A 39' "downeast" influenced design - Feedback Request

[dobsong]

I'm part the way through getting a boat designed and was thinking I sould get some feedback from others before we finalise the design and begin construction (this is scheduled to begin early next year).... So here goes! Any comments, criticisms or suggestions for improvement welcomed.

She is for open water coastal cruising in Bass Strait, around Tasmania and up the eastern coastof Australia. Most of the time I will use her single handed or with a friend (or maybe two), maybe once every month or two there will be 6-8 guests on board for day cruising.

Dimensions are 11.9 metres LOA, 11.7 metres DWL, Beam is 3.3 metres and draft is 1.1 metres. Displacement is anticipated to be 6,100Kgs fueled and loaded for cruising. She has a rounded "ducktail" stern

She will be powered by a 315hp Yanmar and will carry 700 litres of fuel. We are expecting a cruise of 14-15 knots and a top of 19-20 knots. She is to be built using Celery Top Pine (a wonderfully tough timber from Tasmania) in an expoxy composite.

These are the profile and layout drawings.

[messabout]

The profile view shows a very handsome boat. That view also suggests that it will operate in mainly displacement mode which further suggests that the quoted speeds are vastly overstated. Surely you will not need all that power if it is, in fact, a displacement boat.

[apex1]

Uhhh?

http://www.balta.fr/lovstar.html

the most beautiful of her kind as far as I know.
but what do I know............................................

Regards
Richard

[dobsong]

The profile view shows a very handsome boat. That view also suggests that it will operate in mainly displacement mode which further suggests that the quoted speeds are vastly overstated. Surely you will not need all that power if it is, in fact, a displacement boat.

Boats of a similar size and hull shape easily do the speed I have been advised. e.g. http://www.pbmy.com.au/range38_intro.html

So I am surprised at your comment. What do you base this on?

[dobsong]

Uhhh?

http://www.balta.fr/lovstar.html

the most beautiful of her kind as far as I know.
but what do I know............................................

Regards
Richard

Yes a lovely looking boat..........

[dobsong]

The profile view shows a very handsome boat. That view also suggests that it will operate in mainly displacement mode which further suggests that the quoted speeds are vastly overstated. Surely you will not need all that power if it is, in fact, a displacement boat.

She has a very fine entry and then flattens out considerably as you go aft - you could call her a semi-planning design.

[waikikin]

Dobsong, the profile looks nice, I would have assumed the same as Messabout when you track the rabbet line & imagine the buttock lines rising similar, the example Apex has linked is sweet & I admire his taste in that with much more cockpit space with the conventional transom. Are the speed figures as calculated by David? "cos he's known as a pretty cluey guy. All the best with it from Jeff.

[apex1]

She has a very fine entry and then flattens out considerably as you go aft - you could call her a semi-planning design.

Well as her sister of Patric Balta but tha latter with less than half of the power to the same performance!

I could do such a boat btw. at about 300.000$ in wood Epoxy
Finest wood, and prime equipment, and (using now 800 tonnes of Ep resin a year) not the least quality in every aspect.
This was not a business offer, or a advertisement, just to talk about........

[dobsong]

Well as her sister of Patric Balta but tha latter with less than half of the power to the same performance!

I could do such a boat btw. at about 300.000$ in wood Epoxy
Finest wood, and prime equipment, and (using now 800 tonnes of Ep resin a year) not the least quality in every aspect.
This was not a business offer, or a advertisement, just to talk about........

Is that 300,000 US or Aus - has to be delivered to Melbourne, Australia

[dobsong]

Dobsong, the profile looks nice, I would have assumed the same as Messabout when you track the rabbet line & imagine the buttock lines rising similar, the example Apex has linked is sweet & I admire his taste in that with much more cockpit space with the conventional transom. Are the speed figures as calculated by David? "cos he's known as a pretty cluey guy. All the best with it from Jeff.

