Reinforcing the uxter plate

[DHutch]

Which way up are you putting the angle? Welding the edge to the plate to make a C-section?

 

 

Daniel

[blackrose]

Which way up are you putting the angle? Welding the edge to the plate to make a C-section?

 

 

Daniel

No, just welding one flat of the angle to the uxter, the same as the angle that was welded to the baseplate by the builder. Isn't that the way it's normally done?

[blackrose]

Would it not be better to ask the shell builder what he suggests or if no longer around then another reputable one.

 

Neil

Gary Peacock, a boat builder who used to frequent this forum, suggested I reinforce the uxter plates by welding angle onto them, although he didn't say exactly where those pieces of angle should be positioned.

Mike, the structure is already stiff at the edges of the uxter plate in the long direction. I think the long pieces (1.83m) could usefully be omitted altogether. The cross pieces should extend to the very edges, with limber holes at the outside and rounded at the inside edges. Personally I would use flat bar to avoid hidden (more difficult) welding and making inspection and painting easier. You really don't need the 'belt and braces' of angle bar, just local stiffening. 50x6 flat bar should suffice, unless you plan to use the upper leg of the angle as a support for equipment. KISS principle should apply.

 

(chartered engineer)

Thanks, some good suggestions, although I don't think flat bar will offer much support and will be no easier to weld on than angle.

[Murflynn]

No, just welding one flat of the angle to the uxter, the same as the angle that was welded to the baseplate by the builder. Isn't that the way it's normally done?

no.

 

 

ex LB widebeam owner

Edited April 28, 2015 by Murflynn

[cereal tiller]

no.

 

 

ex LB widebeam owner

 

 

The Angle section has a 'Heel' and 2 'Toes'

The Boatbuilder would have welded one of the Toes to your base plate,

 

CT

[The Pipe]

No, just welding one flat of the angle to the uxter, the same as the angle that was welded to the baseplate by the builder. Isn't that the way it's normally done?

Another NO. If your going to do it that way you might as well use 6X50 strip.

[David Mack]

No, just welding one flat of the angle to the uxter, the same as the angle that was welded to the baseplate by the builder. Isn't that the way it's normally done?

 

Welding one of the 'toes' of the angle to the plate, so that the other leg of the angle is parallel to but spaced off the plate gives a much higher stiffness, so is better to achieve your objective of stiffening the uxter plate. For baseplates it also gives a flat flange which the floor bearers can be fitted to.

[SamKingfisher]

I think some people should spend 5 minutes messing around with some cardboard. That should clear up why angle is less flexible than flats.

[Murflynn]

flat bar is not flexible when it is welded to a plate.

please don't try to re-invent fabrication practices.

for straightforward stiffening a flat bar is easier to weld, easier to inspect, easier to paint. For 'easier' read - 'won't be botched'.

 

of course for ultimate moment of inertia (measurement of stiffness) an angle welded by its toe is stronger, but we are discussing very minor stiffening requirements here.

[ditchcrawler]

flat bar is not flexible when it is welded to a plate.

please don't try to re-invent fabrication practices.

for straightforward stiffening a flat bar is easier to weld, easier to inspect, easier to paint. For 'easier' read - 'won't be botched'.

 

of course for ultimate moment of inertia (measurement of stiffness) an angle welded by its toe is stronger, but we are discussing very minor stiffening requirements here.

Agree

[blackrose]

Another NO. If your going to do it that way you might as well use 6X50 strip.

 

You don't think that the vertical part of the angle would increase stiffness?

I think some people should spend 5 minutes messing around with some cardboard. That should clear up why angle is less flexible than flats.

 

Agreed.

flat bar is not flexible when it is welded to a plate.

please don't try to re-invent fabrication practices.

for straightforward stiffening a flat bar is easier to weld, easier to inspect, easier to paint. For 'easier' read - 'won't be botched'.

 

of course for ultimate moment of inertia (measurement of stiffness) an angle welded by its toe is stronger, but we are discussing very minor stiffening requirements here.

 

I disagree. I guess it depends on one's definition of "very minor", but when you've got tonnes of water flexing a plate I don't think we're talking about very minor stiffening requirements. Why would it be any more minor than any other part of the boat? They haven't used flat bar anywhere else.

