cliff
Well-Known Member
Rather than Bruntons have a look at Steel Developments - not auto pitching but adjustable pitch
Could the Brunton autoprop be what I need?
- Thread starter cmedsailor
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duncan99210
Well-Known Member
Oldog, on my Bavaria 38 when we had the old 2 blade prop fitted we burnt about 2.5 - 2.75 litres per hour to keep a steady 5.5knots. The engine was going at about 2,250 - 2,500 rpm. With the Brunton fitted we burn just under 2 litres per hour with the engine at 1,800 rpm. Hope that helps a little.
NormanS
Well-Known Member
If you do any motor-sailing, the Bruntons Autoprop is fantastic.
I got my present boat (motor sailer deck saloon) six years ago, and she needed a new prop. I fitted the Autoprop in the first winter, and it has made a huge difference. Less drag when sailing, but the real benefit is if motor-sailing, when the speed from the engine revs is added to the speed from the sails, up to a point.
I got my present boat (motor sailer deck saloon) six years ago, and she needed a new prop. I fitted the Autoprop in the first winter, and it has made a huge difference. Less drag when sailing, but the real benefit is if motor-sailing, when the speed from the engine revs is added to the speed from the sails, up to a point.
olddog57
New Member
Duncan, thanks a lot: first concrete evidence (at least I couldn't find any before) permitting a cost conscious decision. You saved about 20% (up to 25%) on fuel at cruising speed.. Of course - not apple-to-apple comparison (as you had only 2 blades before), but still very interesting figure.
And, Norman, I, too, have a motorsailer (Fisher 34) - so count a lot on your opinion; thanks
olddog57
New Member
Hey, Cliff, I had a look at that adjustable pitch prop: their Autostream, right?
Couldn't find a clue about the price..
Do you say that such prop should be at least as effective (as autopitch), and in some cases better (under an experienced operator of course)?
A thought/question: prop walk sometimes helps, sometimes has a very negative effect when handling a boat at close quarters; it seems possible with adjustable pitch to make the prop walk to help you in any case (providing you can control the pitch up to negative figures - as you should because SD say you can turn blades 180% for revers)
Some explanation if not clear: having RH screw your boat turns to starboard on twopence, but to turn her to port is quite a task, right? But having the controllable pitch you can actually work your prop as a LH screw if you wish!
Am I right?
And if I (very likely) am: one can save enormously on putting bow-thruster idea aside..
Halo
Well-Known Member
For what its worth I fitted a Flexofold 3 blader last winter. It has given a major improvement in sailing performance and as far as I can tell no reduction in motoring or motorsailing performance. The autoprop would certainly have given better results for motorsialing BUT the Flexofold works extremely well when mooring (both forward and reverse). I mean that I can slow down or speed up easily and in a controlled maner without excess prop walk. If, like me, you find half the stress in sailing is mooring in tight spots I would recommend you consider the Flexofold. The drawback of the Autoprop for mooring is that is gives substantial drive even at low revs which may not be what you want if you a gentle moorer rather than a slam it in quick one.
charles_reed
Well-Known Member
Having had an Autoprop for over 20 years (mine cost £883) I can confirm the following points.
1. The sailing performance improvement does not match that of most modern folding props.
2. The fouling does affect performance more than with a conventional fixed prop, but a sure way of preventing this happening is to use the boat consistently and frequently.
3. The effectiveness for motor-sailing is, IMHO, the greatest benefit of the unit, not so much for achieving increased speed but to maximise light-wind progress.
4. Fuel consumption is vastly reduced - my 3YM20 returns an average of 1.2 - 1.5 litres/hour - any attempt to justify the additional cost over a conventional prop, by fuel savings is, however, far fetched.
5. The vastly improved thrust in reverse, over a fixed or folding prop carries some risks - it takes some few revs to repitch the prop and suddenly increasing revs can pitch unwary crew off the foredeck - in the case of the shaft-clamp of the Yanmar, this can also cause the shaft to be pulled out of the clamp.
I've never regretted the purchase of my Autoprop - for me its greatest benefit has been the ability to motorsail at far more than the simple addition of sail-drive to motor drive. It has been in use in the Med for 8 years. I would be chary of claiming that cruising speeds are improved in all conditions - only those of light airs.
