Repairs

[Tom Myslow]

Repairing 1959 Thompson. When replacing rechromed
cleats etc, old screws do not seem to tighten.

Tried over sized screws but then head sizes
are too large and cause screws to stick up
above fixture.

Is there something I can put in screw holes to
secure the screws beter???

Thanks

[Barry]

Product Info
Application Instructions & Index


Bedding and sealing fittings and hardware
Description of application

All kinds of deck fittings and hardware need to be securely fixed and totally watertight. Some of these fittings are also subjected, on occasion, to very high forces and torsional stresses.

Poorly sealed joints can eventually result in serious damage such as metal corrosion, osmosis and water leaks causing damage to interior furnishings and fittings.

Bedding and Sealing Fittings Subject to High Mechanical Stresses
Deck fittings such as chain plates, winches and guide rollers have to absorb very high dynamic stresses. A high performance product, such as Sikaflex 291, should be used in conjunction with additional mechanical fixation for this purpose.

Sealing Fittings Subject to Minimal Mechanical Stresses

Deck fittings such as ventilators, cover strips etc. need to be sealed against entry of water, but they are not subject to high tensile stresses. Such fittings can be effectively bedded and sealed with only Sikaflex 291.

Important Note:

It is vital to ensure that the adhesive is not simply squeezed out again when the fixing screws are pulled up tight. To prevent this happening, shims approx. 1mm thick should be threaded over the screws on the underside of the fitting to act as spacers. The screw holes themselves should also be filled with sealant prior to fixing.

Spacing the fitting off the deck by 1mm in this way, also facilitates its removal at a later date, when a cutting wire or knife blade can be inserted between the base of the fitting and the deck.

Instructions for bedding & sealing fittings and hardware

Preparation of substrate
Timber decks (gel coat) Aluminium decks (painted)

Abrade contact area on hull with sanding pad (80/100 grit) and remove dust with a vacuum cleaner.
Clean the substrates with Sika Cleaner 205, using a clean, lint free rag or paper towel. Change rag frequently!

Apply a thin continuous coat of Sika Primer 290 DC, using a clean brush or felt applicator Drying time : minimum 10 minutes, maximum 2 hours
Drying time : minimum 60 minutes, maximum 24 hours

Bronze or brass fittings (non-ferrous metals) Aluminium fittings (bright metal)

Clean the substrates with Sika Cleaner 205, using a clean, lint free rag or paper towel. Change rag frequently!
Lightly abrade contact area with a very fine sanding pad. Remove dust with a vacuum cleaner.

Drying time : minimum 10 minutes, maximum 2 hours
Clean the substrates with Sika Cleaner 205, using a clean, lint free rag or paper towel. Change rag frequently!
Apply a thin, continuous coat of Sika Primer 210T, using a clean brush or felt applicator.
Drying time : minimum 10 minutes, maximum 2 hours
Drying time : minimum 30 minutes, maximum 24 hours Apply a thin, continuous coat of Sika Primer 210T, using a clean brush or felt applicator.
Drying time : minimum 30 minutes, maximum 24 hours

For the preparation of other substrates, please refer to Sika-Primer Table for Marine Applications.

Application of adhesive/sealant

Sikaflex 291 should be applied to the deck and the fixing screw holes in a bead of the required thickness. The fitting is then pressed into position.

The fixing screws should be tightened sufficiently to pull the fitting down on the spacers, but no more. Use a plastic spatula to remove excess sealant squeezed out around the edges.

Traces of uncured Sika adhesives or sealants may be removed with Sika Remover 208. On no account should other cleaning agents or Sika Cleaner 205 be used for this purpose.

[Scott Rosen]

Tom,

Here are a couple of solutions, one easy, one more difficult. Which one you choose will depend on the stresses imposed on the fitting.

For decorative fittings and non-stressed ones, you can inject some unthickened epoxy in the screw hole (assuming it's vertical), let it cure and then redrill the pilot hole. For non-vertical applications, make a paste with epoxy and a strong filler like fibers or silica and work it into the holes with a putty knife; then redrill the pilot hole.

For critical applications, you can drill the screws hole substantially wider, say 3/8 to 1/2 inch for a #8 wood screw, and then fill the enlarged hole with epoxy as above. As an alternative to wood screws, you could tap some threads in the epoxy base and use machine screws. That gives you, in effect, an epoxy threaded insert.

I do not like using a strong adhesive goop to bed hardware like cleats, lights, etc. Even the strongest adhesives won't work effectively without the mechanical fasteners being properly set. And you will have a hard time removing the hardware for painting, etc. I like old-fashioned bedding compound like Interlux.

[ 04-01-2003, 01:12 PM: Message edited by: Scott Rosen ]

[TomRobb]

I think the question is reusing screw-holes that prove to be too loose/stripped.
If a longer screw of the same diameter won't do, you might move the fitting to a handier spot and fill the old holes, or if you want them where thay are/were, glue toothpicks stuffed into the holes - redrill & refasten (you could drill out the holes & glue in dowels but you'd be fastening into end-grain - not very strong), or the Brothers Gougeon recomend filling the hole w/ epoxy - coat the screw with some release agent like wax - insert the screws and leave it alone until it cures. Then you have a wood/epoxy/screw interface that may hold up better than new and since you were diligent about the release agent, the screw is easily removable if need be.

[TomRobb]

Looks like Scott answered the question before I hit enter.

[Paul Scheuer]

Driving a few toothpicks in the old holes has been known to work. I little epoxy would help.

[Dan McCosh]

I'd go with Scott's solution as well. Geugeon sells a high-strength filler for such applicaitons. The idea is to drill out an oversize hole, then drill and tap it using a machine screw in the hole. This adds considerable sheer strength to the fixture, particularly important with cleats and chocks. It actually is stronger in sheer than a screw in fresh wood.

[Peter Malcolm Jardine]

I would suggest a combination of a wooden "peg" and some epoxy. I am experiencing the same problem in a couple of areas, and they are typically areas where trim gets worked, or water is constantly in and out of contact. The peg serves as a relatively similiar surrounding that will not fracture like epoxy will in such a small quantity. I know it sounds tedious, but a sliver of mahogany or cedar or whatever dipped in epoxy then shoved in the screw hole will go pretty quickly without a lot of mess if you prepare a few sticks of it. A suitable bedding compound is the finishing touch. Most of the posts here make sense however.... ;)