A 39' "downeast" influenced design - Feedback Request

Kirri (paulownia) is indeed gaining in popularity as a boat building material, primarily as a core material. As RW suggests, it has some pretty positive attributes. I'd be a bit hesitant about using for when using traditional building techniques, however.
I've queried RW before about the $4000 /m^3... I paid the equivalent of a bit under $2800 /m^3 about 12 months ago (42 x 19 bead and cove strips).

I think you'd find that quarrantine restrictions would complicate the importation of timber - though fumigation can't be all that complicated - they do it to ship loads of household decking timber...

 

Kiri / Paulownia

I think you are mistaken. Kiri / Paulownia is not anywhere as durable as Huon nor is it anywhere near Celery Top for toughness. It is a good lightweight timber that with appropriate protection makes a good boat building timber. Because it is very soft it needs good protection from "dings" and because it is moderatly durable it needs good sealing from the elements. Hence its growing popularity for composite boat building.

Plantation grown timber is generally less durable, lighter and not as strong and in this respect Kiri / Paulownia is no different.

Kiri / Paulownia Timber Properties

1. Weight - Paulownia is a very light timber. At a dry density of around 270-280 kg/m3 paulownia is lighter than most common timbers. Density comparisons with other boat building timbers used in Australia are Western Red Cedar (350), Huon pine (550), Celery Top (650), Meranti (580), Oregon (710), Rose or Flooded Gum (800), Spotted Gum (1010), Grey Gum (1055) or Grey Box (1105).

2. Strength - with a modulus of elasticity (stiffness) of 5.6 GPa and a modulus
of rupture (bending strength) of 28 MPa, paulownia is not classified as a structural timber in its natural state. However because of its light weight, paulownia has a high strength to weight ratio, an important feature in the various uses of the timber.

3. Deformation & Warping – The shrinkage co-efficient of paulownia is very low compared to most timbers being 0.094 radially, 0.268 tangentially and 0.362 in volume giving the dried timber a high level of dimensional stability.

4. Hardness - The Janka hardness rating for paulownia is low at 1.3 kN. Western Red Cedar is rated at 1.5 and Meranti 2.6. While modern treatments can substantially harden up a finished surface, paulownia is not suitable for use where physical damage is likely.

5. Durability - The in-ground durability rating for paulownia is 4 and the timber should not be used for that purpose. Paulownia used for other external uses out of ground has a similar durability to western red cedar and should be treated with at least two coats of a water repellent sealant.

6. Thermal Insulation - with one of the lowest thermal conductivities for wood of just 0.07 Kcal/m/hr/Cdeg, paulownia has an excellent heat insulation capability being one of the best heat insulating timbers.

8. Fire Resistance – with an auto ignition temperature of around 400 deg C (most hardwoods around 220 deg C) paulownia is reported to have a flame spreading rate considerably below most building codes.

9. Finishing - The sap of paulownia is not gum or resinous based, thus the application of finishing products with various solvents as carriers does not risk any interaction with the timber, contributing to the very good finishing properties of paulownia products. The timber readily takes stains, estapols and paints with excellent finished surfaces.

10. Workability - a major feature of paulownia timber is its ease of working. All aspects of carpentry such as machining, nailing, screwing, glueing, sanding, sawing and handling are very user friendly with no splinters, cracking or splitting and excellent take-up of glues and finishes.

 

oh Im sure there would be a learning curve to shipping something like that but it seems doable

Ill ask about the yellow ceder
I got western red ceder coming out my ears
but if you want it yellow I can always ask
poplar is stronger, denser, straighter, cheaper, and knot free it mills better takes a fastener better and takes a finish better
ceder your going to have higher waste %

I know a couple mills up in Ketchikan that ship ceder but I dont use the stuff to often so I'm not sure what they want for it these days

back when I was building more regularly I would just order from the mill rather than buy at the local yards
saves a fortune

ps
your not getting a 40' stick from the mill
I can get up to 22' and thats about it
or at least thats the longest I ever ordered and actually got it

 

Timber from USA

Yes the days of 40' clear boards are sadly passed... but I am looking to get 16' as a minimum and hopefully lots of 20'+ lengths in the timber for my boat to minimise the number of joins. The mill that I'm looking at using is hopeful that most of what they mill for me will be in the 20'-25' range with the rest in the 10'-20' range.

