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Old 21-02-2013, 06:53   #1
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Bow Thruster Install on New Boat

Hi all

We're currently getting a new boat commissioned (super excited) but have some concerns with a bow thruster installation that is currently ongoing. To cut a long story short the boat was ordered with a bow thruster but the dealer couldn't secure one off the production line with one installed (in the desired timeframe) so the manufacturer sent out the thruster for local installation. The dealer has a local guy he uses for commissioning and everything has been fine until he started on the thruster installation. I'm not a boat builder so I need some advice because to me it looks like the guy is making a complete arse of it. My concerns are:
1) The holes were cut into the hull for the thruster tube, hole was very out of shape which resulted in gaps up to 50mm in certain areas.
2) The tube was cut and glassed in, the external profile protrudes by about 50mm from the hull profile (looks very excessive but how much should it be?)
3) The tube is approx 1.3m wide and is unsupported beneath for entire length.
4) The space between the inner liner and hull (core) hasn't been sealed and is exposed to any water travelling down the bilge (what typically is this this core material and does it matter?)

Things haven't gotten ugly yet which is why I'm reluctant to post the make/model/dealer details but I would love some input as to whether my concerns are founded or not. I'll try and post some photos shortly.

Thanks
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Old 21-02-2013, 07:02   #2
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Here are some photos...



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View of external tube profile

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View of exposed core between hull and inner liner/transverse stiffener

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Internal view of installed tube and thruster (note tube is unsupported apart from the hull penetrations
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Old 21-02-2013, 07:40   #3
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Re: Bow Thruster Install on New Boat

I would definitely have an independent surveyor take a look before accepting it.
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Old 21-02-2013, 08:02   #4
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Re: Bow Thruster Install on New Boat

i for one am bothered by the protrusion on the exterior of the hull.......
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Old 21-02-2013, 09:09   #5
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Re: Bow Thruster Install on New Boat

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Originally Posted by Capt.Alex View Post
I would definitely have an independent surveyor take a look before accepting it.
+100

You are obviously spending quite a large sum in this new build boat... Divide $100-200 dollars by your total invested cost at this point, and I think you will find it infinitesimal by comparison.... To always wonder... worry... or experience a problem that at BEST voids your warranty.... And at WORST leaves your next of kin collecting an insurance check....

Just isn't worth it....

My depreciating 2 cents...
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Old 21-02-2013, 10:23   #6
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Re: Bow Thruster Install on New Boat

Most manufactures don't install bow thrusters until after the hull is made and most of the boat completed. So the process is very well known.

Happy suggested a Surveyor and I would even go a step farther and pay to have a Marine Engineer look at the install and decide if it is sea worthy.
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Old 21-02-2013, 10:57   #7
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Re: Bow Thruster Install on New Boat

My bow thruster is faired quite smooth to the hull. It is also very "finished" on the inside. It is not supported in the middle, as yours also is not, but seems very strong. My opinion is that you should request (a nice way of insisting) that the interior finish work be completed to yacht standards. (nice way of letting them know it has to be smooth, color matched and pretty). Yank around on the tube. If it is not rock solid, have them install a strut under the tube. It would be very easy to build one out of fiberglass. The flange on the outside of the hull....

This is a tough one. 50 mm is a pretty large protrusion. On my boat the build-up is on the inside of the hull, which allows the outside of the hull to be smooth. It actually would be easy to fix, but time consuming. Epoxy the inside of the hull around the tube, to build up a strong area for bonding. This would have been much easier to grind and fill before the tube went in, but can still be done. Make sure that all epoxy is bonded to well cleaned, non painted, surfaces - hence the grinding. On my boat this collar is several inches thick. You have to decide is this issue is worth the effort to change.

I agree that having a surveyor look at this installation is a great idea. Also you broker should be able to help you find other similar boats that have bow thrusters that you can look at. Get your broker involved, they have a vested interest in your satisfaction - and are usually very happy to help. Don't pay anyone any money until you are 100% satisfied (or at least hold back a significant amount).

