Brainstorming Retractable Drives

[CatBuilder]

Injuneer, there are a lot of problems with the outboards you are talking about.

A displacement boat needs large, slow turning props. These are all for power boats, Boston Whalers and the like.

Wrong gear ratios and wrong props.

[Injuneer]

Originally Posted by CatBuilder

Injuneer, there are a lot of problems with the outboards you are talking about.

A displacement boat needs large, slow turning props. These are all for power boats, Boston Whalers and the like.

Wrong gear ratios and wrong props.

Hmmm... according to Aquawatt, their 13 kW is suited for displacement as well as planing hulls.

But let's look at some numbers. Quite a few catamarans use the Yamaha 9.9 High Thrust. The Yamaha HT uses something like a 12 or 13 inch prop. The Aquawatt 13 kW comes with a 9.25 inch prop, but since it uses standard props, you could specify it with the largest prop that will fit, maybe a 12 or 13 incher. You could also specify a very high pitch prop - basically, try to overprop it.

The Yamaha's gear ratio turns the prop at around 2,100 RPM at top engine RPM. The Aquawatt runs up 3,250. So a couple of choices here - you could ask Aquawatt to give you a higher gear ratio, which should be relatively easy on an electric outboard. Or you could simply run it slower, say up to the 2,100 RPM of a Yamaha prop (assuming you were overpropped). This is not an ICE, so the torque will be more or less independent of the actual motor RPM and will be available throughout the motor RPM range. The worst that could happen is that you might get some higher motor heating at the reduced RPM, but since this is a water-cooled electric motor, there should be some buffer in the system to take care of the extra heat (larger water pump?). It's not ideal, but I suspect it can be made to work.

And lastly, if you don't like any of those suggestions, as I mentioned in my previous post, you could "get a couple of blown outboards, rip out the engines and install electric motors of your choice - DC, BLDC, PMCT, brushed Lynch, or 'industrial-quality' AC motors. That way you could select your own gearing and modify the length of the lower unit leg to exactly match your installation." Frankly, that's exactly what I would do, it's not that complicated.

Unless you are willing to explore some of the above suggestions, my guess would be you will not find anything on the market that fits your ideal configuration.

[tunnels]

what about doing all your drives with hydraulics ? altenater , 2 props and what ever else you want to drive . could all work at the same time or just one at a time or not at all just the motor running with no drives working !!
just means running pipes or hoses here and there .

[masalai]

www.mastervolt.com/e-propulsion - Have you seen this? or is it too small/expensive? - - A pair as a minimum may get 6 knots and maybe even 2 pairs? but that would mean mini-keels, just sufficient to protect the propeller.... Gensets forward for hull-balance and making mains-voltage-house-AC, battery-charger, (mains-voltage to 48VDC), aft with 48VDC LiFePO4 batteries near each engine (aft) and inverters there to take care of silent living when desired... An aft mast and Hitch-hiker-dual-genoa, one to each bow will leave the coach-house roof clear for solar panels

On CNO, I can carry 13 panels 800mm x 1600mm for 2275W nominal output when at anchor in the tropics... My Nanni321SD engines burn about 3 litres/hour at 3000rpm and deliver around 10hp/11Kw each so those electric drives are about on a par with the Nanni321SD at Au16,500 each including OEM installation package... A Nanni mains generator in Australia is about http://seawasp.com.au/docs/6.5%20KVA.pdf I feel more comfortable/secure with fixed blade propellers for long range efficiency and confined quarters manoeuvring...

[masalai]

hehehe

Do you want to buy my cold-fusion-energy package for cats? I need Au$40K for incidental materials... - - and then research access to CERN...

[keysdisease]

Cold fusion, how yesterday. Fund me for dilithium crystal mining and I'll produce a matter / anti-matter drive.

Steve

Originally Posted by masalai

hehehe

Do you want to buy my cold-fusion-energy package for cats? I need Au$40K for incidental materials... - - and then research access to CERN...

[Wingandaprayer]

Catbuilder, I am in a similar situation as yourself, building a 19m cat and playing with various propulsion options, with similar limitations/requirements as you have mentioned. By the way, I know the owners of ZeeVonk and can put you in touch with them if you like. I would like to discuss propulsion issues with you offline, if you are willing. Email me yours and maybe we can invent/discover something.

[CatBuilder]

Originally Posted by Wingandaprayer

Catbuilder, I am in a similar situation as yourself, building a 19m cat and playing with various propulsion options, with similar limitations/requirements as you have mentioned. By the way, I know the owners of ZeeVonk and can put you in touch with them if you like. I would like to discuss propulsion issues with you offline, if you are willing. Email me yours and maybe we can invent/discover something.

I would love to speak with the owners of Zeevonk. I contacted them once, but all they did was give me the hard sell on buying a charter from them. I was trying to ask details bout the boat and the reply was, "we are very happy with the boat, you should buy a charter."

Maybe a warm introduction would make a difference.

I'd be quite happy to discuss propulsion issues offline. I will send you my email after I finish typing this. Thank you for reaching out.

[masalai]

Hi Catbuilder,
I hope this is helpful, and I would appreciate it if you posted your decisions and reasons online as research on second build is growing and additional information is always appreciated... http://www.boatdesign.net/forums/boa...-new-post.html

[keysdisease]

Was setting up at IBEX today and saw the Mastervolt display. Pretty extensive hybrid stuff. Sure there is more, but the place is a mess during setup and I have a mission.

Steve

[brian eiland]

I was just made aware of these....didn't know they existed

http://www.amartech.nl/products/retractable-propulsion

[brian eiland]

And that Amartech retractable drive might make good use of this Thompson coupling hardware
http://www.boatdesign.net/forums/propulsion/u-joint-cv-joint-thompson-coupling-16397.html

[michael pierzga]

Looks nice but what is the advantage over the present designs like the one from Boatspeed Australia ? The unit from the Netherlands looks to consume too much interior space and presents substantial lateral resistance.

[brian eiland]

Originally Posted by michael pierzga

Looks nice but what is the advantage over the present designs like the one from Boatspeed Australia ? The unit from the Netherlands looks to consume too much interior space

over here we had this discussion...
Diesel/Electric Propulsion System Design - Have your say!

Originally Posted by Originally Posted by michael pierzga

Dont know if anyone mentioned the popular Boatspeed Australia retractable drive unit. I see many on the gran prix race boats. looks simple to build. In spring I photo documented the servicing of one of these units. It Could easily be built by a Cat Builder type working in his "spare time"

http://www.boatspeed.com.au/pages/comp.shtml

Originally Posted by Originally Posted by pool

If the folding prop does not fold (completely), as they sometimes do, you'll probably not be able to retract ...

...to which I replied...
Why add in the complicated retraction system if you are going to make use of a folding prop?

Originally Posted by michael pierzga

....and presents substantial lateral resistance.

I don't see this as a problem when you are under power. In fact it could be advantagous in preventing your being blown sideways.

And I don't think it consumes that much more interior space when you look at the total cavity allowed for the non-folding prop verse the stretched out cavity for the folded one? We would have to look at this more closely.

I also would want to look at the servicability of the two in comparison.