SG15 build

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Typhoon
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SG15 build

Post by Typhoon » Wed Aug 07, 2019 4:13 am

Hi all,

Decided to build an SG15 for a bit of exercise and to get out on the water. Liked the size and weight of the SG15- small enough to cartop, but big enough for open water and less than perfect days.
Anyway, got the plans, ordered the materials and made a start.
Here in Australia, we are blessed with some of the highest quality marine plywood in the world. Some people think marine ply is overkill, but I like it for several reasons, mainly consistency of product and the fact you save a huge amount of finishing time buying AA face plywood as you don't have any weird open grain or defects to fill.
I went with locally made Hoop pine plywood instead of the imported BS1088 Wasatree as they couldn't tell me which species of wood it was or the country of origin. Weight was also a consideration, with the Hoop pine being lighter.
I've decided to use 9mm ply for the bottom panel, seat and bulkheads, 4mm for the rest. I'm only fitting one seat and will enclose the bow and stern of the boat from the forward and rear frames at seat height as buoyancy tanks. As I am using 9mm for the bottom panel, I wil scarf those pieces together, but side panels will be butt strapped as I feel it gives a consistently stronger join in such thin ply and you don't get the glass join you need to fair on the outside of the hull like you do with a glass joint.
The 9mm makes for a pretty stiff bottom panel and I can see it adding a LOT of rigidity to the hull. Only issue is that I don't think it'll take the bend it needs to take with just the side panels pulling it into place, so I will temporarily fasten the bottom panel down to my building "table" at mid seat frame and block the bottom panel to the shape it needs to be before I try to fit the sides. With 4mm ply, I am worried about tearing through the ply trying to pull such a stiff panel together.
Anyway, not much progress to look at so far, I have all frames and panels cut out, need to do all the joints on the panels next. I'm only working on the boat a few hours a weekend and in spare time.
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Browndog
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Re: SG15 build

Post by Browndog » Wed Aug 07, 2019 7:31 am

Great start on your project. Good luck and keep the pictures coming.

Jeff
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Re: SG15 build

Post by Jeff » Wed Aug 07, 2019 7:37 am

Good start!! Welcome to the Builders Forum!! Jeff

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Re: SG15 build

Post by piperdown » Wed Aug 07, 2019 7:46 am

Welcome to the builders forum!
Sounds like you have a good plan and off to a great start :D
Eric (aka, piperdown)

"Give an Irishman lager for a month and he's a dead man. An Irishman's stomach is lined with copper, and the beer corrodes it. But whiskey polishes the copper and is the saving of him." --> Mark Twain

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jacquesmm
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Re: SG15 build

Post by jacquesmm » Wed Aug 07, 2019 11:42 am

Good plan.
There isn't much curvature in the bottom panel, it will bend.
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Typhoon
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Re: SG15 build

Post by Typhoon » Thu Aug 08, 2019 10:34 pm

Today I finished cutting the final side panel halves and scarphed up the bottom panel.
I Dexterised my work table and am currently trying to decide whether it's worth gluing up, as it's very cold here at the moment and I don't want the panels sitting there for days waiting for final cure!
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Typhoon
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Re: SG15 build

Post by Typhoon » Fri Aug 09, 2019 1:19 am

Job's on! Decided to go for the glue and put a small heater under the table.
Photo didn't capture it, but I used a laser line to line up the two bottom panels nice and straight. They've been left a little oversize so I can fair up the curves after the joint has cured.
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Typhoon
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Re: SG15 build

Post by Typhoon » Sun Aug 11, 2019 2:54 am

Well, the glue cured well enough to be handled, I kept the temperature in the garage around 15c for the initial cure phase.
I set the bottom panel up and temporarily screwed the bulkheads to the panel to make things a little easier. because I am using a 9mm bottom, the hull REALLY didn't want to start taking shape initially, so I blocked each end of the table with 2" blocks and put a heavy weight in the middle. Made it so much easier to get the initial stitches in place.
Also, because the bottom panel is so rigid, I cut it a little oversize and put a bevel on the outside of the lower panels, so those panels can just slide back and forth on the bottom panel and find their happy place. It's working out very well and at least I know the bottom panel is fair due to it's rigidity, and the sides are turning out nicely as well, as I spent a good amount of time when cutting the panels ensuring I had nice, fair curves.
I'll leave the transom off for now and make sure everything is square and plumb before I start the other two panels.
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OrangeQuest
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Re: SG15 build

Post by OrangeQuest » Sun Aug 11, 2019 5:20 am

Looking very good and clean!
"that it isn't just an ordinary sort of boat. Sometimes it's a Boat, and sometimes it's more of an Accident. It all depends." "Depends on what?" "On whether I'm on the top of it or underneath it."
A. A. Milne

Typhoon
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Re: SG15 build

Post by Typhoon » Mon Aug 12, 2019 3:40 am

Came home this afternon and levelled the boat up. Was actually already very square, I ended up moving one block underneath to raise it about 8mm, which is pretty impressive considering the nature of stitch and glue! The middle seat bulkhead (the one used as a reference for just about every measurement on this boat) was nice and plumb. I trued up the rest of the bulkheads nice and vertical as the bottom being bent had obviously pulled them slightly out of the vertical plane, but it helped a lot having the bulkheads fitted and somewhat stable on the bottom panel.
Also used the laser to mark the forward buoyancy tank on the hull skin, will make things easier later on.
Probably won't get around to bending the upper panels on during the week, but this weekend for sure.
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