Yes calculated by David

[tom28571]

Well yes, if you apply Crouch's speed formula to the given specs, the top speed comes to a bit over 18 knots. Crouch's is pretty good for a full planing hull, which this is not. The aft hull shows the typical highly warped form of Maine lobsterboats with a fairly flat, if highly twisted, aft run. I am also doubtful of the speed prediction. One caution of the speed prediction is the very steep keel rise aft. If it did get to the predicted speed, I would expect the bow to be way high by over 10 degrees and forward view to be almost non existent. The power to make this speed is another issue.

Skeptical arguments here are based on scant information and should not be taken as gospel but should cause a deeper study of this boat's potential.

Beautiful boat, by the way.

[apex1]

Is that 300,000 US or Aus - has to be delivered to Melbourne, Australia

US ex works Turkey.

Richard

[dobsong]

Well yes, if you apply Crouch's speed formula to the given specs, the top speed comes to a bit over 18 knots. Crouch's is pretty good for a full planing hull, which this is not. The aft hull shows the typical highly warped form of Maine lobsterboats with a fairly flat, if highly twisted, aft run. I am also doubtful of the speed prediction. One caution of the speed prediction is the very steep keel rise aft. If it did get to the predicted speed, I would expect the bow to be way high by over 10 degrees and forward view to be almost non existent. The power to make this speed is another issue.

Skeptical arguments here are based on scant information and should not be taken as gospel but should cause a deeper study of this boat's potential.

Beautiful boat, by the way.

Thanks for your comments Tom - the potential for excessive "squatting" is a concern that we will have to work through

[messabout]

My remarks about speed and power were predicated on the appearance of the afterplane of the boat. To plane or not to plane is closely dependant on the angle of the quarter beam buttock in the run. An angle of four degrees is just about all the rise that might allow planeing performance. The normal planeing hull will have zero degrees of rise and some even have negative rise which coaxes the boat to run on an even keel. The choice of negative angle, or not, is somewhat dependent on weight distribution and sometimes decided on the basis of expected sea conditions ang entry shape. Your drawing shows a rise of considerably more than the optimum. In displacement mode you might expect something on the order of 8 or 9 knots. Probably less except when you are content to pull half the ocean behind you. Be that as it may, it is still mighty handsome.

[dobsong]

My remarks about speed and power were predicated on the appearance of the afterplane of the boat. To plane or not to plane is closely dependant on the angle of the quarter beam buttock in the run. An angle of four degrees is just about all the rise that might allow planeing performance. The normal planeing hull will have zero degrees of rise and some even have negative rise which coaxes the boat to run on an even keel. The choice of negative angle, or not, is somewhat dependent on weight distribution and sometimes decided on the basis of expected sea conditions ang entry shape. Your drawing shows a rise of considerably more than the optimum. In displacement mode you might expect something on the order of 8 or 9 knots. Probably less except when you are content to pull half the ocean behind you. Be that as it may, it is still mighty handsome.

My brief to the designer is to optimise for 14 knots - attached is a scanned document of the lines does this make things clearer?

[dobsong]

US ex works Turkey.

Richard

Thanks, when you look at the exchange rate and add in shipping it works out about the same as a build in Australia.

[Tad]

Review of Dobson Lines......

LWL = 11.7m or 38.4'
Disp = 6100Kg or 13,400 pounds
Speed = 14 knots

S/L = 2.25
FNv = 1.70
Ideal CP = .70
Midsection area (Largest section) = 7.8 sq ft.
Optimum LCB for speed(and LCG) = 57 % LWL from Bow
Optimum immersed transom area = 45% largest section or 3.12 sq ft.

[Mat-C]

Tad,
Can I ask how you come up with those numbers?

[Tad]

Mat.....

We know the speed and the waterline length.....thus we know the Speed/Length ratio.

Optimum prismatic coefficient for a given S/L ratio has been published for at least 60 years, see Skene's.

You know the waterline length, the CP, and the displacement, thus you can calculate the maximum section.

CP = disp (cubic ft) / (mid sec * LWL)

Mid sec = disp (cubic feet) / (CP * LWL)

See my article for the ideal curves of areas and LCB location based on S/L.
http://www.tadroberts.ca/about/pdf/power-boat-design-form-and-function.pdf

[Mat-C]

Thanks Tad. Great article.
Amazing that the work of Skene and others of his era is still so readily used today. I guess if it's right, it's right. Has there been more recent work to verify (or refine) his findings, or are they just taken as a given?