Edited April 28, 2015 by blackrose

[blackrose]

 

Welding one of the 'toes' of the angle to the plate, so that the other leg of the angle is parallel to but spaced off the plate gives a much higher stiffness, so is better to achieve your objective of stiffening the uxter plate. For baseplates it also gives a flat flange which the floor bearers can be fitted to.

 

Ok thanks, I'll talk to the fabricator about doing it that way.

 

This looks like it's done the way you describe.

 

Edited April 28, 2015 by blackrose

[The Pipe]

 

You don't think that the vertical part of the angle would increase stiffness?

 

Agreed.

 

I disagree. I guess it depends on one's definition of "very minor", but when you've got tonnes of water flexing a plate I don't think we're talking about very minor stiffening requirements. Why would it be any more minor than any other part of the boat? They haven't used flat bar anywhere else.

Any vertical member adds stiffness if you’re using angle the logical way is to weld one toe of the angle to the uxter plate so you have a vertical stiffener and a horizontal edge which will stop any chance of buckling of the vertical. Doing it this way will also allow you to easily put a board across the stiffening if you ever require installing something in the area.

Orion narrow boats used 10X60 strips for their hull frames.

I’m glad you found a photo for the correct way to install the angle I could not find one.

 

Fortunately the people who pay me as a senior lead design engineer and approval signature for aircraft structures have a better view of my abilities than suggesting I go and play with cardboard.

[DHutch]

If you weld flat strip to the uxter plate, flat onto the plate, it added almost nothing.

If you weld flat strip to the uxter plate, at 90deg to the plate, it adds a considerable amount.

If you then weld flat strip to the top of that, it really stiffens it up a treat making a c-section.

 

Angle iron is basically just two strips at right angles.

 

I could so some sums, but I must say it would take me nearly as long as someone reading the textbook for the first time as so much of what we do at work is either done by intuition or FEA simulation there is very little middle ground left. While I expect as someone who is also a senior design I should also not be making cardboard training aids, I have overseen someone in making a foot of inch box from a sheet of A4, to confirm its torsional capability was far greater than either a L or C shape. Hell of a lot cheaper then some of the rapid prototyped chassis we have had made!

 

 

Do you have a plan view of the uxter plate and the proposed layout?

 

As said, the edges and narrow sections will already be far stiffer than the angle and you would be surprised how much even just one across the would make it, at which point I would not put in extras for the sake of it. The other question is how they interact with the weed hatch, which itself will be very stiff, but if its not braced to anything may be moving around and the hole under it along with the minor weld distortion caused by welding it in originally may well be root of a lot of the issues.

 

You also want to avoid having areas you cannot paint.

 

 

 

Daniel

[The Pipe]

If you weld flat strip to the uxter plate, flat onto the plate, it added almost nothing.

If you weld flat strip to the uxter plate, at 90deg to the plate, it adds a considerable amount.

If you then weld flat strip to the top of that, it really stiffens it up a treat making a c-section.

 

Angle iron is basically just two strips at right angles.

 

I could so some sums, but I must say it would take me nearly as long as someone reading the textbook for the first time as so much of what we do at work is either done by intuition or FEA simulation there is very little middle ground left. You also want to avoid having areas you cannot paint.

 

 

Do you have a plan view of the uxter plate and the proposed layout?

 

As said, the edges and narrow sections will already be far stiffer than the angle and you would be surprised how much even just one across the would make it, at which point I would not put in extras for the sake of it. The other question is how they interact with the weed hatch, which itself will be very stiff, but if its not braced to anything may be moving around and the hole under it along with the minor weld distortion caused by welding it in originally may well be root of a lot of the issues.

 

 

 

Daniel

Ahh, Daniel a stresser who has forgotten how to do hand calcs. I just love the colours you get in fine white elephant analasis.

[DHutch]

I'm design engineer, rather than a 'stresser' as such but yes....

 

Outside of the chassis and boom pretty much everything else its fatigue rather than stiffness that's the issue, stiffness is almost the enemy!

 

 

Daniel

[The Pipe]

I'm design engineer, rather than a 'stresser' as such but yes....

 

Outside of the chassis and boom pretty much everything else its fatigue rather than stiffness that's the issue, stiffness is almost the enemy!

