Atomic Four Prop

[Laker]

Anyone have experience with this prop ? I like the theory , but it almost sounds too good to be true.
http://mysite.verizon.net/resqp86c/performancepropellers/id21.html

[ArtJ]

I have had a Indigo propeller for over 12 seasons with no problems.
Many people on this site have one and swear by it.

The propeller you mention sounds very similar to the one that
that cruising design had out. They mention that they are prone to shedding
propeller blades. I believe they are made of plastic. They also state
that you can hobble home with one blade. Personally, I would rather
have a prop that never sheds its blades. I always keep a zinc on
the prop and like the thrust that it provides when you really need it
in a nasty chop

Regards

Art

[Dave Neptune]

Laker, you ah Laker fan?:p
Yes I have had exoerience on 3 boats with them ande they work fine.
The down side of the break-away blades is that they aren't quite as strong as the bronze and they work fine.
The up side is that if you hit something hard with your prop you will unlikely bend the shaft or damage the transmission.
The neutral side is that with either one you will have a vibration issue if you strike something hard enough to part with a blade. Your call!!!

Personally I love my Indigo and won't go back to a 2 blade of any sort because of my boats performance characteristics in reverse.

Dave Neptune:cool:

[Laker]

Negative re Laker fan , not too much on basketball. I follow Packers football & golf.

So , the plastic blades are designed to break away on impact? It seems to me that impact chances are minimal given the configuration of sailboat hulls , especially if the prop shaft exits the trailing edge of the keel.

What caught my interest was the variable pitch characteristics , if that concept works as advertised.

Currently I am running a 13x8 Martec feathering prop. I took a chance on it a while back because it was well priced , but it is clearly too much wheel for my boat ; the engine is unable to wind out and I am doing nearly 3 knots at idle. I am considering a 12x8 2 blade fixed prop - very affordable , and I figure it HAS to outperform the Martec in reverse. I would be just as well off working over the side with a paddle as I am putting on the brakes with the Martec. My engine compartment would make it fairly easy to center the prop as to trail it in the shadow of the keel.

Comments welcome ,

Laker

[dvd]

Laker,

Its too bad that you dont have the correct sized martec folder as they work very well. Since they fold up when sailing they allow much less drag but do great when motoring. I just took my 30 foot Cal 3-30 on a 150+ mile cruise in all types of conditions and it performed excellent both while motoring and sailing. Before you purchase one of those break away props I would call Martec and just chat with them over the phone. It may be possible to re do your existing prop. My boat has a 2 to 1 drive and calls for a 16'' 10 pitch prop.

DVD

[Mark S]

Laker,

I second what Dave Neptune said.

I had a 13x8 two blade but I couldn't get above 1500 RPM. I switched last spring to an Indigo 3 blade which improved RPM to 1900 with slight sacrifice in top end speed, maybe .2 knots or so. I had thought about that Performance Prop but ultimately decided on the Indigo as more people on this site have it. I'm still not happy with the RPM, but I think my boat is at the limit of what an A4 can push.

Mark S

[Laker]

DVD - Having my Martec machined is an interesting proposition. I will look into that. However , even if that is possible , it would not address my poor ability to put on the brakes ; in fact it might make that factor worse as the blade shapes would remain the same but for reduced area.

I am thinking that the shape which allows the Martec blades to conform when folded is what compromises reverse thrust ... comments?

When I first aquired the Columbia 34 it carried a conventional 3 blade prop. I remember motoring out on a calm day to get to know my new boat ,(which seemed like an enormous ship) , and being rather pleased with the backing characteristics. I could sometimes back up into s-turns and circles if I "got ahead of the boat" with the rudder. Now I apply reverse , wait to see what happens , and react accordingly.
When it comes to stopping , well , I already made the paddle reference...

Mark S - your boat model and displacement is ? The Indigo design makes sense in terms of performance under power. It may be silly , given the big old barge I pilot , but I am still reluctant to drag a 3 blade prop while under sail. Anyone have any solid info on the drag generated by a fixed 3 blade vs a fixed 2 blade which is centered in line with the keel at rest?

