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ranger58sb · 15-09-2018, 10:25

I recently asked for discussion and recommendation in trawlerforum.com (sister site) and one point that resonated with me is to put in the largest that will fit a given tunnel size. IOW, if you need a 185mm tunnel, then pick the most HP they offer for that size.

Considering a bow thruster; best choices? - Trawler Forum

That advice fits for us because we're in between manufacturer lengths/weights, and because we have relatively high windage. Still likely depends on the size/weight of your boat, of course, and whether the incremental cost difference is all that much (your wallet can advise).

I too did not ask for debate about whether we need a thruster or not, nor whether I should consider hydraulic or AC-powered, external thrusters, etc.

-Chris

dangerfield55 · 15-09-2018, 11:32

I had a Catalina 380 under contract

dangerfield55 · 15-09-2018, 11:35

Contract with an added after market now thruster. The survey showed the tunnel leaked. It’s a very narrow area to work in and fiberglass. I passed on the boat after the insurance people got involved. A bolt on unit might be better.

-bliss- · 15-09-2018, 13:15

My apologies for pointing you in a different direction than you wanted. I had the best of intentions!

Now that I realize you are going to install the tunnell, I would strongly advice against fitting a model on the smaller side to save a few bucks. After all, the cost and complexity of the tunnell installation, cables, control panel, the gear house etc will be the same, no matter which engine model you choose for the 185 mm tunnell. Given you have a 40 ft fin keeled, medium displacement, medium windage cruiser, I think thrust of aproximately 80 kg is needed.

In the world of Side Power, the 185 mm tunnell is compatible with 60,80 and 100 kg thrust models. The weight of the se60 is 16 kg and the se80 is 20 kg. The 4 kg/ 8,8 lb difference is pretty marginal, and you need a thruster capable of assisting in considerable sidewind, so in your case I wouldn´t consider anything smaller than 80 kg thrust. If you can accept 31/ 68 lb total weight, I probably would ask for a nice offer on the Side Power se100 which is considerably stronger. After all, added drag of the tunnell is the same no matter which model is fitted on top of it. Bigger engine equals more thrust equals less noise and less risk of overheating.. It also builds confidence when docking.

By the way, the side power thrusters have rubber coupling (galvanic isolation) between gear house and engine. Nice feature.

I Can´t comment on Vetus, as I have no experience with their thrusters. They manufacture lots of other quality equipment, though..

Did you consider a retractable thruster? No added drag and no fouling problems. The effect loss is significant when tunnell and propellers of a conventional thruster are full of barnicals.

Best of luck!
-kjetil-

georgy.goshin · 15-09-2018, 13:31

Quote:

Originally Posted by -bliss-

Did you consider a retractable thruster? No added drag and no fouling problems. The effect loss is significant when tunnell and propellers of a conventional thruster are full of barnicals.

Best of luck!
-kjetil-

My opinion that retractable is not very good idea because when you need a thruster, you need it quickly, and these 1-2 seconds of wait the thruster to open could be very expensive...

CSY Man · 15-09-2018, 13:38

Quote:

Originally Posted by georgy.goshin

Thank you for your opinion, but please advice a bow thruster, advice why not to install in not needed really. On 40 foot boat in a windy marina thruster will be very useful during single hand sailing.

I found cheper Vetus thrusters, will model 55 with 185mm tunnel be enough? Does anyone has an experience with Vetus ?

See above...

As for needing a thruster or not on a 38’ sailboat?
I would install one if I had the spare cash.
Never had one on previous sailboats, but almaot never went to marinas, therefore no big deal.
Had considerable prop-walk on my CSY 33 and used it to maneuver, it did help, but not quite a bow thruster.
Not sure what the KG ratings translates to in Horsepower, but I would shoot for 8 to 10 hp, better to start big as the system gets downgraded with barnacles and slime if not cleaned or used.
(Every time you dive on the boat or the Anchor, check the bow thruster, or at least run it every week for a few seconds in both directions. I do.)

LongRange · 15-09-2018, 14:00

Quote:

Originally Posted by georgy.goshin

My opinion that retractable is not very good idea because when you need a thruster, you need it quickly, and these 1-2 seconds of wait the thruster to open could be very expensive...

I have a retractable Max-power Compact on my 45' mono, and in practice the time-to-deploy is not an issue.

It is part of the docking routine, like tying on fenders, and the fear of not having the thruster available at the right millisecond is more than enough to ensure I don't forget!

The thruster gets powered up a couple of minutes before I begin the docking approach, and it is deployed as soon as I'm in close quarters. It stays deployed until I'm docked.

**chris07732** · 15-09-2018, 14:26

I self installed a Vetus 185TT 6.0kw unit in my 39' full keel motor sailor 2 yrs ago. It's a simple project, Lewmar instructions are excellent. I have some pics if they'd be helpful. Echoing what someone said, I'd go for max power available in your tunnel choice. At my dock, there are wind/current situations when I question if my bow is going to respond enough. Otherwise, I love the unit, gives me the confidence to single handle my boat.

Dr. Sea · 15-09-2018, 14:27

Quote:

Originally Posted by georgy.goshin

My opinion that retractable is not very good idea because when you need a thruster, you need it quickly, and these 1-2 seconds of wait the thruster to open could be very expensive...

I have a Side Power bow thruster with a bow tunnel and I have never needed it when I hadn’t anticipated it in advance. I would like the avoidance of barnacles that a retractable bow thruster offers, but I wonder if having one more moving part isn’t inviting one more potential problem.

georgy.goshin · 16-09-2018, 15:01

I found some very other think - jet thruster, anyone has an expirience

CarlF · 16-09-2018, 15:25

If you are going with a traditional thruster with a tunnel - you will want to investigate the space that is available for the tunnel in you bow. Depending upon the location of grids, tanks and bulkheads it can be tricky to find a space for a 8"+ diameter fiberglass tube running from side to side with the large thruster motor sticking out of the top. Presumably you don't want a large electric motor sticking up from the middle of your V berth.

It's vital that the top of the tunnel be deep enough such that air is not drawn in from the surface -- taking away most of the thrust. You may need to go with a smaller diameter tunnel to get it deep enough.

Sidepower specifies that the top of the tunnel must be a minimum of 50% of the tunnel diameter below the surface. They prefer 75% or 100% of the diameter.

The other problem is tunnel length. Sidepower recommends that the tunnel be around 2-4 times the tunnel diameter. A too short tunnel will cavitate and too long will slow the water from friction.

And as mentioned above, you may need to find space for one or two batteries in the bow. If your boat is 12v, even large cables from the house bank will not be able to deliver enough watts to get full power from the thruster. You then need to find a way to charge them too. If your boat is 24v, large cables will probably work.