VarioProfile Propeller

[dedgell]

I have just installed a VariProfile feathering propeller on Blue Wing, our 2007 Catalina 350.

http://www.varipropusa.com/en/variprofile.html

Our boat was originally shipped with the "new" 14X9 three bladed propeller. Based on what I learned elsewhere on this forum, the 14X9 prop was designed to cure a cavitation problem. I never experienced any cavitation, but I was not completely happy with the performance under power either. Since the 350s abundant storage allows us to bring along all the comforts of home, we typically sail and cruise heavily loaded. Under power the boat seemed to max out at 6 knots irregardless of RPM. I've always felt that we could do somewhat better.

Another motivation for the change was potential improved performance under sail. We do a lot of day sailing as well as cruising on the Chesapeake Bay. Often the winds are light. I've often wondered how much drag the fixed 3 bladed prop created, and if we could sail faster and higher without the drag, especially in very light winds.

So my winter project was to research and select a new prop. The Admiral (my wife) left the decision up to me, as she is responsible for much more serious concerns - like where we are going to sail to next. I have read (probably) every post on this forum that has to do with prop size, pitch, and type. Thank you to everyone who has posted their experiences over the years. The breadth and depth of the commentary on this site helped me immensely as I learned about the options and made my decision. I also spoke with representatives of most of the major propeller manufacturers before making my decision.

I've not come across any other 350 owners who have installed a VariProfile prop, so you are all probably wondering how I came to the decision to purchase and install one. It was not easy because there are so many options and variables.

My first decision point was whether to get a feathering or folding propeller. Both have their merits. Folding props provide less drag under sail, and appear - at least to me - to require less maintenance. Feathering props have more drag under sail, but a benefit to most is that the pitch can be adjusted to fine tune the prop to a particular boat. Another benefit is the reverse pitch on most can be set independently of the forward pitch. This in theory allows for a more aggressive pitch in reverse, improving performance in reverse. Some say prop walk is decreased as well.

After much internal deliberation, I decided on a feathering prop. Since we don't race, the adjustable pitch and improved reverse were more important to me than the decreased drag of a folding prop.

Then it came down to which feathering prop. There are numerous options. I narrowed the field down to the Kiwi, the MaxProp, the VariProp and the VariProfile. I also considered the Autoprop. There are many posts on this forum about the Kiwi Prop. This prop is the least expensive of the feathering props (about $1500) and comes with composite blades which are unique to this propeller. To me, the cost was compelling but I could not get over my questions and concerns about the composite blades. I know that others have had great success with them, but I chose to focus on the metal props.

The Autoprop is interesting as it continuously varies the pitch based on conditions and load, etc. That sounds good, but in the end I was concerned about the complexity of the mechanism. I mean, just how does the prop know what pitch to pick? I think I have read at least one post from a 350 owner with one who swears by it, so it is probably a good choice. It was just not the one that I made.

It was then down to Max Prop, the the two Vari props. The cost of all three was roughly the same ($2500 +/-). The Vari props are both made by SPW, a German company. I've sailed many offshore miles on a friend's Island Packet 420 equipped with a VariProp. The propeller is incredibly well made and durable, and performs very well on an admittedly very different boat. Based on my experience with that prop, I decided to go with one of the SPW propellers.

The VariProp and the VariProfile are quite different designs. The VariProp is promoted as best for traditional full keel boats with small openings between keel and rudder. The hub is very large as it houses the prop nut and feathering mechanism. The overall length of the prop is not much different from a fixed prop, making it great for tight spaces.

This would not be ideal for a C350 as I learned from posts on this forum. Some attribute the cavitation problem with the original 15X10 props to the short distance between the "deadwood" (aka short skeg where the shaft exits the hull) and the prop itself. One of the benefits to adding a folding or feathering prop is that most designs move the prop itself several more inches away from the the deadwood.

The VariProfile became the prop of choice. It is designed as two pieces. There is a hub that mounts on the shaft with a new shaft nut, which is supplied. Then the prop including the feathering mechanism is bolted to the hub. The result is a very streamlined looking prop that is, I estimate, about 4 inches farther from the deadwood than the old fixed prop.

I ordered the prop from AB Marine in RI, which is the US distributor for SPW. They were very professional and responsive throughout the transaction and the install.

http://ab-marine.com/

The props are semi-custom made in Germany based on the specifications selected. AB and SPW recommended a 15X10 VariProfile, so that is what I ordered. This sounded right, especially since the original prop Catalina specified for the 350 was a 15X10 fixed prop. Of course, the pitch of the VariProfile is adjustable if I find I need to.

I installed the propeller myself with the help of a friend with a strong back and a torque wrench. This was a very interesting process in and of itself, which deserves another post or Mainsheet article.

