Moisture content for Canoe Stems - Cellery Top Pine.

[Plane sailing]

Hello,

I'm in the process of starting a cedar strip 18' Prospector, will be using Western Red for the strips and Cellery Top for the stems, seats, inwhales etc.

Having purchased some many years old outdoor seasoned planks of Cellery I'm told the moisture content measured at 14%, is this too damp for laminating the stems? I understand for furniture I should be aiming for around 10 - 12 %, I wonder if slightly higher would be an advantage for bending?

Any advice would be appreciated?

Roy.

[splinterz25]

Hello,

I'm in the process of starting a cedar strip 18' Prospector, will be using Western Red for the strips and Cellery Top for the stems, seats, inwhales etc.

Having purchased some many years old outdoor seasoned planks of Cellery I'm told the moisture content measured at 14%, is this too damp for laminating the stems? I understand for furniture I should be aiming for around 10 - 12 %, I wonder if slightly higher would be an advantage for bending?

Any advice would be appreciated?

Roy.I don't think you'll have ant troubles When I built My boat I used pine and Titebond III; But if you concerned use epoxy resin or Cascophen this is the glue in Marine grade ply.
How ever this is not easy to find here in the States I'm not sure you can get it down under, this is where I buy it.
http://www.aircraftspruce.com/catalog/wppages/cascophen.php?clickkey=3807

Your stem will still be exposed to air for a good bit as you glue up your strips to help it dry some more and finish the out side of the canoe; Make sure to get REAL BRASS -BRONZE nails to hold your strips to the stem.

I saw your post on my build thread; Good luck w/ yours I'll be looking in I hope you show your build progress.

Bruce

[PAR]

If using epoxy, this is on the high side, but on a technical level, anything below 15% will do, it's just there's no margin of error and this is why the formulators recommend 12%. This is also because they know some small amount of moisture gain is possible, even with the epoxy coating, so they leave a error margin, below where rot and other issues usually begin (about 17%). Simply put, if the moisture content is 12% and you do gain a few percent, with an immersed piece, you'll still be safe, but if you start with 14% - 15%, a couple more percent will push the piece into the danger zone.

Bending is best down with heat and moisture content. It's the heat that does the work, but a higher moisture content will help prevent some breakage. You're going to have some breakage, even with the best stock. On strips I just use a heat gun, screw the steam box. If the stock is especially dry, I'll soak it, but it's the heat that does the work.

Don't use brass fasteners or hardware, unless it's decorative and not going to get wet much. Bronze and stainless are the usual preferred choices.

Cascophen is just resorcinol (phenol formaldehyde) and though there are several formulations, the plywood industry mostly uses heat activated melamine adhesives, though some phenols are still used, these too are typically cured with temperatures, while Cascophen is commonly room temperature cured.

[Plane sailing]

If using epoxy, this is on the high side, but on a technical level, anything below 15% will do, it's just there's no margin of error and this is why the formulators recommend 12%. This is also because they know some small amount of moisture gain is possible, even with the epoxy coating, so they leave a error margin, below where rot and other issues usually begin (about 17%). Simply put, if the moisture content is 12% and you do gain a few percent, with an immersed piece, you'll still be safe, but if you start with 14% - 15%, a couple more percent will push the piece into the danger zone.

Bending is best down with heat and moisture content. It's the heat that does the work, but a higher moisture content will help prevent some breakage. You're going to have some breakage, even with the best stock. On strips I just use a heat gun, screw the steam box. If the stock is especially dry, I'll soak it, but it's the heat that does the work.

Don't use brass fasteners or hardware, unless it's decorative and not going to get wet much. Bronze and stainless are the usual preferred choices.

Cascophen is just resorcinol (phenol formaldehyde) and though there are several formulations, the plywood industry mostly uses heat activated melamine adhesives, though some phenols are still used, these too are typically cured with temperatures, while Cascophen is commonly room temperature cured.


