Anybody familiar with the Slipstream folding prop?

I am considering this prop. It is stainless and is reported to be an extremely smooth prop under power and very efficient. Also very good for racing of course. Any thoughts?

I've done the deed.. and it is on order. I mainly cruise but also do some club racing. I am moving from an older model Martec 15" 3 blade feathering prop to the new stainless 2 blade prop. My engine, replaced by former owner, is a Universal M35 4 cyl 30 hp engine - on my E34 1987 boat. After extensive research and actual testing of the reduction ration I found it was 1.8:1 not what is commonly assumed for the HWB 100-2 model. (Everyone should be aware of this... I understand that later similar Universal models had a 2:1 transmission). So I am getting the advise of the prop dealer and getting a 15x9 prop. Will keep you posted about power, sound, vibration, and sailing speed. Hope to race in early Dec.

Sailingdeacon, I would be interested in any comparisons you can make between the new folding prop and the former feathering prop in terms of speed and boat handling, especially in reverse.
Thx.
Frank

The prop is installed. Here are my notes strictly motoring (a M35 Universal 1: 1.8 transmission. Will get back on sailing later.

Just before changing from the 3 blade feathering: At 2250-2300 rpm, 6.3-6.4 kts on knotmeter with light wind - some vibration at higher rpms. (knotmeter readings - checked with gps but varies slightly due to slight current)

Boat had 8 months of hard bottom. After hauling, I lightly sanded much of the bottom with a palm sander using 100 or 120 grit (very hard paint). The area above the water line was very hard, sanded but still had some orange peel. Remainder sanded but not glass smooth at all. Some pitting (due to previous hard water cleaning) were filled with epoxy and those areas painted with ablative.

A 3.5" Prop cutter was removed… possibly was aslow down, but unlikely. (I'm willing to sell this)

Installed Slipstream folding 2 blade

Idle = 3.6 kts, much faster
1700rpms = 6 kts
2200 rpms =6.6 kts
2250-2300 rpm, 6.8-6.9 kts on knotmeter with light wind; very little to no vibration
Max rpm under load 2950-3000 = 7.1 kts; no smoke

So about a half knot increase at old 2250 typical rpms and 2200 rpms. 1 knt or faster at 1700 rpms.

Definitely has a rather hard pull to port at over 2100 rpms. More than with the other prop. Reverse is completely adequate. I have no problems with that.

So far I am very pleased with this prop. It pushes the boat much better that the 3 blade feathering and is smoother.

A key point is that one step in the written instructions were extremely confusing and could lead to problems. The company is rewording that step. I can explain if anyone is interested.

Sailingdeacon,
Can I ask what the Slipstream costs? Ballpark? Trying to decide between that and Kiwi. Thanks, RT

About a 1000 + for a 15" prop. Because of the design they usually recommend a smaller prop and/or pitch that the usual folding prop. Try West By North in Canada and also Martec in Ca. The Canadian guy is my favorite from years past and I got a better price even after the dollar exchange. Both have web sites. ALso google for the Australian manufacturer. The Aussies are super with things like this. A key for this prop is that the blades are not flat and the edges are entirely different from typical folding props.

experience with the slipstream

Now that I have had time to use the Slipstream prop for an extended power run of 6 days, I should add a few other comments - in addition to those glowing comments posted earlier. I am very satisfied with it except for one thing: The power is so strong that there is a significant pull to port at 6 kts and above. At 6.5 for extended times while sitting, I put my foot in the lower right quadrent of the wheel for weight to give it balance as I steer.

I have been in extended conversation with the mfg. They felt for sure that it had to be a hull or rudder problem, but after running at full speed, then cutting the engine, the wheel does not turn. So there appears to be something they are not aware of. We are still in discussion.

Do any of you with a traditional 2 blade folding prop have this problem?

Do not have that problem with my feathering 2 blade max prop. One thing I noticed in your posts was the max rpm number. Seemed a little high as IIRC the engine manufacturer reccomends 2900 as max but maybe your new motor is different? If it is in fact 2900 you may be slightly under pitched but probably not enough to go to the trouble of swaping props. Can you set the pitch on the slipstream? Also you want to make sure your tach is calibrated before doing any conclusive testing at various rpms.

Is this the prop in question?

Loren

The engine is a Universal M35 4 cyl at 3200 max rpm. 1:1.81 transmission.

Loren, yes that is the prop in the photo you submitted.

Tac was calibrated.

I've been in continuous conversation with Seahawk Australia Pty Ltd to try to figure out the problem. Lots of photos, even a movie of the effect. I've tested it at full power, then coast and the boat tracks with no pull or turning with the rudder straight. They are very helpful and have asked all the questions you would expect about shaft alignment, rudder alignment, etc. They have responses from their sources all over attempting to explain the effect of two blades versus 3 with a balanced rudder. Martec of California offered probably the best analysis "It seems that when moving the axis aft even a few inches it sometimes has a profound effect on the prop wash against the rudder. Most likely it's the product of greater thrust created by the Slipstream (high efficiency blades), and it seems to become more exaggerated in some cases. But , again it is just something we hear about from time to time."

Until I haul out and show by photos that the alignment of everything is good I really cant prove it. And of course any misalignment would cause problems... even though the previous 3 blade feathering prop did not cause a problem. Yet that prop did not push nearly as well either.

