Safe to seal a bow thruster tube with sealant?!

[blackrose]

1 minute ago, MtB said:

 

 

Blimey, I bet the arse ends of thems wobbles alarmingly then. Especially thems with square sterns.

 

 

No, you would lose that bet.

Edited March 31, 2023 by blackrose

[ditchcrawler]

13 minutes ago, IanD said:

 

If the OP wants to keep open the possibility of fitting a BT in future -- which will bolt down to a flat flange above the BT tube, with a seal between them -- then there's nothing wrong with having a flat plate where the BT would go, bolted to the flange and sealed in the same way -- this is no worse than having a BT installed as far as leaks are concerned. But a bulkhead is a very good idea just in case a leak *does* happen, whether the BT is installed or not.

 

Either way the solution posted by the OP is a bodge -- no proper plate/seal *and* no bulkhead... 😞

But with no thruster in there the pipe can be blacked all the way through. what about in the hull leaks at one of those hundred feet of welds

[IanD]

Just now, magnetman said:

That is a good approach. I was thinking about the system employed in the OP's boat. I think the water tank is in front of the BT in this instance. 

 

 

Doesn't look like it, I think you can see the sides of the bow quite close to the left and right in the OP's picture.

[magnetman]

Nobody has mentioned the potential usefulness of bow mounted laterally firing torpedoes. 

 

 

[IanD]

Just now, magnetman said:

Nobody has mentioned the potential usefulness of bow mounted laterally firing torpedoes. 

 

 

 

[magnetman]

1 minute ago, IanD said:

 

Doesn't look like it, I think you can see the sides of the bow quite close to the left and right in the OP's picture.

I think what is visible are the prop access hatches. It will be a twin prop bow thruster with a raised access hatch (weed hatch but smaller) for each prop. 

And motor in between. 

[ditchcrawler]

3 minutes ago, blackrose said:

 

I think a flat plate is worse. How does a flat plate seal to the outside of a curved tube - other than with a load of bodged sealant? At least a BT motor is mounted on a curved bracket/seal which matches the curve of the tunnel.

My BT is a curved fitting onto the tube, but reading this thread I thought maybe some were flat and needed a flat bit on the tube. I guess there must be a lot of people on here with bowthrustes for that information to rise to the surface.

[Tonka]

1 minute ago, magnetman said:

Nobody has mentioned the potential usefulness of bow mounted laterally firing torpedoes. 

 

 

Nitromor's on a plunger torpedo. You fire it onto the GRP boat. the sucker sticks onto the GRP. the Nitromors then realeses and is allowed to eat the GRP. When hole big enough the whole torpedo falls off hiding the evidence. Boat sinks

[magnetman]

Spring loaded magnetic limpet mines could be interesting with 5 minute timers. You could ping them onto boats going past to fast and 5 minutes later the semtex blows a 3 inch hole in the shell plating. 

[IanD]

5 minutes ago, ditchcrawler said:

My BT is a curved fitting onto the tube, but reading this thread I thought maybe some were flat and needed a flat bit on the tube. I guess there must be a lot of people on here with bowthrustes for that information to rise to the surface.

They vary, most are single-prop nowadays. This is mine, but I don't know how it was fitted onto the steel BT tube, and I can't see this in any of my photos...

 

[David Mack]

30 minutes ago, IanD said:

 

The BT in mine is similarly close to the stem and is effectively inside the boat, but has a welded bulkhead behind it which extends up to above the waterline -- which is the *right* way to do it.... 😉

 

How high above the waterline does that bulkhead reach? If the bt tube is going to leak it should be 250mm above the waterline for RCR/BSS compliance.

[magnetman]

is there access to the prop for cleaning?

 

from that picture it looks like they weld it on. Seems a bit odd but maybe the image is not exactly accurate ? 

2 minutes ago, IanD said:

They vary, most are single-prop nowadays. This is mine, but I don't know how it was fitted onto the steel BT tube, and I can't see this in any of my photos...

 

 

Edited March 31, 2023 by magnetman

[IanD]

2 minutes ago, David Mack said:

How high above the waterline does that bulkhead reach? If the bt tube is going to leak it should be 250mm above the waterline for RCR/BSS compliance.

