Rotten decks, why so frequent? How does it occur?

HUMBER P4VWL · 20 July 2010, 22:22

Why is it you see so many posts from people who go and see what look like decent boats, only to find from a survey they have a rotten deck?

Why and how does it occur?
What can be done to stop it?

Bought an ex demo Humber and it sits on a mooring, any issues or things I should look for?. The 5.4 SR sat on it for 12 yrs and that never rotted despite being swamped a good 3 times when the bilge packed in!

Nos4r2 · 20 July 2010, 22:26

At a guess, if it's not from a poor initial build it'll be from screws/bolts going into the deck not being sealed properly.

chewy · 20 July 2010, 22:30

As Nos said, deck fittings not been sealed properly is probably one of the biggest causes.

Nos4r2 · 20 July 2010, 22:31

Yep.It's why I parrot on at people about using Sikaflex or the equivalent rather than silicone sealer.

Sprayblond · 20 July 2010, 22:33

Photo from new build. Two holes used to fix plate. Two "spare holes" left unsealed and just hidden with the plate.

HUMBER P4VWL · 20 July 2010, 23:07

Quote:

Originally Posted by Sprayblond

Photo from new build. Two holes used to fix plate. Two "spare holes" left unsealed and just hidden with the plate.

New build by.....?

Poly · 20 July 2010, 23:49

Quote:

Originally Posted by HUMBER P4VWL

Why is it you see so many posts from people who go and see what look like decent boats, only to find from a survey they have a rotten deck?

Do you really see a lot of boats with rotten decks?

HUMBER P4VWL · 20 July 2010, 23:54

Being fair I have never seen a rotten deck. However I recall about 4 cases of posts with people looking for boats who have been to see ones that look fine but surveys show a rotten deck. Also a few posts with rotten transoms. Thought I'd ask the question to check I don't do anything to ours over the long term.

butty · 21 July 2010, 07:02

it would also seem that moisture can get into the deck from the underside of the deck....

water that sits in the hull compartments forms condensation on the underside of the deck, and if the deck is not made properly then this moisture will be absorbed into the wooden deck.

this is really why all decks should be made on a mould and fully encapsulated in glass, then the plywood structure is protected from moisture.

i have also seem alot of 'silicone' sealants used, which are great for your bathroom, but really a sikaflex or saba type marine bedding compound sealant should be used, they can deal with the marine environment far better

HUMBER P4VWL · 21 July 2010, 08:45

Are modern Humber decks made in a mould and glassed?

Xk59D · 21 July 2010, 08:57

the rib i was buying last month had a bad deck and transom (porters 6m). it appears in that case the manufacturer doesn't treat the underside of the deck period which i guess will not exactly help.

cheers

HUMBER P4VWL · 21 July 2010, 11:08

Be interesting to know which manufacturers do and don't treat it. Also which ones mould and glass them. Pretty key to picking a boat I'd say. That's porters off peoples list then!

biffer · 21 July 2010, 11:45

only one reason for rotten decks, BAD BUILD, all wood should be glassed over, on our new build we wax flow below deck as well

chewy · 21 July 2010, 11:55

Is wax flow, flow coat?

HUMBER P4VWL · 21 July 2010, 12:25

Taking a punt here then Biffer, I'd guess Humber would glass the underside of their deck on boats in recent years.

Been on the web site but there isn't much info on how they're put together, not even in the spec section.

willk · 21 July 2010, 12:26

Quote:

Originally Posted by chewy

Is wax flow, flow coat?

Flow coat is just Gelcoat with a wax additive...

... I think

RIBRyda · 21 July 2010, 12:30

Just for our ten penn'orth...

The problem with grp deck mouldings is that future alterations are tricky; in order to achieve proper fixings and support for seats, consoles, bottle racks, liferaft mounts, lockers et al, the entire structure supporting the deck mould, and all inserts and re-inforcements need to be pre-determined - otherwise you've got poor support and nothing to fix to without a lot of remedial work. This is obviously not a problem for the manufacturer in the first place - he will simply supply a fixed configuration and then wash his hands of it.

A wooden deck, properly constructed, will avoid these issues and give the owner much more flexibility in terms of layout etc.

Wood inherently has other problems, usually relating to moisture and in particular retained moisture. There are two ways to avoid this - or at least mitigate the problems; one is to ensure proper effective sealing of all holes into or through a wooden deck, and the second is to use a funny thing called - wait - you've guessed it - marine ply! This isn't just an expensive option cooked up by the timber suppliers; it uses different more durable grades of timber, higher compression in the manufacturing process, and properly formulated adhesives in the laminations specifically to survive in a marine environment. It should be noted, though, that not all marine ply is the same quality and individual manufacturers still need to shop around.

A good quality marine ply deck will offer a perfectly good (some would say) superior alternative to a grp moulding... as long as it is made properly. This MUST include proper sealing on BOTH sides and sealing of any holes cut into it and preferably not just sealing with sikaflex where possible but at the very least a resin coating completely sealing every hole.

There are more complex composite (honeycomb) alternatives which can be used to create a flat deck as with ply; obviously these won't rot but they can be a real pig when trying to find fixings, so are usually not very practical.

As a manufacturer, we supply boats with all three types of deck, with a ply deck being the most commonly requested due to price, durability and flexibility of use. All marine ply deck sheets are cut to size, including all fairing and chamfering; any hatches to be cut into it are formed, and any known fixed bolt holes drilled. Then, and only then, is the underside coated in resin as well as all exposed edges(in some cases with a thin laminate re-inforcement) before the sheets are actually installed in the boat. The upper side is then resin coated, laminated and flow-coated to ensure a complete seal.

I'm sure that our process is no different to that of any other reputable manufacturer using ply decks.......

chewy · 21 July 2010, 12:31

Quote:

Originally Posted by willk

Flow coat is just Gelcoat with a wax additive...

... I think

Correct Willk!

What are the advantages of using flow coat rather than just resin?

9D280 · 21 July 2010, 13:19

Quote:

Originally Posted by chewy

What are the advantages of using flow coat rather than just resin?

At a guess, the clue is maybe in the name?

Any emergency repairs I've done to dinghies with normal resin, the application tool of choce has been a trowel!

jyasaki · 21 July 2010, 15:20

Quote:

Originally Posted by HUMBER P4VWL

Also a few posts with rotten transoms.

Of my three friends who have bought used boats, 2 of them ended up having transoms rebuilt due to rotting wood.

One, a 26' hard boat, had the thing rebuilt as original.

The other, and Apex 19 RIB, had all rotting stuff removed and some sort of resin poured in.

jky