bobm
Well-Known Member
When the boat comes out this winter I will have to "epoxy" after treating for some minor osmosis. Can anyone recomend how to do and suitable products please.
Epoxy treatment for rudder
- Thread starter bobm
- Start date
oldsaltoz
Well-Known Member
G'day Bobm,
Removing what could be osmosis in a rudder can be a bit tricky because the layup is often thin; also worth noting is that in many cases this has developed from inside, so fixing it will only be a temporary arrangement.
Start by removing all antifoul and paint if applied.
When grinding out look for small brown to yellow lines and follow them till completely removed, if this results in going through the laminate into the rudders interior, there's a good chance it started from inside and may still be wet. No need to panic it's fixable. Just let us know what you find.
Assuming we have not got a few holes in the rudder:
When grinding out feather the edges so that you end up with a shallow cone shape, clean the area with some Acetone and plenty of white cotton rags, this needs dry for 10 minutes so now is a good time to cut your glass to shape, start with a small patch that covers only one third of the repair, the next patch should be 60 mm wider / longer that the first, keep cutting till you get to within 15 mm of the ground edge; we don't want to overfill the area as that will mean more sanding later. You can bend a plastic ruler held at 30* to check if you have over / under filled, you may need several layers, cut patches to fill only the low spots and finish with a patch that covers all the others.
Depending on how thick the rudder was built you may need anything from 2 to 8 layers of cloth to get back to the rudder profile, as it's not a huge area you should be OK to lay up all layers in one go, heating should not be a problem.
When all holes have been filled, let the resin cure for at least 24 hours, than wash it before sanding to remove residue left by the curing process, just a running hose and a scotchbrite plastic kitchen scourer is all you need. Start at the top and rub till water no longer forms beads as on a polished car.
Sand off any high spots and fill any low areas with closed cell Micro-Balloons or 'Q' Cells, use the plastic ruler bent to the profile of the rudder to get a smooth finish and reduce sanding, the closed cells should be mined to a loose toothpaste consistency to get wet look finish. Let this cure for 24 hours and wash as above prior to sanding.
You should now have a smooth rudder ready to treat with epoxy. If you are working with the rudder removed from the boat (The best way by far) set it up so that you can coat all areas in one move, Mix your epoxy resin and apply with a roller (Suitable for use with epoxy) and tip off with a long haired brush not less than 2 inches wide. You can save sanding between coats by applying wet on tacky, just make sure it is tacky, if it's still wet you will not be adding, just spreading, if it's too dry you will be adding fresh resin over residue left by curing, not good. If it is too dry let it fully cure for 24 hours and give it light sanding with a 200 grit, just enough to knock the high gloss off.
You will need at least 4 coats, now you know why I like wet on tacky, then another wash and another light sanding as above.
Next apply a coat of epoxy primer, let it fully cure and lightly sand, you are now ready to apply a top coat prior to antifouling. I would use a 2 pot Polyurethane for this, it will last for years, apply with a roller and tip off with a foam brush, keep thin and do several coats for a fine finish, not required on your rudder but good practice for later.
TIPS:
I would use epoxy resins and cloth designed for use with an epoxy, not chopped strand mat as will use a lot more resin than cloth. the last layer of cloth would be a fine roving, this ensures no exposed ends of fibres are exposed.
Mix you resin in large shallow containers, a good surface area will prevent heat build up and give you plenty of pot life.
You can clean up most of you tools in white vinegar and use a lot less Acetone.
Latex disposable gloves are a must, also make sure you have a good respirator, particularly when if sanding off the old antifoul.
Keep us informed on your progress, it's a project any DIY can do.
Good luck. Andavagoodweekend......
Removing what could be osmosis in a rudder can be a bit tricky because the layup is often thin; also worth noting is that in many cases this has developed from inside, so fixing it will only be a temporary arrangement.
Start by removing all antifoul and paint if applied.
When grinding out look for small brown to yellow lines and follow them till completely removed, if this results in going through the laminate into the rudders interior, there's a good chance it started from inside and may still be wet. No need to panic it's fixable. Just let us know what you find.
Assuming we have not got a few holes in the rudder:
When grinding out feather the edges so that you end up with a shallow cone shape, clean the area with some Acetone and plenty of white cotton rags, this needs dry for 10 minutes so now is a good time to cut your glass to shape, start with a small patch that covers only one third of the repair, the next patch should be 60 mm wider / longer that the first, keep cutting till you get to within 15 mm of the ground edge; we don't want to overfill the area as that will mean more sanding later. You can bend a plastic ruler held at 30* to check if you have over / under filled, you may need several layers, cut patches to fill only the low spots and finish with a patch that covers all the others.
