2020. 2. 16. 11:25ㆍ카테고리 없음
- Martec Folding Prop Installation On 1997 Free
- Martec Folding Prop Installation On 1997 Trailer
- Martec Folding Prop Installation On 1997 For Sale
Over the years we’ve worked with Martec folding props, Max Prop feathering wheels, Hundested controllable pitch props, and Gori folders. None of these unconventional (in power boat terms) props have good engineering data.
Specifying the correct prop of this type is very much a black art based on experience (for a more detailed look at this subject see Offshore Cruising Encyclopedia).When we began work on Wind Horse propeller design was high on our agenda. We talked to lots of experts, consulted our various suites of software, and interviewed propeller manufacturers around the world.Our goals were simple: quiet and efficient operation.We ended up going with Henley in New Zealand, using very expensive five-bladed wheels of a new design which were supposed to be highly efficient for our type of application. These were very quiet – dead silent in fact. But as good as our performance has looked, we were not hitting our design targets in terms of speed at various RPM or fuel consumption.This could have been due to being overweight. But we know from measurement marks on the hull and from actual load cell weights prior to launch, that we are exactly on our design displacement. That left our drag calculations – confirmed by tank testing, as well as our two suites of velocity prediction software – or the prop design. Naturally we preferred to believe the latter!We were not comfortable with the feedback we were getting from Henley’s in New Zealand – they were defensive about their recommendation – so we decided to get some real world experience with the boat and then address prop design and efficiency when we got back to the States.This process began by contacting Don McPherson at Hydrocomp.
We use Don’s software and have asked him to consult on projects in the past. Don wanted us to set the boat up in our normal mode – for us that means full load – and then run a series of tests in smooth water, with calm winds. We needed to accurately measure speed and fuel consumption at a variety of RPMs.We made a series of two-hour runs at 1600, 2000, and 2400 RPMs in calm conditions.
Each of these was done one hour out and one hour back, with our navigation software logging GPS speed every ten minutes. These speeds were then averaged to take out any anomalies due to current.
Runs were started and ended inside of the Marina del Rey, CA breakwater. At the end of each run we refilled the day tank in the engine room to the fuel level at which we began the run, giving us a very accurate fuel consumption figure to be averaged over the two hours.We also made wide-open throttle runs on both and one engine at a time. The latter was to check to make sure both props and engines were performing equally.For each diesel engine there are curves of fuel consumption at various RPMs that can then be interpreted to calculate accurate horsepower. We ran these numbers for our Deere 4045TFM diesels, and then sent the data to Don McPherson.Don came back with a recommendation to switch to four-bladed props, staying with our 26″ (650mm) diameter.
For better efficiency he wanted to start with a 20″ (500mm) pitched blade and have it re-pitched to 23″ (575mm). This manufacturing process ends up with more pitch at the tips and less at the hub.
This is more efficient in some situations. We ordered these props from Hall and Staevert in Canada, and installing them was the first order of business when we got back to the Seattle area a week ago. When working with tools and using force, the best policy is to avoid distractions and concentrate on the process. Steve was talking to Linda while cranking on the prop nut with our giant-sized box wrench while Bill was holding the wooden wedges between the prop and hull to keep the prop from turning. The wedges slipped and that blood on the cement is the result.
We’d have shown you the nasty gash on Steve’s finger but it might gross you out, as the saying goes. Suffice it to say that Steve is lucky to have that finger tip intact – and he knows to concentrate on the task at hand from previous hard lessons! One sees all sorts of interesting things in boat yards.
This “dock cart” draped in seaweed has to be one of the more unique photos we’ve snapped.We were excited to get back in the water and test these new props. You can imaging our disappointment when we were immediately serenaded with a high pitched whine. The props were singing noisily at a variety of speeds and loadings. We were also unhappy to find little discernible difference in the boat speed at various RPMs from the old propellers. The new props also let the engine wind up to a higher RPM at wide open throttle than was our target.
But there was one benefit. With the old props the engines would stall if put in reverse while the boat was going more than six knots to put the engines into reverse; but with the new props we did not have this problem.After numerous e-mails back and forth to the factory and Don McPherson, we realized that there had been a miscommunication between ourselves, Don, and the factory. Because these props are made from nibral bronze, a very hard material, the factory had not been able to get as much pitch as specified.
