Props

[tenders]

What is so horrible about zincs that leaving them off is worth risking a $300-400 prop?

Of all the jobs there are to do on a boat, replacing the zincs has got to be the easiest and cheapest.

I just put an Indigo on my boat. No way am I running it without zincs: one on the shaft, one on the strut, and one inside the boat just forward of the shaft seal as a spare and shaft-runout-preventer.

I'd much sooner skip bottom paint for a year. I suspect the layers of ablative paint I've built up over many seasons would still be adequate.

[67c&ccorv]

"Uh 67c&ccorv, stay in fresh water."

Uh, Hanley...I will.

"I'm in the final stages of finishing up my homemade version of the "Indigo" prop and I must say your photos show it best. I just hope those little "winglets" aren't really necessary. I should be able to tell you how it worked out in a couple of weeks."

Thatch, think I can already tell you...apparently the little wingtips are very necessary.

What is so horrible about zincs that leaving them off is worth risking a $300-400 prop?

Of all the jobs there are to do on a boat, replacing the zincs has got to be the easiest and cheapest.

I just put an Indigo on my boat. No way am I running it without zincs: one on the shaft, one on the strut, and one inside the boat just forward of the shaft seal as a spare and shaft-runout-preventer.

Tenders; nothing...I just don't have that much room on the shaft to install them otherwise I would too (just to be sure). Note to self: it is time to replace the rudder zincs!

[ndutton]

67,
I'm in the final stages of finishing up my homemade version of the "Indigo" prop and I must say your photos show it best. I just hope those little "winglets" aren't really necessary. I should be able to tell you how it worked out in a couple of weeks.

Tom,

It'll be interesting to hear how your project turns out. My limited understanding of the winglets is that they are intended to address the inefficiency of tip vortices. The idea is to direct more flow into thrust rather than spinning off the prop tips. This concept isn't new and has been tried in the past with limited success due to the density of water. The previous designs usually involved placing the prop in a shroud of some sort - the Kort Nozzle comes to mind - but the drag of the shroud usually negated any benefit. These little winglets may be the answer.

I'm a big fan of real innovation. Would love to hear more about your design.

[thatch]

"Not for the faint of heart"

Neil, 67, and to whom it may concern,
Having spent about 50 years cleaning up "dings" and reshaping the ears on many ski boat props I felt that cutting down one of my "retired" units would be worth a try before "popping" for the Indigo spinner. I actually used the pictures in Shawn's Indigo thread (#s 1 and 7) to establish the blade shape and dimention. The coke cans were a good reference for size. After developing an ear shape, I mounted the candidate prop to a board and scribbed each ear with this template, making sure that they were all spaced 120 degrees apart. Tappering the ears to shape is actually an interesting science, but I feel that I understand what the engineers are trying to accomplish. My balance table consists of an old propshaft (dead straight) a prop strut and a shaftlog bearing strapped to a picnic table driven by a 2800 RPM, reversible drill motor. The balance process was a matter of, by adding weights to the ears, establishing which ear was the lightest and grinding the others to match. It took several hours but at 2800 RPM there is now very little ripple in my coffee cup.
I do realize that Tom at Indigo has spent many hours developing his great prop and that I will most likely wind up with that unit on my Cat 30, but I am also confident that my version will perform better than the 2 bladed "egg beater" I am currently using.
Tom
P.S. feel free to ask questions if you'd like.

[roadnsky]

Thanks Tom.
Nice to hear from the source on this subject since, as you stated, there are a lot of varied opinions as to what was meant by the "zink/no zink" option.

[Dave Neptune]

Faint of hert??

Tom, a fellow tinkerer at heart. I to spent many a day cutting and banging on props. I have done enouhgh that I am approached quite often to modify and or repair props of friend and friends of friends. I have templates for 5 different props for my 3 ski boats depending on what we're doing and where we take them. I cut many a prop for my A-4 over the years and reducing blade area was one of the more successful endeavors. I played with diameters and made a bit of gain but not so much in a headwind. I took as much as 30% off the area of a Sailor 12 x 10 and left the dia alone. That was my pprop for about 6 years until I heard of the Indigo. I am very pleased with it and did spend a bit of time on the phone with Tom (a very helpful fellow just like Don) on the idealogy behind the design. Everything he stated as what the prop would improve improved for my application. As I recall he said the "tips" did more for reverse and "quieting" the prop in the water while in forward.
There is another company building some highly efficient sailing props and I am helping a buddy with one now. The prop is from Campbell in Canada and the prop does work well in his 30hp 2:1 application. These props do have a different look to them and take a good bight out of the water. They have a thicker leading edge more like an airplane wing that a prop. We are going to reduce the diameter next time he has the time to have it removed.
I have been using "plastic sign" material for my templates, there cheap and easy to cut and they don't cut you back.

Good Luck
Dave Neptune

[thatch]

"Fellow Gearheads"

DaveNeptune,
In the beginning most of my tinkering and building was motivated by ecconomics. I built my first ski boat while in high school simply because my family couldn't afford anything I liked. It was powered by a 45 horse Merc and although not perfect, was a ton of fun and an excellent learning experience. Since then I have built two more boats and rebuilt several other "basket cases". What does all this mean?, If you are a genuine gearhead, it means that you would probably rather build most anything yourself than buy it ready made... On to the prop in question; since I had a few retired ski props, one of which seemed to have a similar pitch to the Indigo, I just had to give "carving" it up a try. Shawn's photos of his Indigo directed the shape and the diameter was dictated by the spec sheet. I actually did shape the leading edge to simulate an airplane wing , with the thrust side being almost flat. You had mentioned the Campbell prop before and I actually contacted a dealer who was very knowledgable about those units and although they build an excellent prop, I feel that their price is a little steep.
I couldn't agree with you more about your comments about Tom Stevens and Don Moyer, I'm sure that their efforts are a major reason for the continued success of the A4.
Cordially, Tom
P.S. I'll be at the Marine Stadium in Long Beach on the 7th and 8th of August with the SS-7 boat (I'll be the oldest crew guy) and would love to chat if you can make it.

