Filling hole in bulkhead

[Hartley18]

Here's the problem: I'm removing an old VDO Sumlog (about 3" round) from the cockpit and wanting to fill up said hole.

The bulkhead it's installed in is timber - approx 1" thick. I plan to cut two circles out of 12mm ply and glue them together, but how to fix them in the hole?

Normally there'd be room to screw in a backing plate from behind to hold the circles in place, bog, sand and paint and the job's done - but as you'll see in the pic below, there is space immediately behind the (outside) bulkhead for a slightly-oversized spacer, but access is kind-of restricted with no way to get said spacer in without taking the front (inside) bulkhead away - which simply is not an option:



(Pic is from the inside of the boat looking out - and I don't care whether the inside hole is fixed or not)

Does anyone know any tricky techniques for fixing a backplate of some description in behind a hole you can only access from one side?? Must be something I'm missing..

Thanks,
Cameron

[mitiempo]

Cameron

Is there a space between the inside and outside bulkhead? There appears to be from the picture. If so, cut a circle that is larger than the outside hole from some plywood that is thin enough to fit in the space. Then cut it in half. Wiggle each half in place after slathering it with thickened epoxy. Maybe put a screw partially in each piece so you have something to grab it with. The 2 pieces don't have to cover the hole entirely, but when in place they have to create a hole smaller than the original hole in the outer bulkhead. Then you will have your backer. Epoxy a piece cut to fit the outer hole in place. The inside can also be filled against the backer you placed in the middle.

Or buy something else that fits the hole.

[john1066]

Screw a temporary batten across the front of the disc to hold it in place on the outside. Fill all round with thickened epoxy and allow to set. Unscrew the batten, fill the screw hole and the two gaps where your batten spanned the hole.

[tdw]

Cameron,
John's idea was the way I'd go if only for the sake of simplicity but Brian's idea, would I'd think make for a better long term fix though. I suppose I'm not giving the expoxy its due but not having a backing plate worries me a bit that the insert could have a tendency to push inwards. You could of course take from both ideas. Screw a batten or two across the inside of the hole and then follow John's plan from there.

[Hartley18]

Whilst John's idea is intriguing, because I'd like a backing plate of some kind, I'll go with Brian's idea for this.

Yes, there is a decent space between bulkheads, but the backing needs to completly cover the hole to prevent the filler getting pushed inside - so a couple of battens wouldn't do. It never occured to me to just cut the backing plate in half to get it in place, but I knew there'd be a simple way to do it!! I must be getting old..

I have a similar, smaller, hole some idiotic PO blew in the galley bulkhead and I'll use John's idea for that since no particular strength is required and a backer there would look obvious.

Thanks, guys - two problems solved!

[hellosailor]

Hartley, a trick from sheetrock repairs will do it. Take a couple of pieces of think wood, furring strips or shims, that are about two inches longer than the hole is wide. Drill a small hole in the center of each one, tie a string through the hole (knock it on the far side).

Butter up the backside of the hole with epoxy, and the ends of the sticks on the front side.

Now you stick one strip through the hole, pull the string tight to bring it up flush to the blind side. Repeat with strip #2 and if necessary #3. You've now got a thin wood "backing plate" made of strips, held by the tight strings.

As the epoxy sets, that backing plate gets glued in place. Then you can cut the strings off, fill in the rest of the hole with thickened epoxy and a plug. Finish the front side as you please.

With a good eposy bond? Your repair will be as good as the bulkhead ever was.

[Hartley18]

Thanks, HS - I'll need to do something like that to hold the backing plate pieces in place.

[tdw]

Oh ... are you just filling the entire hole with epoxy ? I though you would cut a piece of wood to approximate size and only epoxy around the edges.

That boat of yours will end up more plastic than mine.

[Hartley18]

Originally Posted by tdw

Oh ... are you just filling the entire hole with epoxy ? I though you would cut a piece of wood to approximate size and only epoxy around the edges.

That boat of yours will end up more plastic than mine.

Here's a pic of the 6mm ply backing plate, cut and primed on the back side, ready to go in on the boat:



I've cut a plug out of some scrap teak only slightly smaller than the hole (marked in pencil on the backing) and will fill around that with NorFill.

I got the backing in place on the weekend, but forgot to take any pics in my haste to be elsewhere - I'll post a couple when I get to the boat next.

[Mark1948]

We have a couple of holes from auto pilot we no longer use. Out marina fiberglass expert suggested just using a teak plate to cover and seal with caulk and fasten to a backing plate. Cheap and leaves the holes reusable if desired in the future.