Sailors Powerboat

kimbottles

Super Anarchist
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PNW
I might as well wade into this thread since it's a subject close to my heart.

I'm a sailor and yacht designer and have been considering the sail or powerboat conundrum for as long as I've had to motor my 5kt $hitbox back to port on a windless/blowing stink/cold/rainy/dark/hot/day/night. Still love sailing, but if I want to get somewhere comfortably, it'll be on a powerboat.

In the last few years, I started thinking of a smaller powerboat- a day or weekend boat. A boat that could be trailered and stored for the winter, like our 26' sailboat. So she needed to be relatively lightweight, efficient,  max length and beam for trailering, and a reasonable cruise speed in the low 20's. The Tombolo 28 was originally designed for cedar-strip & plywood custom construction. The design was published in a few magazines and now it seems to have a little momentum. https://www.siewertdesign.com/Portfolio/Production_Boat_Designs/tombolo_28.html

Many production boats the size have what I call "feature creep", and try to do too much to appeal to everybody. They have too many and overly complicated systems, which weigh more, which require more horsepower, which weighs more...etc.

The Tombolo 28 is a relatively simple boat, a sailors' boat that I thought you might enjoy.

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Very nice!

 

kimbottles

Super Anarchist
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784
PNW
Feature creep is essentially every production powerboat. Horrible waste of resources.
I am rather proud of the fact that I batted feature creep away from the SLIVER project. It wasn’t easy, all sorts of well meaning people had suggestions of features that “you need” or “must have”. So far we have kept her quite simple.

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Autonomous

Turgid Member
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Feature creep. So true. One of the reasons I liked my C-Dory so much was that it had what you needed and nothing else.

More time boating, less time maintaining stuff.

 

Pertinacious Tom

Importunate Member
62,864
2,003
Punta Gorda FL
Ranger Tugs are all about feature creep. There's almost nothing optional. Thrusters, radar, giant screen, air conditioning, etc, etc, it's all standard.

I'm not a yuge fan, as one of my rules of boating is that the smallest, simplest boat that can do what you want to do will result in the best work to play ratio. They kinda went the opposite way.

As mentioned, I sold them for a while at a dealership. Customers LOVE standard stuff and do not like poring over lists of expensive options. Not my style, as I said, but if I had to sell one of those with every option priced separately or sell one like they do, it's an easy choice. LOAD IT UP!

 
Have you outboard efficiency nuts seen the Sharrow Propeller?  This test just came out (literally hit my inbox a few min ago) & looks quite promising.  ~16% speed & efficiency improvement, pretty rigorous independent test from what I can tell.  
Humph.

First, note that it only works at lower speeds, and is worse at higher speeds. It is at higher speeds when load is maximized that cavitation happens and tip losses become significant, not at mid range speeds.

At lower speeds, more blades work better, and this has always been known, nothing new here.

This is effectively a six bladed prop being compared to a three bladed prop, so the results are not at all unexpected.

A better comparison would be against a six bladed prop without the connections between alternating blades.

Tip loss on a prop is not like tip loss on a wing, where winglets certainly work. No helicopter uses winglets. That is because a rotating wing approaches the fifth power better efficiency with span, so increasing span always wins.

The real problem with reaching best efficiency with this specific (heavy, high drag) boat is that it needs bigger diameter props than can be fitted on those outboards. Better to improve the lower unit to support bigger props in order to gain better mid range efficiency.

Remember that the reason outboards use small props is because gas engines don't have much torque at low speeds. Outboard manufacturers, like all engine manufacturers, don't want you to overload the engine at low speeds to avoid having you blow up your engine. Overloading so the engine simply can't turn faster than the torque peak is the way to get maximum fuel efficiency, and everyone knows that. But it also causes engines to blow up, and everyone knows that too.

It does look cool.

 

Presuming Ed

Super Anarchist
11,050
219
London, UK
John Corby design for Nick Rogers (Beijing 470 silver medalist & nephew of Jeremy Rogers, builder of the Contessa 26 & 32). 
 

I like the cabin. No getting wet in Western Solent chop. IMG_0255.png 0e1ca054-7bb6-422a-82ac-b56444c78707.jpeg

 

Pertinacious Tom

Importunate Member
62,864
2,003
Punta Gorda FL
That outboard looks too big for that boat.

I'm not sure a boat has ever gotten that reaction from me. If you look at hours on the water, I'm definitely a powerboater who also sails and paddles.

Cruising up the harbor yesterday at 20 knots, an offshore fishing type cruised right by doing about 35. My wife commented that we were losing the race. I told her that boat was cruising near our top speed.

Got to the ramp and the boat in question was helping a disabled boat at the mouth of the harbor. About 24' long. The engine? A 400! I grinned. DIdn't look too big.

 

Autonomous

Turgid Member
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PNW
Don't know how closely some of you are watching the outboard motor market but it is brutal. Guys have brand new boats with no motors and no idea when they will come in. Year long waiting lists, etc.

I just got notified my new build was imminent (whatever that means), I thought it would be late spring.

A bit of panic as a specific motor needed to be sourced pronto. Called and surfed around with the same result, 'we can put you on a list.' Finally found just the one I wanted, probably the last one in the area.

It's better to be lucky than good.

 




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