Mast timber question for the masters!

[Wild Dingo]

Okay I guess I got your attention with the title

Now this questions been runnin around me noggin for awhile now... So...

What say you to using Kiri or Pauliwannia as a mast?... I know several blokes who have built or are building various designs using Kiri as the hull timber (strip plank) and reckon its the ducks knuts as its light strong and easily worked

So now Ive met this bloke at work who has a farm and on that farm (sounds like a song eh? :D ) he has about 20 or so 18 to 20ft dead straight no branches till the last 3 - 4ft Kiri trees that he wants to get rid of (note the word he used was free so Im getting them anyways ;) ) but before I go chainsaw the hell out of these trees Im wondering how they would go as masts?

Comments gents?
Cheers

[onthebeachalone]

Never used it but I got to "fondle" some a few weeks ago and it certainly impresses with its strength, lightness and straightness. Seems difficult to get objective, comparative info vs other timbers but one common comment seems to be that while Paulownia has a high strength/weight ratio, it is very light so not very strong for a given size. To me this seems to indicate that you would need to use a thicker section (of mast) to achieve the same strength as another timber.

Anyway, I'm no "master" at this but I'll be getting together with some masters tonight and will see if they have any helpful comments, preferably based on real life experience ragther than theories.

However, as you say, get it anyway!

[echnidna]

Cut the wood first, you don't always get good timber outa dead trees.

[meerkat]

Hi Dingo,

I was introduced to Kirri a few months back and was quite surprised on its weight/strength ratio.

My gut feel is that it wouldn't be too good for a mast in one piece. To get the strength needed you would need to laminate it etc. There is also something about bleaching/soaking it to get the gum etc out. Thats something for the experts to talk about.

It doesn't wear too well, so if it's gonna get knocks and bumps it may be worth trying something else.

The rainbow we picked up from Adrian has a wood mast, boom and spinnaker pole and I was quite surprised with the weight of them but not sure what wood it is.

But as onthebeach said get it anyway.

[Daddles]

Hmm. Take axe. Chop tree. Clean off bark and branches. Mount tree in lathe. Spin down to mast size and shape. Yep, sounds like a Shane exercise to me :D , especially with the three deck Man O War you secretly want to build but are too embarrassed to admit to.;)

Assuming there isn't anything silly in preparing the timber, take it. You're used to cutting and drying timber (yes, I remember the tuart exercise). You can always work out what to do with it later, even if it's just selling it off to other silly gits who want it.

Richard

[bitingmidge]

Shane,

If it's for an 18 footer, about 18' diameter should be ok, if you make it hollow with 4" wall thickness. :eek: :eek:

I don't think that Kiri has any of the characteristics that one would find desirable in a mast timber.

....not one redeeming feature (as a mast!)

Grab the timber anyway, mill it and keep it for other bits.

Cheers,

P

[Boatmik]

Good point of Meercat's about it getting knocked round badly - I wouldn't have thought of it!!!!!!!!!!!!

Would be tempted not to go for a timber too much less dense than spruce or oregon.

There are some structural advantages for going toward higher density timbers as you can make the wall thinner which moves more of the material away from the neutral axis which means that you can reduce the wall thickness even more.

Paradoxically heavier timbers save you weight in masts!!! The same way that aluminium (which is heavier than wood) makes masts even lighter.

But they do need to be engineered.

Any timber for a mast must be of a straight grained variety with good gluing properties. Precoat the end grain of scarfs a few minutes before putting on the glue mix and clamping - stops the end grain sucking up too much resin and leaving the joint dry. Be a bit liberal with the pox for the longitudinal seams - you don't want them to be dry either!!!

Steel would even be better, but generally is getting so thin it crumples like a coke can from the compression loads except in J Class yachts!!!!

(are you gunna build one of those Dingo? Are you? Huh? ....)

MIK

[Wild Dingo]

ssshhh... ahm huntin wabbits :D

[bitofascallywag]

well u got a wabbit....can i ask a question here???.......my 27 footer...what can i do in the way of making some sort of steel contraption to make my mast foldable as in trailer sailor,the mast is solidly keel stepped now and is solid 25 odd foot round king billy pine.or should i forget about it....