[Al Schober]

CDI Propellers / Drivesaver

Just thought I'd muddy the waters here a bit. My 2 blade Michigan dissolved down to 9 1//2 inches several years ago due to a bad battery ground cable. I installed a Drivesaver to electrically isolate the shaft & prop from the engine, and replaced the prop with a 12x7 from CDI. No electrolysis problems as the propeller is a reinforced urethane (I think). It works fine. Check out:

https://www.sailcdi.com

[thatch]

Al,
As long as you don't "muddy the waters" by running aground then a little mud in the water is okay with me. My main reason for wanting to switch to a smaller diameter 3 blade prop is to gain some better low speed, under power handling ability. The factory 2 blade on my cat 30 acts more like a bow thruster at the wrong end of the boat sometimes, and I'd like to cure as much of that as possible. It's my understanding that the theory behind the smaller 3 blade unit is to create a smaller, higher velocity cone of thrust. An added bonus is the smoothness the 3 blade has over the 2. My bottom cleaning service maintains my zincs and electrolysis does not seem to be a problem in my marina.
Tom

[Al Schober]

Tom,
I don't know that the smaller & higher velocity cone is going to help you. I'm familiar with the Cat30, and the shaftline arrangement is such that there's little flow from the prop over the rudder - the offset is too great. It's similar to my Tar30, where the offset is too far! Your prop wash goes to port of the rudder, mine goes to stbd. And my prop is about 5' fwd of the rudder!
The only way to steer is to get flow over the rudder, and this means to get the boat moving BEFORE you try to turn. I have to back to get into my slip, and I've got this down to a science (almost). Let's just say I've never hit another boat backing into my slip, but I did split one guy's bow pulpit while coming out forward. The difference is that in backing, I'm able to develop some way on the boat before having to make the sharp turn into the slip. On the way out, I've got zip for way and I'm trying to make a turn - cross your fingers (and check your insurance policy).

Al

[sastanley]

Tom H, Was it the pic of the Indigo chillin' in the beer fridge that helped you with the critical dimensions???



Al, I have a lot of experience on a Tartan 3000...I realize it is not the same beast as a Tartan 30 (engine under the stairs, M-15 diesel w/ reduction drive Hurth trans, etc..) but, I am familiar with both and their layouts... There are few boats I've experienced that have the propwash of a direct drive A-4 powered Catalina 30, despite the 'extensive' distance between the prop & rudder. I also have a tiller, so I don't get the dampening effects of the wheel system...
The Tartan 3000 also has a tiller and it has nothing in terms of 'torque steer' like the C-30.

I will agree 100% with you that the only way to steer a boat in reverse is to get some way on. I learned that as a kid.

Even though I've only got 2 hours on the Indigo in protected waters, my right inner thigh is thanking me since it took the abuse of the tiller smashing into it for hours on end with the 12" x 7 two blade Michigan Wheel prop now hanging on my workbench. BTW - That prop is for sale

[ndutton]

I second Shawn's assessment of propwash over the Catalina 30 rudder. My boat was originally tiller steered and under power the heavy helm was misery. Converting to wheel steering (for other reasons) solved the problem.

[thatch]

"Sounds like an add for props and beer"

Al,
My decision to change from the 2 blade to a smaller 3 blade is an attempt to reduce the severe "prop walk" that seems to be inherent with the Cat 30 with it's factory issue prop. Based on testimonials from many owners like Neil, I'm sure it will be worth the change. I actually owned a cat 27 with the stock 2 blade and experienced very little of the side push that I do in the 30.
I'm not expecting the "thrust cone" to have any effect on the rudder, I'm just hoping for a little more "user friendly" low speed handling.
Shawn, You picked the right picture. I used the can of "Mic" on the upper shelf and drew an imaginary line from about 11 o'clock to 5 o'clock through it and the left hand ear of the prop as my scale model. The ears on my version are about 3-1/4" wide and the diameter is at 10". The "Indigo" ears are probably a little narrower than mine but I wanted to save some room for adjustment. I hope to have the "poor man's clone" on the boat this week and will (for better or worse) report back on it's performance. I'll also invite a computer savvy friend over so that I can post some pics of this "conversation piece"
Tom

[2dogsfishin]

Need a prop 7/8" shaft

[QUOTE=sastanley;
BTW - That prop is for sale :

What size shaft?

How much?

Where are you? I am in Pensacola

Tom 850 572 1225

[Dave O]

I have a C&C 29 Mark I which had the original 2 blade prop when I bought the boat 4 years ago. The shaft is offset .

With the two blade prop, prop walk was severe. Getting enough way on in reverse to steer without having the boat walk severly to port was terrible. Leaving the dock was always the worst part of the day ... and made those in neighbouring slips a bit anxious as well.

Switched to the Indigo in the spring of 2009 and am pleased. Prop walk is much reduced. I can easily power up the boat in reverse and keep a reasonably staight line. In forward gear vibration is reduced and power improved.

I bought the Indigo to improve low speed handling around the club and it has done that nicely. I don't race so can't comment upon drag.

Dave O
Port Credit, ON