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Atomic4/Indigo Prop
- Thread starter jkm
- Start date
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- Tags
- atomic4 or indigo prop
I used an Indigo prop on my E-27 with an Atomic 4, and absolutely loved it. I got it in stainless, so I can't speak to the anti-fouling version. As I went through repowering and hence reproping this past winter, I kept wishing that I could use an Indigo again, as it would have been a no-brainer. (was replacing a 2QM15 with a 3GM30 - Yanmars)
Joe Benedict
Member II
Bought an Indigo prop for my E29T. Works a lot better than the standard 2 blade. You actually have a reverse and generally more "bite" at slow speeds - takes a lot of the adventure out of docking. Max speed still about the same. CDI has also started making their Performance Props again. I believe there is an older post on this site about it. The cost/benefit for the upgrade is well worth it.
Three-blade vs Two-blade... compromises...
All engineering is really a study of compromises, though, truly, there's a lot of variables involved. I do NOT know whether the advice I heard is authoritative or not...
The Marine Architect who did my C&V survey, on seeing the two-blade prop, suggested that I mark the shaft in the two positions where the prop is vertically arranged, especially if I intend to do spend most of my time sailing-- or, as I call it, "on the rag"-- so that, on powering down, I can align the prop to be in the "shadow" of the keel.
Obviously this would only work with a two-bladed prop, and, truly, I wonder if the difference in drag (and, hence, speed) is measurable if you're not travelling more than 20-30 miles.
Heck, I suspect the slightest amount of hull fouling would render this difference moot.
I realize that the three-blade provides more "bite"-- it has to-- but does this come with more prop steer?
All engineering is really a study of compromises, though, truly, there's a lot of variables involved. I do NOT know whether the advice I heard is authoritative or not...
The Marine Architect who did my C&V survey, on seeing the two-blade prop, suggested that I mark the shaft in the two positions where the prop is vertically arranged, especially if I intend to do spend most of my time sailing-- or, as I call it, "on the rag"-- so that, on powering down, I can align the prop to be in the "shadow" of the keel.
Obviously this would only work with a two-bladed prop, and, truly, I wonder if the difference in drag (and, hence, speed) is measurable if you're not travelling more than 20-30 miles.
Heck, I suspect the slightest amount of hull fouling would render this difference moot.
I realize that the three-blade provides more "bite"-- it has to-- but does this come with more prop steer?
Joe Benedict
Member II
Maybe Penguin is back in the water and the issue is mute - but after spending the last 3 days on Lake Michigan here are some thoughts. It really depends how you want to use the boat. If getting in and out of a slip or traveling under power to the ocean are an issue, the prop needs to be upgraded. The "bite" does not increase prop walk but allows better steerage at slow speeds and a functional reverse. The prop actually appears to have less prop walk but this may have more to do with the increase in helm control.
Now for the 2 blade vs 3 blade. If you are a good enough sailor that this such a big issue - we need you desperately in the next Americas Cup Challenge. The Indigo prop has a smaller diameter than the original 2 blade so there may not be a big increase in drag - the prop is shaped differently and is just more efficient. A prop is designed to go through the water so once you hit about 5 knots and the prop starts spinning it is going to produce less drag anyway. Lining up the 2 blade with the keel will reduce drag but not elliminate it. In order to keep it lined up the gearbox needs to be engaged which will put additional on the bearings. The CDI prop is a 2 blade so this may be a better fit for a racer.
My suggestion is put the 3 blade on, tell the race committee and they will adjust your rating, and be ready to impress people with your docking skills.
Now for the 2 blade vs 3 blade. If you are a good enough sailor that this such a big issue - we need you desperately in the next Americas Cup Challenge. The Indigo prop has a smaller diameter than the original 2 blade so there may not be a big increase in drag - the prop is shaped differently and is just more efficient. A prop is designed to go through the water so once you hit about 5 knots and the prop starts spinning it is going to produce less drag anyway. Lining up the 2 blade with the keel will reduce drag but not elliminate it. In order to keep it lined up the gearbox needs to be engaged which will put additional on the bearings. The CDI prop is a 2 blade so this may be a better fit for a racer.
My suggestion is put the 3 blade on, tell the race committee and they will adjust your rating, and be ready to impress people with your docking skills.