bow thruster tubes?

[Jackphilps]

Hello there, fitting bow thruster tubes 200mm dia, just intrested in ideas or the 'correct' way to fit them?

[Submarine Tom]

Athwartship at the bow...

[Jackphilps]

oh sorry, bow

[apex1]

oh sorry, bow

Ahh, ja.

This may become the most informative thread since the invention of foot powder.

We just must try hard enough.

[daiquiri]

Hello there, fitting bow thruster tubes 200mm dia, just intrested in ideas or the 'correct' way to fit them?

Check this Vetus manual I've enclosed here. You should find the info you need. You can see some informative pics in this site:
http://www.cantierelatino.com/installazione_elica_di_prua.html
The site is in italian, but I think those pics are pretty clear even without translation. ;)

[gonzo]

It depends on the hull design. Is it a displacement or planing hull, etc.

[jehardiman]

It depends on the hull design. Is it a displacement or planing hull, etc.

I concur with this. You can easily double or triple the drag penalty of the tube by improper placement as well as give yourself a living nightmare of a structural problem. The best case would be to see if the hull designer/manufacturer had already done the work and has recomendations. 20cm is not a small tube to be putting in one of the most highly loaded areas of a vessels structure. Tabbing and reinforcement will be substantial on a glass boat and weld joint design critical to prevent cracking on a metal one.

[Jackphilps]

Its an aluminium boat and it has double bow thrusters. i have dimentions and and the tubes ready, thats not the problem, just looking for advice into the correct way to fit the tubes, to get them installed as accurate as possible. If there is a method or procedure?

[jehardiman]

What type of boat, bow shape (V, spoon, or other), and speed? My gut feeling is to recommend a shell insert just to resolve weld and strength issues as well as improve thrust output. Depending on speed and slamming, just using a corner weld (C2v.2) for the tube/shell connection is not the best way.

[gonzo]

Depending on shape and speed, a fairing may be adviseable.

[Jackphilps]

What type of boat, bow shape (V, spoon, or other), and speed? My gut feeling is to recommend a shell insert just to resolve weld and strength issues as well as improve thrust output. Depending on speed and slamming, just using a corner weld (C2v.2) for the tube/shell connection is not the best way.??


v hull, the rest of the information is not needed. Everything else has been designed, shell insert allready in place, as is said i have dimentions, all i want to find out is how to cut the hole's for the tubes accuratly, so they sit level and paralell. Is there a tool i can use, is there a method ? sorry if im confusing people.

[Jackphilps]

im looking for advice from a builder

[apex1]

Jack,

you would have had advice from a builder, if you would provide the info requested!
But when the "rest is not needed" to quote you, it will be hard to get what you look for!

Regards
Richard
boatbuilder

[gonzo]

If you need instruction on how to cut a hole level and parallel, this job is way over your head.

[Frosty]

I saw a tip section in a magazine on how to cut the hole level and parallel.

It was surprisingly easy and obvious with little tools.

Every thing is easy if you know how to do it!!

Fairing is always advisable. Keeping the tube deep enough is important --I seem to remember 1 foot min ( I dont know where I got that from) but some power boats will be able to plane with it out of the water which would certainly give you peace of mind that it wasnt dragging you down.

[Submarine Tom]

What does the manufacturer recommend?

[jehardiman]

v hull, the rest of the information is not needed. Everything else has been designed, shell insert allready in place, as is said i have dimentions, all i want to find out is how to cut the hole's for the tubes accuratly, so they sit level and paralell. Is there a tool i can use, is there a method ? sorry if im confusing people.

So you want shipfitting advice? As Richard and Gonzo implied, this is a relatively simple layout job. There are many ways to cut a hole like this in the yard, lots of shipfitter tricks and specialized cutters or custom built tool jigs. As you asked how to do it, I will assume that you don't have those yard skills and only common hand tools.

Ok, here is an example of how it can be done, especially for large dimensions where you can't just buy or make a cutter bit. The more precise you are, the better the fitup, but remember it is always better to cut the first hole too small but in the right place:

Locate and determine the level of the Baseline, the forward reference point, and any list as the hull sits on the blocks. Using a transit or laser level construct several level transverses perpendicular to the vessels CL in away of each thruster tube. Lift a set of offsets from the hull in way of the tube opening remembering to correct for list and trim as she sits, you will need both sides as boats are rarely symetric within throat tolerances. Regardless of any other way to make the opening in the shell, you will need to accurately layout the axis of the tube on the hull shell if you want it correctly positioned.

Go to the loft floor and project the INNER intersection of the tube to the insert to the OUTER shell. This is also the time to lift from the loft floor the circumfrential offsets of the tube from CL so you can cut the tube to near net shape. From the outer shell projection offet a second ellispe the width of the cut kerf inward towards the axis of the thruster tube. This will mark the ellispe you need cut. Make the cut (at the proper list and perpendicular to CL, normally you drill a set of reference holes), then dress the throat and cut the bevel. Fit the tube and mark the trim line. Trim the tube, tack, then weld.