2:1 A-4 Props???

[Dave Neptune]

Too all, there have been many discussion on the characteristics of how well the Indigo 3 blade works for the direct drive model however at this time I would like the reduction guys to chime in if they can. I have been working a bit with a friend on his Cat 36 with a 2:1 23HP diesel engine. He is now on his second prop from Campbell Porps an outfit in Canada. The prop has most of the same features as the Indigo ie the thicker leading edge for a much more efficient low RPM bite against the water. It also is a very narrow blade as the Indigo and relies on efficiency instead of blade area. While trying the prop I noticed that it has very good control in both directions and is considerably quieter in the water. We are working on getting 300 more RPM on a redo by reducing the pitch slightly and reducing the diameter as well. His boat has never moved as fast as it has with the Campbell and this is the fifth prop he has tried to date, including Martec, Vari Pitch, Michigan ~~etc. There is also very little tubbulance felt through the rudder as with the Indigo. The prop itself looks more like an airplane propeller as the blades are very narrow producing very little drag while sailing which is a big light air advantage.

Have any of you with the reduction set-ups had any experience with the Campbell Sailor prop. My thoughts are that if one gets worked out it should be fine for most any other A-4 with the reduction drive. The Cat 36 that we are playing with is about the same size as my boat and he is getting all of the same advantages I do with my Indigo which is one of the reasons he went to the Campbell after my bragging about how well the Indigo worked out for me.

Anyone?
Dave Neptune

[hanleyclifford]

reduction gear prop

Dave - You did not mention the specs on the prop. I am also interested in this discussion. Currently I am using a 3 blade cupped prop intended for a power boat 13 x 13. Seems a bit much for my 10000lb full keel configuration. I cruise at about 1600rpm, but would like to go up to around 1900. I'm shopping.

[lat 64]

Hey, Thanks for the 2:1 info.
I have a 16" two-blade on my Columbia 36 that was used by Nelson at Traflagar. I would like to see what's a modern upgrade for us reduction gear folks.
russ

[Dave Neptune]

Prop

Guys, my buddy started out with a 14 X 8 and it was to much prop! Now he is trying a 13 X 7 and it seems to be working pretty good and we will be doing a bit of tweeking (reducing diameter). He may have some more figures later today and I will attempt to post a picture of the props. The Campbell seems to rely on efficiency as with the 13" X 7" (not much pitch but it bites well) we are also working on a tach issue at the same time. Some of the RPM figures will only be relative until we have the tach error calculated. Will get some more numbers this afternoon perhaps, he may be doing some testing and I may beg a ride to play as well.



Dave Neptune out

[thatch]

"This will probably "Spin" out of control"

Dave,
Thank's for opening up this discussion; based on your attention to fuel figures and engine performance I feel quite comfortable with all of your input. Now on to the business at hand. As you well know over the years many different types and sizes of props have been tried with varrying degrees of success. Since it is relatively difficult to swap props around like the ski boat crowd does (myself included) most of us just kind of live with what we're given. Actually if you looked under the average prop driven ski boat you would probably find something in the neighborhood of a 12/15-3 blade full cup unit. What I'm getting at here is that since we have such a limited "target audience" here, we should be able to come up with some pretty close parameters by taking a poll. Of course we have the 1:1 group and the 2:1 group to consider but I feel a pattern will show up to make some sense of things. Recently the Indigo prop has gotten a lot of praise and I was about ready to leap in that direction until you mentioned how smooth the Campbell unit felt in comparison. I will try to contact them this week and see what they have for the Catalina 30 crowd.
Hanley, Question and comment: Is your A4 a 1:1 or a 2:1 motor? If you are happy with the "feel" of your current 13/13 prop, why not try having it downsized a little bit to increase your Rs.
Here we go, Tom

[hanleyclifford]

propped up

Tom - I sort of inherited the 13x13 and it has several trips to Florida under it's belt, but I want a few more rpm and I am intending to have the prop pitch lowered to 12 or maybe 11. But if I see the gang going for something better, I'll join up. I've been with the 2:1 group for quite a while now. Regards, Hanley

[thatch]

Hanley,
Thank's for the gearbox info. My Catalina 30 with a 1:1 trans has the factory 12X7-2 blade which leaves a lot to be desired. Although the hull speed at about 6.4 kts. at about 1800 RPM? (no tach yet) is bearable, I would really like to get rid of the "egg beater" feeling 2 blade and hopefully gain some reverse steering ability in the process. I wonder if there is anyone out there with a Campbell prop on a Catalina 30 who would care to give an opinion?
Tom

[Dave Neptune]

prop

Tom, the biggest reason I tried the Indigo was for the possibility that I could make my boat actually have some control in reverse. The ability to reverse was the most impressive of the positive characteristics, although the "egg-beater" prop wash was right there with it.

Dave Neptune

[sastanley]

C-30 data

Tom,

With a clean bottom & prop I could get 2,050 wide open on my Catalina 30. My cruising with my 12 x 7 prop was usually about 1,600 RPM. You can get the $30 Sunpro (or similar) tach at an auto parts store that will function perfectly well. Granted I'd like one of the nice ISSPro's mounted in my gauge pod, but at least I have a tach..the engine speed is a lot lower than I thought, but I think it is a good gauge to have.

In reverse, I didn't really have trouble. I learned long ago with my Stepdad's Tartan 3000 with a folding Martec was that you get it going and then throttle down and coast...The key is really to get enough speed for the water to reverse flow over the rudder & overtake the prop wash. Once you get going & throttle down, it's easy.

[thatch]

Shawn,
Thank's for the numbers on my twin boat. Since I have changed from tiller to wheel steering I will be building a new guage pack which will include a tach and vaccum guage. I'm having a little difficulty finding a recessed guage mount panel to cut into the lazerette area that is big enough for those units plus the other oil, water and electric pieces. Maybe someone knows of a source. I'll try to get some accurate performance numbers to add to our data bank before I make the prop change.
Tom

[Dave Neptune]

size

Tom, my vac guage is the 2 1/16" diameter S/W forom a parts house and doesn't take much space. I have mine mounted next to a "minnie" console that I added to the nav station. My boat has a tiller so as I am throtteling up I just look in the cabin. It works well for me there with a V-meter and the tach. I mounted them there as my engine is in the middle of the boat so when I am tinkering or even cursing a bit I have what I need next to the engine. The only thing I "watch" is the water temp and oil preassure which are mounted in the cockpit with the ampmeter~~simple. I do have a static oil preassre guage on the engine as well as a fuel preasser guage mounted just before the carb, having them there really makes diagnosing easy when something goes amiss.

Dave Neptune