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Thread: To bolt or not to bolt
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13th June 2013, 10:09 AM #1New Member
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To bolt or not to bolt
Hi Guys
I am just about to start construction on a Ross Lillistone Phoenix III, in fact I have already cut out all the bulkheads and a few of the smaller timber items. In the next week
or two I plan to build a strong back and set up the molds. I think Ross has recommended in the instructions somewhere that the strong back should be bolted
to the floor. I have fairly limited workshop space and a strong back on wheels would make it a lot easier for me to use my bandsaw etc, not to mention the fact I relaid the shed floor
recently (the old floor was 200mm out of level!) and don't feel like drilling holes in it just yet. Not having built glued lapstrake before my question is this - is there enough strain put
on the strong back when hanging planks etc that would cause the strong back to move around and become annoying? I have faith in my ability to build a sturdy strong back that won't rack
or move within itself(I'm a builder) but wasn't sure on other forces.
Cheers
Matt
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13th June 2013, 11:21 AM #2Senior Member
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Will be watching with interest but can't help with your query. I plan on building a Phoenix when I finish the renovations, the new house and the car restoration.
Rickey
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13th June 2013, 03:08 PM #3
You can try the wheels thing, but the first plank you "hang" (read force) will easily move the wheels (even if locked) and the whole assembly (strong back, boat, etc.) I too like rolling strong backs, but for planking operations, you'll need to stoutly fasten it down. The term strong back should give you an idea of what it must endure.
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13th June 2013, 09:12 PM #4New Member
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Thanks guys, looks like I will be taking the Hilti to the new floor and epoxying in a few nuts. Rickey, it
sounds like we should be finishing our boats at about the same time!
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20th June 2013, 05:07 PM #5Intermediate Member
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A frame bolted/glued etc securely fixed is nice and the preferred method, but that said you can stiffen a strong back significantly by increasing the depth of sections. Consider a strong back with 4" by 2" compared to a 10" by 2" beam. Deflection is proportional to the section inertia and to find the inertia we use the depth cubed times a few other things. So 4" cubed is 64 while 10" cubed is 1000 so you get 15.6 times less deflection for the same load. While your strongback will be heavier using some 10" by 2" old hardwood rafters or something you can get a very stiff frame without bolting. I am part way through my 26' carvel planked and used two 8" by 2" rails old Oregon verandah bearers on my strong back and I got about 3/16th inch flex when the keel etc was clamped down allowed for by adjusting the moulds. On your phoenix if you used 10" by 2" I reckon the flex would be insignificant and after all how accurate is your boat going to be. Its not a piece of furniture, its a boat.
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23rd June 2013, 09:42 AM #6New Member
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Thanks for the advice Wizened, I have a length of 300 x 45 lvl left over from a job that I intend to rip into two for the strong back along with various other offcuts/left over lengths of treated pine etc. I'm hoping that it may be heavy enough to get away with not bolting it to the floor.
The plan with this build is to use pretty much only timber that I have on hand. I occasionally find a nice bit of tight grained old growth oregon mixed in with the plantation grown stuff when I'm demolishing decks and pergolas that I can't bear to put in the skip. Recently I pulled down a pergola that was predominantly built of Alaskan yellow cedar which was stunning after a run through the thicknesser.
Matt
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