RingProp

http://www.ringprop.com/
Has anyone looked at this website? Any comments? I am still looking for ways to avoid prop/lower unit damages on our commercial boats. However, this site as well as Sword Marine has not changed in regards to what they are offering (if anything at all) since more than 1.5 years.

 

Without great in-depth study it's impossible to say if you get any hydrodynamic improvement. Probably a bit.

I would have thought the easiest solution to protecting the prop (or anything near it) was to mount a stainless-steel cage around the prop to stop things getting in in the first place. That's an old outboard trick, seems to work OK

Tim B.

 

Thank´s Tim

I have wasted $ 800 + purchasing "propguard". We installed 2 simultaneously on two identical boats.

The first one could not get on plane and since he was already on a usually 1 hr. trip with 15 passengers on board he could not turn around and had to complete the trip. The result was 80% more fuel consumption and and a 25 minute longer trip. The manufacturer had claimed higher performance and higher speed because the "PropGuard" (TM) forces the water to be pushed back.

The second one did not give us any problems in that regard because it broke (sheared) off about 200 m after the boat left the dock.

My wife suggested to make lamp shades of the 3 remaining propguards we have left.

We are running 5 boats with 200 hp, 1 with 250 hp and 1with twin 250. I have learned the hard way that prop guards produce too much drag for fast moving boats. This is why I was thinking that the Ringprop might be worth a try since it is part of the prop, turning with the prop instead of being a static contraption mountet on the lower unit. I would not expect an increase of speed and would accept a decrease of a few miles, but the boats must be able to get on plane which has never been a problem even with more than 20 people on board.

 

Ringed props are for heavily loaded wheels where you can trade off blade area loading for tip span and twist. For large OB's you could do a ringed prop, but I'm not sure about the economics. The stresses and the blade to ring join get large rapidly and there is a diameter*RPM limit for cavitation on the ring itself. This means that a fair amout of design needs to go into the structural design of the blade to ring join. The concept itself is fairly old (late 19th century) and well documented, but there have been major structural problems. This is why I think RingProp plc limits itself to small OB's (though I see that they will introduce this year a wheel for up to 115 HP).

 

Hey, It's just a suggestion, I'm only here to propose a possible engineering solution. I was not trying to endorse a commercial product in any way.

Tim B.

 

Thank`s for your replies. Jehardiman I now realize the limitations of the Prop design. However looking at their web videos they seem to have some good size motors on the demo boats. Isn`t marketing great?

Tim, I did not have the impression that you tried to market any product to me and I fully understood that you just made a suggestion and I appreciate that. Sorry if my reply did not make that clear. I am just sooo frustrated looking for solutions and not being able to find one. I am spending about 70,000 a year on repairs and big part of it is for lower units and props. A prop runs from 450-500 and a lower unit from the "authorized Yamaha dealer" is now 3,300. I am sitting in Banana Republic here and feel pretty helpless that´s why I joined this forum in first place. This brings me to the other topic that I have posted, but nobody seems to be willing to state an oppinion.

The jetpac. The theory behind the design makes perfect sense to me and I was hoping that this could be a solution for me. However, I have been sending e-mails and filled out online request forms since 1.5 years now. I got one reply about 15 months ago after sending a pretty nasty e-mail and was told that the concept was taken over by another company and that they will have a full line of engine optons etc. by the spring of this year. Since then I have filled out online forms again, sent numerous e-mails and received no response. By the way the engine options are still the same as they were a year and a half ago and the website is basically unchanged. The only difference is that they announced that Zodiac is now offering one of their models equipt with the "jetpac". I would feel silly to write to Zodiac to find out about the jetpac.

If you would take the time and look at their site: www.swordmarine.com
and give me your oppinion?

Thank you all.

 

Peripheral Prop/RingProp

Those interested in the 'RingProp' concept should also find this new 'Peripheral Prop' posting of interest.