[Willallison]

I have to agree.... damned fine looking craft!
I also have to agree that the unusually curvaceous and upswept buttock lines are likely to result in some pretty extreme trim angles and far higher power consumption to reach the sort of speeds that you have quoted.
All that, however, is for your designer to figure out. I'm more interested in your adoption of the ducktail stern. As a styling feature I quite like it, but as an integral feature of a cruising design, I'd need more convincing. Easy access to and from a tender, or to and from the water, are essential to anyone who wants to cruise Tasmanian waters. As is the ability to stow a tender.
It also has a significant impact on the cockpit space available.

I know a number of well qualified builders in Tassie too, if you are looking for someone....

[dobsong]

I have to agree.... damned fine looking craft!
I also have to agree that the unusually curvaceous and upswept buttock lines are likely to result in some pretty extreme trim angles and far higher power consumption to reach the sort of speeds that you have quoted.
All that, however, is for your designer to figure out. I'm more interested in your adoption of the ducktail stern. As a styling feature I quite like it, but as an integral feature of a cruising design, I'd need more convincing. Easy access to and from a tender, or to and from the water, are essential to anyone who wants to cruise Tasmanian waters. As is the ability to stow a tender.
It also has a significant impact on the cockpit space available.

I know a number of well qualified builders in Tassie too, if you are looking for someone....

Thanks for comments re looks.

Trim angle at cruise speed (14 - 15 knots) seems to be a contentious issue – advice from the designer is that there will be some squatting and this is because he is concerned about “balancing” the behaviour the boat (i.e. in a following sea avoiding a tendency for the bow to dig in).

Access (egress and ingress) to the boat when away from marinas or piers etc is to be handled by concealed steps in the transom and a wide(ish) sponson. The tender will be a small inflatable (to be stored under aft seats) and I don’t see this as a significant issue.

Cockpit space is more than I need as I will not usually carry many guests and anticipate taking her out solo frequently (part of the original concept for this boat). I’m not after a boat crowded with accommodations and seating for larger numbers of people – this is a boat for me to enjoy in my retirement and I anticipate frequently my friends or partner will busy and I will go out alone.

What is important is that I get a boat that is optimised for efficient, seaworthy cruising at around 14 knots and is built well with timber. I also want a bit of speed in reserve (say 18-20 knots) for those times when I want to run from bad weather.

I have a preferred builder in Paynesville, Victoria and want to be involved in the build process so that rules out using a Tasmanian builder.

[dobsong]

Review of Dobson Lines......

LWL = 11.7m or 38.4'
Disp = 6100Kg or 13,400 pounds
Speed = 14 knots

S/L = 2.25
FNv = 1.70
Ideal CP = .70
Midsection area (Largest section) = 7.8 sq ft.
Optimum LCB for speed(and LCG) = 57 % LWL from Bow
Optimum immersed transom area = 45% largest section or 3.12 sq ft.

Tad, don't really understand FNv etc what I'm really trying to get is an increased level of confidence about this design in terms of the hull performance.

Critical aspects are getting the balance right between seaworthiness, efficiency (power requirements/fuel use) at intended cruise speeds (normal cruise 14 knots – low speed cruise 7-8 knots) and achieving low wake (for hull type) at low speed cruise. I’m also keen to avoid excessive changes in trim across the intended cruise range.

I’m very happy with the layout and the way she “looks on paper” and I’m sure with a few minor “tweeks” (like sheer, portholes, some more crown on house tops etc) I will have a great looking boat – to my eye at least.

This process has taught me how challenging balancing conflicting requirements (like house height vs headroom vs beam) are in completing the design. No doubt there will be some more “lessons” for me when I move into the build stage!

Thanks again for taking the time to provide comments/input into my retirement project. Please feel free to comment further.

