Modified GV10 - Aluminum

[redneckdan]

Hi all yall!

I'm building a modified version of the GV10 Fast Garvey. I am using 6061T6 for the frames and hull sheets. Welding is being done with an Everlast 255EXT with 5356 filler. The hull shape will be modified to use a set of zodiac style tubes for floatation and stability. Tube attachment will be done a bit differently, to allow for rapid replacement/repairs. The hull will be built much heavier than most, realistically any, GV10.The boat will be used for surf/swiftwater rescue. Power will likely be in the 40-60HP realm with potential to convert to an inboard jet at some point.

I cut, fixtured and welded Frame 1 last night.

[Jeff]

Welcome to our Builder's forum!! I look forward to your aluminum build!!! Jeff

[redneckdan]

One more butt weld test before I splice the panels this weekend, testing filler metal and root gap limits. 6061 is very prone to cracking during cooling due to the Mg content. A 6061 weld needs to have a fair bit of filler metal to move is down (4043) or up (5356) from the 1% Mg content that is the sweet spot for cracking. I fiddled with filler metal content of the bead to find the limits. Butt joints are the most susceptible. Fillets tend to have enough filler in the profile to significantly move away from the 1% Mg realm. There are other techniques as well to help prevent cracking and end of weld craters.

[redneckdan]

Fitting the pieces for the transom frame. Outer and inner skin is 1/4" 6061-T6. 1/8 would have been a little light, 3/16" would have been perfect but not available at the time. Doing the 1/4 plate to 1/8sq tube filets is working my new 255EXT pretty good. It keeps chugging right along.

Looks like I might have the frame elements done this weekend and will be ready to install the inner face plate of the transom this week. After that it will be time to start setting up the frames and installing the skin.

The big hole with the ground clamp is one of the thru holes for the 4" scuppers.

[OneWayTraffic]

How will you be sealing the scuppers? Tubes, rib style?

[redneckdan]

4" 1/8 wall tube with fit through the transom and be welded in place. Then a hyplon sleeve about 12" long is clamped on the end. Normal operation the sleeve is held up, crimping the hose and sealing the scupper. When things start getting a bit spicy the sleeve is released, straightens out and the water is allowed to flow out.

[redneckdan]

I've been picking away at the project as time allows. I got the panels tacked together last night. Next I will tack the transom to the hull then flip the assembly into a cradle for installation of the frames and internal braces.

[redneckdan]

It's off the strong back. Appears to have turned out pretty square. Need to weld the frames in and add more bracing.

Transom is heavy, really heavy. 1/4 outside and 1/8 inside would have been plenty for my needs.

[Fuzz]

I must be missing it but what is the hull thickness? I am asking because I do not see any distortion from welding. I know just enough to know distortion can be a major problem with thinner metals.

[OneWayTraffic]

Most NZ Al boats are welded. Just about the only pressed boats we have left are imports from Aussie. Nobody in country makes riveted boats these days. Typical is 2.5mm for sides, 3mm bottoms even in the smallest boats. About 1/10th" to 1/8th". Typical trailer boats go up to 1/4" max.

I don't think it's possible to weld any less, and I've never seen weld distortion in a boat made by a reputable company here.