Finally , is it reasonable for me to predict the a fixed 2 blade will out perform my Martec in reverse ? ( To keep this in perspective , if my Martec was compatible with my A-4 I would be inclined to continue to cope with the poor reverse performance. Since I need to make a change , I am sorting through the options...)

Laker

[Dave Neptune]

Laker, FYI reverse in these direct drive A-4's can be a bit problimatic due to the way it operates. There is actually a reduction from 1:1 in reverse it is something like 1.3:1 so YOU the operator need to rev her up quite a bit more for two reasons. One you need to spin the prop faster as they (any prop) are less efficient in reverse and the trans is "naturally" much noisier~:eek:~no problem! Two you have a bit more rpm's and power available due to the reduction and there is no locking into reverse as there is in forward (the detent), so you should hold the shifter to keep the band tight and limit the slippage. Learning this made a difference for me!;)
The three blade works better in reverse and is the biggest reason I went to the Indigo as I have a mooring on Catalina Island and it sits next to rocks and a kelp bed so when I need to manuver I need to manuver. The Indigo is suprisingly small and the blades are a bit narrow, it has less drag than the 2 blade I removed and works far better in forward. It also will almost completely eleviate the rudder wobble caused by the 2 blade as well. It made a huge improvement on my ole E-35MkII.

Dave Neptune:cool:

[ArtJ]

Check out the comments that Tom Stevens has assembled on his
website atomic4.com regarding comparison of 3 and 2 blade props.

Regards

Art

[wlevin]

This topic seems to come up as often as overheating issues. I suppose it is because prop type and sizing is critical to getting performance out of our engines, especially when they are near the top of their capacity to push a boat, such as a 35 foot, deep keel cruising sailboat. The wrong prop can be a disaster. Low revs and nothing in reserve in a headwind being the worst consequences.
We have used both the Indigo 3 blade and the plastic CDI prop you asked about on our Tartan 34 and like both. I think the performance is quite close between the two, with the Indigo getting the nod for better performance in reverse. However, the CDI is on our boat and the Indigo is the backup because we sail so much more than we motor, and I find the CDI has less drag because we can line it up with the deadwood and sail with less drag.
That's all.
Bill and Jeanne
T34C #453
Otter

[Mark S]

Following is a picture of our new Indigo on our new shaft at the beginning of the sailing season and two pictures of the same today after hauling out. We did not use a zinc due to yard reasons not pertinent here. We moor out in the harbor, not in a slip. I examined the propeller and shaft closely since hauling out and I see no evidence of adverse galvanic action. Nevertheless, I will use a zinc nut next season.

Mark

[ArtJ]

I have a stainless steel Indigo prop on a bronze shaft on my Tartan 34C.
I have always used a sacrificial zinc, but am curious what the result would
be if I went zinc less.

Regards

Art

[Laker]

How important is/are the use of zinc(s) in fresh water? I have none , and have observed no problems. However , I have seen sacrificials on a lot of boats hereabouts.

Laker

[hanleyclifford]

Regarding the use of zincs in fresh water, I have done some crude testing which indicates that although in theory fresh water (pure H20) is not an electrolyte, and thus will not support a galvanic cell, in practice all environments in which boats travel have some conductive ions which support a cell. However, the effect is greatly reduced and if I were in "fresh" water I would run with no zinc and make continuous observations. The advantages of running with no zinc include greatly reduced attraction of barnacles. Since Art has a stainless prop on bronze shaft he should stick with the zincs in salt water. But why not go with a stainless shaft for the real Cadillac set up?

[ghaegele]

I have the Indigo on my C&C 35. I feel that I am at the end range of power for my boat. When powering into a stiff wind and significant sea my engine can barely push the boat--2 - 3 knots. In calm seas I get almost 6 kts at 2000 RPM. Any thoughts on whether a larger prop might get me more drive in wind and sea?

[ArtJ]

My Tartan 34c is 34.5 feet and 11,500 lbs . The Indigo is able to push
the boat at least 5 knots in a nasty chop when running rpm at
2200 to 2400 rpm.

What rpm are you able to achieve? Maybe the distributor may need
to be turned. Is the bottom clean?