Graeme

[dobsong]

I have to agree.... damned fine looking craft!
I also have to agree that the unusually curvaceous and upswept buttock lines are likely to result in some pretty extreme trim angles and far higher power consumption to reach the sort of speeds that you have quoted.
All that, however, is for your designer to figure out. I'm more interested in your adoption of the ducktail stern. As a styling feature I quite like it, but as an integral feature of a cruising design, I'd need more convincing. Easy access to and from a tender, or to and from the water, are essential to anyone who wants to cruise Tasmanian waters. As is the ability to stow a tender.
It also has a significant impact on the cockpit space available.

I know a number of well qualified builders in Tassie too, if you are looking for someone....

Will,
Just checked out your web site and saw your in Hobart. I lived in Trumpeter Street opposite "Shippies" for almost 4 years while working at the smelter down on the river. Nice part of the world! Looking forward to cruising down when I get my new boat (sometime in early 2011 - 12-15 mth build).

Graeme

[rwatson]

I'm part the way through getting a boat designed .... She is to be built using Celery Top Pine (a wonderfully tough timber from Tasmania) in an expoxy composite.


Have you sourced, and priced your Celery Top yet ?

I noted that Celery Top is not in the list of approved West Systems timbers (of course) when I was considering it for a project. Its not all that oily, so it should be OK, but it might be worth a few test panels.

[dobsong]

Have you sourced, and priced your Celery Top yet ?

I noted that Celery Top is not in the list of approved West Systems timbers (of course) when I was considering it for a project. Its not all that oily, so it should be OK, but it might be worth a few test panels.

Hi, Celery Top is one of Australia's best boat building timbers. Sourcing it can be difficult particularly for boat building but I have found a suitable supply. The following from the university of Tasmania may assist in developing your understanding of this timber.

Celery Top Pine
Phyllocladus asplenifolius
Colour
Celery Top Pine has a pale straw colour, darkening to a beautiful gold, with age. There is an occasional hint of red. The timber has a straight, fine and even grain with a close even texture. It is highly durable, resilient, and exhibits low shrinkage across the grain. In ground durability of heartwood is very good.
Use
A sturdy versatile and durable, workable timber admired and used for its stability, finishing qualities and its light base colour. Celery top pine has been used for boat building, benchtops, flooring, decking, joinery,indoors outdoor furniture, external cladding, wall panelling, beams and poles.
Workability
Celery Top Pine can be worked to a smooth flat surface. It planes well with the grain, drills cleanly to size, bends and turns well, and accepts paints, stains and varnishes readily.

[rwatson]

Hi Dobsong

Thanks for the info, but I am an old tasmanian, and am very familiar with all the great timbers available. I have contact with a Celery Top Mill in the Huon Valley, but am always on the lookout for new sources.

The price is astronomical these days as is all timber.

If its not a secret, I would be interested in hearing about new sources and indicative prices.

Once again, I have little knowledge of Celery Top being used in epoxy work, as boats built with it rarely need any additional structural support until they are much much older.

Huon Pine was another major jewel of a Timber, but you would not be able to use Epoxy on it without a lot of treatment for the oils.

I suspect some sources of Celery Top could be a bit oilier than others, and may need to be treated accordingly berfore epoxying.

Were you going strip planking for the design ?

[masalai]

I suppose dobsong, you have considered your cruising grounds carefully and the range you will get... At a wild guess, 300 miles if you are lucky and have calm seas and stay in displacement mode? and 700litres to refuel? near Au$1400 at best and likely lots more later

I will admit that you have a very pretty vessel, but the question begs, for what and when???

[Willallison]

Mas -
Setting aside any issues of squatting and any subsequent inefficiency, the boat would require approx 136 SHP to run at her semi-displacement cruise speed of 14 knots (SL = 2.26). Again setting aside any losses occured thru the transmission etc, the Yanmar 6LP 315 hp engine should consume around 25 lph at that speed, giving a 25 hr (or 350 nm range) with a 10% reserve.