 

 

Daniel

In the aircraft industry we suffer from everything stiffness, fatigue and weight but these days the biggest problem is design to cost!

[Murflynn]

Dan is right, but it doesn't need analysis.

 

 

 

You don't think that the vertical part of the angle would increase stiffness?

 

 

 

I disagree. I guess it depends on one's definition of "very minor", but when you've got tonnes of water flexing a plate I don't think we're talking about very minor stiffening requirements. Why would it be any more minor than any other part of the boat? They haven't used flat bar anywhere else.

nobody would weld a stiffener bar horizontally.

 

The stiffening requirement increases with (as far as I remember) with the square of the unsupported length.

I can assure you that very little stiffening is needed for your uxter plate, the forces do not amount to tonnes. A flat unsupported 6mm plate 4ft wide could (would) flex under a very small repetitive load like waves under the stern of the boat.

 

However if you want to listen to the most conservative (and probably unqualified) advisors you will certainly get a very strong result. The art of design is to do it neatly and economically. If you want to do it clumsily and over-egg it then that is your choice and will certainly do no harm.

 

If you are interested there are design guides for scantlings of typical narrow and wide beam canal boats. I got a reference on this from Gary Peacock, previously of this forum. But seriously, your issue is so straightforward that it doesn't merit detailed analysis, it just requires nominal stiffening.

Edited April 29, 2015 by Murflynn

[DHutch]

Here we are my 'seat of the pants' comments.

- Indecently, I mentioned which way up I would be putting the angle in my post back on Dec'13 earlier in this thread!

 

 

A) Might no bother with the 0.62 on of the far left but it would do no real harm.

Would certainly continue the one that stops for the batteries all the way, if this really not feasible, I expect I would omit it all together.

C) I presume the hatched one is the one we are going with, this looks the best, again I would certainly aim to run it all the way not stop it for the fuel line mounting brkt.

D) Don't really see how you would run the fore-aft 1.8 long one unless you are placing it on top of the others which would then become a right pain. I expect it is overkill and not adding a lot.

E) The other side can then just be symmetrical to the side shown below which if nothing else will look tidier.

F) Stiffness is is inversely proportional to length, so you want to largest spans to be going perpendicular to the span, although also what I presume is the fuel tank? Will help the longest one by the looks of it.

G) You have a choice of which way you put them, but I would select which ever way makes painting easier.

H) Do you have a photo looking directly backwards, and or show how the weedhatch is braced into the deck or however that's welded in?




I presume from the scale you are planning to use 2"/50mm angle 5-6mm thick? As said, angle is better for stiffness then strip and also means you don't have an edge but a nice flat face to fasten things like the battery tray to. It also doesnt flop about when you are trying to tack it in place!

 

Also, for what its worth, I agree that 6mm seems thin for such a large flat surface.

 

 

 

Daniel

[DHutch]

In the aircraft industry we suffer from everything stiffness, fatigue and weight but these days the biggest problem is design to cost!

 

Weight is not really an issue for us, we do occasionally have to loose some mass, but we do also fairly often use 20-25mm plate for chassis members (See JCB 560-80) and even the booms are often 8-10mm steel. The 20m machine (JCB 540-200) goes down 6mm with a corresponding increase in the grade of steel but we dont even cut thinner than 4mm steel on site! Thinner than that and its bodywork....

 

 

Daniel

[onionbargee]

If you look at metal boats where no linings have to be attached, ie work boats fabricated by shipbuilding firms, the framing Is usually flat strip. Angle would just be a waste of metal and extra cost. The rigidity comes from the height and thickness of the flats, the extra leg on the angle would only stiffen the stiffener, not the plate, totally pointless. unless you want to lay a floor over the top, which seems unlikely on an uxter plate.

 

 

Like you, I don't have any.

 

.

Wrong again twinkle.

[blackrose]

 

Fortunately the people who pay me as a senior lead design engineer and approval signature for aircraft structures have a better view of my abilities than suggesting I go and play with cardboard.

 

Get yourself some cardboard and a bit of stickyback plastic and then we can talk... (I'm just joking)

Edited April 29, 2015 by blackrose

[blackrose]

nobody would weld a stiffener bar horizontally.

 

The stiffening requirement increases with (as far as I remember) with the square of the unsupported length.

