Aluminum Skiff

Hey folks,

Welded aluminum boats... I’m after a small skiff in the 15 to 20 ft range and have a few questions:

1. Does anything like this already exist?
2. What’s the closest production or semi-custom option you’ve seen?
3. Who would be a good builder or fab shop for something custom?

Here’s what I’m after:

• Ultralight and shallow-draft. Likely narrow beam. Light enough to hand-launch into an 8-inch tidal creek if possible.
• Surface drive-friendly. Planning to run a ProDrive XRF 50 with a welded-on keel cooler.
• Self-bailing deck. I’m on the SC coast and want to run up to 5 miles offshore on calm days without relying on a bilge pump if I take a wave crossing the inlet.

Layout could be tiller, side console, or small center console. Target hull weight is under 800 pounds.

Final question: What do you call the style of boat that has a single continuous panel from bow stem to transom corner, with no welded knuckle bow corners? I like the looks of the 15' Grumman Sport Boat, 20' Alumaweld Sport Skiff, and 23' Roosterfish Panga. I'm looking for something in that family.

Bonus question: Can a keel cooler be used on a riveted hull, or does it need to be welded?

Appreciate any leads, thoughts, or recommendations. Thanks

 

Dont know the East coat, but about 15 years ago there was something like 250 registered boat builders in the pacific northwest. Since your talking trailer able boats it might be worth considering west coast builders. Wild how temperature and use has cause some wild regional material specialist.

Cope has some designs that are probably close to what your looking for, would thing adapting for a skin keel cooler would be fairly easy.

Having owned a few aluminum hulls with keel cooled engines, my preferred method was to use an extrusion that was an integral hull strake/stiffened that was a bit thicker than the hull plating used as a coolant tube. Alaska copper and brass has done several different extrusions over the years in marine alloys ranging from pipe to a squared off tube.

Im not sure what the biggest sheet size is by we used a lot of 5 x 26 foot ones on projects over the years. Certainly doable for a single panel on a boat size your looking at.

 

Keel Cooling Calculator & Tank Design - Marine Propulsion Engines Beta Marine https://betamarinecanada.com/keel-cooling-calculations/

There are two different types of keel coolers. External and internal.
If external, it would be exposed to any impact to the rivers bottom.
You should find someone who builds a cooler in aluminum to reduce dissimilar metal corrosion.

Generally, keel coolers are installed on slower moving vessels.

 

Does pro drive have numbers on cooler sizing relative to substrate your plowing through? Seems like you'd need a little extra for heavy load with slower flowing stuff stuck to the hull.

 

The company that makes the motor makes the weld on keel cooler system. They also make boats, but not the boat that I'm looking for.

You can fast forward to 2:53 if you want to get to the keel cooling part.

 

Since your on a salt estuary it might be worth an extrusion thats marine grade.

Cant imagine those fins and that extrusion with rock contact from even an average beach.

Looks like a tohatsu ob head linked to a custom gear leg. If that level of delicate is viable maybe an rw fernstrum cooler recessed in a pocket. They make all manner of aluminum grid coolers, would be relatively easy to size and adapt a hull. Buy whatever boat you want and have someone weld in a recess and add the cooler.

 

These extrusions are not that weak. Where would you mount a fernstrum cooler ?These are small jonboats.
External fluid pump I don't like it.

 

Just throwing out ideas. The grid coolers come in some small sizes. Not saying it would be my first choice.

The video posted a finned small multi pass cooler right on the middle and bottom of the keel... i.e. a great place for rock and log strikes. My initial concern would be strikes and the concern over corrosion on a non marine alloy that works in fresh water but the op mentioned tidal creek.

External fluid pump is probably not an issue, some of the modern coolant circ pumps have tremendous lifespans.

 

Maybe the best solution is kind of air radiator .

 

I can call and ask about the alloy of the keel cooler. I would assume it would be the same as the rest of the boat. So if it's a problem for the cooler it's a problem for the whole boat.

South Carolina is mostly mud and sand, few rocks. The worst worry would be a tree stump.

I looks through the COPE Designs. I think a few of those could be modified to work. Weight would be my biggest concern.

 

If your bottoms soft (I've only occasionally been to the sc coast over the last 20 years so don't have a heavy familiarity with its substrate) that would be a different level of rigidity needed for sure. Id still probably want the cooler tucked on one side of the midline or the other. On even a really shallow v there is some protection from not being smack dab in the middle of the keel.

No doubt the cope style welded boats will be heavier on average than say a riveted lowe. Although the thicker skins usually mean savings in other aspects and Id guess the total weight gain isn't a spectacular jump when comparing as close to similar sized boats as possible.

 

Yeah, I'm not sure if what I'm looking for is doable. I have a 8hp two stroke on my skiff now and it's easy for me to move around. If I put the 50hp pro drive on it it would be a death trap, but if I built a boat appropriate for that motor it might be too large to move around. Beach launching would be cool but not required. I could pull it up a bank with a come among as long as I can push it back into the water.

 

Consciously I gave up aluminum ideas for the planned jon boat in favor of CFC.
When it comes to engines, I always used 2 strokes.
26kg - 6-9.8hp, 36 kg 15hp, 53kg 30HP, 62kg 40HP.
After one weekend we had a 40hp problem in the rain to take it uphill.
In general, with larger engines, there may be a problem, e.g. you can stuck on sandbank at speed and what will you do? I sailed a lot on shallow rivers and a large engine can be a problem.
Tohatsu prod is probably 130kg. This is a completely different game than 8HP.

 

I hear you on that.

In a similar situation, we always had an inflatable dingy that inevitably gets a solid leak and never seems rated for enough horsepower for size. On the flip side can't go a lot bigger without making it impractical to pack up a beach.

In my case we found a very tolerant outboard sales outfit that let me shoulder and pack various models through the grass filled adjacent lot to see what I could move.

Packed the 25 just fine but the 35 was doable on the level but more than I wanted up a tide flat.

Trying to build a dingy around absorbing 25 hp and still pack 3 big guys. Difficult balancing act for sure.

Do they have a curb weight on the 50 with all its extra attachments?

 

I can't find a weight for the prodrive. It's a newer unit.

I think carbon fiber could get a 3 man boat moving at reasonable speed with an outboard that can be carried by hand, but shallow water and carbon don't mix well. Maybe a hybrid? Aluminum hull with composite decks?

If Prodrive made a smaller version with a 20hp power head that might solve my issue. I just don't think I'm willing to go to air-cooled.