Poplar sounds interesting especially if its yellow poplar (Liriodendron tulipifera).

But given I only need enough timber for a 40' boat displacing 6,100Kgs I'm guessing importing from the states won't be a realistic option.

Regards, Graeme

 

The differences between timbers like huon pine and kirri shouldn't be viewed in terms of superiority. Both have boat building applications for which the other is entirely inappropriate.

 

if you build a scarfing jig it takes about ten seconds to route a scarf

16~20 isnt any big deal and any decent mill should have em
in relatively clear stock
depends
in hardwoods no way
but in soft its not generally an issue
the poplar is yellow poplar but mostly second growth which isnt as good as first

and ya
the way to keep it most economically viable is to buy a whole container full and sell the leftovers to the next guy

not sure what shipping costs are these days but it cant possibly add more than say a buck or two to the total cost per brd/ft

what is a container anyway 8x8x40
thats about 31,000 board feet
jam packed
poplar is 28lb a cubic foot or 430 tons
not sure that box can hold that
I wonder if they have a weight limit

 

I understand it is. They quote 200 year old coffins that are exhumed as sound as they were built. Kirri buried in termite infested WA ground remains unnafected by them after 12 months. http://www.highpointtimber.com.au/images/pdf/kiri_panelling_mouldings.pdf

Personal tests of leaving samples in alternating wet/dry/hot /cold environments (my shower) without any treatment show only slight discoloration, no rot, no splitting or distortion over 2 years.

I have several samples of both timbers, and they dent to the same depth with 15 lb hammer dropped on them

I have never heard any evidence for wild and plantation timber to vary for the same species - it is more the age of the tree than the manner of growing I would have thought.

 

Feel free to check my calculations - i am no maths wizard

42mm wide 12 mm thick @ $2.15 per lineal metres = $4,265 per m3
32 mm wide 12 mm thick @ 1.47 per lineal metre = $3828 per m3

 

Maybe we can go shares Graeme - I would be interested in organising some good value timber from the US

 

Hmmm where do I start - firstly there is very little publically available information on Kiri that is not provided by those marketing and growing the stuff. Its not that Kiri is a bad product its just that I see too many "unfounded" claims for it being a miracle timber.

For starters the best way to look at "toughness" is something like the Janka hardness Test. The test involves measuring the force required to press a steel ball into a test specimen of wood until the ball has penetrated to half its diameter, forming a cavity with a projected area of 100 square millimetres.

When you look at Kiri it has a Janka rating of 1.4kN. Celery Top is 4.5kN. So Celery is about 3 times tougher than Kiri.

Most people I speak to in the timber industry are very clear that there is a difference between plantation and forest grown timber, especially plantations who are trying to maximise growth rates - I would suggest that is most of them! Try talking to any of the larger importers of Teak about the difference between plantation and forest sourced Teak - they are very clear about the differences (not their marketing BS artists but the guys who work in their yards) .

The Queensland DPI&F has done a lot of work on fast-grown plantation timbers. They are clear that plantation timber has different characteristics from the same species grown in their natural environments in native forests. A lot of their work is now to develop technologies to address plantation growth issues such as growth stress, lower durability & strength and increased proportion of sapwood, and defects.

I have even found papers detailing differences in New Zealand grown plantation Oregon and old growth Oregon from forests in America.

I hope this assists.

Regards,
Graeme

 

Selecting Timber for Boat Building

Will,
Exactly - "horses for courses".

