Boat flexing

[Tracy D'arth]

solvent entrapment due to applying coats too soon.

[peterboat]

26 minutes ago, Tracy D'arth said:

solvent entrapment due to applying coats too soon.

I think you might be right 

[howardang]

4 hours ago, blackrose said:

 

Hence it's easier said than done. Many of us don't have a broad choice of yards we can get to within a reasonable distance of our moorings, and for those like myself who live aboard that choice may become even more limited. For my boat I only know one yard on the Nene which happens to be a day's cruise away, though there may be others further downstream that I don't know about. I work so I really can't spend a week getting to the perfect boat yard plus the time off work to do the work. It's got to be within a days cruise. 

 

My boat has been out the water in all sorts of places including tidal river beds and craned in/out so the extent of hull support has been varied. I know the hull can take it but the fit-out can shift around inside. However I'd never reject a yard on the basis of the hull support offered. Next time I come out at Blackthorne I'll just ask them to put the 2 rail bogeys a bit closer together. 

 

I don't think I've seen the spreaders you're talking about. Do you have a picture? I've been craned using spreaders several times but they've only ever used 2 strops. 

A quick look  found this photo of a wide beam being lifted using the type of spreader I was talking about..

 

https://www.star-line-boats.co.uk/

 

Another method of making sure there are no crushing forces is to use three separate spreaders. A transverse spreader on the crane hook and a fore and aft spreader on each side with their legs attached to each end og the transverse spreader. I can't find a suitable photo but imagine a letter H with the boat sitting between the two parallel arms.

 

Howard

 

Howard

[nb Innisfree]

FWIW:

Innisfree took nearly 2 yrs to fit out, throughout that time it was supported on 2 lengths of timber approx 45' apart, not exactly level but adjusted to eliminate any twist. On launching there was zero issues with doors etc, but with during subsequent dry docking the central bathroom door would refuse to fully close. I assume was down to twisting. 

Also during fit out I regularly eyeballed the edges of the baseplate and couldn't see any sign of sagging, even when I once needed to jack the bow up at the apex of the bottom plate (3 point support) 

[blackrose]

5 hours ago, Tracy D'arth said:

solvent entrapment due to applying coats too soon.

 

Could be but his coats were very thin (unlike mine!) and he was leaving each coat for the prescribed time. And the blistering wasn't over the whole boat, just in a few places and only on the sunny side of the boat. 

2 hours ago, howardang said:

A quick look  found this photo of a wide beam being lifted using the type of spreader I was talking about..

 

https://www.star-line-boats.co.uk/

 

 

Yes, but as I've said a couple of times, irrespective of the spreader the boat is only supported on two strops - that's two points of support with both ends of the boat unsupported. All the spreader does is keep the strops away from the cabin sides, it offers no additional support to the hull. 

Edited August 14, 2022 by blackrose

[howardang]

3 hours ago, blackrose said:

 

Could be but his coats were very thin (unlike mine!) and he was leaving each coat for the prescribed time. And the blistering wasn't over the whole boat, just in a few places and only on the sunny side of the boat. 

 

Yes, but as I've said a couple of times, irrespective of the spreader the boat is only supported on two strops - that's two points of support with both ends of the boat unsupported. All the spreader does is keep the strops away from the cabin sides, it offers no additional support to the hull. 

I have never  disagreed with that comment. I was answering your request to see a photo of the spreaders I had  mentioned.

 

Howard

[David Mack]

12 hours ago, howardang said:

A quick look  found this photo of a wide beam being lifted using the type of spreader I was talking about..

 

https://www.star-line-boats.co.uk/

[alan_fincher]

5 hours ago, David Mack said:

 

This Account has been suspended.

Contact your hosting provider for more information.

 

 

Gives above message....

 

[George and Dragon]

9 hours ago, David Mack said:

Works fine with Brave browser on my Mac. Not tried anything else.

[Alan de Enfield]

40 minutes ago, George and Dragon said:

Works fine with Brave browser on my Mac. Not tried anything else.

 

 

It worked 1st time for me (with Edge) but the 2nd time I tried it it gave the error message.

[ditchcrawler]

7 hours ago, George and Dragon said:

Works fine with Brave browser on my Mac. Not tried anything else.

[Momac]

On 13/08/2022 at 22:55, howardang said:

All steel vessels flex, not just trawlers but much larger vessels such as tankers, cargo ships and passenger vessels , especially  when  afloat. Canal craft also need adequate support when on the blocks, and also when being craned in or out of the water when ideally they should employ the use of spreaders.

 

Howard

I agree.

Everything deflects when load is applied to it or when the load path changes . The only question is whether the deflection is within acceptable service limits.

[Naughty Cal]

On 13/08/2022 at 22:55, howardang said:

All steel vessels flex, not just trawlers but much larger vessels such as tankers, cargo ships and passenger vessels , especially  when  afloat. Canal craft also need adequate support when on the blocks, and also when being craned in or out of the water when ideally they should employ the use of spreaders.

 

Howard

Not just steel boats.

 

Our small GRP cruiser had specific points to be lifted and supported ashore. They were clearly labelled so no excuse for not doing it right.

 

If it was lifted and chocked correctly there was very little movement and all of the doors and latches closed fine.

 

When the support points were missed it was very obvious. One time the Hull twisted so much we couldn't close the sliding door or bathroom door. It settled back in once it was relaunched. 

 

Quite by contrast the van flexes in a different way pretty much every time it is driven and parked up. It is always parked at different angles. We are a bit bow down tonight which means the drop down bed will creak on the front runners🙄