Thanks for the wonderful advice, I'm using Titebond III for the stems.
I decided they are wholly encased in glass towards the end of the project so there is a bit
more time for the moisture to make its escape.
Bending went surprisingly well, I did experiment with different thickness strips until I
was happy with the ease of bending without looking too spindly. Just a bit of patience is all it
took (and another pair of hands to put the clamps on). It's all dry clamped
for a little time, just to make glue up a little easier.

My main issue at present is air temperature, or lack thereof, Titebond suggests a minimum temp of 45f or 8C.
Being in Tasmania it's just a bit too cold ambient in the workshop for me to be comfortable. I'm uncertain if the
lower end of the scale for the Titebond is just a guide and all I need to do
is clamp for a few days longer or is there something a little more sinister with
the activation/cure at lower temps. It talks about something called "Chalking point" associated with the lower
temp. A bit more reading is needed.

Ok here we go, straight from Titebond tech info:

Chalk Temperature

When glue dries, the loss of water pulls the adhesive particles together with

enough force to form a continuous film. If the drying temperature is below a
critical point, water evaporation is not sufficient to pull the particles together,
leaving them in the joint. The dried film in the joint will appear whiter than
normal. This is known as "chalking" and the critical temperature is the "chalk

temperature." When chalking occurs, the glued joint loses strength and could

result in a failed bond.



I wasn't planning on using a brass protection strip on the bow/stern - my thoughts are so much time
is spent encasing the stems, why would you go drilling a hole into it and compromise this.
At this stage my plan is to epoxy the seats to a block on the hull rather than bolt/hang from the inwhales.

Cheers for the awesome response.
Roy.

[anewhouse]

My main issue at present is air temperature, or lack thereof, Titebond suggests a minimum temp of 45f or 8C.
Being in Tasmania it's just a bit too cold ambient in the workshop for me to be comfortable. I'm uncertain if the
lower end of the scale for the Titebond is just a guide and all I need to do
is clamp for a few days longer or is there something a little more sinister with
the activation/cure at lower temps. It talks about something called "Chalking point" associated with the lower temp.

Cheers for the awesome response.
Roy.
I had an issue with chalking when I was building a strip built kayak and the temperature was about 4 degrees C.
I tried warming the glue joint with the heat gun. It took just a couple of seconds for the chalkiness to disappear and even though temperature remained well below 8 degrees, the glue then seemed to continue to set.
It didn't seem to affect the strength, but as it was only a strip kayak, the glue joint didn't need to be particularly strong.
It seemed as if just a couple of seconds of warming was enough to get rid of the chalky appearance and kick start the reaction.

[Plane sailing]

Once again, thanks for the advice, the more I read the more I have decided it's just going to be sensible to run the fan heater in the workshop for 24hrs or so to keep the ambient temp well above 8C and be happy that I get a sound cure. Its probably warmer than that anyway. Heating may have worked for the strips, for a large volume like the stems I'm just not prepared to risk it.

Cheers,

Roy.

[PAR]

I'm fortunate in that it's very rare for me to need a heater, just to get a cure, but in our winter, it happens occasionally enough that I bought a few of the hot oil filled heaters. Toss them under a tarp with the work and let them warm everything up. PVA's don't need to be at 45 degrees for the whole cure, just the first portion, until it's no longer tacky (an hour or so). It'll still need to have sufficient temperature to fully cure, but 80% of it is done in the first hour or two. This is usually enough to let the full cure wait until it warms up a bit the following day (roll her out into the sun and put a dark tarp over it).

[Plane sailing]

I'm fortunate in that it's very rare for me to need a heater, just to get a cure, but in our winter, it happens occasionally enough that I bought a few of the hot oil filled heaters. Toss them under a tarp with the work and let them warm everything up. PVA's don't need to be at 45 degrees for the whole cure, just the first portion, until it's no longer tacky (an hour or so). It'll still need to have sufficient temperature to fully cure, but 80% of it is done in the first hour or two. This is usually enough to let the full cure wait until it warms up a bit the following day (roll her out into the sun and put a dark tarp over it).
Cheers,
ill run the fan heater in the workshop and might take the laminates into my house to warm up the bulk of the timber and of course warming the glue prior to gluing. Once the workshop is warm I should be fine with the cure.

roy