PCUK
Well-Known Member
Ah, but as the Vetus jobby didn't work it's unlikely that a DIY version will.
Pneumatic bow thruster
- Thread starter Barleycorn
- Start date
penfold
Well-Known Member
There's a reason small bow thrusters all involve propellers in tubes, it's because that's the cheapest practical solution. Most are driven by 12/24v motors because it's the cheapest practical way of doing it; hydraulic, which is the only other option, is a lot more expensive unless you already have a hydraulic power pack on board. It's doubtful if a 27' has enough space in the forefoot to fit even the smallest tunnel thruster, and retrofitting one of those fancy retractable ones will probably cost as much as the boat is worth. Then there's the loss of space taken by the installation and the extra weight forrard, which will be felt more in a small boat.
You could use an eductor with a compressed air supply to act as a bow thruster, but the compressor needed to drive an eductor big enough to thrust a 27' in anything other than millpond conditions will weigh 100kg+ and need 20hp to drive it. Having a large enough compressed air tank to allow the use of a smaller compressor will mean finding perhaps a cubic metre of space, will weigh a lot, and need regular inspection to ensure it isn't rusting internally and about to explode and kill you and anyone else nearby. Pressure vessels are a pain in the bum.
You could use an eductor with a compressed air supply to act as a bow thruster, but the compressor needed to drive an eductor big enough to thrust a 27' in anything other than millpond conditions will weigh 100kg+ and need 20hp to drive it. Having a large enough compressed air tank to allow the use of a smaller compressor will mean finding perhaps a cubic metre of space, will weigh a lot, and need regular inspection to ensure it isn't rusting internally and about to explode and kill you and anyone else nearby. Pressure vessels are a pain in the bum.
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Barleycorn
Well-Known Member
Thanks for all the constructive replays. It was just a thought, and yes I am not used to the boat, and am getting better. My previous boat was 30', but did steer better astern. This boat has a big prop and small rudder, so the paddle wheel effect is strong. I have been advised to get a good bit of way going then go into neutral, thus negating the paddle wheel effect.
I absolutely agree that it is better to drive into a small hole, and reverse out into a bigger one, but for different reasons I need the starboard side to the pontoon.
You will be terrified to hear that I am not the only incompetent maniac sailing the high seas, when I was looking at boats to buy several of this model, (Aqua-Star Pacesetter 27). were fitted with bow thrusters. Obviously not owned by our forum experts then!
I absolutely agree that it is better to drive into a small hole, and reverse out into a bigger one, but for different reasons I need the starboard side to the pontoon.
You will be terrified to hear that I am not the only incompetent maniac sailing the high seas, when I was looking at boats to buy several of this model, (Aqua-Star Pacesetter 27). were fitted with bow thrusters. Obviously not owned by our forum experts then!
Hadenough
Well-Known Member
OFOYPP
sarabande
Well-Known Member
air inction into water jets is not new !
I found this link
http://www.google.co.uk/url?sa=t&rc...=WT3uI0d6fX0pLJn0_oeWNA&bvm=bv.53537100,d.d2k
"Even if the efficiency is not as high as the primary propulsor, a thrust-augmenting device might be an attractive alternative to increasing the primary pump size for short-duration peak thrust requirements.
Application of boost thrust might include over-coming the added resistance for transitioning to planning mode on a
planning boat, for example."
Work on a water-ski motor has shown power increases of between 10% and nearly 100% !
When you come to think of the part the forum has played in the introduction and development of
underwater LEDs
stabilisers
Can Air Augmentation be far behind ?
I found this link
http://www.google.co.uk/url?sa=t&rc...=WT3uI0d6fX0pLJn0_oeWNA&bvm=bv.53537100,d.d2k
"Even if the efficiency is not as high as the primary propulsor, a thrust-augmenting device might be an attractive alternative to increasing the primary pump size for short-duration peak thrust requirements.
Application of boost thrust might include over-coming the added resistance for transitioning to planning mode on a
planning boat, for example."
Work on a water-ski motor has shown power increases of between 10% and nearly 100% !
When you come to think of the part the forum has played in the introduction and development of
underwater LEDs
stabilisers
Can Air Augmentation be far behind ?
Hadenough
Well-Known Member
I think that the pertinent message the OP needs is that his best bet is to fit a normal bow thruster, or not bother. Bu**ering about with alternatives has always proved to be more costly in my experience.
mikeinkwazi
Well-Known Member
Ha! I bet you have a Twister like me. If Jumble Duck can control one of them he gets a lifetime membership of the Twister assoc!!
tugboat
Well-Known Member
You don't want to be introducing bubbles anywhere near your boat, it causes loss of buoyancy!
cliff
Well-Known Member
I might just take you up on that as I am based in Troon whenever I am in the UK which thankfully is not so much now - better weather and sailing where I am.
charles_reed
Well-Known Member
Harsh, but justified.