[masalai]

Oh thanks my rough guess was 50 miles on the safe side of 10% reserve - PHEW - I thought I may be in for another bollocking with my big mouth :D:D:D - - saved (sort of) by a friendly expert - appreciation has been deposited:D:D:D:D

[dobsong]

Mas -
Setting aside any issues of squatting and any subsequent inefficiency, the boat would require approx 136 SHP to run at her semi-displacement cruise speed of 14 knots (SL = 2.26). Again setting aside any losses occured thru the transmission etc, the Yanmar 6LP 315 hp engine should consume around 25 lph at that speed, giving a 25 hr (or 350 nm range) with a 10% reserve.

Hi,
Anticipating a little less consumption (say 20-22 lph) wanted 350 nm range as minimum @ 14 knots. Expecting that range will increase very significantly for a slow cruise (say around 8 knots). Trying to get all elements (prop, hull, engine etc) optimised for 14 knots. There are other similar boats that indicate all is achievable.

[dobsong]

Hi Dobsong

Thanks for the info, but I am an old tasmanian, and am very familiar with all the great timbers available. I have contact with a Celery Top Mill in the Huon Valley, but am always on the lookout for new sources.

The price is astronomical these days as is all timber.

If its not a secret, I would be interested in hearing about new sources and indicative prices.

Once again, I have little knowledge of Celery Top being used in epoxy work, as boats built with it rarely need any additional structural support until they are much much older.

Huon Pine was another major jewel of a Timber, but you would not be able to use Epoxy on it without a lot of treatment for the oils.

I suspect some sources of Celery Top could be a bit oilier than others, and may need to be treated accordingly berfore epoxying.

Were you going strip planking for the design ?

Yes the hull is to be strip planked (cove & cusp 23mm x 42mm) with exterior 450 gsm DB + 600 gsm DB and interior 2 X 450 gsm DB. I have not heard of any problems with glue or epoxy adhesion for Celery Top.

Celery Top logs available for milling on the west coast. Around $20,000 for the quantity (+15%) I need. Will use celery top for other parts (in addition to the hull) also using marine ply for a few places. Builder, designer and myself all agree we will end up with a very solid hull.

Apart from the expense and some problems with oils, my view is Huon is too soft. Also its very hard to get it in suitable lenghts for a 40' boat.

[dobsong]

Mas -
Setting aside any issues of squatting and any subsequent inefficiency, the boat would require approx 136 SHP to run at her semi-displacement cruise speed of 14 knots (SL = 2.26). Again setting aside any losses occured thru the transmission etc, the Yanmar 6LP 315 hp engine should consume around 25 lph at that speed, giving a 25 hr (or 350 nm range) with a 10% reserve.

With a displacement of 6,000 Kgs (now 6,100) and a conservative co-efficient applied the designer has calculated the following:

For the 315 hp max output using 85% (again a very conservative approach) of this figure (268hp) shows that the craft should do 21.7 mph or 18.9 knots.

To do 14 knots or 16.1 mph, same coefficent, the actual HP required is 125 hp.

[Willallison]

So, essentially the same as my quick estimate. The consumption I gave was based on Yanmar's own prop & power curves. If they are correct, I'll be surprised if you can get much better than that - it equates to 2.5 nmpg, which is pretty good going for a semi-displacement boat. Having said that, my own recent experience with a Yanmar 6BY260 showed that (in my instance at least) Yanmar's figures were quite conservative.
Just as an aside, I reckon you'll find the engine is happier running at around 2400 rpm - which should give you 100shp and around 12 knots, or thereabouts.
You will certainly see a BIG jump in your mileage if you slip back into displacement mode: 8 knots max

I'm a bit short on time at the minute, I'll take up the debate with you about tender access at another time...:D

[dobsong]

So, essentially the same as my quick estimate. The consumption I gave was based on Yanmar's own prop & power curves. If they are correct, I'll be surprised if you can get much better than that - it equates to 2.5 nmpg, which is pretty good going for a semi-displacement boat. Having said that, my own recent experience with a Yanmar 6BY260 showed that (in my instance at least) Yanmar's figures were quite conservative.
Just as an aside, I reckon you'll find the engine is happier running at around 2400 rpm - which should give you 100shp and around 12 knots, or thereabouts.
You will certainly see a BIG jump in your mileage if you slip back into displacement mode: 8 knots max

I'm a bit short on time at the minute, I'll take up the debate with you about tender access at another time...:D

Advice from the designer is that conservatively I will need 125 hp at the prop to achieve 14 knots. From the propeller curve we see that this is delivered at around 3,000 rpm. From the fuel consumption graph we see that the engine uses 30 litres per hour at full load at 3,000.

