Reinforcing the uxter plate

[blackrose]

My widebeam has a very large uxter plate and it's only 6mm thick. It's completely unreinforced and while that's fine on canals and non-tidal rivers, on lumpy water it groans and I think it must be flexing.

 

I want to have some angle welded in (on the inside) to reinforce the uxter plate, but where would it go and at what centres? Should it go square across the uxter or be positioned at an angle?

 

Where the ends of the angle meet the hull sides should they be welded to the hull sides? Also would 2" angle be ok or should it be bigger?

 

Here is a diagram. The baseplate is also unreinforced in the engine hole but the engine bearers are fully welded in and the baseplate is 10mm thick so I don't think that's a problem. It's when waves roll under the uxter plate that the disconcerting noises start.

 

Yes, it's a tapered square stern. The uxter plate sits about 3" under the waterline.

 

Edited December 21, 2013 by blackrose

[MtB]

Mike, is diagram accurate? The forward ends of the swim widen out the meet the hull sides surely....

 

MtB

[blackrose]

Mike, is diagram accurate? The forward ends of the swim widen out the meet the hull sides surely....

 

MtB

 

Yes, but the swims meet the hull sides about 5ft forward of the watertight bulkhead, not in the engine hole.

 

I drew it as best as I could but it's not completely accurate.

 

You can see what I mean here. Actually, it's probably more than 5ft forward. The bulkhead between the engine hole and cabin is the same as the bulkhead above the deck with the stern doors, so you can see exactly where it is in relation to the swims. Anyway, the point is it's a bloody big uxter plate!

 

Edited December 21, 2013 by blackrose

[GUMPY]

 

Is that a high water mark just below the tops of the risers? No wonder you have kept your dingy

[blackrose]

Is that a high water mark just below the tops of the risers? No wonder you have kept your dingy

 

No I don't think so. The risers are telescopic and the mooring warden raises them in winter or whenever it looks like the levels are going to rise. I think that rust mark is where the inside part of the riser has been laying inside rain water that collects inside the outer part. Having said that, people here tell me that last year the river levels got to about 2ft from the top of the extended riser - so just below the rust! It certainly makes you think and I wouldn't be without the dinghy & outboard!

Edited December 21, 2013 by blackrose

[MtB]

I see.

 

Seeing the shape of the swim in the foto I can imagine the whole thing wobbling up and down. I'm inclined to suggest some vertically diagonal bracing. A strut or struts from where the uxter plate meets the swim on one side, diagonally up and across to where the side deck meets the hull side opposite. The triangulation will add a LOT of stiffness and hopefully clear the engine too.

 

I'm inclined to suggest 3" x 3" angle though, or 2" box section or the struts themselves might flex.

 

 

MtB

 

 

(Spellin edit)

Edited December 21, 2013 by Mike the Boilerman

[blackrose]

I see.

 

Seeing the shape of the swim in the foto I can imagine the whole thing wobbling up and down. I'm inclined to suggest some vertically diagonal bracing. A strut or struts from where the uxter plate meets the swim on one side, diagonally up and across to where the side deck meets the hull side opposite. The triangulation will add a LOT of stiffness and hopefully clear the engine too.

 

I'm inclined to suggest 3" x 3" angle though, or 2" box section or the struts themselves might flex.

 

 

MtB

 

 

(Spellin edit)

 

You may well imagine it, but that's not what happens or I would feel it when I'm standing on the deck. When waves roll under the stern the deck doesn't flex, it's just the uxter plate that flexes. The vertical hull sides strengthen the stern.

 

It's essentially the same design as a narrowboat - just bigger. What you're suggesting is way over the top.

 

Do you think this stern would wobble up and down too?

 

Edited December 21, 2013 by blackrose

[MtB]

 

I don't think the whole thing wobbles or I would feel it when I'm standing on the deck. It's just the uxter plate that flexes. The vertical hull sides strengthen the stern.

 

It's essentially the same design as a narrowboat - just bigger. What you're suggesting is way over the top.

 

I see.

 

I was imagining a similar flexing to that I get on Aldebaran when the K1 is running at the resonant frequency of the counter. It makes the counter wobble up and down alarmingly and I change the engine speed immediately.

 

MtB

[PaulJ]

I would have thought 50 x 6mm angle to be sufficient but that depends on how far apart they are of course. I made a 10 ft 6 wide pontoon/boat once using 6mm plate and 50mm angle-had a 600 gallon waste tank sat direct on the angles and that never seemed to flex.

I would be suprised if uxter plate actually moves much- could it not just be bonging due to welding distortion? That wouldnt need alot more strength to stop it.

Edited December 21, 2013 by PaulJ

[blackrose]

Yes, I don't actually know for sure that the uxter is flexing, it's just an educated guess. It could just be the noise of the waves underneath. I guess I should get under there while someone else steers the boat through some waves, but lifting the deckboards and getting into the engine hole on a tidal river isn't really very appealing!

I would have thought 50 x 6mm angle to be sufficient but that depends on how far apart they are of course. I made a 10 ft 6 wide pontoon/boat once using 6mm plate and 50mm angle-had a 600 gallon waste tank sat direct on the angles and that never seemed to flex.

 

Did you take it on any lumpy water?

Edited December 21, 2013 by blackrose

[PaulJ]

Did you take it on any lumpy water?

Er no. It was a portable (and unpowered) pump out boat. Water was only ever lumpy on very windy days..