 

Far enough -- the photo is a bit deceptive, it's not a Josher bow so the baseplate is pulled up towards the stem, the bottom of that bulkhead is already some way above where a flat baseplate would be.

[Tonka]

5 minutes ago, IanD said:

They vary, most are single-prop nowadays. This is mine, but I don't know how it was fitted onto the steel BT tube, and I can't see this in any of my photos...

 

How do you change the blade if it gets damaged

[IanD]

3 minutes ago, magnetman said:

is there access to the prop for cleaning?

 

 

Yes because the BT tube is so short (BT was pushed forward as far as possible), you can easily reach the prop from both sides of the boat.

Just now, Tonka said:

How do you change the blade if it gets damaged

 

Through the tunnel, it it's actually fitted like shown in the Vetus photo (which I can't confirm, that shows a GRP tunnel). There are grilles at each end of the tunnel to stop debris getting in.

[magnetman]

From the canal bank? Can you get the prop off?

[Tonka]

Just now, IanD said:

 

Yes because the BT tube is so short (BT was pushed forward as far as possible), you can easily reach the prop from both sides of the boat.

yes but the same device could have been fitted into a widebeam so your arm was not long enough.

Surly the motor should be higher up. the shaft longer and the hole into the tube bigger and then you could unbolt the whole thing and removed without taking the boat out of the water.

[IanD]

2 minutes ago, magnetman said:

From the canal bank? Can you get the prop off?

Yes the prop comes off. Might be possible from the bank, or might have to get into the water. Don't expect to need to do it very often. Loads of thrusters around like this, so long as they're close enough to one end of the tunnel to reach in that's how they're accessed -- in my case you can reach the prop from both sides to clear it (but only remove it from one, obviously).

[MtB]

9 minutes ago, magnetman said:

is there access to the prop for cleaning?

 

What struck me was the difficulty of removing/replacing the angled gear prop-drive assembly when it fails. Boat would need docking I reckon. 

[magnetman]

1 minute ago, Tonka said:

yes but the same device could have been fitted into a widebeam so your arm was not long enough.

Surly the motor should be higher up. the shaft longer and the hole into the tube bigger and then you could unbolt the whole thing and removed without taking the boat out of the water.

I think usually people would think of docking the boat to do this sort of job but of course it is always worth remembering that bow thrusters are not needed in the first place.

 

 

 

Its called the "girly button" for a reason. 

[IanD]

3 minutes ago, Tonka said:

yes but the same device could have been fitted into a widebeam so your arm was not long enough.

Surly the motor should be higher up. the shaft longer and the hole into the tube bigger and then you could unbolt the whole thing and removed without taking the boat out of the water.

 

That's not how these thrusters are designed to be fitted or maintained. The motor/controller part can be unbolted and removed without breaking the seal. The prop is accessed via the tunnel.

[Tonka]

1 minute ago, magnetman said:

I think usually people would think of docking the boat to do this sort of job but of course it is always worth remembering that bow thrusters are not needed in the first place.

 

 

Yes I appreciate that. 

[IanD]

2 minutes ago, MtB said:

 

What struck me was the difficulty of removing/replacing the angled gear prop-drive assembly when it fails. Boat would need docking I reckon. 

 

Quite possibly, but a properly designed/built assembly shouldn't need this for a very long time -- which I would certainly hope this is, given the cost. These thrusters are targeted at the heavy-use "professional" market, they'll run at full power for ten minutes and much longer at lower powers (they're variable speed). Lots of them out there...

[magnetman]

Christ a bow thruster running for ten minutes is enough to wake the dead. 

[Tonka]

2 minutes ago, IanD said:

 

That's not how these thrusters are designed to be fitted or maintained. The motor/controller part can be unbolted and removed without breaking the seal. The prop is accessed via the tunnel.

Are you really saying that you have a GRP tube somehow attached to a steel boat. In that tube is a propellor which you can only access by getting into the water and putting you arm up a tube having removed the guard. But you can remove the motor from inside the boat but not the gearbox.