Hull thickness measurement

[Scholar Gypsy]

The hull thickness measurements I have had in recent surveys (25 30 and 35 years) have had only limited coverage due to limited access to the underside of the baseplate when in the dry dock.

 

I had the mad idea that I might try to deal with this when sitting on the sand during my crossing of the Wash in a few weeks time, with a bit of judicious digging...

 

For this to be workable I need access to a reasonably priced ultrasound detector: can anyone recommend one? Google searches seem to find either things to do with fetal heart monitors, or seriously expensive bits of industrial kit.

[W+T]

would be a big digging job i bet, to get in with a grinder aswell to clean back the areas needed.

 

I looked at getting one myself a few years back when i had a NB, i found the same as you, either not the correct item of very dear.

[mrsmelly]

The hull thickness measurements I have had in recent surveys (25 30 and 35 years) have had only limited coverage due to limited access to the underside of the baseplate when in the dry dock.

 

I had the mad idea that I might try to deal with this when sitting on the sand during my crossing of the Wash in a few weeks time, with a bit of judicious digging...

 

For this to be workable I need access to a reasonably priced ultrasound detector: can anyone recommend one? Google searches seem to find either things to do with fetal heart monitors, or seriously expensive bits of industrial kit.

 

Hi

 

I bought one about five years ago that was not expensive and did the job last time I used it. I think it was about 200 quid. I will still have it somewhere I think in a box. If you are interested I could probably dig it out and post it to you to borrow if you wish. Pm me if you want.

 

Cheers

 

Tim

[Scholar Gypsy]

would be a big digging job i bet, to get in with a grinder aswell to clean back the areas needed.

 

I looked at getting one myself a few years back when i had a NB, i found the same as you, either not the correct item of very dear.

 

Thanks for this, and to Tim for his kind offer.

 

Another stupid question: do I need to get back to bare steel to do this measurement, or just clean the bottom of the boat of gunk? I don't think I fancy doing the former in the middle of the Wash, not least as I would have not have time for the paint to dry before the tide comes in again.....

[Timleech]

 

Another stupid question: do I need to get back to bare steel to do this measurement, or just clean the bottom of the boat of gunk? I don't think I fancy doing the former in the middle of the Wash, not least as I would have not have time for the paint to dry before the tide comes in again.....

 

Basically yes you do. Some of the more sophisticated kit will work through a paint coating, but only if the stars are in exactly the right conjunction. Useful if you want to avoid damaging a nice smooth 2-pack coating, but they won't work through rust and cr*p.

 

Tim

[OldGoat]

May be a dumb question - but could you not do it from the inside of the boat.

After all you should have access to some parts of the hull for general inspection purposes (... yeah!)

Obviously not a good idea for survey purposes - but as SG had already suggested digging a couple of holes in the seabed....

[swift1894]

The hull thickness measurements I have had in recent surveys (25 30 and 35 years) have had only limited coverage due to limited access to the underside of the baseplate when in the dry dock.

 

I had the mad idea that I might try to deal with this when sitting on the sand during my crossing of the Wash in a few weeks time, with a bit of judicious digging...

 

For this to be workable I need access to a reasonably priced ultrasound detector: can anyone recommend one? Google searches seem to find either things to do with fetal heart monitors, or seriously expensive bits of industrial kit.

You wouldn't get me under a boat, resting on damp sand, with the possibility of getting stuck there with an incoming tide!

A "mad idea" is right.

[Scholar Gypsy]

You wouldn't get me under a boat, resting on damp sand, with the possibility of getting stuck there with an incoming tide!

A "mad idea" is right.

 

Thanks - I wasn't intending on getting myself under the boat, just doing some measurements near the edges.

 

Other comments make me think I will stick to plan B, namely a game of cricket on Roger Sand...

[swift1894]

Thanks - I wasn't intending on getting myself under the boat, just doing some measurements near the edges.

 

Other comments make me think I will stick to plan B, namely a game of cricket on Roger Sand...

A much better idea!

[clbrof]

Instead of digging under the boat when its already resting on sand, why not get some sleepers, tie them underneath your boat (whilst its still afloat), allow the tide to go out, and hopefully the sleepers wont sink into the sand if you use enough, allowing relatively "safe" and easy access?

 

*I take no responsibility for any damage or harm caused by stupid idea above*

Edited April 30, 2015 by clbrof

[gazza]

Instead of digging under the boat when its already resting on sand, why not get some sleepers, tie them underneath your boat (whilst its still afloat), allow the tide to go out, and hopefully the sleepers wont sink into the sand if you use enough, allowing relatively "safe" and easy access?

 

*I take no responsibility for any damage or harm caused by stupid idea above*

You are one of bizzard's relations and I claim my £5

[clbrof]

haha great. I thought it was a plausible plan?

[W+T]

haha great. I thought it was a plausible plan?

 

 

Maybe but if its on soft sand then the weight of the boats would just push the sleepers into the sand i reckon, unless you use a lot.

 

The hull can be checked on the inside, aslong as its fully cleaned back to clean at at worst a little surface rust. I did that with my old NB, some on the out side but the floor from the inside

[system 4-50]

If you don't get the sleepers level and they find something solid underneath, can you determine the condition of the base plate from the distortion of the hull?

[OldGoat]

 

 

Maybe but if its on soft sand then the weight of the boats would just push the sleepers into the sand i reckon, unless you use a lot.

 

The hull can be checked on the inside, aslong as its fully cleaned back to clean at at worst a little surface rust. I did that with my old NB, some on the out side but the floor from the inside

 

That's what I thought (post #6) - so thanks for corroboration!

[FadeToScarlet]

May be a dumb question - but could you not do it from the inside of the boat.

After all you should have access to some parts of the hull for general inspection purposes (... yeah!)

Obviously not a good idea for survey purposes - but as SG had already suggested digging a couple of holes in the seabed....

I tried exactly that on a friend's boat.

 

The probe ended up going through the steel, and needed sealing in a hurry!

 

That particular patch was a bit thin!

[Scholar Gypsy]

May be a dumb question - but could you not do it from the inside of the boat.

After all you should have access to some parts of the hull for general inspection purposes (... yeah!)

Obviously not a good idea for survey purposes - but as SG had already suggested digging a couple of holes in the seabed....

 

Plan A seems to be back on, as I can now find someone with a JCB to dig an inspection pit for me to use ...

 

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