Dont know if you are familar with Hertford Hansers? Wide ish 40 ft steel boats with 6mm flat bottoms and little cross members-they bong alot too

[blackrose]

Er no. It was a portable (and unpowered) pump out boat. Water was only ever lumpy on very windy days..

 

That's what I mean. Mine doesn't seem to flex either until you hit some waves. I'm sure your pontoon boat would flex in waves too.

Edited December 21, 2013 by blackrose

[PaulJ]

Maybe.

I would weld in some angle like this(not recomending three a side-thats just to show what I mean)-ensuring good size drainage where angle meets hull side. It would be very strong.

[blackrose]

Maybe.

I would weld in some angle like this(not recomending three a side-thats just to show what I mean)-ensuring good size drainage where angle meets hull side. It would be very strong.

 

Yes, that's the sort of thing I was thinking of, plus one more right across the back. I think it's the wider areas that are more prone to flexing.

[mark99]

Transverse angle iron? consider the effect on handling. Unless done on the dry side of course!

Edited December 21, 2013 by mark99

[PaulJ]

 

Yes, that's the sort of thing I was thinking of, plus one more right across the back. I think it's the wider areas that are more prone to flexing.

At the back I would be tempted to go more diagonal-reason being that the angle is shortest possible length between the hull and swim uprights and so alot stronger.

[Ron T]

I'd tend to run them fore and aft,less plate in between to drum.Decent walled box section rather than angle.

[Biggles]

As a welder..........

 

I would use 50 to 75 x 6 flat and bend/tack along the line of the swim with centers of about 250mm. This would be easy inside and easy outside if in dry dock.

 

I wonder if this will solve the problem though. I have a 10mm uxter and the resonance from the double mounted genny still finds its way in.

 

IMO when you are on the move noise has to be accepted much like a car. If you have a RR the noise will be less than a Fiat/Ford/Dacia/ same with Liverpool boats.

 

There's too many variables. When you stop just enjoy the peace and quite.

 

My ambition is to have someone helm my boat while I sleep. I'm sure I could as the sound of the engine and prop in the bedroom is quite hypnotic.

[blackrose]

Transverse angle iron? consider the effect on handling. Unless done on the dry side of course!

 

See post 1

 

"I want to have some angle welded in (on the inside) to reinforce the uxter plate..."

 

Why would anyone even think about doing it on the outside?

[Biggles]

 

See post 1

 

"I want to have some angle welded in (on the inside) to reinforce the uxter plate..."

 

Why would anyone even think about doing it on the outside?

 

Because it would create an uneven surface that might be needed in the future? For say storage, or equipment.

[blackrose]

As a welder..........

 

I would use 50 to 75 x 6 flat and bend/tack along the line of the swim with centers of about 250mm. This would be easy inside and easy outside if in dry dock.

 

I wonder if this will solve the problem though. I have a 10mm uxter and the resonance from the double mounted genny still finds its way in.

 

IMO when you are on the move noise has to be accepted much like a car. If you have a RR the noise will be less than a Fiat/Ford/Dacia/ same with Liverpool boats.

 

There's too many variables. When you stop just enjoy the peace and quite.

 

My ambition is to have someone helm my boat while I sleep. I'm sure I could as the sound of the engine and prop in the bedroom is quite hypnotic.

 

You might be right. I think I will climb down into the engine hole one day if I can find someone to steer my boat in a tideway.

 

When I crossed the Bristol Channel with a pilot it was an odd experience for me to be able to walk about inside the boat and make a cup of tea as I'm always steering. It was calm then and we didn't really have any waves until we got close to Sharpness.

 

 

Because it would create an uneven surface that might be needed in the future? For say storage, or equipment.

 

Yes. but rather that than an uneven uxter on the outside. You can always lay some 18mm ply over the angle on the inside if you want a flat surface for storage.

Edited December 22, 2013 by blackrose

[PaulJ]

I wouldnt have thought adding any steel running along the length of boat to be worthwhile. Lengthwise the steels would just sit on the curve of plate (assuming it does infact curve up and into the boat if you see what I mean) and flex up and down with it.

Think of your baseplate, which is even wider and the steel channel/angle always run across the boat.

I worked on a nb recently that had the last two floor bearers 4 ft apart (dont know why, perhaps run out of steel!), had 10mm base plate and that had quite a curve to it in the middle.

[mark99]

 

See post 1

 

"I want to have some angle welded in (on the inside) to reinforce the uxter plate..."

 

Why would anyone even think about doing it on the outside?

 

 

Ok didn't see that. Just saying - you would have to be a tiny ooopah lumpah to be able to access the dry side of our uxter and weld it.

[Biggles]

 

You might be right. I think I will climb down into the engine hole one day if I can find someone to steer my boat in a tideway.

 

When I crossed the Bristol Channel with a pilot it was an odd experience for me to be able to walk about inside the boat and make a cup of tea as I'm always steering. It was calm then and we didn't really have any waves until we got close to Sharpness.

 

 

Yes. but rather that than an uneven uxter on the outside. You can always lay some 18mm ply over the angle on the inside if you want a flat surface for storage.

 

if you can afford the loss in height that would be fine.

[Tam & Di]

 

Yes, that's the sort of thing I was thinking of, plus one more right across the back. I think it's the wider areas that are more prone to flexing.

 

A thing maybe worth bearing in mind is that IF it is the uxter flexing in these conditions it will likely be flexing overall forming a gentle arc. If you stiffen the width of the plate any continuing flex will be uniquely at the weld, which could cause failure there. It's a fatique point on some working narrowboats where the frame angles finish just short of the central kelson for exactly that reason.

 

Tam