It is a bit of a “SWAG” (scientific wild arsed guess) but given we are using less than half the available horse power at 3,000 rpm (or half allowing for losses) I am hopeful 20 litres per hour is achievable. This seems to be supported by outcomes achieved by similar boats.

What do you think?

Regards, Graeme

[rwatson]

Yes the hull is to be strip planked (cove & cusp 23mm x 42mm) with exterior 450 gsm DB + 600 gsm DB and interior 2 X 450 gsm DB. I have not heard of any problems with glue or epoxy adhesion for Celery Top.

Celery Top logs available for milling on the west coast. Around $20,000 for the quantity (+15%) I need.

Thanks for that info. If you get the chance anytime, I would be interested in the cost per cubic metre. I costed Plantation Kiri recently - its over $4000 per cubic metre.

[Willallison]

Propeller curves can only ever be regarded as an estimate IMHO. There is simply too much variation from boat to boat and installation to installation for it to be regarded as anything more than that. The only definitive consumption figures come when the boat hits the drink. They should, however, give a reasonable approximation and anyone with a bit of common sense would make allowances for any variation from theoretical to real life. Your designer has suggested that you'd need 700 L to run 350 nm at 14 knots and my quick estimate would suggest that that's pretty much on the money, allowing a 10% (70L) reserve. That is (as Mas pointed out) assuming calm conditions.
My quick look at the 6LP's prop curve earlier (I assume it is the LP that you're planning to use...?) suggests that 27-2800 rpm ought to yield aound 130 hp at the crankshaft. This is under load - that's what the prop curve is intended to estimate. At 2800 rpm the engine will use around 25 lph, according to Yanmar's figures. Based on that, 20 lph may be a bit hopeful... but as I said, my recent experience with the 6BY yielded substantially better fuel consumption than the published Yanmar figures. Personally, I would expect the worst and (hopefully!) be pleasantly surprised when the boat performs better than expected.

[dobsong]

Propeller curves can only ever be regarded as an estimate IMHO. There is simply too much variation from boat to boat and installation to installation for it to be regarded as anything more than that. The only definitive consumption figures come when the boat hits the drink. They should, however, give a reasonable approximation and anyone with a bit of common sense would make allowances for any variation from theoretical to real life. Your designer has suggested that you'd need 700 L to run 350 nm at 14 knots and my quick estimate would suggest that that's pretty much on the money, allowing a 10% (70L) reserve. That is (as Mas pointed out) assuming calm conditions.
My quick look at the 6LP's prop curve earlier (I assume it is the LP that you're planning to use...?) suggests that 27-2800 rpm ought to yield aound 130 hp at the crankshaft. This is under load - that's what the prop curve is intended to estimate. At 2800 rpm the engine will use around 25 lph, according to Yanmar's figures. Based on that, 20 lph may be a bit hopeful... but as I said, my recent experience with the 6BY yielded substantially better fuel consumption than the published Yanmar figures. Personally, I would expect the worst and (hopefully!) be pleasantly surprised when the boat performs better than expected.

Yes – conservative/realistic 25 lph @ 14 knots x .9 = 352 nm but hey I’m a hopeful sort of guy and my optimistic “hope” is 20 lph @14 knots x .9 = 441… sweet!

Also the displacement calcs are "realistic" with full tanks and cruising gear included.