[ghaegele]

I've tuned the distributor to maximum RPM at cruising speed and can get about 2200 max. The boat gets hauled every year and the bottom never gets very bad. I like the Indigo but sometimes feel like I got better drive from a larger diameter two-blade that I had on years ago. But that could just be a selective memory.

Art, I'd say your Tartan is close in specs to my C&C. (Actually, I have 35.5 feet and 13,800 displacement. But that's not a huge difference) Five knots in a chop, maybe. But not in wind and sea. I sail in the LI Sound where we often get more than a chop. I might be expecting too much from my engine, but I feel like going to power is just not an option when I am heading into significant wind and sea.

[ArtJ]

I just took a look at the Michigan propeller that was on the Tartan when
I bought it I believe it was a 12 X9 . I was able to get 6 knots
in calm seas at 1700 rpm. But the boat would lug in a steep short chop.
and only do around 3 knots.
I changed both pitch and diameter, reducing both. The current diameter
is around 10 inches. It made little difference in rpm.

I then went to the Indigo.

I have sailed Buzzards bay often, including Long Island sound.
Even in rough seas off woods hole I could do 5 knots with the Indigo.

If you are talking about heading into significant seas with a lot of current
against you, you may be losing headway due to current. There is always
some conditions which will try any combination.

Tom Stevens experimented with the propeller on his Tartan 34C
and found the best thrust combination was with the current design.
I know that he has made some minor improvements to the prop.
You might want to check with him at Indigo and see if your prop
has the latest "twists". Tom upgraded my prop at no charge.
I doubt that this would solve your issue. I think you should
speak to Tom Stevens because a larger diameter prop will give
you less thrust, not more.

Regards,

Art

[ghaegele]

My prop is probably more than 10 years old. I think I will give Indigo a call and see if he has any suggestions. (And no, Art, I'm not talking about heading into current. That's silly.)

[Mark S]

Art,

Do you have direct drive or reduced drive? My boat is 35 feet and weighs 13,000 lbs. and I can't get above 1900 rpm with a direct driven Indigo. With the previous 13x8 I couldn't get above 1500 rpm. I'm beginning to think that the direct drive A4 is simply not strong enough to push boats this size.

Mark

[ArtJ]

I have a direct drive. If your engine is in reasonable shape the
timing can be set to produce 2400, or close as possible.
Note it must be set
at the rpm you desire in order to achieve the max or near max rpm.
This is set by running your boat flat out open in forward, or as close as possible and then turning the distributor for max rpm.
You may wish a compromise between flat out and your usual cruise
speed rpm.

[ghaegele]

I agree that we're underpowered. I set it at my cruising speed, which is just about 2100 RPM. I rebuilt my engine (direct drive also) two years ago and have under 100 hrs on it. Still I don't get much beyond 2200 RMP. (Perhaps its still breaking in?) I have played with the timing and don't think that I'm going to get much more RPM by adjusting it at full-out.

[ArtJ]

I should add the Tartan 34C, Intrepid inspired design, has only a 10 ft 4 inch
approx. beam which may make it easier to push to weather than a beamier
12 foot plus vessel.

[ArtJ]

I agree that we're underpowered. I set it at my cruising speed, which is just about 2100 RPM. I rebuilt my engine (direct drive also) two years ago and have under 100 hrs on it. Still I don't get much beyond 2200 RMP. (Perhaps its still breaking in?) I have played with the timing and don't think that I'm going to get much more RPM by adjusting it at full-out.

IF you are getting 2200 rpm and the bottom and prop are clean, you are
getting most of what the atomic 4 can produce for horsepower, the other
200 rpm won't change things that much.

[ArtJ]

When the going gets really tough, I tend to "tack" upwind, allowing the
sail (if hoisted) to assist the engine rather than take it totally on the nose.

[Mark S]

This is set by running your boat flat out open in forward, or as close as possible and then turning the distributor for max rpm.


You mean to advance the throttle beyond where the engine's current max rpm are achieved and then set the timing, noting whether the engine speed increases or decreases? You know, I've never fiddled with the timing. I've simply assumed that it was correctly timed by the people who maintained it for the prior owner. This will be a good experiment for next spring.

