Sea Sled madness. It’s in my brain.

Your amazing scenery, the glassy water, Serenity underway at 1.1 gallons per hour speed, your poor collapsed tidal grid, interior photos if anything has changed since your previous photos.....

 

Yesterday's commute into a stiff breeze.
Our paid job. House built on duff (look it up), sliding into the sea. I'm cutting down to the mineral horizon, driving pins, and building footings, under a house that's already sagging over, to jack it back up.

 

I think it would take a long time to get fed up with a commute like that - although it will probably be a different story in mid winter and with a gale blowing.
At least you don't have to worry about traffic congestion!
What speed were you doing at 1.1 gallons / hour, and what was the motion like while bashing into that stiff breeze?

That house repair looks very complicated and major.

 

At 1.1 its about 6.5 knots. Bashing into those waves, I was standing with one hand in my pocket and the other holding a cup of coffee.

The reno is awful. Dirty, dangerous, difficult

 

Like this?

 

Yes!
Photos and reports like this make the last few years of work on the boat all worthwhile.
And getting just under 6 mpg is pretty good going I reckon - especially with a comfortable motion while bashing into a short head sea.

Good luck with the three D's of your house reno - I hope that you include a suitable 'feck-around-factor' for this in your labour rate.

 

Jumping wakes (didn't need to take my hands out of my pockets)
Serenity at another paid job.

 

Nice, what's the difference between ordinary high/low tide at your place?

 

Typical tidal range in our area is ~2.5m

 

Well, finally some data to post. The seesnake, with it's integral LEDs make the transition from the bubble field to green water quite visible. But only in dark conditions. In daylight the little screen is overwhelmed. So it's an overcast day, and I carped that diem.

At 1350 rpm and 6.5 knots, the flow is almost entirely green water, with occasional wave of bubbles, at 12" or 300 mm from the lower edge of the transom. The OB has an L or 20" or 510mm leg. At the moment we're driving to a job site, so I can't really measure the intake depth right now. I posted it some time back. But it's clear that even at this speed, the prop disk is partially in foam.

 

The question is wether the bubbles have their origin at the forward spray root or if they are entrained/following the recirculating water aft of the transom. The medicine required depends on where the bubbles come from. If you traverse the transom from engine to chine, we might get an idea about the bubble source. If the boundary is deeper towards the center it would indicate a fw source, as I see it.

The cooling water inlet is certainly within the bubble field as it is located just above the torpedo body.

 

Right. The middle 1m is so bubbly the water is opaque. Outside of that area there are certainly bubbles, but it's mostly water with bubbles. The middle meter is mostly air with some water.

I measured everything at the dock. The lower horizon of the bubble field runs through the axis of the prop. So even under moderate conditions like this, the cooling intake is getting some air.

The transom extension you originally suggested, @baeckmo , what effect is that likely to have while backing up. At the moment, top speed in reverse is the same as forward.

 

I'm guessing the source of the foam is this.

And the second image shows quite well how centered the entrained air is.

 

I agree, this means we must focus on the central bubble stream, just as with my boats. Since lowering the engine is a tricky operation to be avoided if possible, a "bubble diverter" pod is required. This is the solution I used, but your bottom shape is different, so I have to scratch my head a bit to come up with a shape for the Serenity. The simple bottom extension is not the solution here, sadly enough.

 

There's a company called Bay mfg that makes 5"/127mm insert for the outboard leg. The extra depth seems like it might be enough.
Hopefully
Johnson & Evinrude http://www.baymfg.com/kits/johnsonevinrude/

@Ad Hoc , I wonder if it might be possible to determine displacement and longitudinal CofG, with accurate draft numbers. How versatile is the software? Draft at the transom is 15.5cm. At 74% loa forward it's 30.5cm