WotEver Posted February 22, 2019 Report Share Posted February 22, 2019 8 minutes ago, JJPHG said: I remember when I was researching a case once (a good few years ago) that the temperature difference can be as high as 50C, but that was in a slightly more favourable latitude and was with a very dark matt paint. That said your point is still very valid and even under these extreme and favourable conditions the expansion is not going to get anywhere close to the 1" quoted Yup. You’d need about a 120C difference to get close to 1” Link to comment Share on other sites More sharing options...
frahkn Posted February 22, 2019 Report Share Posted February 22, 2019 4 minutes ago, WotEver said: Yup. You’d need about a 120C difference to get close to 1” And the inch would be over the 60 feet not across the width or height of a window, let alone a tile. Link to comment Share on other sites More sharing options...
WotEver Posted February 22, 2019 Report Share Posted February 22, 2019 14 minutes ago, frahkn said: And the inch would be over the 60 feet not across the width or height of a window, let alone a tile. Indeed. 0.1” across 6’. Link to comment Share on other sites More sharing options...
Fly Navy Posted February 22, 2019 Author Report Share Posted February 22, 2019 This looks easy to use: 60 foot boat, Hot day @ 35 degrees celcius (approx 100 farenheit) HULL CREEP About 0.4" Link to comment Share on other sites More sharing options...
WotEver Posted February 22, 2019 Report Share Posted February 22, 2019 25 minutes ago, Fly Navy said: 60 foot boat, Hot day @ 35 degrees celcius (approx 100 farenheit) I can’t imagine any day in the UK where you would have a difference in temperature between the two sides of the boat that would be anywhere near 35C. At 35C it’s about 67 thou per foot. Link to comment Share on other sites More sharing options...
Chewbacka Posted February 22, 2019 Report Share Posted February 22, 2019 When I painted my boat it was facing north so in the morning one side was shady, it was an ideal temp for painting, when I turned it to do the other side it was much to hot to touch let alone paint. So I can believe a 35c difference if the sun is directly on one side. Link to comment Share on other sites More sharing options...
Fly Navy Posted February 23, 2019 Author Report Share Posted February 23, 2019 It doesnt have to be a delta between sunny side and shadow side, does it. The whole boat will expand equally if the ambient temp rises that 35 degrees. 0.17mm / foot of boat. I'd say that, coupled with the natural flexing of a NB, could and does cause cracks. Theoretically - IF the sun beats down on one side of a boat and the other side of your boat is in shade, the boat could expand assymetrically and become...................wait for it.................. a banana boat ? 1 Link to comment Share on other sites More sharing options...
Keeping Up Posted February 23, 2019 Report Share Posted February 23, 2019 Certainly I have seen a lot of movement due to temperature on our boat. It often shows as a gap between the side of a bulkhead-mounted cupboard and the adjacent wall, or as a cupboard door which suddenly won't open or shut properly. Last summer the outside of our boat, which is painted black, reached 65 degrees - definitely not to be touched! Link to comment Share on other sites More sharing options...
WotEver Posted February 23, 2019 Report Share Posted February 23, 2019 1 hour ago, Fly Navy said: The whole boat will expand equally if the ambient temp rises that 35 degrees. 0.17mm / foot of boat. You’re out by a factor of 10 again (or I am), but this time the other way. 67thou is 1.7mm. Link to comment Share on other sites More sharing options...
Dr Bob Posted February 23, 2019 Report Share Posted February 23, 2019 2 hours ago, Fly Navy said: It doesnt have to be a delta between sunny side and shadow side, does it. The whole boat will expand equally if the ambient temp rises that 35 degrees. 0.17mm / foot of boat. I'd say that, coupled with the natural flexing of a NB, could and does cause cracks. Theoretically - IF the sun beats down on one side of a boat and the other side of your boat is in shade, the boat could expand assymetrically and become...................wait for it.................. a banana boat ? Its not theory. I said in a post a few pages back that our boat gets to 60-70°C on the roof (painted dark blue) whereas the hull and sides on the shaded side will be 20°C or so. Never seen it not go through locks. Link to comment Share on other sites More sharing options...
Fly Navy Posted February 24, 2019 Author Report Share Posted February 24, 2019 Wotever Use my link in post 29, convert to mm rather than inches. I make it just shy of 0.2 mm. Now if what Dr Bob says is correct (and I have no reason not to believe him) then this figure needs doubling!!! No wonder Keeping up had issues!! Link to comment Share on other sites More sharing options...
WotEver Posted February 24, 2019 Report Share Posted February 24, 2019 20 minutes ago, Fly Navy said: Use my link in post 29, convert to mm rather than inches. I make it just shy of 0.2 mm. Your link (or rather its maths) appears to be broken. I switched to metric, entered a length of 305mm (1ft), and with a temperature of 100 degrees the result is 304.97224. 35 degrees gives 304.83347 Makes no sense to me. Post #11 gives the correct maths. Link to comment Share on other sites More sharing options...
Fly Navy Posted February 24, 2019 Author Report Share Posted February 24, 2019 (edited) Works fine! Enter: 1, Steel 2. 12 inches 3. 100 degrees farenheit 4. click on "calculate" Answer: 12.00657" (which is the amount of expansion per foot of boat - yes?) 0.00657" x 60 feet = 0.4" overall. All of the above however, was @ 100 degrees farenheit. Dr Bob said he'd experienced 70 degrees celcius temperature change (159 degrees farenheit). This therefore equates to 0.7"! So a 60 foot boat 'crept' a further 3/4".....not far off what the expert said - be fair! Edited February 24, 2019 by Fly Navy Link to comment Share on other sites More sharing options...
WotEver Posted February 25, 2019 Report Share Posted February 25, 2019 I don’t do Fahrenheit or feet these days. Switch to metric and try it, see if you get the same results as me. Link to comment Share on other sites More sharing options...
Dr Bob Posted February 25, 2019 Report Share Posted February 25, 2019 9 hours ago, Fly Navy said: All of the above however, was @ 100 degrees farenheit. Dr Bob said he'd experienced 100 degrees celcius temperature change (212 degrees farenheit). 100°C!! Did not! Link to comment Share on other sites More sharing options...
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