We all have our dreams though, the more fanciful when our learning curve is at its beginning.
He should be able to tie-up a 27', single-handed, undrer sail and would do well to ponder how to set about the task.
JumbleDuck
Well-Known Member
No, but also a long keel, with a small engine as well. Reverse is always entertaining. I wouldn't fit a bow thruster, because they cost a lot and the boat is light enough at 3 tons + kit to make pushing, pulling and warping around pretty straightforward on the rare occasions when I use marinas.
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pelissima
Well-Known Member
On the other hand, if installed, an aditional jet at the stern could a significant plus in days of little or no wind.
vyv_cox
Well-Known Member
My son had a boat that was pretty much unsteerable astern. He bought an electric outboard cheaply on Ebay, mounted it on the transom. Made a considerable difference.
Barleycorn
Well-Known Member
Thanks for this advice. I did exactly the same. Bought a cheap electric outboard and mounted it on the bathing platform, pointing at 90 degrees. Rigged up a push button to operate a relay. I tried it today and it was excellent, came off the pontoon perfectly. The boat simply won't go to starboard in reverse, end of. And the pontoons and other boats are too close to allow much faffing about going forward to straighten her up.
£70 on eBay very well spent, thanks again!
Narrowboat
Active Member
I remember my uncle talking about this on a ship,when air was pumped in small bubbles to the side of the ship it created a void and the ship moved to the side where the bubbles where,cant ask him now as I would need a Ouija board and this was when he was In Egypt in the 1940s
Poignard
Well-Known Member
FFS!
That's got to win the 'over reaction of the week' award.
A new subscriber to the forum, having problems with a new boat he isn't used to, and he gets treated like that.
PC may not be your strong point Cliff, (something you're obviously proud of), but what about good manners?
Poignard
Well-Known Member
I have a 28' Twister which can't be steered astern (by which I mean that when she is going astern the rudder has practically no effect whatsoever). Windage on the bow is the dominant force acting on the boat. With a strong wind dead aft she will go astern more or less towards the wind but that's about the best I can hope for.
My advice is to just to learn and practice tricks and techniques to try and avoid situations where you might find yourself having to reverse into a confined space or narrow channel.
Get someone with more experience of that type of boat to go out with you; ask advice from people with similar boats but above all try and analyse what the wind and tide are going to do to your boat.
Also get plenty of fenders, and learn to smile and wave nicely.
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vyv_cox
Well-Known Member
I have a 28' Twister which can't be steered astern (by which I mean that when she is going astern the rudder has practically no effect whatsoever). Windage on the bow is the dominant force acting on the boat. With a strong wind dead aft she will go astern more or less towards the wind but that's about the best I can hope for.
My advice is to just to learn and practice tricks and techniques to try and avoid situations where you might find yourself having to reverse into a confined space or narrow channel.
Get someone with more experience of that type of boat to go out with you; ask advice from people with similar boats but above all try and analyse what the wind and tide are going to do to your boat.
Also get plenty of fenders, and learn to smile and wave nicely.
Within the past couple of years I recall that Tom Cunliffe used Twister Ken's previous boat, amongst others, in a YM piece about reversing. I suspect from my memory of the article that he was confident of his ability to reverse anything. When it came to the Twister his faith was shattered! He found himself totally unable to make it go reliably where he wanted it. My 1973 Colvic Northerner is pretty much the same - its reversing is totally unpredictable, giving me many difficult experiences trying to get it into my berth, even in a flat calm.
CAPTAIN FANTASTIC
Well-Known Member
Also get plenty of fenders, and learn to smile and wave nicely.
Also, you need plenty of those two things if you are trying to reverse in a marina with a Macwester.
Kurrawong_Kid
Well-Known Member
A friend of mine had a catamaran and a large family. When entering marinas one of his offspring was lowered into the dinghy which had a powerful motor and was used as a "tug" to push the boat into a berth. My boat is hopeless astern but has electric winches: if necessary I use warps and the winches to pull her out of the berth, turn her round etc. It's a matter of horses for courses. Even bow thrusters can be overcome by the wind and give a false sense of security. As demonstrated at Parkestone Quay this summer even professionals sometimes make a hash of it despite thrusters. It's all part of the challenge of seamanship.