This is why and how I made the decision that I did. I have no idea if the propeller improves motoring or sailing performance, or if it even works. The boat was just lanched Friday, and I've not had a chance to do any testing. I will follow up in a few weeks with my impressions of performance. I'm not an engineer, and I did not do any "before" tests with the old prop to compare it to. But I've sailed and motored the boat for the past 8 years in a wide variety of conditions, so I'll at least have some good observations to share.

Happy sailing and motoring,

David Edgell
s/v Blue Wing
C350 #442
Rock Hall, MD (Middle Chesapeake Bay)

[wolfe10]

David,

Nice write-up.

Pretty easy to tell of the prop is proper pitch:

With a clean bottom, you should be able to get within 100 or so RPM of governed RPM in gear. If it won't get that high, the prop is to big/too much pitch. It is quickly goes there and then as you build speed goes to governed RPM, it is too small/too little pitch.

Not familiar with the adjustments for your prop, but this may help you to fine tune it.

Brett
2004 350

[dedgell]

Brett,

Thanks for the advice on pitch. I will definitely take advantage of that technique when I do my sea trials, which could be as early as next weekend weather permitting.

The adjustments on the prop are in the form of two Allen screws on the prop, one for forward and one for reverse. The prop shipped set to the 10 pitch, or so I'm told. Hopefully this is close to where it needs to be. I think it is recommended that the boat be out of the water to make the adjustment. Ideally I will be able to live with it until I do a short haul mid-season.

Thanks again,

David Edgell
Blue Wing

[dedgell]

We had our first "sea trial" with the new prop two weekends ago. My first impressions are very positive.

The boat was loaded with full water, fuel and regular gear. We went out on a day with light winds, between 4 and 8 knots from the NW.

Under power the engine ran notably smoother with less vibration. I typically cruise at 2650 rpm as that seemed to be the sweet spot with the old prop. With the old prop the boat would struggle to maintain 6 knots under power, and any adverse tide or current would have it drop back to 5.6 - 5.8. All speeds are GPS SOG, as our knot log is not hooked up.

With the new prop, the boat powered at 6.8 knots at the same 2650 rpm. It confidently reached this speed both with and against the tide. Engine temp was normal, just below 160.

I did a full speed test and the boat reached 7.4 knots at an indicated 3300 rpm. I quickly backed off, as I know the engine is not supposed to turn this high. I've never had the tach checked for accuracy, so I don't know if it was actually turning that high.

It was a beautiful spring day, so of course we put up the sails and sailed for about 2 hours. In these winds, especially under 5 knots, the boat used to be difficult to sail and would loose steerage as the wind dropped below 4 knots. That day we noticed no such sluggishness. The boat sailed very well, and we were surprised that we made so much distance in such light winds during our day sail. We sailed upwind up the channel to the creek that leads to our marina. From this wind direction, we would have ordinarily made several tacks or given up and powered in. On that day we pointed right up the channel and took the sails in at the creek entrance. I didn't say anything to my wife about how much better I thought the boat sailed. In the car on the way home she commented, unsolicited, that the boat sailed better and pointed higher. So I call that a positive result, at least in light winds.

Backing into the slip, there was a noticable lack of prop walk. I've become so accustomed to the prop walk that it actually took me two tries to back into the slip as I was not used to backing straight. There was more thrust in reverse too. I noticed no delay in shifting from forward to reverse.

So for right now I'm happy with the change. I'm sure I will have more reflections after using the boat for the summer. I don't know if the VariProfile is the best prop you can get for a C350. But I do think that it delivers on the advantages that are advertised for feathering props in general.

David Edgell
S/v Blue Wing

[william vanwagoner]

David,

I would be interested to know how your experience with your new prop is progressing. Also, can you tell me what engine you have, is it the Universal M35b?

Thanks,
Bill

[dedgell]

Bill,

Thanks for asking, I was thinking about posting an update. And yes, I do have the Universal M35.

I am still very happy with the prop, and the decision to change to a feathering prop in general. Under power the boat is consistently .5 to .75 knots faster. And this is cruising at 200 RPMs less than I did before with the old prop. Power in reverse is also much better, and prop walk is reduced (but not to zero).

The biggest surprise to me is the improved performance under sail. I would say that the boat is between .25 and .5 knots faster under sail, but that is only part of the story. The boat will now sail well in very light winds of less than 10 knots, which we have a lot of in the Chesapeake during the summer. The boat now also points noticably higher. So we are sailing more and under diesel power less.

I'm probably going to adjust the pitch this winter while the boat is out to try to get the max RPMs close to 3000. As you will note from my earlier post, the engine will spin faster than that with the new prop indicating the need to adjust it. Of course, I picked feathering over folding for the ability to adjust.

All of the benefits I've described above are probably true for most if not all of the folding and feathering prop options. It is well worth the investment, in my opinion, no matter which one you choose. I've very happy with the VariProfile specifically, and would recommend it if you are considering.

Happy sailing,

David Edgell
S/v Blue Wing