[onthebeachalone]

Would be tempted not to go for a timber too much less dense than spruce or oregon. Kicked this around with some "Masters" last night. The main points seemed to be -

1. Paulownia is very strong compared to BALSA, but you would need an awfully thick section to acieve anything like the strength of (e.g.) spruce or oregon.

2. Farm clearance paulownia is probably too immature to be of much value as "pulownia timber for any boatbuilding purpose should be taken from trees over 15 years old" (I guess there's not much heartwood before that).

[Daddles]

well u got a wabbit....can i ask a question here???.......my 27 footer...what can i do in the way of making some sort of steel contraption to make my mast foldable as in trailer sailor,the mast is solidly keel stepped now and is solid 25 odd foot round king billy pine.or should i forget about it....

Oh I'd forget about it. In fact, forget the whole boat. Just drop the Mad Dingo and me a note telling us where she'll be berthed and we'll quietly take her away and you'll never have to worry about her again :D

Richard

[Boatmik]

Farm clearance paulownia is probably too immature to be of much value as "pulownia timber for any boatbuilding purpose should be taken from trees over 15 years old" (I guess there's not much heartwood before that).

I would disagree a little bit. Certainly if you were building a trad boat then you want heartwood.

With epoxy it doesn't matter so much as the structure is effectively one piece. Also the moisture transfer problems are minimised.

Certainly I would prefer to work with heartwood, but I don't think it is a critical issue.

Best regards to all

MIK

[viking]

who what never heard of the stuff or do you mean dame kirri she a bit short for a mast but those dresses would catch some wind:p
Okay I guess I got your attention with the title

Now this questions been runnin around me noggin for awhile now... So...

What say you to using Kiri or Pauliwannia as a mast?... I know several blokes who have built or are building various designs using Kiri as the hull timber (strip plank) and reckon its the ducks knuts as its light strong and easily worked

So now Ive met this bloke at work who has a farm and on that farm (sounds like a song eh? :D ) he has about 20 or so 18 to 20ft dead straight no branches till the last 3 - 4ft Kiri trees that he wants to get rid of (note the word he used was free so Im getting them anyways ;) ) but before I go chainsaw the hell out of these trees Im wondering how they would go as masts?

Comments gents?
Cheers

[Wild Dingo]

Viking... mmm I understood you to say you had been a shipwright for 20+ years? funny you dont know about Kiri otherwise known as Pauliwanna (or various spellins)... Anyways its a great timber for boatbuilding and quite a few blokes are building everything from 30ft Proas to Catamarrans and monos from it with great success...

History is I believe it is an ancient Chinese timber wherein the story goes that a girls father would plant a Kiri tree at the birth of his daughter and by the time she was of marrigable age the tree would be big enough for the father to chip down and make the happy couples new homes furniture from... very fast growing.

No problems as I said Im getting it anyways... I was seriously wondering about the mast thing as by gar it would be good to get the wood for the masts free but no sweat... I have my eyes and ears open continuously for such things ;) Sometimes I think Im the George Bueller of Aussie boatbuilding! Nothin like a good scrounge to offset costs boats and boatbuilding dont necessarily have to cost an arm two legs and your gronicles to achieve :D

Mik, I have decided not to put me foot in me gob again with regard to "the boat" since recieving my re-draw Luggar plans from Tony Ive been mucking about with them again... I have pretty much come to the conclusion that shes doable... still some things to do but the numbers for the hull deck keel ballast are done and through FreeShip they seem to work out beautifully... a few more excersizes and I will decide weather to trust myself to design and build a boat or if I just buy a set and be done... actually Ive stopped looking at any other boat since they arrived

Anyway!! No decision made yet... still figureing and sourcing... although ive begun work on the canoes again so am getting my fingers wet once more albeit on a smaller level... I do tend to do things rather steady steady... sorta suits my manic nature :D