Mark

[ArtJ]

You mean to advance the throttle beyond where the engine's current max rpm are achieved and then set the timing, noting whether the engine speed increases or decreases? You know, I've never fiddled with the timing. I've simply assumed that it was correctly timed by the people who maintained it for the prior owner. This will be a good experiment for next spring.

Mark

Make relatively small changes, noting the previous position in case you wish
to back out. Do not make drastic changes, i.e. changes more than 1 inch
in either direction would be drastic. If the engine stalls. backfires, or pings
excessively, you know to back off a little.

[ArtJ]

You don't need to set the throttle beyond the point of max rpm, just
play with timing to get more rpm for that throttle setting.

[sastanley]

When the going gets really tough, I tend to "tack" upwind, allowing the
sail (if hoisted) to assist the engine rather than take it totally on the nose.

Bingo!!!

Art, thanks for mentioning this...it is key. Going straight into it is always slow..A displacement boat will always make better time sailing around the waves...Even a deeply reefed mainsail will help in these conditions. You don't have to go real far off..If motor sailing, pull the traveler up to windward and the mainsail will often fill and draw at as little as 10 degrees apparent.

[smaarch]

just a quick question: do you folks have tachometers on your boats?
i have no idea what rpm we are turning....so maybe this is a good idea.

[hanleyclifford]

Tachometers are a great idea. I would be lost without mine. Check out the MM online catalogue for tachs.

[sastanley]

smaarch, I agree with Hanley.

If you want to do it right, get a nice tach from Moyer...I cheaped out and bought a $30 Sun-pro tach from Autozone. One of my first posts here at the Moyer Forum was about hooking up a tach. SIMPLE!

It is really enlightening, and is one more tool to help you with the motor.

[Dave Neptune]

ghaegele, I too am pushing 35 ft @ 14,600 lbs towing a ten foot rowing lapstrake dinghy through the water with a 40 year old motor. My engine is in good tune however it is getting a bit tired. I am very happy with my Indigo and it works better than any of the 4 two blades I tried. Some would match the speed but the engine wasn't as happy lugging so much at 1600~1700 rpm max. Noe I get the same speed but I can get 2300 when I need it. I cruise between (7.5" ~ 10" of manifold vac)1800~2000 rpm and get about 6 kts in calm water and about 4.5~5 into a stiff 15~18 kt breeze, a bit slower if the waves are big. I motor across the Catalina channel 12~15 mornings a season and it is into the wind or waves all the way.
I have played with the carb and use an electronic ignition with a standard coil. Since going to the Indigo prop I have gone back to the RJ8C plugs and gained 150 rpm in doing so:rolleyes:.

Dave Neptune:cool:

[hanleyclifford]

A couple of notes on the earlier discussion of zincs with the Indigo prop. A check of the galvanic charts show that silicon bronze is the most noble of the bronze alloys, very near the stainless steel; this is why you can get away with not using a zinc. However, the website does state that the prop is good for about six seasons if used in this manner. I would not consider that acceptable for a quality prop. I don't mind scraping the prop once in a while.

[sastanley]

hanley,

I am still seeing good performance after using 1792 Pettit Zinc spray on my prop & shaft. My top speed with a fresh bottom in early July was about 5.8-5.9 @ 2,100 RPM, wide open.

Now in November, I am slightly slower, 5.4-5.5 (the bottom is fuzzy now) but I can still get about 2,050 RPM max.

Last year, after just a few weeks in the water, I could tell the boat was much slower with even just the beginnings of a few tiny barnacles on the prop...I don't recall the exact numbers, but the engine could not spin anywhere near 2,000 RPM.

In summary, I would not spend several hundred $$ on a prop either just to let it slowly get eaten away thru galvanic corrosion to avoid barnacles...I am extremely pleased with the Pettit paint & it seems to do a decent job of at least keeping barnacles off the prop to let our little A-4 spin freely, even after four months. Maybe it is possible to have the best of both worlds! :cool:

edit - just to make sure there is no confusion, I have a regular zinc on the prop shaft for the galvanic corrosion issue..the 1792 paint is almost like a cold galvanizing spray, hence the "zinc spray", and is designed as an anti-fouling paint. They advertise that the once the propellant evaporates that the product on the prop & shaft is 93% zinc.