So.... folks, have any of you had any strong push to one side or the other under forward power with your Ericsons? Or noticed this when going to any version of a 2 blade prop. I have heard there was a Catalina design that had that problem.

We've got a pretty significant propwalk with our Martec 2 blade folder in reverse at low RPM's... It's great for practice turning the boat on a dime. But we've never had any issues with the prop in fwd.

Forward propwalk or pull would really make me nervous about what I was doing to everything connected to the prop forward all the way to the tranny. That can't be good long term.

I'm not a prop expert, but could that be just too much pitch?

Chris

I have a somewhat similar experience that would jive with it being prop-wash from the greater thrust. On my E-27 I installed an Indigo prop as part of repowering. The boat originally had an A4, when bought had an outboard, and I put an A4 back in. I selected the Indigo prop and absolutely loved it, but the one thing I did have was a fair amount of what I'll call torque steer when cranked up. I attributed this to the prop-wash. The Indigo prop has a lot of thrust based on other props I've experienced, and had no problems sustaining 6+ knots dead into 20+ wind with 2-3 foot chop (what we get on the Chesapeake if it's not flat). I have a friend with an E-27 and a YSB8 - little 8hp Yanmar and a three blade prop. He does not even begin to have the torque steer that I had with the A4 and the Indigo. He also doesn't even begin to have the thrust I had. I came away from this with the feeling that if you mount a high thrust prop in front of a hanging rudder, you're going to get torque steer from the prop-wash. Do you have any ability to shorten your prop shaft and increase the distance between the blades and the rudder. You don't want a bunch of shaft on the aft side of the strut anyway, and I've seen many boats with too much shaft hanging out the back of the strut. Perhaps increasing that distance, if it's an option, will help alleviate some of your affect. Do look at your hull to tip clearance when shortening the shaft. I'd have to double check my notes, but I believe on a sailboat you want no less than 10%, and really 15% (of diameter) tip clearance between the blades and the hull.

Emerald, that is very helpful. I feel my new thrust will be similar to your experience. It is just unbelievably powerful. I'll be in the Pamlico Sound soon and will know for sure about powering through a similar chop, but I suspect it will just like your situation. My feeling is that if the prop is that powerful there probably is going to be prop-wash like you describe.

A key question to you: Is your Indigo prop a three blader? The company has suggested that the 3 blade folding prop which they sell would not cause nearly as bad a problem. I might be able to work something out with them. But if your 3 blader also had the problem.....

By the way the attached photos show there is little room for moving the prop forward. Also everyone should consider that I have an unusually large 4 cyl Universal M35 30 HP engine. Typically the boat had something like a 25 or less HP engine. So the prop will almost hit its rated high rpm's under load. 2950 vs 3200. So if may be slightly over pitched, but even if I reduce the pitch once the boat speed got to a higher speed I think the prop problem would still be there.

Hi,

The Indigo is indeed a three blader. I should clarify that I long ago sold the E-27 when I bought my current 31. I believe the current owner still checks in on this board - are you out there hcpookie? Anything to add to my experiences?

Looking at your pictures, you don't have any meaningful room to move your prop forward. When I repowered Emerald from the 2QM15 to the 3GM30, I had about 4 inches of extra shaft I was able to lop off. Do note that Emerald has somewhat of a skeg in front of the rudder, so it's not a good comparison on the hanging spade type rudders. Here's a link to a picture just for reference:

http://home.comcast.net/~independence31/misc/onland2c.jpg

My local marine mechanic whom I trust in about all these issues feels that a reduction to the diameter just might work. The company has mentioned an upgrade to their 3 blade folding but I'm not sure we can work out a price agreement. My mechanic feels I am borderline on the 250 rpms off the max of 3200 - he would rather it be no more than 200. And thinks a diameter reduction would be better than a pitch reduction. I'm still talking to the prop mfg in Australia. Your suggestions are welcomed.

We took the boat out for an overnight trip and I continue to have an overall very positive opinion about the prop. My usual cruising preferred speed of 6-6.2 kts is around at 1800 rpms whereas it was originally around 2100 rpms or a bit more.. I definitely like the lower fuel use at lower rpms and less engine noise. The prop wash is a slight nuisance at this speed, and becomes an irritant at higher rpms. - but I do love the knowledge that I can power through bad weather if needed, regardless of prop wash !! Sure do not want to give that up.

The manufacturer has been more extremely helpful and interested. He has suggested a few things that might help. Our approach right now is to swap the blades for a 1" reduction in pitch which has a good potential to address the problem as will as get the rpms up to spec.

The nice thing about this type of prop is that it takes only an easy blade change without removing the core to the shaft. It has a really good design for blade attachment, including a special pad to reduce clunking when going in gear.

Will get back later this summer.Will be racing this weekend.

After extensive emails with the manufacturer we agreed to replace just the blades and reduce the pitch by 1". They have been extremely helpful and eager to resolve this. Since the max rpm's is slightly low (marginal says my mechanic - even though there is no smoke with this 30 HP engine) this change should fix that, and they feel this should resolve most if not all the concerns. In general I am highly satisfied with the prop - with the pulling to port at over 6 knots the only drawback. Based on their experiences with past sales, my situation appears unique.

One more question please. Have any of your experienced the problem of the boat (preferably the 87 E34) pulling left or right under high speed forward power while using a two blade prop?