expancian joints

[Richard Bustens]

Hi all

When fitting out the woodwork do you leave any expantion joints in the panels etc,

as the boat yard say the boat will increase and decrease over 1'' from hot to cold?and if i fit the panels up tight they will buckle and bend.

Edited December 14, 2004 by Richard Bustens

[John Orentas]

Hi Richard.

 

I didn't bother but I think you may agree plywood is very stable in it's own right.

 

The only bother I have had along those lines. I used pine T & G on the deckhead a bit of natural flexing, humidity or thermal loosened it off after 2 or 3 years but that was my fault, I tried originally to secret nail it to the battens I have had to go around screwing it where required.

 

There is a poular missconception that boats are damp, my boats certainly never suffered from damp, the salt cellar will always sprinkle freely even when the boat has been left for three weeks.

 

One inch from hot to cold. Rubbish. Does he mean the steel expands that much or the wood shrinks?

 

John Squeers

Edited December 14, 2004 by John Orentas

[DHutch]

Emilyanne is done out in ash panneling, from the walkway up, and it was put up with 2-3mm gaps between the planks (secret nailed) and that wasnt enoght, every winter they get damp and swell with the ceiling lifting places to acomdate the swelling, or sides pushing the edging off.

- partley this is due to ash's natural tendacy to swell a lot when damp, but its still quite impressve the amout it swell, i'd sat its about 1-2cm of a 4foot distance

- but in winter it is damp on board certainly (the salt still flows, but thats only becuase of all the anticaking agents they use nowadays)

 

so i'd be temted to leave gap in any T & G, i dont know how the plywood that does under walkway was laid, but it seams be much better - (you can see it though the carpet anyway)

 

daniel

[dor]

Richard: Interesting suggestion, change in length of one inch, so I looked into it.......

 

coefficient of expansion of iron 12X10^-6. (can't find a figure for steel at the moment, but it is probably a bit less.

 

Temperature rise say 25degrees

 

70 ft boat = 840 inches.

 

I make that about 0.25 inch.

[DHutch]

Richard: Interesting suggestion, change in length of one inch, so I looked into it.......

 

coefficient of expansion of iron 12X10^-6. (can't find a figure for steel at the moment, but it is probably a bit less.

 

Temperature rise say 25degrees

 

70 ft boat = 840 inches.

 

I make that about 0.25 inch.

 

hehe, somone else has benn doing some sums!!

[John Orentas]

I should know the figures, I used to calculate such things.

 

From school days the length of railway lines (the old ones) they would expand / contract less than 1/8 inch winter / summer.

 

They were a lot longer than a 70ft. boat

 

John Squeers

Edited December 15, 2004 by John Orentas

[dor]

Just for interest, found this:

"Thermal Expansion and Thermal Stresses:

When the temperature is rising, the rail is expanding. As an example, a rise in the temperature with 50 degrees © on a 50 meter long rail results in an expansion of 29 mm. If this thermal expansion is prevented (intentionally or unintentionally) the thermal heating will give rise to normal forces acting in the long direction of the rail. "

 

this suggests a 20 metre boat (66 ft) would expand 11 mm (0.45 inch) over 50 deg. C if it expands at the same rate as steel railway lines.

 

Or about a quarter of an inch over 25 deg. C.

[John Orentas]

Dor.

 

29mm.! Thats 1.25 inches per rail joint, can't be right.

 

The rails weren't restrained that was the point.

 

Anyway narrowboats don't expand in a symetrical way. The underwater bit stays fairly constant, the top gets as hot as hell so presumably they go bannana shaped.

 

John Squeers

[ChrisPy]

Dor.

 

29mm.! Thats 1.25 inches per rail joint, can't be right.

 

The rails weren't restrained that was the point.

 

Anyway narrowboats don't expand in a symetrical way.  The underwater bit stays fairly constant, the top gets as hot as hell so presumably they go bannana shaped.

 

John Squeers

<{POST_SNAPBACK}>

standard old fashioned rails are not 50metres long. they fit on a bogey car, so they are probably about 15metres long?

 

I believe new welded rails are restrained and I suppose there is no allowance for expansion

[John Orentas]

Chris.

 

If I remember the had special waggons probably 100 ft at a guess. Modern rails as I understand it have a special 'scarfe' joint on straight lengths and I think they are allowed to bow outwards on the bends

 

John Squeers

[dor]

Modern CWR track is pretensioned to allow for expansion. This coupled with being fixed to the sleeper and sleepers being heavier and more firmly bedded is supposed to prevent buckling. Also shoe is designed to allow a small amount of vertical distortion to take some of the expansion.

 

Remember 29 mm was for a 50 degree range, I think the source was canadian, hence the wide range. Anyway, the figure agrees almost exactly with my previous calculation, with standard figure for coefficient of expansion, so I'll stick to that.

 

Wasn't Concorde supposed to stretch by 2 feet at Mach2 due to high skin temperature? Or was it 6 inches. Maybe a foot.

[John Orentas]

I'm not convinced. There must be a Railways Nerd out there.

 

John Squeers

[Richard Bustens]

So that means that my steel is going to expand/contract about 1/4 of a inch

and i only have to allow for the wood moving.?

[John Orentas]

Richard.

 

You are straying from the point again.

 

John Squeers

[ChrisPy]

So that means that my steel is going to expand/contract about 1/4 of a inch

and i only have to allow for the wood moving.?

<{POST_SNAPBACK}>

Richard

 

1/4 inch is nothing for several lengths of timber. The joints will just tighten a bit. I wouldn't worry about heat.

 

But the timber will move much more for varying moisture content. That's why your timber floor is laid with a gap round the edge.

 

Plan accordingly!

[DHutch]

yeah, i was talking to my grandad (who laid the plywood sides of the boat) and he sayed he left an inch gap anywhere where it wouldnt notice, ie where partition walls mean, behind the heating pipe from the stove (which is im the middle of a long bit of wall) and generaly anywhere it was consealed, and then he didnt leave any gaps where they would be seen (infact he epoxyed the ends together)

 

- seams to work though (better then the ash T&G anyway)

 

daniel

[Richard Bustens]

Richard.

 

You are straying from the point again.

 

John Squeers

<{POST_SNAPBACK}>

 

 

 

 

 

 

 

 

 

well John i usualy do but for once i thought i was keeping to the point .

[DHutch]

well John i usualy do but for once i thought i was keeping to the point .

 

I though that, unless he's just joking?

[John Orentas]

Richard.

 

We had digressed nicely into railway lines, then you go on about boats again.

 

John Squeers

[Richard Bustens]

LOL

Then Dr it is you that duss digress.

[John Orentas]

Meant as a joke Richard. but at 4.30 in the morning it may not seen so funny!

 

I had only just gone to bed.

 

John Squeers

[Richard Bustens]

O i get it now.....lol

[maffi mushkila]

LOL

Then Dr it is you that duss digress.

 

 

That'll be doth, me thinks

[Richard Bustens]

LOL Hi Maf No one likes a cleverdick.

[maffi mushkila]

LOL  Hi Maf  No one likes a cleverdick.

Then you really must stop trying to be one.

 

Wheres ya boat moored Richard?

Edited December 19, 2004 by maffi mushkila