Lastly, congratulations on the new boat! That is so cool!! You're going to love the bow thruster. I don't use mine too often, but when I do, it really adds a level of control that makes maneuvering easier.
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Old 21-02-2013, 18:57   #8
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I just went through the same installation last fall. A couple points, tube not supported is not an issue, exterior protrusion is good if done right, bad if done wrong. The forward end of the protrusion should stick out far enough that when viewed from head on you can't see the inside of the tube.this is done so that the flow passes over the tube and doesn't impact on the tube interior side. You are attempting to keep boundary layer attached as much as possible and not create turbulent flow at tunnel entrance which would increase drag.

I will try to attach a photo of my install.
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Old 21-02-2013, 19:02   #9
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Re: Bow Thruster Install on New Boat

I can't figure why the builder of your new boat isn't intensly interested in follow up and inspection. Its their reputation and your butt.
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Old 22-02-2013, 02:50   #10
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Re: Bow Thruster Install on New Boat

I agree with some of the above posts about the tube being fit flush with the hull. I have never seen an installation whereby the tube actually sticks out from the hull. I would consider that to be an amaturish botched job.Click image for larger version

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Old 22-02-2013, 08:20   #11
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Thanks for all your responses guys, I will get a marine engineer on to have a look next week. On further investigation is appears that little to no reinforcement was carried out on the inside of the hull to thruster tube connection which probably explains the excessive external profile.
Out of interest, when a keel gets bolted on is it normal practice to measure the bolt torque? does the manufacturer specify a torque?
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Old 22-02-2013, 09:31   #12
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Re: Bow Thruster Install on New Boat

Good question about keel bolt torque. My understanding is that Catalinas do have torque specs. Call the builder for your boat.
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Old 24-02-2013, 06:25   #13
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Re: Bow Thruster Install on New Boat

Quote:
Originally Posted by Sandy Feet View Post
Thanks for all your responses guys, I will get a marine engineer on to have a look next week. On further investigation is appears that little to no reinforcement was carried out on the inside of the hull to thruster tube connection which probably explains the excessive external profile.
Out of interest, when a keel gets bolted on is it normal practice to measure the bolt torque? does the manufacturer specify a torque?
There are many posts here with regard to keel bolt torque... Do a search... Synopsis: If there is a specific torque number available, it is always from the original manufacturer.... The problem usually lies in discovering said value decades after the original build.... You most likely will have to resort to the standard path of determining an approximate value from torque tables based on your particular fastener dimensions... Then comes the famous "lubed or dry" head scratching event.... Again... it's all here.... easy search...
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Old 24-02-2013, 06:56   #14
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Re: Bow Thruster Install on New Boat

PM MINARET on this forum he is very adept at fitting round tube thrusters, ours is a swing arm so my info is of no use.

My feelings are they have done it wrong, i've seen no thruster with the tube hanging out like that. Mineret will assist i'm sure.
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Old 24-02-2013, 07:06   #15
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Re: Bow Thruster Install on New Boat

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Originally Posted by Sandy Feet View Post
Thanks for all your responses guys, I will get a marine engineer on to have a look next week. On further investigation is appears that little to no reinforcement was carried out on the inside of the hull to thruster tube connection which probably explains the excessive external profile.
Out of interest, when a keel gets bolted on is it normal practice to measure the bolt torque? does the manufacturer specify a torque?
Here is the link to the installation of a side-power thruster which I have on my boat and you will see starting on page 7, that the tube should extend far enough from the hull so that when you sight down the direction of water flow, you can't see the back edge of the tube. The other technique is to cut away the trailing edge. Remember that if you cut away the trailing edge, you will need to add that glass back to the inside. That is why most installers use the first technique. This will maintain the laminar flow across the face of the tube opening. Fair the leading edge about 12" for a 1" protrusion of the leading edge of the tube. Round the trailing edge radius. The tube needs no support on the inside as the addition of the tube will by itself make the hull stronger that it was before. On the inside, it needs to be laminated to the interior of the hull with a 2 to 4" lap onto the hull and tube. First create a radius at the hull/tube junction about the radius of a 60 watt light bulb with fairing compound or epoxy/cab-o-sil. The trick is to cut oval shape pads and the wet them up and apply to the joint, overlapping each pad so they will lay smooth around the curve. Build this up until you have a glass thickness close to the thickness of the tube.
Hope this helps.
http://www.imtra.com/Collateral/Docu...130_Manual.pdf
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