GV10 Stop and Start Project

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MikeyGnz
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Re: GV10 Stop and Start Project

Post by MikeyGnz » Sat Mar 16, 2019 4:39 am

Been a bit busy but have now started again. Side and bottom panels all welded up.

Welding some reinforcement onto the transom I've managed to get a fair bit of distortion so need some more alloy. Just waiting for that now then I can finally start on the assembly.
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Last edited by MikeyGnz on Sat Jul 13, 2019 2:36 am, edited 1 time in total.



Fuzz
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Re: GV10 Stop and Start Project

Post by Fuzz » Sat Mar 16, 2019 6:16 pm

From what I have seen it is really tough to not get distortion when welding thinner material.
Glad you are able to be moving forward.

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Netpackrat
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Re: GV10 Stop and Start Project

Post by Netpackrat » Sat Mar 16, 2019 10:54 pm

Are your chine seams going to just be plain butted corner welds, or are you going to have some additional bracing there? Plain butt welds are difficult to make in thin aluminum especially without a lot of distortion. When I was making fuel tanks out of .050" 5052 for an aircraft project a few years ago, I found that corner welds with a flange on one of the pieces (making it a lapped weld) were not so bad, but without the flange it was much more difficult. But those were 90 degree joints with no curve. Also I was using tig.... With mig it should be easier to control distortion if you keep the welds short and skip around a lot.

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Re: GV10 Stop and Start Project

Post by MikeyGnz » Sun Mar 17, 2019 5:00 pm

Netpackrat wrote:
Sat Mar 16, 2019 10:54 pm
Are your chine seams going to just be plain butted corner welds, or are you going to have some additional bracing there? Plain butt welds are difficult to make in thin aluminum especially without a lot of distortion. When I was making fuel tanks out of .050" 5052 for an aircraft project a few years ago, I found that corner welds with a flange on one of the pieces (making it a lapped weld) were not so bad, but without the flange it was much more difficult. But those were 90 degree joints with no curve. Also I was using tig.... With mig it should be easier to control distortion if you keep the welds short and skip around a lot.
I'm using TIG. On the transom I was fillet welding on some reinforcing members, did not have the transom clamped to anything, welding in one direction and had the current a bit low so was having to do a multi-pass weld. The 2nd and 3rd beads caused the worst distortion. Next time I will backstep with a higher current and temporary reinforcing clamped to multiple places and should not have the same issues.

With the sides and bottom the distortion is perpendicular to the welds causing the end of the panel to lift slightly as seen in the photo. This is where the design calls for a curve in the panels and I should be able to bend it back out when I assemble the hull, especially once the bead is polished off the outside. On the transom the distortion was parallel to the weld causing a twist in the panel. I will grind off the welds, beat the panel back flat and use it for some non-structural work but I'm not happy reusine it as a transom.

For the chine/keel I will be screwing 4 by 2 parallel to the panels from the middle seat to the transom to brace the panel during welding. With enough screws and careful welding I'm hoping to get away with standard corner welds. As the panels are already cut adding a flange at this stage isn't possible. I'm making this as a small project in alloy welding practice/learning before I decide on building a big aluminium kitset boat so I am expecting to run into problems.

I'm using 2.5mm/100 thou thick alloy so not quite as difficult as your fuel tanks.

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Re: GV10 Stop and Start Project

Post by Netpackrat » Sun Mar 17, 2019 11:13 pm

Thanks for the informative reply. Are you using air or water cooled torch?

MikeyGnz
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Re: GV10 Stop and Start Project

Post by MikeyGnz » Mon Mar 18, 2019 3:42 pm

Gas/air cooled size 26 torch. I would love a water cooled but don't really do enough welding at high enough amps to make it worth the cost.

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Re: GV10 Stop and Start Project

Post by OneWayTraffic » Mon Mar 25, 2019 2:00 pm

I'm not sure if anyone else has posted this yet, but I am sure that you will need to add a lot of stiffeners/frames in there. Aluminium isn't nearly as stiff as glass/ply/glass at equal weight. According to my Maths 4mm aluminium should be not quite as stiff as 6mm ply glassed both sides with 400g. Stiffness is a cubic relationship to thickness, but also a inverse cubic relationship to span. I'd put reinforcements in the middle of all panels, or two to be safe.

Gerr has scantlings for light aluminium construction in "The elements of boat strength".

I'll look some up as I have his book if you like.

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Re: GV10 Stop and Start Project

Post by MikeyGnz » Sun Mar 31, 2019 3:54 pm

OneWayTraffic wrote:
Mon Mar 25, 2019 2:00 pm
I'm not sure if anyone else has posted this yet, but I am sure that you will need to add a lot of stiffeners/frames in there. Aluminium isn't nearly as stiff as glass/ply/glass at equal weight. According to my Maths 4mm aluminium should be not quite as stiff as 6mm ply glassed both sides with 400g. Stiffness is a cubic relationship to thickness, but also a inverse cubic relationship to span. I'd put reinforcements in the middle of all panels, or two to be safe.

Gerr has scantlings for light aluminium construction in "The elements of boat strength".

I'll look some up as I have his book if you like.
I'm definitely planning for reinforcement, just waiting to get the hull in shape to measure and decide exactly how to do it. I'd like to cut some 2" or 3" pipe in half lengthwise and use it in the flat sections. There should be enough off-cuts from the original sheets to cut some curved longitudinal stringers for the not so straight sections at front.

The other option is to use angle or box on the exterior so I have strakes as well as reinforcement.

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Re: GV10 Stop and Start Project

Post by MikeyGnz » Sun Mar 31, 2019 3:59 pm

Got some more done in the weekend. No new photos just tidying up welds on frames. Now that they are completely welded I will drill out all the rivets holding the frames together and fill the holes, then on to assembly.

I'm off on holiday so will be pushing pause here so I am not taking up the whole garage while I am away. As is I can stack everything against the wall and fit cars inside but once I start assembling there is room for one less car. Starting again in about 9 weeks.

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Re: GV10 Stop and Start Project

Post by Netpackrat » Fri May 24, 2019 2:12 pm

MikeyGnz wrote:
Mon Mar 18, 2019 3:42 pm
Gas/air cooled size 26 torch. I would love a water cooled but don't really do enough welding at high enough amps to make it worth the cost.
Was going through this thread again for ideas, and thought I would mention I have been told if you have a faucet and drain in your shop, you can get a fitting to hook a water cooled torch up to your faucet, and then run the outflow right back into your drain, and thus avoid the cost of a radiator and coolant setup.

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