Bow Thruster prop upgrade

mjf

mjf

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Hi

You might recall that I recently changed the prop on my thruster but due to strong gusty winds was unable to tell how much improvement was evident.

Well, I can now as it been used in more controlled conditions and yesterday was a good test in 15knots of breeze without too many gusts.


Its a big improvement.

Not only does it sound soooo much better than the egg whisk of before but the 'grunt' is there when it bites the water. Much better control - instant action and much more power IMHO. Its a significant improvement. Before anything more that F3 it useless now it fights back and will turn into such a breeze.

Without any doubt an good modification. recommended hugely.

jfm - have you changed yours yet?
 
mjf said:
jfm - have you changed yours yet?
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Hi, glad to hear it's good. I have mine here in a box ready to install at next lift out, but haven't done it yet. Kindly supplied by Osmotech. I will need to be good cos it cost £520 according to the cr card slip enclosed in the box. I thought she said £120 on the phone when I ordered it. Must be going deaf... :-)
 
Ouch, makes the £88 for a Vetus one look like a bargain (though I paid £42 back in May '07).

FWIW, I found the bowthruster prop made a big difference, but I went back to the old prop on the stern-thruster as it didn't seem as good. No definitive measurement, just gut feel - perhaps the fact its closer to the waterline makes a difference?
 
Thought you were going to do it with a tank on your back which is possible.

There is something wrong with your price - mine was £80, from memory, at SIBS from the same supplier. Although your prop will be larger I cannot see how the price could be so much higher.

I think the box said it was up grade kit and had all the bits I mentioned in the orginal post; the anode alone is over £10...
 
I must have missed the original post, is it a new pattern of prop that's more efficient in the same tunnel with the same motor and gearbox? If so, i'm interested, can you provide more details, or a link to the earlier post.
 
Nick_H said:
I must have missed the original post, is it a new pattern of prop that's more efficient in the same tunnel with the same motor and gearbox? If so, i'm interested, can you provide more details, or a link to the earlier post.
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Exactly. Supposed to cause less cavitation, so quieter (a bit) and more useful thrust (definitely noticable on the bow-thruster). Basically, a new blade design that I think Vetus started and everyone has their own version now:

6BladeProp.jpg
 
My old BT was pathetic (3 blade) so I bought a new sidepower unit complete with 5 bladed prop from Osmotech.

Had it fitted in April and immediately noticed the 5 blades are more efficient.

I was limited to motor size by the size of the tunnel 185mm so could not increase the motor much so must be the 5 blades.

However here is a strange thing. I pulled up at the waiting pontoon in Smir last month only to find the bow thruster motor free spinning. It worked when we left Gib two hours earlier.

Next day we get hold of a snorkel and flippers my firend dives down and comes up with the prop in his hand, said it was wedged in tunnel sort of on its side.

Since then I have been trying to fit the bloody thing over the enghineers head.

How the hell does a prop come off? Fixing procedure as follows, push prop onto shaft locate the drive pin into prop moulding, fit washer and nylock nut, tighten then push on anode and secure via an allen screw into thread on end of shaft simples

Grrrrrr I have now had to buy all the aforementioned fittings and will need to dive down at anchor with me mini B and refit. Moral of the story fit the damn thing yourself
 
mjf said:
jfm has either purchased a new gearbox etc or they have enclosed the incorrect cc reciept :-)

Its under £100 incl P&P for 4HP so say £120 for larger Sq58 one.
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Blimey. I just checked by calling the helpful Osmotech guys. My price was "right". The prices go up with prop dia and mine are 10inch, for an 11hp thruster, and I have 2 props, and they're about £200 each, plus I bought the upgrade kit which has washers and stuff that I perhaps don't need, then VAT and carriage, hence £500.

They seem to be made from something quite high tech. It's a plastic (becuase the black colour goes right thru) yet it has the feel of metal - if you twang the blades they ping like metal. They have nothing like the softness or fexibility of normal plastics. Injection moulded or die cast onto a metal (alu bronze I'd guess) bushes. Manuafacture cost might well be quite a bit more than £5 each but of course (and you know this Nick!) you're paying for design, tooling and R&D a bit :-)
 
Well it would admittedly be a reasonably complex tool to make, but such tools can be sourced cheaply in China, and the incremental cost of making one (ignoring recovery of investment in tools and R&D) would not be more than a fiver, whatever high spec material is used. I had a plastic moulding company for a while, and we made complex radiator end tanks (typically about 400mm x 80mm x 80mm) in glass filled nylon with brass inserts, and they cost about a quid to make, so in my guesstimate i'd multiplied by five for posh materials and low volume. I think they're trying to recover their investment on the first 100 sold! :-)
 
Nick_H said:
Well it would admittedly be a reasonably complex tool to make, but such tools can be sourced cheaply in China, and the incremental cost of making one (ignoring recovery of investment in tools and R&D) would not be more than a fiver, whatever high spec material is used. I had a plastic moulding company for a while, and we made complex radiator end tanks (typically about 400mm x 80mm x 80mm) in glass filled nylon with brass inserts, and they cost about a quid to make, so in my guesstimate i'd multiplied by five for posh materials and low volume. I think they're trying to recover their investment on the first 100 sold! :-)
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OK, see your point. I'll show you the things sometime in France, cos it'll be a while before I lift the boat to fit them. £Fiver or so tops. Blimey, I've been fleeced. Again :-)
 
Expect you have all checked this out but with a prop shifting more fluid you may want to check the motor running current and the cabling/fuse size to ensure it can take the aditional load. But I expect the manufacturers have checked all this for you, just a thought! I'll go back to my beer.....
 
Well I suppose compared to fitting a bigger bowthruster it's cheap :-) I somehow think that fact hadn't escaped their marketing people when they set the price of these things
 
Jeez - I just hope when you finally look that your new boat actually has the 'old' style....

It would be a bit of a buggar to discover that the new props were there all the time:-)

Saying that as you are familar with Sq58 I'm sure you would have discovered the diffrence by now.

You are right about the material its does 'twang' like metal and the blades are fine - and sharp even
 
They seem to be made from something quite high tech. It's a plastic (becuase the black colour goes right thru) yet it has the feel of metal - if you twang the blades they ping like metal.

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That sounds like mind black looks like metal and pings when you flick it, oh and expensive.

Imagine how I felt when the bloody thing fell off
 
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