Nick_H
Well-Known Member
Fuel price for commercial craft is about half that, as no duty.
Outdrives - a commercial perspective,
- Thread starter kashurst
- Start date
Portofino
Well-Known Member
But they will use less so save .i guess those Thames Police boats - its taxpayers £ they are burning up !
Nick_H
Well-Known Member
Yep, if you're looking for examples of effective cost driven decision making, I wouldn't start with any publicly funded body!
Portofino
Well-Known Member
Yup-agree, but chance/ accidents happen -this may have been one .No dought the decision maker back then now has a gong ,but he would have had a trip to Buck Palice and mention in the new years honours list - anyhow irrespective of his performance in his " public funded body "
Charter Skipper
New Member
I have been running sterndrive Charter boats in the Med for the past ten years and shaft drive Commercial vessels in UK waters since 1976.
Shaft drive vessels have never given any trouble except once when I got hooked up on an underwater rope attached to a wreck we were diving.
If I never have to use a Volvo sterndrive installation again I will be a happy man. They require incessant maintenance & too much money spending on them to make them viable even for pleasure use.The slight benefit in fuel economy & speed in no way offsets the maintenance costs.
In the Med it is essential to replace drive shaft bellows annually,regardless of what Volvo might state in their manuals.
Also, working on installations which are 'crammed into ' the stern of the boat is a very onerous task!
Shaft drive vessels have never given any trouble except once when I got hooked up on an underwater rope attached to a wreck we were diving.
If I never have to use a Volvo sterndrive installation again I will be a happy man. They require incessant maintenance & too much money spending on them to make them viable even for pleasure use.The slight benefit in fuel economy & speed in no way offsets the maintenance costs.
In the Med it is essential to replace drive shaft bellows annually,regardless of what Volvo might state in their manuals.
Also, working on installations which are 'crammed into ' the stern of the boat is a very onerous task!
Charter Skipper
New Member
Not in Spain,unless you are Spanish!
tinkicker0
Well-Known Member
Christ. Anyone would think that a outdrive was not an extremely uncomplicated bit of kit. 4 gears and 3 shafts. How easy do you want it?
Latestarter1
Well-Known Member
All housed in light alloy casing, immersed in seawater.
I have regularly attended Seawork, the very few commercial outdrive installations on show have always ended in tears a few years on........
oldgit
Well-Known Member
Lets be fair outdrives do have a place in the boaty world.
Usually on a bench in a workshop somewhere, a drip tray catching weeping oil/water/hydraulic fluid and the owner sitting outside in the bright sunshine weeping after looking at the repair guestimate.
Usually on a bench in a workshop somewhere, a drip tray catching weeping oil/water/hydraulic fluid and the owner sitting outside in the bright sunshine weeping after looking at the repair guestimate.
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RogerRat
Well-Known Member
So true, still we all have our points of view and some very strong feelings, even phobia and some on here have fairly closed minds. I've had outboards on fishing boats, out-drives on another and 3 planing motor cruisers, (no problems and excellent economy - 40+% saving) I am now just changing back to shaft driven boat because I feel it is more suitable for this type of boat.
My feeling is that you choose the 'compromise' type of drive / transmission you need for the size of boat and style of boating, whether you plan to use it for:
Commercial Cruising
Commercial Fishing
Instruction PB2 to Ocean
Offshore cruising
Harbour pottering
Dashing off to local pub on the river
Tenders
Workboats
Quote: "The Skipper is a mate of mine. They are D3 200's driving DPS."
http://www.bumblebee.gg/
Although, 'Bumblebee' looks great and 200Hp should be plenty, the D3 set up has not proven too well, I hear. It appears to be too weak in some experts' opinions, it was really designed for use on light weight sub 30 footers for weekend use.
I would have thought that for commercial use a D4-260 or D6-350 would on DPH drives (even with the extra weight) would have been much more industrial and with the extra power and torque, comes the lower operating revs, fuel savings and greater duty cycle.
A Targa 40 on D6's 350 Hp for example, uses about 25% less fuel that a Targa 40 on Kad300s' 285Hp. Not my opinion but proven.
I hope this brings you back on thread.:encouragement:
RR
DAKA
Well-Known Member
I cruised on a parallel course with Bumble bee 2 or three times in the Summer, I was impressed that he managed to keep up with us even in choppy conditions however the boat was only lightly loaded (two passengers).
I suspect if he tried to thrash the D3 with a full payload it will soon end in tears.
the leg I expect to last for 14-18 months , a commercial operator should have a recon leg on standby , as long as it breaks in Guernsey it will be a quick repair, if it breaks in Alderney he will have to wait for it to be transported by ferry , perhaps it would make more sense to change if for a recon leg every 12 months making a saving on annual service costs.
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Spi D
...
In these respects an outboard beats the i/o.
As said elsewhere one really big reason for people to have sterndrives is that manufacturers widely offer these as only option in entry level boat sizes (give and take a few feet
)Since sterndrives come with a mandatory service (read 'pension') plan for manufacturers, workshops, dealers and more it is no wonder they think it is a fantastic idea.
When shafts are OK for Maersk, they'll do for me as well
lynall
Well-Known Member
Can someone explain to me in simple terms why an outdrive is supposedly more efficient than a shaft?
Remember simple terms!
Remember simple terms!
rbcoomer
Well-Known Member
I understood that a percentage of shaft energy is pushing down whereas the outdrive is pushing 100% parallel to the hull (unless otherwise trimmed to alter the hull attack angle.
Given the added efficiency/lower drag of surface drives, I'd guess that the prop profile, being half, is also a factor?
D
Deleted User YDKXO
Guest
Shaftdrives have a rotating propshaft, P bracket and rudder causing drag. Sterndrives only have a smooth housing causing drag
Shaftdrives drive at a fixed down angle whereas sterndrives can be trimmed to drive horizontally or at whatever the most efficient drive angle is
Sterndrives generally have 2 counter rotating props for additional efficiency
Portofino
Well-Known Member
Rudder=drag along with shaft+ P bkt
Angle of thrust ( see above)
Duo prop On VP
One more- optimal trim of the hull -more achievable if you want ?
MapisM
Well-Known Member
Actually, they have a few "raisons d'être", but efficiency is not one of them.
At VP they can say what they wish, but whenever top efficiency is critical, you will never see a duoprop sterndrive.
MapisM
Well-Known Member
Well, comparing surface sterndrives with traditional shafts is a bit unfair, TBH.
If a hull is suitable for surface legs, the alternative (if any) are surface transmissions, whose drag is on par with outdrives, if not lower.
D
Deleted User YDKXO
Guest
Are you saying that Volvo are lying?
Duoprop provides up to 30 % faster acceleration and produces a top speed some 5 % faster than any conventional single propeller system - without increasing the fuel consumption. At partial load you can expect between 10 and 12 % lower fuel consumption.
MapisM
Well-Known Member
Short answer, yes. On speed/fuel burn at WOT, at least.
Otoh, partial load and acceleration are among the "raisons d'être" I previously mentioned, together with the neutralization of prop walk in single installations.