Hull planking, how soft is too soft?

[Georgio]

I have been looking at a boat for sale and having a good poke about the hull and so far it all seems pretty sound.

However, and this is where lack of experience shows, the hull planking (clinker built) may or may not be a little soft in places but how soft is too soft and requires caution.

While applying moderate but not great pressure I was able to push the end of a small/medium sized screwdriver in 1-2mm.

Is this soft enough to ring alarm bells?

From what I have read the boats were known to be built of high quality materials and the quality of fit-out internally is good.

Any thoughts or rules of thumb to apply?

 

[pmagowan]

Sounds fine to me but the only way to know is to strip it down a bit. No big deal anyway as a bit of soft timber can be saved or patched. Mind had a few bits where the screwdriver went right through but they didn't extend very far. I just spliced a new bit in.

 

[chinita]

I think a lot depends on the wood and it's attraction to rot. If clinker it may be mahogany or larch? The former more prone to rot, the latter cheap and cheerful and more resilient.

Also bear in mind where the 'softness' is - in the general planking, ok. Near the hood ends or transom is more worrying.

I don't know of a rule of thumb but a proper wooden boat surveyor (or boatbuilder) will poke their spike in and tell you within seconds if it is ok or rotten as a pear.

Good luck.

 

[Georgio]

Thanks for the advice, I believe the planking is iroko which I think is a little unusual although I know it is a durable hardwood.

I expect the planking will be ok but it all needs stripping back anyway so will get a decent inspection.

Thanks again.

 

[johnlilley]

Iroko planking is quite durable, but can soften as a cause of electrochemical damage as can nearly any other timber. This damage occurs near fastenings, anodes, rudder tubes stern tubes etc. In fact anywhere where there is metal and possible corrosion or electrical action. This damage is not bacterial rot as might be expected with fresh water & iroko (provided it is not sapwood) is resistant to this to a degree. Comparison spiking with other similar planking away from this point will give you the best comparison. Larch will often be surface soft throughout but would not be seen as decayed, the same softness in oak or iroko would be seen as deterioration.
One test to assess the degree of acceptable softness in some circumstances would be to test how secure a screw fastening would hold. On a keel for instance, one would expect a stout screw to shear before it stripped out the timber. If it cannot hold a screw then it cannot hold a plank fastening. Obviously on thin planking the test would have to be adjusted to take into account the weight of plank.

John Lilley

 

[Bodach na mara]

If you can get hold of a bit of virgin timber of the same sort, you can get an idea of how hard you need to press to make an indentation and thus gain the experience of what is "soft." I noticed that the surveyor that I usually use (Ian Nicolson) used a spike with a flat point (not a needle-sharp item) and I use a similar splicing spike, or the point of a small flat screwdriver pressed "sideways" onto the timber, as I can get a feel for the timber without making a visible mark in sound timber. Well, not too visible anyway!

 

[Georgio]

thanks again for the info.

some areas have lots of paint build up and some have flaked off so I have had to try and take that into account when probing. I can find nothing so far that is worryingly soft but there is plenty of work required, fortunately for me, most is only semi-skilled so can be taken care of by my fair hand, assuming a price can be agreed where it is worth me taking it on.