Could the Brunton autoprop be what I need?

[cmedsailor]

I had never in the past though of buying a fancy and expensive propeller because I mainly either do cruising (with family) or just a little of bit of sailing around the bay during weekends. My only plan was to replace my 2-blade fixed propeller with a 3-blade fixed (during the next lift out which was initially planned for last November but now postponed for October this year!), mainly to get rid of some annoying vibrations (this is a different story).
Nevertheless, I have lately started thinking how I could make my passages last less (yes, it’s the trip not the destination that counts but when you have two kids aboard anxious to arrive priorities change…). Living in the Med I do a lot of motor sailing especially during those long passages of 80 - 160 miles non-stop. For a 36ft boat at an average speed (let’s ignore sails, head winds and nasty Med short waves for the moment) of around 6 knots and motoring at 2400rpm (Volvo Penta MD2030) this means around 13-27 hours. Quite long. And if you add now some chop/waves facing the bow, even if sails are up (and I do use them in every single possibility; the joy of having a furling main sail) some more hours are sometimes added. Buying a bigger, faster boat is not allowed even in my dreams for the next 150 years. Running the engine harder is a possibility but I would like to avoid due to less comfort, higher noise, more vibration and higher consumption (not very convenient when you have a 75lt diesel tank). So, could the autoprop offer me what I need? Could it increase my average speed? And how much (to justify the cost)? Is the autoprop good when motoring against waves/head seas (I am a bit confused there trying to understand various older posts; seems that it pitches down in those conditions and needs higher rpm).
Thanks

 

[Tranona]

The Bruntons will do part of what you want - it pitches the prop to suit the conditions so will give you the same speed at lower revs and deal better with adverse conditions. However, don't think it will significantly reduce passage times because the constraint is not engine power, but boat size. Try cruising a 6.5 knots in anything other than flat water and see how uncomfortable it can be. The advantage of the Bruntons is that it does help maintain speed into headwinds and sea. Whether that is worth the £2500 they cost only you can decide. Your usage pattern fits fairly closely with what the product is claimed to be good at.

Clearly many people do think it worth the money as it has been established on the market for a long time.

 

[Skysail]

+1, they are often recommended. But most people buy them to improve sailing performance, the motoring benefits are less obvious.

 

[cmedsailor]

The Bruntons will do part of what you want - it pitches the prop to suit the conditions so will give you the same speed at lower revs and deal better with adverse conditions. However, don't think it will significantly reduce passage times because the constraint is not engine power, but boat size. Try cruising a 6.5 knots in anything other than flat water and see how uncomfortable it can be. The advantage of the Bruntons is that it does help maintain speed into headwinds and sea. Whether that is worth the £2500 they cost only you can decide. Your usage pattern fits fairly closely with what the product is claimed to be good at.

Clearly many people do think it worth the money as it has been established on the market for a long time.

Thanks Tranona. Always appreciate your answers.
£2500?????? Are you sure about this? I always though they were around £1800-1900 including VAT and everything. Anyway I could only ask for a quotation and find out myself (....and then stick to my 3-blade fixed decision!).
"The advantage is that it does help maintain speed into headwinds and sea." Now, this is something I haven't concluded reading lots of older posts (I did a bit of homestudy) unless I got it completely wrong. I know that a fixed 3-blader will push much better than a fixed 2-blader at same rpm. But I am getting the impression that Brunton will automatically reduce the pitch in these conditions and force me to increase rpm in order to keep pushing at same speed. The exact opposite from what I would like. I am not sure if Brunton is a good prop for the Med.

 

[cmedsailor]

I would definately buy a Flexofold if I was after this.

 

[Hoolie]

We have an Autoprop in the Med and when it's clean it's very efficient - much better than our previous 3-blade.
But we have problems with fouling, mainly barnacles that grow impressively quickly and large round here. This unbalances the prop and affects its dynamics so it loses efficiency. If you can't keep the prop clear then in my view a fixed prop would be better.

