Fitting a skin fitting

[seaesta]

I need to fit a new skin fitting for an engine sea water inlet (22,mm or 3/4"). Having never done this before I woul appreciate any thoughts or experience from the Forum. My plan would be
1. Prepare a hardwood "ring" to fit over the fitting and to act as backing on the inner surface
2. drill a hole in the hull to match the diameter of the fitting
3. Put mastic on the shoulder of the skin fitting and push it into the hole
4. Put the hardwood ring over the inner part of the fitting and secure with the nut
Questions
1. How do I secure the fitting so it does not turn when fitting the stop valve etc
2. What is the best sealant
3. What have I missed
Thanks
Martin

 

[trouville]

I paint the wood very well and use lead paint, but i dont paint the fitting,as this prevents isolated electrolisis, and prevents the wood from sofening due to the current,at least it helps! I take it you have a wooden boat? If its plastic just drill and glue it in with the polyurathen!!!
Wooden boat 5 day job--five coats of paint.
Plastic Quater hour job!!!

 

[tugboat]

It is important to locate the fitting in the right place, by which I mean conveniently close to the engine but also in a convenient place for you to operate it quickly and comfortably.
Thoughts-
Hold the valve unit in various positions and decide exact positon and also orientation of the valve handle.
If the hull has any curvature, profile the underside of the wooden backing piece to match it.
Some skin fittings have a lug designed to locate in a notch cut into the side of the hull aperture - it is important to make this notch in the right place so you finally end up with the valve facing the right way for convenient operation. To this end, tighten the valve onto the skin fitting and place it in the chosen position inside the hull so you can see where the notch needs to be. The notch/lug will stop the skin fitting turning while you fit the valve.
If no lug/ notch, fit the skin fitting loosely (with Sikaflex sealant) fit the valve (using a pipewrench or Stillson wrench on the skin fitting to prevent it turning) then turn the assembly to the required orientation and finally tighten the nut on the skin fitting. Don't overtighten or you'll squeeze out all the sealant.

A bit longwinded but hope that helps.

 

[aidancoughlan]

I'll be doing the same over the next while, and found an article in one of my PBO back issues July 2004. summary...
1.mark hole (diamter of outside of fitting!)
2.drill hole at same angle fitting will be inserted
3.make plywood backing panel with hole in middle (eg in photo approx 1 inch all around fitting)
4.coat the flange of fitting with "underwater" sealant & push up gently into hull
5.insert plywood pad over fitting on inside
6.tighten compression nut
7.optionally before putting the valve on the skin fitting, use Heldite (liquid sealant) on threads
8.screw on the valve & line up to ensure hose on right direction
9. watch it for a while after launching (this one I'll be doing !)
it looked quite straightforward really, nothing more than the above.

 

[poter]

Nothing much to add to the above contributions except make sure you do get Sikaflex sealent, it will cost a lot more than the other sealents but it is the best...
how much is your boat worth?


poter

 

[JimMcMillan]

glass or wood ? big curvature or small?need more info!

 

[seaesta]

Thanks for the very useful comments so far. She is thickish (1960's) GRP and the spot I have in mind has minimal curvature. I will have a look for the fittings with a radial locating lug - from experience I need to put a fair bit of torque on to remove valves and strainers for maintenance / replacement and do not want the fitting to turn.
Any more thoughts
Martin

 

[macca]

Couple of additional points-

Marine ply may be a better material than hardwood, as it will have a greater resistance to carcking along the grain.

Soaking the pad in epoxy before installing won't hurt.

When I did it I set up the pads temporarily, then drilled the hole through the fibreglass and pad at the same time, in order to ensure the holes were aligned, then glued the pad to the FRP with epoxy. Then Sikaflex a salready discussed.

 

[aidancoughlan]

with regard to the skin fitting turning, the article in PBO showed the expert using a Vice grips or similar to hold the fitting while the nut was tightened with another tool in his other hand. I presume where the skin fitting protrudes into the hull, the top portion of this doesnt have any thread, and this was the part he was holding.

 

[ShipsWoofy]

Most skin fittings have lugs accessible from the outside person. I found wide chisels and mole grips prevented the fitting turning. The last 1/2 turn would always beat the outside person and a tiny little twist was inevitable.

This might not be the professional way, just my experiences.

 

[Zeus]

Re: teak deck

Does anybody know if sikaflex is affected by teak oil? I have notest a softening of the seams that I blame to the teak oil affecting the rubber /forums/images/graemlins/confused.gif