Loose rudder pivot brackets- advice, please

[tobermoryphil]

I have just noticed that the rudder pivot brackets on my Swift 18 are a bit loose.
They are fixed with cheese head machine screws; tightening or loosening these has no effect, as the nuts the other side turn with the screws. The problem is the double skinning means there is no access to the nuts without hacking holes in the inner fibreglass skin.
Who designed that one!
I was thinking of running thin cyano down the gap, to try and stop the movement.
Any better ideas?

 

[PhillM]

I have just noticed that the rudder pivot brackets on my Swift 18 are a bit loose.
They are fixed with cheese head machine screws; tightening or loosening these has no effect, as the nuts the other side turn with the screws. The problem is the double skinning means there is no access to the nuts without hacking holes in the inner fibreglass skin.
Who designed that one!
I was thinking of running thin cyano down the gap, to try and stop the movement.
Any better ideas?

Could you drill new holes through the plate and both skins and put new bolts through, with a suitable backing place to spread the load. Seal it all up with silkaflex or similar and away you go?

 

[tobermoryphil]

I would need to grind the stainless screw heads off, plus I don't know how much compression the foam core would take.
However, I have a 25mm hole cutter for the inner skin, and have sourced some 30/25 mm white hole plugs, so I think I have sussed the neatest way out. It will need a bit of accurate measuring on both sides of the transom though.

 

[Clydewanderer]

Phil, when u locate the screw positions on inner side of transom, use the core from inside and take out a core of inner grp skin and foam as far as the inner surface of the outer grp skin. This will allow u to remove the screws (towards the inside) complete with nuts along with the cores as u drill them. Then you are left with a 25mm hole through inner grp and sandwich foam but not through the outer grp skin. Then fill the 25mm holes with epoxy resin and filler mix. Then from outside drill through holes to suit new screw/bolt dia. Fix backing plate behind each pivit bracket.
Edit, i should have said to grind heads of old screws first.
Cw

 

[macd]

Clydewanderer's suggestion is a fairly standard method of installing fasteners through cored decks. What is absolutely crucial is that there should be no possibility of allowing water to penetrate the foam core.

For this reason, after the removing the plug of core with the holesaw, foam should be dug out laterally for 10mm or more. (A suitably adapted allen key spun in an electric drill is often used for this.) Thickened apoxy is then introduced to entirely fill the void (Microfibres gives the strongest epoxy mix.) Then drill and fasten, with a hefty backing plate, as described.

That's a proper job and will be stronger than when the boat was new. Just slobbering Sikaflex about isn't.

 

[vyv_cox]

I would need to grind the stainless screw heads off, plus I don't know how much compression the foam core would take.
However, I have a 25mm hole cutter for the inner skin, and have sourced some 30/25 mm white hole plugs, so I think I have sussed the neatest way out. It will need a bit of accurate measuring on both sides of the transom though.

I was about to suggest something similar, a technique I used when fitting a windlass to my deck. I agree about the epoxy replacement of internal foam and have posted an extract from a book I own about doing it but the white plugs method is perfectly acceptable provided the outer hull thickness is adequate on its own.

 

[tobermoryphil]

After 34 years, the outer hull still seems ok!