348 Bow Thruster: Tunnel or Folding

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   Hi,I am thinking of having a bow-thruster fitted to my 348.   I understand there are two basic options: tunnel, in which the thruster impeller sits in a tunnel that passes through the hull, close to the stem and below the water-line, or folding, where the impeller "flips out" downwards from the hull.

Looking at my hull close to the stem, there seems to be very little of it submerged.  Hence, I find it difficult to see how a Tunnel Thruster would get much "grip" on the water.

Plus, I've been told that Tunnel Thrusters create extra drag, costing you a 1/4 knot or so.

A Folding Thruster would get the impeller deeper in the water, and, I believe, would add much less drag in the folded position.

The main disadvantage of the folding type is the much higher cost.

As long as it's not ridiculously expensive, I'm tempted to go for the folding type.

Any advice/opinions?

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Caulkhead Members Profile Send Private Message Find Members Posts Add to Buddy List Lieutenant Joined: 26 April 2021 Location: Solent Status: Offline Points: 26	Post Options Post Reply Quote Caulkhead Report Post Thanks(0) Quote Reply Topic: 348 Bow Thruster: Tunnel or Folding Posted: 24 August 2022 at 20:10
	Hi, I am thinking of having a bow-thruster fitted to my 348. I understand there are two basic options: tunnel, in which the thruster impeller sits in a tunnel that passes through the hull, close to the stem and below the water-line, or folding, where the impeller "flips out" downwards from the hull. Looking at my hull close to the stem, there seems to be very little of it submerged. Hence, I find it difficult to see how a Tunnel Thruster would get much "grip" on the water. Plus, I've been told that Tunnel Thrusters create extra drag, costing you a 1/4 knot or so. A Folding Thruster would get the impeller deeper in the water, and, I believe, would add much less drag in the folded position. The main disadvantage of the folding type is the much higher cost. As long as it's not ridiculously expensive, I'm tempted to go for the folding type. Any advice/opinions?

Fendant Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 03 November 2012 Location: Switzerland Status: Offline Points: 1671	Post Options Post Reply Quote Fendant Report Post Thanks(0) Quote Reply Posted: 24 August 2022 at 23:52
	Hi Richard, the 348 hull is too flat for a tunnel system. It will only produce noise and has a low efficiency due to cavitation. On my 345 there was not enough room for the retractable system , so I had to go for the external exturn solution. This one is deep in the water, does not have caviation and does not wake the whole Marina up early in the morning. Finally it was the lowest cost solution. If you have space for the retractable system and if you get a "reasonable price" go for it. Pro: Deep in the water and good efficiency Con: Mechanically complicated , try the search function here in the forum In any case make sure that you get a wireleyy remote AND a wired solution.
	Frank

AndyS Members Profile Send Private Message Find Members Posts Add to Buddy List Captain Joined: 14 June 2016 Location: River Dunes, NC Status: Offline Points: 206	Post Options Post Reply Quote AndyS Report Post Thanks(0) Quote Reply Posted: 25 August 2022 at 03:01
	We put an external thruster on our 385 last year. I think it is definitely the way to go and we have loved it over the past 15 months. I highly recommend going the external route. Here is a link to what I posted last year:https://www.myhanse.com/yacht-thruster_topic12758_post104611.html?KW=thruster#104611
	Andy Moonraker River Dunes, NC

NK1 Members Profile Send Private Message Find Members Posts Add to Buddy List Commander Joined: 24 October 2019 Location: Ireland Status: Offline Points: 110	Post Options Post Reply Quote NK1 Report Post Thanks(0) Quote Reply Posted: 25 August 2022 at 12:15
	I’ve put a Vetus 125mm tunnel on my H350. Worked out great. This small tunnel might work for you.

CrocDundee Members Profile Send Private Message Find Members Posts Add to Buddy List Commander Joined: 12 December 2018 Location: Dundee Status: Offline Points: 88	Post Options Post Reply Quote CrocDundee Report Post Thanks(0) Quote Reply Posted: 26 August 2022 at 21:58
	Our H345 had a SidePower tunnel thruster fitted when we purchased. Seems to work fine, and it easy to service and clean. Thrusts the bow to port and starboard. Wired to the house batteries. Prop anode to change every couple of years. Just changed the switch at the helm recently, after the panel light started to stay on, after being switched off. All good now. I'm interested in the 1/4 knot estimate off speed for the tunnel, this would be good to know for sure. Unless you get a solution with a door, you will have this to consider too.
	Hanse 345 - Tenacious. Sailing on the Solent and now to the west coast of Scotland.



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