1980 Grumman 4.6 Sportsman all aluminum build

[Flatbotm]

Yesterday I bought a 1980 Grumman 4.6 sportsman. I regret selling my 1542 I built so I decided to build another boat. I picked up the boat, trailer, and 35hp Johnson for $650. I built my 1542 pretty heavy so I have new goals in mind for the Grumman. Light weight and all aluminum. I chose this Grumman for its size. It's a 1554 and 71 at the beam. I love my little 12' crestliner but I miss being able to walk around. Here are the pics of what I'm starting with. I started stripping the boat as soon as I got it home last night.

 

[thudpucker]

I LIKE that Bow arrangement. I wonder if I could convert my little 14' Jon to that?
Nice looking and functional too.

i never thought I'd like Yellow, but it looks good on your boat.:lol:

 

[Flatbotm]

I probably won't keep the boat yellow. It doesn't look bad. I'm going to return the boat to a layout more like the original. The flooring that was put in by the previous owner was 1/2 plywood. It is already rotting and has a lot of flex. I'm tearing it all out and putting in the alluminum floor.

This is how the sportsman originally came.

 

[Flatbotm]

Does anyone have a suggestion of what thickness aluminum to use for flooring? 1/8th?

 

[Ranchero50]

Flatbotm » 23 minutes ago[/url]"]Does anyone have a suggestion of what thickness aluminum to use for flooring? 1/8th?

.062 or .080" if you plan on supporting it every foot or so. .100" get's heavy quickly. My front deck is .062 with a pair of 13" x 21" spaces with no support and I don't notice it flexing. What is supported is 1/8" x 1" angle or some 1" x 3" C channel extrusions with a couple risers. Most folks really underrate aluminum's strength and go way oversize.

 

[Zum]

Most factory floors on aluminum boats,are no where near 1/8".
Like Ranchero50 mentioned,depending on your spacing,you can go smaller.

Nice find BTW,does the outboard run fine?

 

[Flatbotm]

The 35 Johnson purrs like a kitten. Thanks for the info on the aluminum thickness.

 

[Flatbotm]

Last night I got the floors all tore out.

 

[thudpucker]

Now it looks pretty good, and a good place for a Shop Vac too. :LOL2:

That Yellow is a good color for that boat too.
I envy you the energy to take on that much of a project. If we lived closer, I'd come over and watch you work! :mrgreen:

 

[shaggs]

I'm using 3mm or 1/8th checker plate on my floor and casting decks but thats because I'm over 220lb
The aluminum is actually lighter than the timber I pulled out

 

[Flatbotm]

I decided to go with 1/8th as well. I had a half sheet already and my dad fishes with me some and he is 265. I didn't want the floor flexing on him. I picked up the sheet yesterday.

 

[Flatbotm]

I did the calculations and I should still be able to save 50ish pounds

 

[Flatbotm]

Looks like I have more work cut out for me. While inspecting the stringers I found a dozen cracks. It's amazing that the outer skin didn't crack! I started prepping last night and got my spoolgun hooked up.

 

[Flatbotm]

I ordered the rest of my materials today. 64 ft of 1" .125 6061 and 4 yards of nautolex storm grey vinyl.

 

[magoo]

Those stringer cracks are worse than i thought. Good thing you tore her down.

 

[hercdrvrwo]

Obvious aside -- what are some long term effects of not welding those cracks back up? Had a similar issue with mine -- I have 4 cracks on 2 different stringers from the bunks on the trailer. The boat hadn't leaked before and seemed structurally sound, so I bondo'd them and epoxied right over em!

Thanks!
Herc

 

[magoo]

Honestly what you did to fix your stringers was more of a "bandaid". Nothing wrong with that but it does depend how you treat your boat. I for one show no mercy and if there is something cracked it needs welded. Longterm will be it needs fixed for good. But ya ain't gonna sink. I bet my 1983 15' smokercraft was worse than his boat and she didnt leak or sink.
That poor boat took a beating.

 

[Flatbotm]

Herc Magoo nailed it. It definitely would depend on how you use your boat? Bondo is for cosmetic repairs only. At a minimum I would rivet some aluminum stock across the cracks and spread out the load across the stringer. I suspect much of the damage to my boat was caused from power loading on the trailer. I wouldn't want to have to worry about the boat every time I cross a wake.

 

[Flatbotm]

I just worked on getting all the cracks welded u this weekend. The spoolguns not pretty but gets the job done.

p

 

[hercdrvrwo]

Thanks for the info -- I didn't mean to hijack your thread either man! So are you a welder or did you just go pick that up? Wondering if its something I can get for my very miner repairs so I don't have to keep taking my boat to the welder everytime I need something small done or working up some weird fabrication because I cannot afford the welder but need to keep moving ahead on the project.