H28 bath - opinions on how long to let her soak?

[shamus]

I'm moderately confident that this will turn out to be the right thing to do and will turn out OK. I don't know if they still do, but Forestry Tas used to pond blue gum in salt water for use as keels- now they didn't do that to have it dry did they? Wilson Bros used to build those big sailing barges in about a year. The first job being to fell a tree for the keel. How dry is an 18" x 18" keel going to be in 12 months? They also planked green, but promoted a moderate amount of airdrying in the (much smaller dimensioned) planking by hanging every second plank and then planking the gaps. (Good spilers those boys). All this is documented with photographs and interviews with old timers in Gary Kerr's book.
I have a friend who built a fifty foot fishing boat about 30 years ago in Bernard Wilson's yard. He said Bernard told him to build the keel and deadwood wet and never let it dry out. Now this one has dried out, but from my experience a dry piece of blue gum will return to its original dimension, or very close, upon immersion.

[JoshuaIII]

Larks at the stage we are at, I think you should take bet!
I bet a local beer that it will get close but won't fill entirely the gap...
Somebody taking this bet, would sure like to taste a exotic beer paid by someone else

[Larks]

Larks at the stage we are at, I think you should take bet!
I bet a local beer that it will get close but won't fill entirely the gap...
Somebody taking this bet, would sure like to taste a exotic beer paid by someone else

Difficult to bet against you when you're betting on what I'm expecting myself. My unknowns are the extent of how much the planks will return so that I can estimate what thickness of splining, if any, may be needed (or what and how much caulking to use) and how long to give it to reach it's potential maximum swelling.

I'm moderately confident that this will turn out to be the right thing to do and will turn out OK.

Thanks Sean, I reckon you are right, while it's great to see and consider all of the opinions on the forum here and weigh up all of the pro's and cons, nothing beats your local knowledge

[PeterSibley]

Still watching Greg !

[Larks]

You might be watching for a while Peter, I'll leave it soak for a bit yet before I empty the "bath" and take a look at the results. In my earlier bath set up I had installed a tap and drain so that I could easily empty the bath but that seemed to be one of the leak points (not easy to get a tap to seal into a piece of plastic sheet) so I've left it out of this new membrane set up, so it's not such a quick and easy thing to empty (and I don't want to drain the salt water into the paddock until I need to).

So at the moment I'm just taking some measurements on the test samples at regular intervals to see what rate they expand and if they seem to plateau at some stage, which I hope will then give me an indication of when to have a look at the hull. If I can work out how to, I hope to be able to post some sort of an "expansion curve" (???) here when I have enough measurements to make it worthwhile.

Meanwhile I have now also set up a separate linseed oil and kero V. salt water "expansion" test as well, following which I'll put both samples to a "burn test", to see if the kero impregnated wood is actually that much more flamable than the salt impregnated wood.

[Lucky Luke]

It certainly will be interesting to see just how much it does swell back up, and how long it takes. I, for one, am grateful that you're sharing this with us!
Rick

+1!
....as for the time it will take before it "stabilizes": surely many weeks, but how many months...?

[PeterSibley]

Meanwhile I have now also set up a separate linseed oil and kero V. salt water "expansion" test as well, following which I'll put both samples to a "burn test", to see if the kero impregnated wood is actually that much more flamable than the salt impregnated wood.

Are you taking bets on that one ?

It's all very interesting Greg ,it's just a pity the test bed are your keel timbers .I've done quite a few test on different species over the years ( and of course forgotten to write down the results !) but usually milling up samples exactly 100mm wide by 5mm thick,air dry then putting them in a jar of water for various periods,weeks to months .The results are usually similar to Bootle when radial /tangential are factored in .

[Duncan Gibbs]

Just to give you an indication of the tension in Eucalypt timbers as they come off the saw:



If you go to a proper mill they'd "cut" the bow out of the timber by re-sawing the timber, which would be cut to a larger dimension that that I've shown to begin with. Needless to say, on a green piece of timber cut to final dimension, if it's allowed to dry out it will reveal these tensions again. Soak it and they will head back to it green shape.

[Larks]

If anyone is still interested, here is a bit of an interim report on my wetting out experiment that I have sitting alongside my boat bath to see if I can get an indication when saturation and the expansion limit might be reached, as well as an interesting finding re linseed oil.

The time frame is yet a bit short, in this first set of samples only 3 weeks, from 5 May 2011 to today (27 May 11)

I have three pieces soaking in salted water, covered with plastic, a piece of Tassie mountain ash taken from my sampson post; a quite large piece of blue gum taken from the old engine bed and a smaller piece of blue gum from the engine bed as well:





Firstly, the Ash, (I don't have a control piece to compare it with in this case). I have taken four measurements on this one, three across the grain and one along the grain - which is the top line below and which has only changed by approx + 0.05%, the other three have changed by approx +6.2%, +6.5% and +6.6%.

Most importantly, the measurements show a steady growth that has not yet topped out:



Secondly, the piece of blue gum engine bed. Although I have a few more measurements on this piece, the measurement accross the thin side shows the most change, albeit only a 1.5% increase. The broader side shows only 0.4% and the length measurement shows no change. Despite the smaller numbers, the growth is still steady and not yet topped out:

In this graph, I do actually have measurements from a dry control piece, represented in the bottom line:

[Larks]

Finally, I added a third piece to the test bed to include the comparison between soaking in salt water and soaking in a 50/50 linseed oil kerosene mix, as suggested by Hanley:



Again I measured both across the grain and along the grain and included a third dry control piece.





Interestingly, this also being the same hardwood as the larger engine bed frame, in the salt water soak over only two weeks it hs shown a 2.4% increase accross the grain, with only a 0.4% increase along the grain.

More surprising though, the linseed oil/kero soaked sample has shown no discernible increase in either measurement.

In the following graph, the green line is the control, also showing no increase as would be expected, the red/pink line is the linseed/kero sample and the blue line the salted water sample. The pieces are all "roughly" the same size.




The main outcome for now though is that I am not yet ready to remove the bath to have a look at what has been achieved.

[PeterSibley]

Assuming the large timber in your keel assembly is ash Greg , what percentage swelling would close the gap ?

[Larks]

Assuming the large timber in your keel assembly is ash Greg , what percentage swelling would close the gap ?

I'm pretty sure the large timber in the middle is blue gum and the top piece ash. At a very rough estimate I reckon I need something like about 8 - 9% overall, but going on how the timber is working I think I'd need to get perhaps 10-12% from the ash and perhaps 4-5% from the blue gum.

Rob, I don't really need to do any more drying tests, I saw how it dried out when it came out of the water and tracked the timeframe while I was going back and forward to Darwin so I hope to keep this moist right through until launch once I've dealt with it after this soaking so that I don't have to worry about it again.

[skaraborgcraft]

interesting reading. My oak koster can take up to 2 months to swell after 8 months ashore every year. Last year before winter onset,i sprayed the hull down inside with a cuprinol/linseed mix, and then an anti freeze spraydown before the temperture went below zero. She has remained tighter this spring than previously. It could definately take some months to swell,but as already quoted,wether she takes up fully is another thing. I find hard cooking fat/lard is a great filler for any open seams before launching,just dont let the boat stand in the sun too long after though.....
Will be watching with interest. Cheers

[RFNK]

Gyro lives!

This is great!
Rick

[skuthorp]

Check your PM's Rick

On the subject of linseed, when I owned a wooden spoked wheeled vintage car I had 2 sets of wheels, one of which more or less lived in linseed whilst the others were on the car (an old Dodge).