How to design aluminum dinghy

Barry's last sentence probably the most important one, and one I often overlook.

What kind of tools do you have at you're disposal? What aluminum services do you have in the area? And what's your relative comfort?
What the various aluminum processes?

 

I plan to build it from 11 or 10 Ga 5052-H32 alu (0.090'' or 0.100'' thick) in order to shave a bit of weight compare to 0.125''.
Actually, Solidworks give me a weight of around 170 lbs, so I expect 190-200 lbs when finish.

I have to confirm with laser cut/bending company, but I expect to build them out of a single sheet. There will have some deformation for the last bend, but it's fully acceptable... at least for me.
Like in picture below with the die in blue.

I plan butt weld with some reinforcement by the exterior. Maybe handle near the joint or something like this. To me, esthetic pass way after toughness, reliability and easy to repair.

Tig weld aluminum since almost 20 years now, but rarely. This will be the biggest aluminum job I have ever done.

 

I have a 200A TIG AC/DC and laser cut and bending will be done in a large shop (800 workers) I work with since many years.

 

Gotcha, helps tailor advice. Some guys are cutting plate by hand with saws and welding with with budget migs, big difference if you have easy access to cnc bending and laser cutting....

 

You can open the search box at the right hand side of the page and insert Kevin Morin and it will show all of his contributions about aluminum boat welding. It will take you to quite a few aluminum boat building threads which contains a lot of good advice.


Below is an excerpt from a thread in 2015. A bit long but is food for thought.
small welded aluminum row boats

Fritzdfk,
those are some good questions so I'll make a stab at some (hopefully good) answers. First, I agree mostly with gonzo's remarks as regard stitch-n-glue requires developed panels layout as does sheet metal. Aluminum, generally, requires the same flat sheet panel outlines that will curve into flats & cones & cylindrical development from the flat sheet metal origins.

what is not addressed (2nd) is the welding part of the concept. Unfortunately for welding smaller thinner metal boats- welding aluminum comes in three groups; < .100" (#1); 0.125" < 0.50" (#2) ; 1.0"<THICKER (#3).

Welding ease (skill level) = #1 is 10 to 100 times more difficult than #2. # 3 is not important for the boats in question. Welding equipment is ten to a hundred times more critical for category #1 welding.

Therefore, while I agree that any ply stitch and glue row boat design or kit would convert to welded aluminum that implies case #1 welding; (so) it would make a world of difference who tried to weld and with what exact equipment in that category.

So what can we use to compare and help understand this circumstance? Let's refer to what is done by the thin scantling small aluminum builders; they don't weld. And the reason is that the cost of that skill level and equipment is not as cheap as press forming and riveting those thinner materials.

That is why you see a riveted planing skiff being used now as the tender. IN order to handle thin aluminum cost effectively they choose one or two simple widely appealing designs (your row boat in question) and make millions of them to afford exotically expensive tooling needed to make the boat affordable.

What can be done, well- if you already have good welding skills (I'd have to say that a minimum of 1,000 hours of welding begins 'good skills') and you have the needed TIG or MIG welding equipment and can spend time graduating decent or good skills to a higher level? (I'd have to say that was another 500 t0 1,000 hours in thinner work and exercises) THEN.... I'd say you can follow gonzo's concept of getting a successful stitch and glue boat and make it from sheet aluminum- welding it together.

I'd like to make some further examples of some hurdles thin material presents. Willy-Boat on this Coast and many other builders build thin wall welded boats using 0.080" and other thin aluminum and they weld their boats.

BUTTT... (you knew this was coming) this group of builders own a series of extrusions (own their own dies and control the sales of those shapes) that allow the sheet edges to be inserted into the heavy wall extrusion at the chine and the sheer so the open dories are welded in lap welds. Those extrusions are not generally for sale as they are proprietary to each welded drift dory maker (welder) so copying their design or build is very difficult when a newer/low hour welded is presented with two sheet edges that are 0.080" or even 0.100" thick.

I'm reporting facts of life regarding aluminum welding both MIG and TIG, as I know them, of course always willing to learn how to work in thin stuff better but here's my efforts.



This 1"=1'-0" model of 0.040", 0.060" and 0.080" is a seascape of welded aluminum I built as a memorial for a friend's son's passing. I welded for plural decades before I welded this and it was still pretty taxing to weld this little boat.

For any welders reading, and for others I did the project using a cold wire feed TIG Gun that made it possible for me to do this work, I could not and don't personally know anyone who could have done this work with free hand/two hand TIG.

I'm not saying all small boats of the class you're proposing to discuss are this thin, but the scantlings of that boat would be in this class unless the boat were to end up being quite heavy. This is category #1 welding required.



Its 17' LOA and about 4' wide will haul five people and row from three stations but... its all 0.100" or thinner and weighs about 175. lbs dry without rowing machines or oars.


So... you've asked about thin small rowing boats, I'm very interested in working in this end of welded aluminum boats. I've shown a few examples of my work to help you weigh my 'credentials' pointing to the welding critical path going forward with your project.


The issue is aluminum welding scalability or weld proportionality to the parent metal's cross section. If anyone welds depositing cross sections much larger than the parent metals' (very common in aluminum) the resulting boat can be distorted, beyond homely and potentially dangerous depending on the lack of skills and knowledge of the welder.