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Plevier
Well-Known Member
That looks interesting. I have a feathering Kiwiprop which is good but has a big drawback, the non-adjustable excessive pitch in astern. My setup (VP 2020D with MS10L-A gearbox) is higher geared astern than ahead and doesn't like it a bit. I note the Autostream has adjustable pitch astern.
More info here http://www.seahawk.com.au/images/Autostream_2010.pdf seems to be Australian not made by Steel developments at all!
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cmedsailor
Well-Known Member
What prop have you replaced? 2-blades or 3-blades fixed?
What size was the old prop and what size is the Flexofold?
Any comparison of speed vs rpm between old and new?
Thanks
Halo
Well-Known Member
3 Blade fixed with 3 blade folder on 3YM30 with SD20 saildrive
Dia about 1" less but increased pitch on folder (will have to dig out records for sizes)
RPM about same but can now get to max engine speed - before she stopped about 400 r.p.m short
Albert Ross
Well-Known Member
Autoprop: Excellent
Autoprop anodes ... IMHO grossly overpriced and (on my boat) last a few months at most.
Autoprop anodes ... IMHO grossly overpriced and (on my boat) last a few months at most.
Cantata
Well-Known Member
I splashed out on a 2-blade autoprop this year, replacing an ancient Flexo-o-fold 2-blade folder.
Very pleased overall for the reasons that others have outlined, especially motor-sailing performance and the response in astern (this particularly was dire with the Flex-o-fold).
I too suspect that its drag when sailing is slightly more than the folder, but not that much.
Very pleased overall for the reasons that others have outlined, especially motor-sailing performance and the response in astern (this particularly was dire with the Flex-o-fold).
I too suspect that its drag when sailing is slightly more than the folder, but not that much.
charles_reed
Well-Known Member
Some tests were carried out in the Wolfson tank - the figures unpublished - but, from memory the Gori 2-blade folder and the Maxprop produced less drag than the Brunton.
What is significantly different about the Autoprop is that it is the ONLY true self-pitching prop varying it's pitch according to conditions/effort needed.
Kiwi and MAxprop are variable pitch props, very different devices.
Tranona
Well-Known Member
Not strictly correct. They are adjustable pitch props. You can change the angle of the blades, usually by altering the internal stops, but once you have set it the angle is fixed. Variable pitch props can have the pitch changed from full forward to full astern, usually by mechanical means. Among the most common (many years ago) wee the Watermota and the Sabb systems
penfold
Well-Known Member
Nomenclature strikes! variable pitch conventionally refers to ordinary props that have blades where the pitch varies along the length of the blade. What you've described there is normally called controllable pitch.gwebster
New Member
Brunton autoprop
I put one on my Dufour 41, also in the Med, 3 years ago and it is brilliant. Normally when motoring i only need to do 1200 revs to achive 5.7 to 6 knots, using little fuel, no oil ( we used to use a lot) and very quiet.
If I need to get a move on, or motor into a sea, I have at least 50% more power than before with the old 2 blade prop.
You will need to service it, which is using a grease gun, and learn how to remove it each winter.
There is no issue of it not working in a sea, the pitch is automatic.
I recommend it.
I put one on my Dufour 41, also in the Med, 3 years ago and it is brilliant. Normally when motoring i only need to do 1200 revs to achive 5.7 to 6 knots, using little fuel, no oil ( we used to use a lot) and very quiet.
If I need to get a move on, or motor into a sea, I have at least 50% more power than before with the old 2 blade prop.
You will need to service it, which is using a grease gun, and learn how to remove it each winter.
There is no issue of it not working in a sea, the pitch is automatic.
I recommend it.
GrahamM376
Well-Known Member
Controllable pitch is just another name for variable pitch which is the most commonly used term, whether for aircraft or boats. Most propellors have a varying (not variable) angle of attack along their length. As the pitch/angle of attack along the length is fixed, it can't be variable.
Tranona
Well-Known Member
The two terms (variable and controllable) are used interchangeably to describe props where the angle of the blades can be changed when the prop is rotating. More commonly used in aircraft than boats. Google the term for references.
Never seen variable pitch being used to describe the twist in a propeller blade.
cmedsailor
Well-Known Member
Is it a MUST to lift the boat and grease every year? Can the grease last for 2 years?
davidfox
Well-Known Member
H. The drawback of the Autoprop for mooring is that is gives substantial drive even at low revs which may not be what you want if you a gentle moorer rather than a slam it in quick one.[/QUOTE said:
