Balsa cored deck-(re)bedding fittings technique?

[LittleSister]

I’m going to be needing to re-bed some fittings on a balsa cored deck (stanchions, etc). I think I understand the basics, but would appreciate guidance, especially on the details.

As I understand it:
(1) Use bent nail or allen key in drill through upper hole to clear balsa (or balsa remains) from around hole.
(2) Cover lower hole with tape.
(3) Fill void from above with epoxy & allow to set.
(4) Remove tape and drill new hole for fitting from above.

My questions are:
(a) How wide an area should I be aiming to clear in the balsa?
(b) What should the epoxy be mixed with to give it body and strength?
(c) What sort of consistency should it be mixed to for this purpose (presumably too thick is difficult to get in through hole and to spread; too thin all runs away, sags, or is too weak to take any load).
(d) How the hell do you get it in through the hole, rather than all over the deck? (Presumably it’s too thick for a syringe, and/or you’d need a new syringe for every hole.)

Any other tips?

 

[mitiempo]

Here's a link to what i consider the best way to re-bed fittings in cored decks.
http://www.pbase.com/mainecruising/sealing_the_deck

 

[vyv_cox]

Here's a method I have used successfully several times.

I have also used a similar method but without bothering with the epoxy filler. The hole saw matches the diameter of the plastic plugs sold at B&Q for capping the hinge holes in their furniture. The nut is then hidden but can be removed if necessary.

 

[LittleSister]

Here's a link to what i consider the best way to re-bed fittings in cored decks.
http://www.pbase.com/mainecruising/sealing_the_deck

Thanks very much. That is absolutely brilliant for my purposes.

What an excellent article. Always great to read an article by someone who really knows what they are talking about that also recognises that much of what they take for granted is unkown to many readers, so explains what to do in detail, and why.

I note he uses butyl tape for 90% of his sealing jobs. Why is this not more popular here?

Any further tips/advice welcome.

 

[LittleSister]

Here's a method I have used successfully several times...

Thanks, Vyv.

 

[lw395]

I have successfully used the bent nail method with a balsa cored deck.
I wanted good strength as the fixings were for mooring cleats.
Slight variations I used:
The hole going all the way through was kept small.

Having vacuumed out the balsa debris, I stuffed the hole/cavity with chopped glass cloth. Doing this dry, you can take your time. I aimed for most of the strands to be around an inch long.
I then masked the deck, sealed the bottom hole with duct tape, and filled the cavity with liquid epoxy.
Warming the deck with a hot air gun thins the epoxy, a lot of air comes out.
I finished by pushing a piece of dowel into the hole to compact things a bit and leave an easier drilling task than glass-epoxy.

I think this method can mean the plug is bonded to a much bigger area of the lower moulding than with Vyv's method.

Anyway, it worked and seemed very strong.
Syringes are much cheaper on ebay by the way!, but you can clean them with hot water and copious fairly liquid after getting the worst off with meths or IPA.
This also works for brushes, to a 'good e nuff' standard.

 

[oldsaltoz]

I’m going to be needing to re-bed some fittings on a balsa cored deck (stanchions, etc). I think I understand the basics, but would appreciate guidance, especially on the details.

As I understand it:
(1) Use bent nail or allen key in drill through upper hole to clear balsa (or balsa remains) from around hole.
(2) Cover lower hole with tape.
(3) Fill void from above with epoxy & allow to set.
(4) Remove tape and drill new hole for fitting from above.

My questions are:
(a) How wide an area should I be aiming to clear in the balsa?

at least 5 times the width of the fixing.

(b) What should the epoxy be mixed with to give it body and strength?

Micro-fibres and epoxy.

(c) What sort of consistency should it be mixed to for this purpose (presumably too thick is difficult to get in through hole and to spread; too thin all runs away, sags, or is too weak to take any load).

As thick as Peanut butter or Toothpaste, best if loaded into a syringe available form most chemist shops, start at the bottom and pull up slowly as the resin mix is injected.

(d) How the hell do you get it in through the hole, rather than all over the deck? (Presumably it’s too thick for a syringe, and/or you’d need a new syringe for every hole.)

have all the holes ready before mixing, it tales less than a minute to fill so no chance the resin will go off. You can clean it for reuse with Vinegar, then warm soapy water, do not use Acetone.

Any other tips?

Put masting tape on the area before you do anything else and remove it no later than 30 minutes after filling.

Good luck and fair winds.

 

[vyv_cox]

I think this method can mean the plug is bonded to a much bigger area of the lower moulding than with Vyv's method.

I'm sure that's true but my headlining moulding is barely thicker than paper so the difference is not a lot.

 

[lw395]

I'm sure that's true but my headlining moulding is barely thicker than paper so the difference is not a lot.

Is it a separate moulding rather than a cored moulding?
I think on my deck there was a similar amount of grp top and bottom.

 

[vyv_cox]

I'm never quite sure how Sadlers built their decks. It appears that the inner and outer are two separate mouldings, some of it stuck together with PU foam but some of it left empty. Some of the flat, inner sections are extremely thin but corners are thicker. The lips at the edges are several millimetres thick. The topsides inside the foam are also very thin. When I fitted my yachlegs I cut pieces out to mount the reinforcing pads. I cut the skin with a padsaw but I could have used a sharp knife.

 

[lw395]

I'm never quite sure how Sadlers built their decks. It appears that the inner and outer are two separate mouldings, some of it stuck together with PU foam but some of it left empty. Some of the flat, inner sections are extremely thin but corners are thicker. The lips at the edges are several millimetres thick. The topsides inside the foam are also very thin. When I fitted my yachlegs I cut pieces out to mount the reinforcing pads. I cut the skin with a padsaw but I could have used a sharp knife.

I think that is an inner moulding where the outer moulding takes all the load. A classic balsa or foam core deck needs all three elements- top, bottom and core to be well fixed together to have any stiffness. In which case I'm happier trying to get a strongly bonded pillar around the bolt.

 

[Deleted member 36384]

... I note he uses butyl tape for 90% of his sealing jobs. Why is this not more popular here? ...

After reading these articles and some opinion from here I have started using a butyl mastic. So far 2 Lewmar hatches, a pair of handrails on the coach roof and 4 sets of U bolts later I believe the the product is working well. One of the fears expressed on the forum is that is does not set and it always at risk of oozing out. At first this looked like the case on an excess bead I left around the inside of the hatches. However, after a month (between boat visits) it had set up somewhat, not solid, but firm, similar to window putty. The excess bead just rolled off with finger pressure.

When I bought the tube of the stuff the assistant at the marina claimed that one of the fitters only ever uses this stuff.

I like the fact that it doesn't set completely, nor glue with such strength that the gel coat lifts off when th emitting is removed. Its not my sealant of choice where a bolted or screwed fitting requires sealing. It's very easy to clean up as well.