 

[duncan99210]

We have an Autoprop with the same motor as you do on a Bavaria 38, which is in fact about 40 feet long, so a little bigger than your boat. We had to replace it with the original Volvo 2 blade for a short period a couple of years back (don't ask, anodes is all I'll say) and found that to get the same speed through the water (5 knots) required an extra 600 rpm. We also found that when the wind is right, we get about 1/2 - 3/4 knot better sailing speed than with the egg whisk.

However, the thing does seem to attract the hard growth - we call them coral worms - at quite a rate during the summer. That said, it is pretty simple to keep it clean out here - mask on and it take about 15 - 20 minutes to get it good and clean, less if you have scuba gear. Just use a narrow paint scrapper to keep the bronze clear.

As to whether it'll get you there any faster, I'd doubt it. What it should do is get you there at the same sort of speed but with lower engine revs and therefore less fuel used. Also, when motor sailing, it is a real joy, as it will add to your speed no matter what revs you use as the baldes adjust to best suit the effort being called for.

 

[JonJon]

Am very pleased with my Autoprop, I feel the boat motors much better/faster for a given engine speed. It stops quicker and reverses better than my old fixed 3 blader - very handy for marina work the old 3 blader took a month of sundays to stop the boat. ( you should experience Cleopatra marina in Preveza with the tide under it and the afternoon wind bearing down on you to know what I mean!)
The blades align fore an aft under sail alone and it gives a lot less drag not as good as some of the folding props but the boat is noticeably faster. Think it cost me about £1600 not cheap but what is....

 

[samwise]

Thanks Tranona. Always appreciate your answers.
£2500?????? Are you sure about this? I always though they were around £1800-1900 including VAT and everything. Anyway I could only ask for a quotation and find out myself (....and then stick to my 3-blade fixed decision!).
"The advantage is that it does help maintain speed into headwinds and sea." Now, this is something I haven't concluded reading lots of older posts (I did a bit of homestudy) unless I got it completely wrong. I know that a fixed 3-blader will push much better than a fixed 2-blader at same rpm. But I am getting the impression that Brunton will automatically reduce the pitch in these conditions and force me to increase rpm in order to keep pushing at same speed. The exact opposite from what I would like. I am not sure if Brunton is a good prop for the Med.

A less expensive solution might be to talk to Darglow who offer a range of folders and featherers that could provide an answer. I'm pretty sure they don't self adjust and as other posters have said, the primary benefit is for sailing performance. That said, we have found that our Darglow Featherstream provides excellent stopping power and astern performance and can reduce propwalk ( althiough that can be an advantage in some circumstances). We looked at the Brunton and while it is an excellent piece of kit,m it was way beyond our budget.

 

[SHUG]

Nother vote for Autoprop.
When fully deployed it develops the same thrust in reverse as in forward.....but you may have to blip the engine to make sure it is fully deplyod and not messing around with two blades wanting to go in reverse and one wanting to go forward.

 

[dovekie]

My comments echo those of others above. We have a 38 foot, 8 ton old fashioned GRP AWB. Changing from a fixed 3-blader added 1/2 to 3/4 knot sailing speed in light airs. Motor-sailing requires less rpm for a given speed. And I can detect no difference in its ultimate pushing power into heavy seas. So it does what Bruntins say it does. BUT, we lift out twice a year to clean the thing and change the anode. The autoprop was expensive, and the anodes are too. If money is big factor I think the firts hand comments of those with alternatives will be valuable to you.

 

[Coaster]

But I am getting the impression that Brunton will automatically reduce the pitch in these conditions and force me to increase rpm in order to keep pushing at same speed. The exact opposite from what I would like. I am not sure if Brunton is a good prop for the Med.

You've got it back to front.

The Brunton's Autoprop adjusts to a coarse pitch, under benign conditions, thus producing more speed for a given RPM. At least that's what ours does!

