Screwing into coachroof/sidedecks ???

[Ship's Cat 73]

We have that pesky problem that seems to visit many yachts of 20 years + vintage ~ and that's the dreaded headlining droop.
We've already attempted (with only partial success) to re-attach the linings with contact adhesive.
I'm now considering the possibility of attempting to use wooden battens attached to the underside of the coachroof and the sidedecks to hold the linings in position.

The question is:- is there sufficient thickness in the coachroof and sidedecks to accept (and hold) screws of around 20 - 25mm in length?

I've already screwed a few battens onto the anchor locker from inside the cabin for the same purpose and found that there was plenty thickness there.

(1987 Gib'Sea 76)

(Please excuse this question as I suffer from F.B.D.Q syndrome [First Boat - Dumb Question syndrome])

 

[forelle541]

You could attach the battens with resin or a decent adhesive, the ones on my boat are held up this way and are very firm, then use ply boards with the lining attached.

 

[knuterikt]

We have that pesky problem that seems to visit many yachts of 20 years + vintage ~ and that's the dreaded headlining droop.
We've already attempted (with only partial success) to re-attach the linings with contact adhesive.
I'm now considering the possibility of attempting to use wooden battens attached to the underside of the coachroof and the sidedecks to hold the linings in position.

The question is:- is there sufficient thickness in the coachroof and sidedecks to accept (and hold) screws of around 20 - 25mm in length?

I've already screwed a few battens onto the anchor locker from inside the cabin for the same purpose and found that there was plenty thickness there.

(1987 Gib'Sea 76)

(Please excuse this question as I suffer from F.B.D.Q syndrome [First Boat - Dumb Question syndrome])

It depends on how the deck / coachroof is made..
Often there is a balsa core with GRP inside and outside.
Without knowing how your deck is built and thickness of the deck it difficult to answer.
Mine have a 25mm balsa core and there is no need to go more that 5-10mm in to get hold, but there are places where there is no core and the deck in not so thick there.
Screws in pure GRP is not any good.

I have used battens this way, a 5x15mm batten with 12 mm screws is works fine.

I did replace the lining with new, the problem with the type use on my boat was that foam backing was disintegrating making it difficult to glue back in place.

When we replaced we cut plates out of 4mm plywood for the large moderately curved areas and covered it in lining before we screwed into the deck.

 

[Norman_E]

Personally I would not screw the battens on. On my boat all of the battens are fixed with epoxy putty. They are very firmly attached, The headlining is vinyl on plywood panels. The battens are about 12mm thick and the only screws are the ones holding the panels to the battens.

 

[rob2]

I'd agree that screwing to a batten is a better practice, but I'm quite a fan of No Nails or equivalent to stick those battens to the GRP. If the batten is full length side to side, the curvature springing it against the abutment each side will hold it in place meaning very little load on the adhesive bond. In fact, some people just jam long battens below the headlining to hold it in place!

If you're using headlining on removeable ply panels, the same applies - the curvature will hold a well fitted panel in place so all they need in addition is some industrial strength velcro patches to keep them perfectly in place. The added bonus is you can pull them down to chase wiring problems behind them.

Rob.

 

[savageseadog]

Glue the battens on with a construction epoxy, it's very quick, or PU/Sikaflex type adhesive

 

[laika]

In my initial forays into boat maintenance I was terrified of accidentally putting a screw through to the outside. Although I obviously try and avoid doing it to this day, I don't consider the consequences of a mistake to be nearly so dire since discovering the joys of epoxy and gelcoat.

 

[Lakesailor]

Don't use screws GRP is not elastic enough to accept the forces of self-tappers and will crack and craze.
I would use Sabatack 750XL which is easier to use than Sikaflex. Doesn't go off in the tube and is cheaper.

 

[oldsaltoz]

The foam backed linings seem doomed to fail, the no foam backed liners also seem to fail but mostly because the glue used was not up to the task.

I have used carpet tiles with good results, but recently replaced the head lining in the cat 16 x 18 feet using battens glued with epoxy and micro-fibres, then applied white gloss sheeting a bit like Formica, with small 'H' section white plastic jointing strips ti cover the joints under the battens, rounded on the underside.

Looks fantastic and very easy to keep ir clean, also made the saloon a lot lighter.

Good luck and fair winds.

 

[cpedw]

If I've interpreted OP's question correctly (I think other respondents have grasped the wrong end of this stick) the saggy headlining will be between the battens and the GRP. So gluing can't work.

I have solved this problem in a 1980's Westerly using brass wood screws. The screws were 3 or 4mm diameter, 12 or 15mm long. The batten thickness after countersinking was around 5mm so the depth into the GRP was always less than 10mm. I used a pilot drill (2mm)into the GRP. Go carefully; that's where you are most likely to find the thickness of the GRP.

In deference to other responses, not every screw got a grip, though most did. Many screws at less than 150mm spacing were used so the occasional failure didn't let the headlining sag.

Derek

 

[Grumpybear]

Our boat (Jeanneau) was built with vinyl glued on plywood sheets, held in place with Velcro. In a few places, such as under the wide decks, the panels are screwed into battens epoxied to the GRP. 15 years on, still fine.

 

[Ship's Cat 73]

If I've interpreted OP's question correctly (I think other respondents have grasped the wrong end of this stick) the saggy headlining will be between the battens and the GRP. So gluing can't work . . .

Derek

Derek ~ you've sussed it! . . . gluing wouldn't work for the very reason you stated.
I think I've probably given the impression that all of the headlining is drooping . . . but it's only the lining that should be attached to the inside of the hull that's affected. The lining on the 'ceiling' is held up by screwed-on panels.
The following picture should make it clearer, and it also shows the problem we previously had with the lining on the inside of the anchor locker >>>

The next pic shows what I did to remedy the anchor locker problem >>>

I think that in referring to the "screwed-on panels" it would seem that I've partly answered my own question (as there appears to be sufficient thickness there) but it's actually into the underside of the sidedecks that I'll be requiring to fix a few screws. Also, I previously stated a grip depth of around 20 - 25mm, but I used 25mm screws when I attached these battens to the anchor locker and as they pass through about 12mm of wood there is only about the same length penetrating the GRP sandwich ~ and there is plenty grip there.

There only needs to be about 3 points along each sidedeck where I would have to attach screws . . . so I'm tempted to try a pilot hole (about 2mm dia.) of about 8mm depth at one of these points in order to 'plumb the depth' of the GRP . . .

 

[Slocumotion]

Don't use screws GRP is not elastic enough to accept the forces of self-tappers and will crack and craze.
I would use Sabatack 750XL which is easier to use than Sikaflex. Doesn't go off in the tube and is cheaper.

Looks good. Bet you could even use it to fix a wobbly vice to your bench too.