The graphs I forgot on my last attached

Some information that supports my fuel consumption "guesstimates"
- The Rumery 38 with the 315 hp Yanmar is reported in the Wooden Boat article as having a top speed of 32 mph and using 6 gallons (23 litres) per hour at 30 mph. A surprising figure! I’m guessing what was actually meant was that it averaged 6 gallons an hour for 100 hours operation at speeds of up to 30 knots, still OK in my book.
- Given the boat being designed for me has more beam, bigger tanks and a bit more in the cabin fit out (an extra 1,100Kg displacement fully loaded above the 5,000Kg reported for the Rumery – was it 5,000??) I’m assuming we will loose around 10 knots top end speed and have some increase the fuel consumption.
- The 32’ Cheviot (32’ x 10’ 10” x 3) built by Tim Phillips is shown in her trip across Bass Strait as having a top speed of 24 knots and that with a 300 hp Yanmar at 3,000 rpm she travels at 15 knots using 22 litres of fuel per hour.
- The Fairway 36, a semi-displacement hull that displaces 7 tonnes fully loaded, has a top speed of 19 knots when fitted with a single Yanmar 6LP-STP. With this engine at a cruise speed of 15 knots the fuel consumption is reported to be 19 litres per hour.

But at the end of the day these are interesting "facts" that I use to give me some comfort (along with calculations from the designer) - the real test will be when she is launched and I do a decent run in her with some accurate measurement of fuel, speed and distance.

On thing I am sure of, she will do a whole lot better in "real world" cruising than a lot of production boats - you just have to read some of the reviews where they say 3-5 liters a nautical mile is economical cruising. And I think she will look a whole lot better doing it.

Regards,

Graeme
dobsong@bigpond.com

PS email me for more details on the $$ for Celery Top

[Boston]

Thanks for that info. If you get the chance anytime, I would be interested in the cost per cubic metre. I costed Plantation Kiri recently - its over $4000 per cubic metre.

holly empty wallet bat man
you folks pay a fortune for timber down there

1 cubic meter = ~27 cubic feet
1 cubic foot = 12 board feet
12x27=324 board feet
$4,000/324=~$12.35 a board foot
dam
you guys would die if you knew how cheep wood is round here

[rwatson]

holly empty wallet bat man
you folks pay a fortune for timber down there


Yes, its exciting, isnt it! Mind you, these are premium boatbuilding timbers, and Kiri is plantation grown.

The next step down "malaysian red cedar" is about 2/3rd the price, but destroys rain forests and OranguTangs.

By the time we ship timber from you to me, take into account the exchange rate, that makes it even dearer.

How about a couple of Care packages :-)

[dobsong]

holly empty wallet bat man
you folks pay a fortune for timber down there

1 cubic meter = ~27 cubic feet
1 cubic foot = 12 board feet
12x27=324 board feet
$4,000/324=~$12.35 a board foot
dam
you guys would die if you knew how cheep wood is round here

Yes it hurts when you pay around $Aus100 a metre for 240mm x 42mm dressed hardwood and get told thats a good price! Makes you think about all the really great Australian hardwood that is chipped and sold for a few dollars a tonne.... but thats the "economic rationalist arguement that has enamoured our policy makers here! Let the buggars charge what the market will pay (rather than what it costs.... and because we are a captive audience we pay... and pay... and pay

[dobsong]

Yes, its exciting, isnt it! Mind you, these are premium boatbuilding timbers, and Kiri is plantation grown.

The next step down "malaysian red cedar" is about 2/3rd the price, but destroys rain forests and OranguTangs.

By the time we ship timber from you to me, take into account the exchange rate, that makes it even dearer.

How about a couple of Care packages :-)

Kiri a premium boatbuilding timber?? Strange I'd never considered that to be the case.....

