Aluminum Barrelback

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

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whsoxfan
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Aluminum Barrelback

Postby whsoxfan » Tue Nov 14, 2017 1:30 pm

Hello Fellas

anyone ever attempt building a metal barrelback with rivets?

Any pics?

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steveh41
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Re: Aluminum Barrelback

Postby steveh41 » Tue Nov 14, 2017 4:02 pm

Here's a vintage aluminum runabout... sort of the same idea. Adapting the Barrelback plans to aluminum would be a project in itself but would make up into a really unique build.

aluminum runabout.jpg

Steve
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JimmY
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Re: Aluminum Barrelback

Postby JimmY » Tue Nov 14, 2017 8:00 pm

They clean up pretty well too...

20170916_133802.jpg
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Roberta
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Re: Aluminum Barrelback

Postby Roberta » Wed Nov 15, 2017 6:35 am

Might be kinda cool!! Maybe anodize the AL in different colors for an interesting effect.

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Kevin Morin
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Re: Aluminum Barrelback

Postby Kevin Morin » Fri Nov 17, 2017 10:55 pm

Using the pics as a jumping off point- there are lots of shape related issues to overcome in a one-off, home build of this hull in aluminum. First is the fixturing- to get sheets into this shape, especially the topsides with their radical 'roll' or twist from flam to tumblehome (!) would be an expensive investment in time.

The shape of the topsides' bow would not be unique by itself, nor does is present a challenge- however combined with the gorgeous tumblehome in the after 1/3 fo the hull- this implies some from of collapsible fixturing- either end is simple by itself but when combined - how would you removed the hull of the fixture that held framing/sheathing in place? Not impossible but then, a complex fixture I suspect was justified by the manufacture of the hull shown?

Next main one off challenge would be doing the various components shown- as they are shown- the edges of most panels shown- almost all transverse sections are flanged or edge beaded and that implies a -non-marine alloy (meaning not 5000 or 6000 series alloy) so the material could be formed/ shrunk and stretched adequately to create the transom/bulkhead/dashboard/other transverse panels with their built in stiffeners and rounded flanged perimeters used to rivet the thin skin too.

Last, and not the least challenge is the design of the chine- not shown in detail in the photos- as this would seem to be a formed section that holds rivets for the topsides and the bottom panels. This piece would need to have a changing cross section- in the stern the angle between topsides and bottom may be nearly 90deg- however at the bow- depending on the chines' rise in profile view(?) the chine rivet strip will be nearly flattened?

Taken together, this beautiful example of the barrel back run-a-bout in aluminum would sure be a challenge to build one-off.

If, as steveh41 mentions, this boat were converted to aluminum - it looks to me that it would be easier to build in welded metal- but that would still be a challenging project for even someone with lots of experience in welded aluminum skiffs.

Pretty skiff, evokes Carlos Riva's lines for the Florida, but smaller and with more pronounced tumble home.

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Kevin Morin
Kenai, AK
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JaTro
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Re: Aluminum Barrelback

Postby JaTro » Mon Jan 08, 2018 2:44 am

Hi Kevin,
does that mean that marine aluminium alloys are hard to stretch and shrink?
I saw some 60ft al sailing wessel and they were using english wheel for forming the hull.

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Re: Aluminum Barrelback

Postby Kevin Morin » Mon Jan 08, 2018 1:51 pm

JaTro,
The term 'hard' to form (stretch or shrink) is relative to other aluminum alloys. Yes by comparison to softer, more malleable alloys the 5000 series (5052 easiest to form of the three; 5086 & 5083 so close in properties as to make that discussion "splitting hairs") are harder to form than other series of aluminum.

Tools rated to stretch steel (English Wheels, stretchers, planishing hammers) really don't have much problem working aluminum! Tools rated to shrink steel, likewise, don't have much trouble working aluminum so... aluminum is considered, overall, "easy" to form if compared to iron based alloys.

Also to note: the compound curves usually associated with a 60' sailing hull would typically be many times less curvature in comparison to the thickness of the scantlings of hull plating than would be required to create a Riva-like 'Aquarama' bow flam plating. The longer waterline, sail hull form and general shape of the larger sail boat very likely involved almost exclusively simple conic and cylindrical plates with some very gentle cupping or compounding. While a Riva-like bow on a shorter hull would require much more extreme curvature in both directions.

My previous remarks were about the specific Barrelback design here in the Glen-L catalog. It turns out, as near as I can see there is little or no flam in the forward topsides and the beautiful tumble home shown appears fully developable surface? ( I don't know that, and haven't seen the lines plan to examine in detail, so I'm not positive- this is my current opinion only! Others who know more about the lines could correct me for more accuracy in this matter.) As a result of the hull's shape; no forming would probably be needed, depending on the sheet/plate scantlings in the design done in aluminum.

Some shops, especially some in Louisiana, do plate their small welded aluminum boats' bows with flam. I believe they use an English wheel to form 'wine glass' sections of the topsides forward- then weld them butted side by side in vertical transverse seams? So while the metal work implied to stretch or shrink is common in some shops- the added work often moves the boat up one or two price groups for the final hull.

Hope my response helps?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

JaTro
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Re: Aluminum Barrelback

Postby JaTro » Tue Jan 09, 2018 1:31 am

Thanks for clarification.
Your contributions here are really helpfull.
It will be nice if you will have youtube chanell similar to Louis Sauzedde:-)

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Re: Aluminum Barrelback

Postby Kevin Morin » Tue Jan 09, 2018 2:30 am

JaTro, thanks for the vote of confidence in my future channel on YouTube! Perhaps if Glen-L creates a channel I'll join? but the work to mount a channel seems a bit ambitious for me at this point!

Glad to help clarify your question. That's why Glen-L has mounted the Forum- to help individual builders to increase their knowledge and improve their builds and I'm happy to help with that goal.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

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steveh41
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Re: Aluminum Barrelback

Postby steveh41 » Tue Jan 09, 2018 9:21 am

Kevin,

Add my name to the list of potential subscribers to your video channel... sounds like a great idea for Glen-l to pursue! Resources for amateur boat building in metal are pretty limited compared to wood and I'm guessing there would be a lot more aluminum builds if that changed. Your expertise is greatly appreciated. :D

Regards,

Steve
The longest journey begins with a single step… then repeat as necessary!

Kevin Morin
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Re: Aluminum Barrelback

Postby Kevin Morin » Tue Jan 09, 2018 2:48 pm

Steveh41, thanks for the vote of confidence but.... I'd hope to be making light of the potential for me to create a channel! And... I suspect the same goes for Glen-L's organization? lots of work- little gain unless the viewership is very wide!

While I'm intensely interested in welded aluminum boats- I suspect the number of people who will buy the needed equipment to build one is fairly low. There are plenty of welding video people and most of them deal generically with welding overall or car parts.... I think the car parts channels may have viewership in the numbers required to pay for the effort to put up a video channel (not sure of course)?

Thanks again for your kind thoughts, but I'm not sure anyone will find much audience for the esoterica of welded aluminum boat building!!

I think it is more effective to try to help out by posting a few comments and creating a thread or two- on those few sites that are genuinely involved and interested in the subject? Even among those few posters who're considering welding their own boats, on Glen-L and other boat building sites, there are a remarkable few who are able (maybe not willing?) to spend the time required to master the "metal fusion" processes to the levels needed to make such a video effort worthwhile.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin


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