[wlevin]

Picking up on ArtJ's comment, when we face heavy headwinds and the short, steep chop (3-6 foot) on Buzzards Bay we motorsail upwind. On our T-34C that means a reef in the main and NO genoa. We also pull the main traveler upwind and run the motor at about 1500 rpm. These settings are very specific to this boat. Previous boats have liked different combinations. When we get it right we get quite close to the eye of the wind, travel about 4 steady knots and the motion of the boat is MUCH easier than if we tried to motor directly into the waves and wind at 2200-2400 rpm. At those rpm's the motor sounds unhappy, and that makes my wife unhappy which, in turn.... Also, no amount of rpm's on our boat will prevent our repeatedly getting knocked down to nearly zero progress by a particularly nasty set of steep seas that come close together.
I contend that we get where we are going faster and are more comfortable motorsailing this way, even if we have to tack.
Bill and Jeanne
T-34C #453
Otter

[Mark S]

When the going gets really tough, I tend to "tack" upwind, allowing the sail (if hoisted) to assist the engine rather than take it totally on the nose.

Tacking in this manner not only avoids resistence directly on the nose, it also lengthens the traveled distance between swells and waves which further reduces resistence and makes travel smoother.

A couple of notes on the earlier discussion of zincs with the Indigo prop. A check of the galvanic charts show that silicon bronze is the most noble of the bronze alloys, very near the stainless steel; this is why you can get away with not using a zinc. However, the website does state that the prop is good for about six seasons if used in this manner. I would not consider that acceptable for a quality prop. I don't mind scraping the prop once in a while.

Agreed. We opted to have the yard contractor install our new shaft, cutlass bearing and Indigo so we could get into the water faster. My schedule did not permit me to do the project myself. He was supposed to supply a zinc and for whatever reason did not and we got launched before I had a chance to complain. I figured one season without a zinc wouldn't be too harmful, although I did formulate what I would write to Tom at Indigo if we wound up with a dissolved prop!

The photos I posted earlier in this post were taken after the post haul-out power wash. I assume there was no growth, but I don't really know.

Mark

[ArtJ]

Picking up on ArtJ's comment, when we face heavy headwinds and the short, steep chop (3-6 foot) on Buzzards Bay we motorsail upwind. On our T-34C that means a reef in the main and NO genoa. We also pull the main traveler upwind and run the motor at about 1500 rpm. These settings are very specific to this boat. Previous boats have liked different combinations. When we get it right we get quite close to the eye of the wind, travel about 4 steady knots and the motion of the boat is MUCH easier than if we tried to motor directly into the waves and wind at 2200-2400 rpm. At those rpm's the motor sounds unhappy, and that makes my wife unhappy which, in turn.... Also, no amount of rpm's on our boat will prevent our repeatedly getting knocked down to nearly zero progress by a particularly nasty set of steep seas that come close together.
I contend that we get where we are going faster and are more comfortable motorsailing this way, even if we have to tack.
Bill and Jeanne
T-34C #453
Otter
In the 13 season I have owned my T34C I have never had reason to
reef the 12 ft boom based main. I have pulled in down occasionally when a very
nasty squall has loomed though. Usually I just pull in the Genoa and
go with the unreefed main. My sails are Neil Pride cruise plus heavy duty
Regards,

Art

[dcneuro]

For wht it's worth, I looked at both the performance prop and the indigo prop all season and have decided on the indigo, which I will be installing on my Bristol 32 this spring before launch.

[hanleyclifford]

Hey Laker - Speaking of getting upwind: the word is that the Patriots will defeat the Packers in the Superbowl this year.

[Laker]

Green Bay has lost several offensive linemen , the top WR , the running back , and roughly half of the starting defence to injury. The practice squad defensive subs have worked miracles in the last 2 games (shut out the Jets 9 to 0 !) , but I doubt that you will get the chance to see your prediction play out.

I hope I'm wrong.

Laker