If conditions worsen the pitch becomes increasingly fine. It's the equivalent of an automatic gearbox (or more properly a CVT drive). With our boat (LOA 34', LWL 27', about 8 tons in cruising trim) we achieve an easy 6 knots, in calm conditions, at say 1800 RPM. The engine is a Beta 38. In rough weather we'll still do 6 knots (conditions permitting) but RPM may be around 2800.

As far as I can remember we paid about £1500 for our new Autoprop, 3 years ago. It is carefully cleaned each October when the boat comes out of the water, to remove small growths, and greased before relaunching in February. If you haven't yet done so I suggest you speak to Bruntons about size, cost and availability.

We are very pleased with our Autoprop.

 

[Dockhead]

The Autoprop is a brilliant bit of kit. It's best feature is relaxed motoring. You back off the throttle until the speed drops off too much, then just inch it up a pinch from there. Like that we manage 8 knots at a relaxed and almost silent 2200RPM, in reasonably flat water.

There are many complaints about Autoprops throwing blades. We have not experienced this so far.

 

[Kurrawong_Kid]

The Autoprop is a brilliant bit of kit. It's best feature is relaxed motoring. You back off the throttle until the speed drops off too much, then just inch it up a pinch from there. Like that we manage 8 knots at a relaxed and almost silent 2200RPM, in reasonably flat water.

There are many complaints about Autoprops throwing blades. We have not experienced this so far.

I think that problem was with the earlier ungreased ones. The new design is much sounder. They also altered the design of the tab washer with the earlier units.

 

[emandvee44]

Autoprop

Well we are more than happy with ours - just finished polishing it again, greased it, but the sad part is that it is going in the water tomorrow and no doubt the beasties will be looking for a home.

Michael.

 

[Sybaris]

Whether that is worth the £2500 they cost only you can decide.

Bruntons sometimes offer fully refurbished props at a much reduced price, it is worth checking with them.

Cheers,
Per

 

[GrahamM376]

A less expensive solution might be to talk to Darglow who offer a range of folders and featherers that could provide an answer. I'm pretty sure they don't self adjust and as other posters have said, the primary benefit is for sailing performance. That said, we have found that our Darglow Featherstream provides excellent stopping power and astern performance and can reduce propwalk ( althiough that can be an advantage in some circumstances). We looked at the Brunton and while it is an excellent piece of kit,m it was way beyond our budget.

+1

We went from 2 blade fixed to 3 blade Featherstream. Gained about 1 kt sailing at low speed and much better bite motoring into wind and chop.

 

[HermanD]

Disadvantages Autoprop

Autoprops have also disadvantages.
I:
You cannot go very slow in a canal if you must. It always go's to minimum 3 knots or so,
to slow down you have do disangage every time.
II:
If the units grow older, you get play on the bearings, this leads to vibration, it can drive you mad.
For the rest the work fine, saving fuel.

 

[Dockhead]

Autoprops have also disadvantages.
I:
You cannot go very slow in a canal if you must. It always go's to minimum 3 knots or so,
to slow down you have do disangage every time.
II:
If the units grow older, you get play on the bearings, this leads to vibration, it can drive you mad.
For the rest the work fine, saving fuel.

Very true about not going slow. Mine actually won't go less than 4 knots. So I have to shift in and out of gear if I want to go slower than that. It can be a real problem and it's a real disadvantage of the Brunton.

Bearings are cheap and easy to replace, so no excuse for putting up with vibration.

 

[temptress]

Autoprops have also disadvantages.
I:
You cannot go very slow in a canal if you must. It always go's to minimum 3 knots or so,
to slow down you have do disangage every time.
II:
If the units grow older, you get play on the bearings, this leads to vibration, it can drive you mad.
For the rest the work fine, saving fuel.

we have an AUTOPROP - great bit if KIT.

Herman - I disagree with you - we can motor along just in gear as slowly as we like. Perhaps your prop is mismatched with your engine or gearbox?

Our prop i snow 7 years old and dome a lot of miles - we have no problems with the bearings - we always put fresh grease in them every time the boat is out of the water.