Kiri is a great timber in some situations (especially smaller boats where weight is a key consideration and it will be well protected and Celery Top is also great for some jobs. Huon is a fantastic timber (ease of working, stability and longevity) but sadly a rare and diminishing resource.

What I'm clear about is for the hull of the boat I am having designed and built Celery Top is a far superior timber in terms of toughness, longevity and strength. The trade off is cost, weight and availability.

Unfortunately there seems to be a lot of claims out there that are not supported by the science or by widely experienced builders….. by the way something I learnt a while ago is worth considering “Has the experienced person who is advising you had 1 years experience 20 times over or 20 different years of experience?” but I digress.

It has been an enormously educational process working with a designer and builder on my project. I have had to continually adjust my ideas (preferences or prejudices) in developing the best possible design for my needs (and means)… I guess this will continue as we begin the build phase early next year.

Thanks for your comments….. and yes some timber is better than others for specific purposes and some are good for many purposes.

Regards,
Graeme

 

Thats why I conducted my own tests, in hardness and stress performance.

I notice you didnt comment on the remarks I made on longevity, and its inherant durability. This is too important a feature to ignore.

As I say, my steel hammer test gave me confidence. Mind you, timber can vary so much from tree to tree, and even plank to plank.

Anyway, given that Kiri, and strip plank in other woods, will be 'glassed, its probably no a big issue. No-one is building traditional planked boat hulls much anymore.

Kiri (or Pawlonia) is a very different tree to the 'standard' timbers.

A young tree, has hollow limbs. If you saw off a trunk or a limb of a 1 year old tree, you will find that it is like bamboo - hollow in the centre.

Thats why it is able to grow so fast, it has its own "exoskeleton."

Mature trees gradually "infill" the interior of branches and trunks, and become more dense, as well as add layers to the exterior of the surface. This is in direct contrast to the more standard cambium growth, where dry seasons, fire and very wet conditions have a great impact on timber quality.

So, I dont think you will be able to reliably state that plantation Kiri is inferior to wild Kiri by comparing studies on other timbers.

Generally, plantations develop higher quality timbers, as they are forced to grow straight and tall, and may even have branches removed (like Kiri Plantations).
The big factor will be the soil types and available nutrients of the environment.

In the end, the quality of the timber is readily observable and measurable, so its up to the user to determine.

As compared to Celery Top Pine, it has very comparable characteristics of lightness, longevity and ease of working.

Did you come across some actual quotes for Celery Top yet ?

 

RW Clearly your a Kiri convert...

Yes have lined up some sawn Celery Top will ship it to Victoria for drying and milling. My earlier post suggested you contact me directly via email for more details...

Another post had a comment on longevity... your right good composite construction with Kiri should last.... but watch the dings

 

interesting read
I know exactly nothing about either woods you are refering to but
as far as farmed wood goes
Ill take natural growth any day over farmed stock
I buy almost exclusively hard wood for my biz ( assuming I have any work ) and although Im about to buy a bunch of poplar and its probably going to be farmed stock I greatly prefer natural growth timber
to each his own I suppose
best with your builds guys
B

 

hey guys
I wasnt even looking and I found poplar fir $600MBF

which is way high cause I just looked up the average high paid for white oak on the stump and its $175MBF

at the local yard ( which I wont even walk into ) they sell the same W O I buy at $1.50 a foot for ~$7 a foot and poplar for $2 a foot
so Im sure I can find it for probably 1/4 of that price sawn
and way less for logs

kinda stumbled on it and thought Ild pass it along
cheers
B

ok Im board so I went and looked up the timber and log price reports in various states were I know they cut certain species

western red cedar averages $529MBF cut and loaded on a truck
thats out of Montana
yellow poplar averages $280MBF cut and loaded on a truck
out of Illinois
and thats not the cheapest price thats just the mills closest to me that would have those types of timber
if I were shipping it out Ild find mills as close as possible to the port of lading
dam when Im board I go figure out the oddest stuff sometimes