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Old 31-08-2017, 06:14   #1
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All Aluminum Dinghy

This subject has come up a few times, and while I can see that an all aluminum dink wouldn't be for everyone, it seems a good choice for some. I can't for the life of me figure out how you could wrap up $6-7k in a boat that size, but I've been wrong before. I would like to build one, just for grins and to feel like I'm moving us toward our long term goals. I would like to start with something 10' or so. I know I need to keep the weight down, and the alloys to use.......What I need to hear are your opinions on function. How wide? How much displacement in the tubes? Wire it for running lights? How tall from the bottom of the hull to gunwale, or gunnel, as it's known here in hillbilly country? Deadrise? Dry storage? Etc.....
I suppose I could figure out how to roll my own pontoon logs, but I'll probably just use the brake and make square or rectangular tubes. I suppose that for safety's sake, I'll bulkhead the tubes? I was thinking that a dry storage hatch or anchor locker integrated into the forward tubes would be useful? A front deck/seat with storage would be useful, but adds weight. Lets hear your design ideas, and for the sake of argument, a maximum weight.
Thanks!
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Old 31-08-2017, 06:27   #2
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Re: All Aluminum Dinghy

Here’s a (12 Ft) Skiff Kit boathttps://metalboatkits.com/product/12-foot-skiff/
LOA : 12
Beam: 5 5″
Depth : 20″
17″ (at engine notch)
Vessel Weight: = 256 lbs.
Power: 9.9 – 20 HP

See also:
https://metalboatkits.com/guide-marine-grade-aluminum/
https://metalboatkits.com/case-large...g-metal-boats/
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Old 31-08-2017, 06:37   #3
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Re: All Aluminum Dinghy

Thanks Gord. I've built some skiffs, and Jon boats, but I was thinking that something "unsinkable" would be more appropriate. Are my thoughts flawed? I've never gone the "kit" route. I like the process of shaping a boat as I go......Too many years of self employment I suppose, but I like to be in control of the final product. lol
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Old 31-08-2017, 07:01   #4
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Re: All Aluminum Dinghy

I would Keep it as simple as a brick., by shape
Buoyancy by means of closed cell foam inside
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Old 31-08-2017, 07:07   #5
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Re: All Aluminum Dinghy

Aluminium dinghies 3 metres and up are very common in Australia. Actually aluminium is definitely the most popular material for building smaller boats here. They are not expensive here. $2.5K should get you a 3.1m one.

Here is a link to a 2.5m alu dinghy.

250 Explorer

I wouldn't have one as a dinghy. They are too subject to electrolysis and when they do spring a leak, expensive to repair. Fibreglass is tougher and far easier to repair, but heavier I think.
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Old 31-08-2017, 07:09   #6
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Re: All Aluminum Dinghy

If you look on the net, you'll find a blog post about building a Chameleon nesting dinghy in aluminium (instead of ply). The Chameleon has buoyancy chambers and is unsinkable.

Also, check out Brent Swain's "origami" dinghy in aluminium. It looks like it would be easy to build and I'm use you can add buoyancy under seats etc.
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Old 31-08-2017, 09:02   #7
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Re: All Aluminum Dinghy

3.4 meter Aluminium Pontoon Dinghy - Frews Marine

I guess this is what I had stuck in my head. I'm not a fan of foam. Even the "closed cell" eventually becomes waterlogged and heavy, in my experience.
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Old 31-08-2017, 09:13   #8
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Re: All Aluminum Dinghy

Great Lakes Skipper sells prefab aluminum pontoons on 20 feet and under lengths.
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Old 07-09-2017, 15:47   #9
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Re: All Aluminum Dinghy

The aluminum will be here tomorrow for a prototype. If my math is on, I should be 8" wider than a 12' Highfield, and about 55 lbs heavier. I'm going with .100 on the hull, and .090 on the "pontoons". I'll probably go with .125 on the transom. This one will be all 5052, since it'll probably never see salt water. Any thoughts on length of rake and angle of deadrise?
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Old 17-09-2017, 08:40   #10
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Re: All Aluminum Dinghy

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Made a trip to the neighbors house to brake boat parts yesterday.
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Old 17-09-2017, 08:56   #11
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Re: All Aluminum Dinghy

I see 10-14 foot aluminum Jon boats selling at outdoor stores like Cabellas and Bass Pro Shops for under $1000. I don't know how others get away with selling pretty much the same thing for $2500.

They have built-in positive flotation. They are required to by law.

http://sanjose.trackerboatcenter.com...ss=Jon%20Boats
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Old 17-09-2017, 09:03   #12
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Re: All Aluminum Dinghy

Awesome! I love the idea for a larger boat.

Please keep us updated with plenty of photos.

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Old 17-09-2017, 09:06   #13
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Re: All Aluminum Dinghy

Quote:
Originally Posted by David M View Post
I see 10-14 foot aluminum Jon boats selling at outdoor stores like Cabellas and Bass Pro Shops for under $1000. I don't know how others get away with selling pretty much the same thing for $2500.

They have built-in positive flotation. They are required to by law.

Boat Inventory - San Jose, CA Bass Pro Shops Tracker Boat Center SAN JOSE

Likely, it's because they aren't "pretty much the same thing". The spectrum of Jon boats available is quite broad. How thick? Welded or riveted? Built in dry storage? Plywood transom or all welded aluminum? Etc, etc..... You can find yourself comparing apples to ribeyes in short order.
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Old 17-09-2017, 09:24   #14
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Re: All Aluminum Dinghy

How big is the mother ship going to be? A couple of the examples were 250# which doesn't include motor or gear. Even at 250#, that's a lot for most sub 40' boats (and even a lot of larger one)

I built a 10' tunnel hull stitch & glue. It was good in use but it's been in a pole barn for 10yrs as it was too heavy to conveniently hang on the davits. It would be easy to do something similar with aluminum.

https://valhalla433.files.wordpress..../photo0046.jpg
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Old 17-09-2017, 10:07   #15
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Re: All Aluminum Dinghy

Quote:
Originally Posted by valhalla360 View Post
How big is the mother ship going to be? A couple of the examples were 250# which doesn't include motor or gear. Even at 250#, that's a lot for most sub 40' boats (and even a lot of larger one)

I built a 10' tunnel hull stitch & glue. It was good in use but it's been in a pole barn for 10yrs as it was too heavy to conveniently hang on the davits. It would be easy to do something similar with aluminum.

https://valhalla433.files.wordpress..../photo0046.jpg
Right now, we have a 73' houseboat, and that's where we'll use this one. We might trailer it to FL on occasion to fish the backwaters of the ICW, but not likely. I agree that it will be too big and heavy to consider for the sub 40' boats. My line of thinking on this one is just to prove that the design is worthwhile, and to see where I could shave weight from the next one. This one will be fairly large......too large probably. I think I've made the bottom a little too wide, but it won't hurt a thing for what we will use it for.
Now, about this tunnel hull..... I had considered a tunnel on this little boat, but am not sure how well that'll function on a smaller boat? What say you? Is it worth the sacrifice of buoyancy to run 4" shallower? How much does the one you built weigh?

The bottom piece that we've bent up is 10' long, but that can be trimmed down if need be. By the time it's said and done, we could end up with a LOA of 12' or so. I'd like to hear some opinions on length. The bottom is roughly 40" wide, and the toons will add 13" to either side, assuming I use them in a vertical orientation. They measure 18" the other way. Also, how far would you think the pontoons should run past the transom? On bigger boats, we've gone up to 18", but I'm guessing that's too much for this little guy? I do plan on leaving about 2" of "trim tab" running out the bottom of each toon.
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