. The fine dust and odor requires face masks, I understand this is not as bad with Kiri.

[Willallison]

A fellow Taswegian! !st up, welcome...

Where did you source the Kiri from - and indeed the WRC?

King Billy Pine is another fabulous Tasmanian boatbuilding timber - it's pretty hard to come by these days too....

[rwatson]

Hi Will

yes, Kirri discussion can continue here.

If you get a cost comparison from the plantation timber versus the imported timber - I would be very interested. Also, the phone, address of the plantation source would be great.

[nordvindcrew]

Kiri sounds like a viable alternative to western red cedar which is getting more and more expensive. Is it exported to the USA?