Dimensional timber for Stringers?

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OneWayTraffic
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Dimensional timber for Stringers?

Post by OneWayTraffic » Wed Jan 15, 2020 4:19 pm

In another thread I detailed my issues with laminating the plywood for my stringers. I do not trust the bond enough to put them in my boat. Another sheet of 9mm Meranti marine plywood will cost me about $80. I do already have however some Radiata pine dimensional timber, clear, dry, knot free and untreated. They are 18mm by 135mm and 4700mm long.

I was going to use these for cleats and other bits and pieces, but is there any reason why they would not work as stringers? I would only need to do minor triming to get them to fit.



Aripeka Angler
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Re: Dimensional timber for Stringers?

Post by Aripeka Angler » Wed Jan 15, 2020 5:23 pm

OneWayTraffic wrote:
Wed Jan 15, 2020 4:19 pm
In another thread I detailed my issues with laminating the plywood for my stringers. I do not trust the bond enough to put them in my boat. Another sheet of 9mm Meranti marine plywood will cost me about $80. I do already have however some Radiata pine dimensional timber, clear, dry, knot free and untreated. They are 18mm by 135mm and 4700mm long.

I was going to use these for cleats and other bits and pieces, but is there any reason why they would not work as stringers? I would only need to do minor triming to get them to fit.
If you mix the epoxy correctly and thicken up the mixture with wood flour, you can’t blow apart the cured stringer bond with a grenade.
I like to mix the “glue” to a consistency of ranch salad dressing when I’m laminating stringers or a transom together.
A strait mix of epoxy/hardener without filler doesn’t work correctly.
At some point, you will need to laminate multiple layers of plywood together and trust the bond. :D I would try again, IMHO.
I’m also not a big fan of 4/1 or 5/1 epoxy. Too easy to make mixing mistakes.
For a D-5, the wood you describe will work fine. Assuming no joints...
Richard
Completed boats...XF20 "Red Alert", Aripeka Angler's Strip Canoe, FS18 “Bare Bones”, GF12
Currently building...PY12 Kayak
If there is magic on this planet, it is contained in water. - Loren Eiseley
Bare Bones build thread...
viewtopic.php?f=12&t=62146

joe2700
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Re: Dimensional timber for Stringers?

Post by joe2700 » Wed Jan 15, 2020 5:23 pm

I would guess a softwood is not a 1-1 replacement for tropical hardwood from the strength perspective, but Jaques will have the final answer on that. Since you will need cleats and all later anyway I'd probably just spend the money on plywood, but I know some people have trouble getting it locally.

OneWayTraffic
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Re: Dimensional timber for Stringers?

Post by OneWayTraffic » Wed Jan 15, 2020 5:49 pm

Aripeka Angler wrote:
Wed Jan 15, 2020 5:23 pm
OneWayTraffic wrote:
Wed Jan 15, 2020 4:19 pm
In another thread I detailed my issues with laminating the plywood for my stringers. I do not trust the bond enough to put them in my boat. Another sheet of 9mm Meranti marine plywood will cost me about $80. I do already have however some Radiata pine dimensional timber, clear, dry, knot free and untreated. They are 18mm by 135mm and 4700mm long.

I was going to use these for cleats and other bits and pieces, but is there any reason why they would not work as stringers? I would only need to do minor triming to get them to fit.
If you mix the epoxy correctly and thicken up the mixture with wood flour, you can’t blow apart the cured stringer bond with a grenade.
I like to mix the “glue” to a consistency of ranch salad dressing when I’m laminating stringers or a transom together.
A strait mix of epoxy/hardener without filler doesn’t work correctly.
At some point, you will need to laminate multiple layers of plywood together and trust the bond. :D I would try again, IMHO.
I’m also not a big fan of 4/1 or 5/1 epoxy. Too easy to make mixing mistakes.
For a D-5, the wood you describe will work fine. Assuming no joints...
Boats a C17. Sadly there is no supply of 2:1 or 3:1 epoxy in NZ from a known brand. I am going with WEST produced under licence here in NZ. The alternatives are 4:1 "marine epoxies' that supply no real engineering data, while WEST gives all sorts of useful information. I would use Marinepoxy if it were available as I know it works. At least the WEST is cheaper here than there. About $60 USD a gallon equivalent.

First mistake in mixing, hopefully the last.

Aripeka Angler
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Re: Dimensional timber for Stringers?

Post by Aripeka Angler » Wed Jan 15, 2020 6:29 pm

Gotcha, a C17. 8) Wonderful boat, All the more reason to go with the laminated stringers.
I hear on not being able to get 2/1. Use due diligence and you’ll be fine.
Richard
Completed boats...XF20 "Red Alert", Aripeka Angler's Strip Canoe, FS18 “Bare Bones”, GF12
Currently building...PY12 Kayak
If there is magic on this planet, it is contained in water. - Loren Eiseley
Bare Bones build thread...
viewtopic.php?f=12&t=62146

fallguy1000
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Re: Dimensional timber for Stringers?

Post by fallguy1000 » Wed Jan 15, 2020 7:22 pm

You can use the radiata. It doesn't have equivalent strength to ply, so Mertens might modify the glass schedule; not sure.

I would use a minimum of 3 tapes of 1708 staggered; not sure what he specs. And this is not to cite or challenge a spec, but what I would do with radiata.
My boat build is here -------->

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OneWayTraffic
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Re: Dimensional timber for Stringers?

Post by OneWayTraffic » Wed Jan 15, 2020 7:47 pm

Well I made a decision. With a bit of pondering the answer was right in front of me.

I have already got three layers for the transom and clamping board cut. Two 12mm and one of 9mm. I had marked out a fourth but not cut it yet. That would make my transom thicker than spec. Instead I will use that 9mm for stringers and use left over 6mm for the last layer of the transom. 6+9+12+12=39mm. Or 1.5”. Perfect. And I don’t need to buy more ply yet.

joe2700
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Re: Dimensional timber for Stringers?

Post by joe2700 » Thu Jan 16, 2020 10:16 am

There are some higher performance epoxies than west 105 these days, that are a little easier to work with. That said it has been used successfully for many years on tens of thousands of boats. It's a genuinely great product, that has just been passed by even better ones. Like all epoxy, mixing it correctly is imperative but I really don't think it's much harder than any other epoxy. Use the metered pumps or a scale, probably a scale for small batches and you will be good to go. Don't rush it and make a mistake.

With west you want to use the fillers for different jobs, so for glueing the panels together make sure you are adding 404 or 406 adhesive fillers(or the same stuff from another brand) after mixing the epoxy. You could also see if you can get six10 which is the west system pre thickened adhesive epoxy, instead of mixing your own. A little easier but a little more expensive. Like you said west has great guidance on how to do each type of operation with the 105 system on their website. Glassing, gluing, fairing. They will tell you what to mix and how.

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