Sail Drives VS direct drives

[DotDun]

I thought this lift bag was under the bridgedeck?

Pretty good size bag to lift the saildrives out, 30" of bridgedeck clearance and ~45" of lift for a 75" total??? How would you keep it from 'squirting' out from under the bridgedeck?

[Training Wheels]

Velcro?

[clockwork orange]

Airbag jacks are used by serious off roaders when their 4x4 gets bogged down in soft sand or mud where a conventional high lift jack would just sink in, so they can just slide the deflated bag underneath and plug it into the exhaust pipe of the vehicle and up it comes. I imagine an airbag for lifting your cat to be the same but bigger. Shopvacs produce high volume, low pressure so are ideal for inflating a large volume low pressure bag in a reasonable amount of time, (as well as being cheap of course).
It seems to me that the size of the bag would be dictated more by how high you need to lift the boat than by lifting capacity. With HH66 adhesive you can add tie down straps wherever you need them to keep the bag from squirting out.

Steve.

[ejlindahl]

I'd seen pic of a cat on a bag on this forum a year ago. Link
We used ~1 - 10 square foot bags in the fire dept to lift really heavy things, but much higher pressure.

Also google air docks, a friend has one for his 32' Farrier. Sounds like a shop vac doing the work.

[admiralslater]

If I recall they did have a couple of ropes on it. But all in all a very relaxed attitude. I beleive less traumatic than we are making it

[beiland]

HARMO:
THE NEW REVOLUTIONARY ELECTRIC PROPULSION SYSTEM BY YAMAHA?

Interesting new product/technology presented at this years METS show

NEW YAMAHA HARMO ELECTRIC PROPULSION SYSTEM

Little is known about it. Presented in absolute preview yesterday at Mets, Yamaha Harmo arrived in Amsterdam just few hours before the opening of the event: for the moment, there are no official data but just the first prototypes exhibited before a curious audience.
According to the engineers of the group, Harmo is an innovative electric propulsion system designed for motorboats. It can envisage a single or double installation and it is made up of two pods rotating 90 degrees around their own axis and which can be controlled by a joystick. Like the already established competitors on the market, they allow the boat to shift laterally since propellers rotate in both the two directions.

The model exhibited in Amsterdam has the same push as a traditional 10 Hp inboard-outboard. The propellers’ blades rotate inside the circular supporting structure thanks to an electromagnetic bond while a thin layer of water between the two parts acts as a conductor. The prototype arrives after over a year of planning and trials and the first samples have been tested on some cruiser boats along Dutch channels. Harmo is specifically designed for professional applications and inner waters and it doesn’t like

[StuM]

Originally Posted by beiland

HARMO:
THE NEW REVOLUTIONARY ELECTRIC PROPULSION SYSTEM BY YAMAHA?

Interesting new product/technology presented at this years METS show

NEW YAMAHA HARMO ELECTRIC PROPULSION SYSTEM

Now that IS innovative

It will be interesting to follow developments.

(I wonder if the use of "revolutionary" was a deliberate pun )

[rabbi]

Originally Posted by StuM

Now that IS innovative

It will be interesting to follow developments.

(I wonder if the use of "revolutionary" was a deliberate pun )

Has been around for som time for bigger ships / yachts :
voith-inline-propulsor

[EWOL Props]

Originally Posted by beiland

HARMO:
THE NEW REVOLUTIONARY ELECTRIC PROPULSION SYSTEM BY YAMAHA?

Interesting new product/technology presented at this years METS show

NEW YAMAHA HARMO ELECTRIC PROPULSION SYSTEM

Yes it looks appealing but I have seen it live last week in Amsterdam...a pretty large system that has only 10 hp ! and big drag due to the nozzle around the prop. An in fact the article says "Harmo is specifically designed for professional applications and inner waters and it doesn’t like high speed." So....not for sailboats

[beiland]

Originally Posted by EWOL Props

Yes it looks appealing but I have seen it live last week in Amsterdam...a pretty large system that has only 10 hp ! and big drag due to the nozzle around the prop. An in fact the article says "Harmo is specifically designed for professional applications and inner waters and it doesn’t like high speed." So....not for sailboats

Yes I was afraid this would be true for this particular system, but I am glad that others entities are back at working on perfecting these rim-drive propulsion units rather than just bow thruster applications.

[beiland]

Originally Posted by beiland

This is what I would want, a silent-chain drive leg like the one that PYI built at one time.

And I would mount mine in a Tennant style CS hull

Tennant Hull V ChainDrive

Meantime I was doing a little house cleaning on one of my storage disc and ran across this little diagram that had existed in a PDF form, but I managed to convert to a jpg image.

[beiland]

And to go along with that material....

Concentric Pin and Rocket Joint on Silent Chain
The concentric pin and rocker joint is used in some designs of silent chain. This joint, together with the involute sprocket tooth reduces chordal action to a minimum. The joint consists of a pin and rocker, each with identical cross-sections and concentric radii. When the chain engages the sprocket, the curved surfaces roll on one another, thus eliminating sliding friction and joint galling.

Before the chain engages the sprocket, the contact point of the pin and rocker remains below the pitch line as shown in Figure 18 Top . As the chain engages the sprocket, the contact point moves upward and the pitch of the chain elongates as shown in Figure 18 Bottom.






https://www.myodesie.com/wiki/index/...e%20Advantages

[beiland]

Quote:


At one time I was doing quite a bit of study of this subject in anticipation of producing some units...maybe over in Asia. But the boat market is less than well at the moment, so I'm not persuing that subject at the moment.

I started out favoring the idea of toothed belts over chain. But over a period of time I came to the realization that the silent chain approach made much more sense, and would be easier to impliment. This is particularly true when you start talking of HP greater than 20-30.

If you start looking thru the tables of pulley diameters (minimum dia) recommended by the belt manufacturers for specified powers transmitted you will find the diameters of the pulleys getting quite big which might require thicker struts, and all of this interferring with the prop...etc...etc

This was another reason I chose the chain drive vs belt drive option. Look closely at the interface of the chain with the teeth of the sproket compared to the sliding action you would experience withe the fiber belt arrangement. And look at the size of the contact patch.