I can assure you that very little stiffening is needed for your uxter plate, the forces do not amount to tonnes. A flat unsupported 6mm plate 4ft wide could (would) flex under a very small repetitive load like waves under the stern of the boat.

 

However if you want to listen to the most conservative (and probably unqualified) advisors you will certainly get a very strong result. The art of design is to do it neatly and economically. If you want to do it clumsily and over-egg it then that is your choice and will certainly do no harm.

 

If you are interested there are design guides for scantlings of typical narrow and wide beam canal boats. I got a reference on this from Gary Peacock, previously of this forum. But seriously, your issue is so straightforward that it doesn't merit detailed analysis, it just requires nominal stiffening.

 

Ok, I do apologise because I honestly thought that's what you meant. However, a couple of other people thought that too, so either we are completely stupid or you could have explained yourself a bit more clearly without assuming we knew what you meant. After all, on a largely anonymous forum such as this it's difficult to know the level of anyone's qualifications or experience.

 

Anyway I will take your opinion onboard and I'll probably just get the angle welded with one flat on the uxter because it's an easier and cheaper job and from what you're saying about the forces involved, it should provide sufficient stiffness. Also, from what I can make out there is one difference between welding flat bar upright onto the plate being supported, and using angle with one flat against the plate: The flat bar would have to be fully welded to the plate to provide equivalent strength as a length of angle that is welded for 1" say every 6" . That's what I plan to do - and again it makes the whole job much quicker and cheaper.

 

Anyway, thanks for your input - most useful.

Do you have a plan view of the uxter plate and the proposed layout?

 

 

Not yet but I'll try to post one.

Edited April 29, 2015 by blackrose

[blackrose]

Here we are my 'seat of the pants' comments.

- Indecently, I mentioned which way up I would be putting the angle in my post back on Dec'13 earlier in this thread!

 

 

A) Might no bother with the 0.62 on of the far left but it would do no real harm.

B ) Would certainly continue the one that stops for the batteries all the way, if this really not feasible, I expect I would omit it all together. Ok

C) I presume the hatched one is the one we are going with YES, this looks the best, again I would certainly aim to run it all the way not stop it for the fuel line mounting brkt.

D) Don't really see how you would run the fore-aft 1.8 long one unless you are placing it on top of the others which would then become a right pain. I expect it is overkill and not adding a lot. Ok, that will save some time and money.

E) The other side can then just be symmetrical to the side shown below which if nothing else will look tidier.

F) Stiffness is is inversely proportional to length, so you want to largest spans to be going perpendicular to the span, although also what I presume is the fuel tank? Will help the longest one by the looks of it.

G) You have a choice of which way you put them, but I would select which ever way makes painting easier. Now the engine room is empty I plan to scurf out all the rust and paint it after this job has been done.

H) Do you have a photo looking directly backwards, and or show how the weedhatch is braced into the deck or however that's welded in? I will post one tomorrow.

 

 

I presume from the scale you are planning to use 2"/50mm angle 5-6mm thick? Yes, 5mm thick As said, angle is better for stiffness then strip and also means you don't have an edge but a nice flat face to fasten things like the battery tray to. I might be getting the angle welded in with the flat to the uxter. I know it's wrong, but I think it will be ok. That area is just used for storage so I'll just store stuff between the angle. It also doesnt flop about when you are trying to tack it in place!

 

Also, for what its worth, I agree that 6mm seems thin for such a large flat surface.

 

Thanks for your help.

Edited April 29, 2015 by blackrose

[Timleech]

 

 

I presume from the scale you are planning to use 2"/50mm angle 5-6mm thick? Yes, 5mm thick As said, angle is better for stiffness then strip and also means you don't have an edge but a nice flat face to fasten things like the battery tray to. I might be getting the angle welded in with the flat to the uxter. I know it's wrong, but I think it will be ok. That area is just used for storage so I'll just store stuff between the angle. It also doesnt flop about when you are trying to tack it in place!

 

Also, for what its worth, I agree that 6mm seems thin for such a large flat surface.

 

Thanks for your help.

 

 

 

Apart from being the weakest way to use the angle, it gives you a wonderful moisture/rust trap between angle and plate.

 

I haven't read every post, but my reading of your spec for the amount of weld seemed far to little. Maybe I misread or someone has already picked up on this.

 

Tim