[Boston]

not sure what shipping costs but I could organize a container in about a heartbeat of any north american hardwood you want
about the only ones I dont have a handle on are live oak and black Locust
everything else this new mill I been going to has got it
and dirt cheap
most in clear premium is $2 a foot
cherry and black walnut is $4
half that for lesser grade lumber

white oak is my personal fave which I got for $1.50 a foot just a few months ago
they cut heavy at around 5/4 or 9/4 on the white oak

they will plane it for you if you want to avoid shipping mill but I prefer to mill my own when Im ready to use it
course your paying for that shipping
I think planing is C 0.20 a foot

the mill is stacked to the gills with lumber at the moment
if you guys wanted any large quantity Im sure I could do even better than that

give me a species and a quantity and I can get you a quote tomorrow
I gotta call em anyway so its no big deal

I wonder how much a container can hold

[dobsong]

not sure what shipping costs but I could organize a container in about a heartbeat of any north american hardwood you want
about the only ones I dont have a handle on are live oak and black Locust
everything else this new mill I been going to has got it
and dirt cheap
most in clear premium is $2 a foot
cherry and black walnut is $4
half that for lesser grade lumber

white oak is my personal fave which I got for $1.50 a foot just a few months ago
they cut heavy at around 5/4 or 9/4 on the white oak

they will plane it for you if you want to avoid shipping mill but I prefer to mill my own when Im ready to use it
course your paying for that shipping
I think planing is C 0.20 a foot

the mill is stacked to the gills with lumber at the moment
if you guys wanted any large quantity Im sure I could do even better than that

give me a species and a quantity and I can get you a quote tomorrow
I gotta call em anyway so its no big deal

I wonder how much a container can hold

What about Chamaecyparis nootkatensis (Yellow Cedar, Alaska Cedar, Nootka Cypress)? Would have to be a 40' container (to get the lengths that are useful) so I guess we are talking about a lot of timber. If sawn it would need to be 2" thick and a reasonable width say 6" at least (8" - 10" better) so it could be ripped/milled here.
________________________________________

[rwatson]

Kiri a premium boatbuilding timber?? Strange I'd never considered that to be the case.....

Oh yes, nearly as light as balsa, close to WRC for strength, virtually rotproof (like Huon Pine) but hard enough (like Celery Top).

When the Plantations get large enough, and the price is driven down, we may be able to start building guilt-free wodden boats again.

[Willallison]

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...

[dobsong]

Oh yes, nearly as light as balsa, close to WRC for strength, virtually rotproof (like Huon Pine) but hard enough (like Celery Top).

When the Plantations get large enough, and the price is driven down, we may be able to start building guilt-free wodden boats again.

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.

[Boston]

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

[dobsong]

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

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

[Willallison]

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.

[Boston]

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

[rwatson]

I think you are mistaken. Kiri / Paulownia is not anywhere as durable as Huon .... 5. Durability - The in-ground durability rating for paulownia is 4 and the timber should not be used for that purpose.... moderatly durable

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.


nor is it anywhere near Celery Top for toughness. .

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

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

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.

[rwatson]

Kirri
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).


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

[rwatson]

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

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

[dobsong]

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.

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

[dobsong]

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.

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

[rwatson]

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. .

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.

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. .

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.

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

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 ?

[dobsong]

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

[Boston]

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

[Boston]

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

[apex1]

Paulownia tomentosa is a superb boatbuilding material, but has to be seen as a strong core in a sandwich. In fact it is the best core material I know.
It is sometimes available from chinese sources at much lower rates as the ozzie timber farmers ask for.
And of course natural grown timber is almost always superior in comparison with farmed one.
Regards
Richard

[rwatson]

Paulownia tomentosa is It is sometimes available from chinese sources at much lower rates as the ozzie timber farmers ask for.


Let me know if you come across any. All inquiries I made put imported Pawlonia logs much dearer, which is why the plantations are so keen to get established.

The Chinese government puts a big export tax on non-processed timber.

[apex1]

Let me know if you come across any. All inquiries I made put imported Pawlonia logs much dearer, which is why the plantations are so keen to get established.
The Chinese government puts a big export tax on non-processed timber.

The trick is to get it processed in China before exporting it! And that makes sense too, a bead and cove cut made there is near to nothing in cost!

In May the m³ of 19mm x 70mm x 300mm was around 1.200$ US fob Shenzen.

But there is a problem, this source does´nt exist any longer, and I am not in that business any longer. So I doubt that I can assist you, you would have to make your own investigations.
Start here:
http://www.globalwood.org/market/market.htm
http://www.timberhunt.com/

Regards
Richard