We had an effective pitch of just 21.5 inches, when we needed 10% more.This resulted in the suggestion to add “cupping” to the trailing edges of the propellers. Cupping looks like a very high aspect ratio trailing edge flap on the wing of a high-performance glider, and was supposed to do away with the noise, and increase lift (the same as increasing pitch). Here’s another photo. It is hard to see the cupping because it is very slight. We were doubtful that this small modification would have much of a performance difference, although it was likely to reduce noise.On our way out of Lake Union we stopped at Kovich and Williams to top off our diesel tanks (at US$2.30/gallon). Once through the Ballard Locks, back in salt water, with the engine turning 1900 RPM, we were doing 11.3 knots (at full load).
This is close to our optimum and what Don had predicted (our old props had us at 2000 RPM for this speed). At wide-open throttle RPMs are at the same RPM as before, which is fine.
We hit ten knots at 1640 RPM, again on Don’s calcs and close to our original optimum. It appears fuel consumption has dropped as well, indicating a substantial improvement in propeller efficiency. We need to do more testing on this – it takes a long time to do this right – but it appears we are down to just under seven US gallons (27 liters) per hour at 11.3 knots, around a 10% improvement.And the singing noise?
Gone, except for a slight serenade at idle speed on the starboard prop. We still have to test how these props will do when heavily loaded in big head seas. However, Don assures us that our previous capability in this situation will not be compromised.One question we’ve been asking is why the difference. Some of this has to do with the fact that props with less blades are more efficient that those with more, assuming you have enough blade area.
The trade-off is fewer blades can mean more noise and vibration. And indeed, these new props are not as smooth running as the old five-bladed wheels.There is another factor at work in our situation. The Henley propellers had a very high blade area ratio. They filled 95% of the circle, whereas the new propellers have a blade area ratio (BAR) of a more normal 68%. For our application the Henleys had more BAR than required. The extra propeller blade area was creating substantial drag.We still have a full day of testing ahead of us to tie down fuel consumption data, and then we need to test how these props do when highly loaded, punching into big head seas. However, all indications are that we’re now on the right track.
We’ll report on these tests when they are completed.When we started the Wind Horse design cycle we were told it was not unusual to go through half a dozen propeller iterations before arriving at the perfect solution. We’re not yet sure if we’ve achieved nirvana with these new wheels – but we know we are close. And we’ve only used two of the allotted six tries. We also now know that our original calcs on drag and the tank testing analysis were correct. So, we can use our software with confidence, along with Don’s help, to look at additional propeller options.
Hello 36'ersMy 1989 C36 #1015 is on the hard this week since the first time we bought her in San Diego almost 2 years ago.The issue is that my Martec 2 blade folding prop is done. The holes are worn out and the thing looks like its been used as part of the sacraficial metals chain under my boat (bad pitting).The current prop numbers are RH16X10 - 10P 3I can motor all day (and all night) at 2800 rpms making about 5.5 kts.
It just seems to me that she should motor well over 6 kts. I am not sure if I have the M25 or the M25XP. I have a call into catalina to see if they can help with the HIN # to determine which is which.Has anyone gone to a 16x10 12P?If so how did the motor behave?at 2800 to 3000 I have no smoke (indicates lugging) from the engine whatsoever.Any suggestions comments appreciated.thanks in advanceCapt BillMaverick#1015 std rig Fin keel. Bill,I second the suggestion by Bill Miller. Check your tach. I'm guessing you are motoring at an RPM far less than 2800.The M25XP was first seen in 1987 model C36's, so if you have a three cylinder Universal, it is most likely the M25XP.Prop sizing is generally labeled as (direction) diameter x pitch x bore, so there is no such thing as a 16x10, 12 pitch.
Martec Folding Prop Installation On 1997 Free
Martec Folding Prop Installation On 1997 Trailer
It would be a 16x12. It seems like your prop was stamped by the Office of Redundancy Office:-) Also I'm wondering what the 3 is. A three bladed prop? If so, you've got the wrong prop. A 16x10 two blade is a fairly large prop for the M25XP (another reason I think your tach is off). Most C34s and C36s came from the factory with either a 15x9 three blade or a 15x10 two blade prop. A 16' prop would not be recommended by many because of prop tip clearance with the hull.
Martec Folding Prop Installation On 1997 For Sale
A 16x12 prop would be overkill with the M25XP. You would not be happy with it. I'd suggest checking the tach first. Hope this helps.
Folding prop replacement project update with photosI have decided to stay with the 16X10 spec prop that came off the boat. This should be ready late next week from Martec.Removing the very corroded shaft was easy with a large cutting wheel.