Depending on how thick the rudder was built you may need anything from 2 to 8 layers of cloth to get back to the rudder profile, as it's not a huge area you should be OK to lay up all layers in one go, heating should not be a problem.
When all holes have been filled, let the resin cure for at least 24 hours, than wash it before sanding to remove residue left by the curing process, just a running hose and a scotchbrite plastic kitchen scourer is all you need. Start at the top and rub till water no longer forms beads as on a polished car.
Sand off any high spots and fill any low areas with closed cell Micro-Balloons or 'Q' Cells, use the plastic ruler bent to the profile of the rudder to get a smooth finish and reduce sanding, the closed cells should be mined to a loose toothpaste consistency to get wet look finish. Let this cure for 24 hours and wash as above prior to sanding.
You should now have a smooth rudder ready to treat with epoxy. If you are working with the rudder removed from the boat (The best way by far) set it up so that you can coat all areas in one move, Mix your epoxy resin and apply with a roller (Suitable for use with epoxy) and tip off with a long haired brush not less than 2 inches wide. You can save sanding between coats by applying wet on tacky, just make sure it is tacky, if it's still wet you will not be adding, just spreading, if it's too dry you will be adding fresh resin over residue left by curing, not good. If it is too dry let it fully cure for 24 hours and give it light sanding with a 200 grit, just enough to knock the high gloss off.
You will need at least 4 coats, now you know why I like wet on tacky, then another wash and another light sanding as above.
Next apply a coat of epoxy primer, let it fully cure and lightly sand, you are now ready to apply a top coat prior to antifouling. I would use a 2 pot Polyurethane for this, it will last for years, apply with a roller and tip off with a foam brush, keep thin and do several coats for a fine finish, not required on your rudder but good practice for later.
TIPS:
I would use epoxy resins and cloth designed for use with an epoxy, not chopped strand mat as will use a lot more resin than cloth. the last layer of cloth would be a fine roving, this ensures no exposed ends of fibres are exposed.
Mix you resin in large shallow containers, a good surface area will prevent heat build up and give you plenty of pot life.
You can clean up most of you tools in white vinegar and use a lot less Acetone.
Latex disposable gloves are a must, also make sure you have a good respirator, particularly when if sanding off the old antifoul.
Keep us informed on your progress, it's a project any DIY can do.
Good luck. Andavagoodweekend......
Talbot
Well-Known Member
I have some pox on my rudders and skegs. They are both GRP skin over ply, and both have through fixing bolts,
My surveyor told me that this was basically normal for this type of configuration, and not to bust a gut doing anything as it would only erupt again anyway. thus not worry unless I wanted to fair it.
My surveyor told me that this was basically normal for this type of configuration, and not to bust a gut doing anything as it would only erupt again anyway. thus not worry unless I wanted to fair it.
oldsaltoz
Well-Known Member
G'day Mark (Talbot),
Or is it delamination because the ply inside is wet?
I can't believe you "surveyors" response. Still I suppose if you can maintain full control without a rubber and steer by sail balance you don't really have a problem at all do you.
I Think I would be taking the rudder off, sanding clean and through the pox bubbles to see if the ply underneath was dry of soggy. Then drill out the fittings holes oversize by 10 mm, filling them with resin and Micro-fibres then re drilling to the required size, thus reducing the chances of more problems with water ingress.
But hay, that's only what I would be doing, after all the 'surveyor' did say it would only erupt again. I wonder how many poor souls have purchased boats based on his reports?
Avagoodweekend.....but don't go too far.
Or is it delamination because the ply inside is wet?
I can't believe you "surveyors" response. Still I suppose if you can maintain full control without a rubber and steer by sail balance you don't really have a problem at all do you.
I Think I would be taking the rudder off, sanding clean and through the pox bubbles to see if the ply underneath was dry of soggy. Then drill out the fittings holes oversize by 10 mm, filling them with resin and Micro-fibres then re drilling to the required size, thus reducing the chances of more problems with water ingress.
But hay, that's only what I would be doing, after all the 'surveyor' did say it would only erupt again. I wonder how many poor souls have purchased boats based on his reports?
Avagoodweekend.....but don't go too far.
Talbot
Well-Known Member
somehow thought that might be your reaction. /forums/images/graemlins/laugh.gif
oldsaltoz
Well-Known Member
I somehow think that might be everyones reaction. /forums/images/graemlins/smirk.gif
thalassa
Well-Known Member
Brian, I've a similar problem with delamination on the head of the rudder. It is made of Bangkiraï, glassed over. It pivots up, so the end where the pivot hole is, always is about 12 cm in the water; presumably, water got in via the downhaul line opening. I've completely removed the epoxy and glass from the area to let it dry out. Now my question is this: is it wise to treat the wood first with hardening oil (Decks ölje or similar) to limit capillary action? Do I put on epoxy on the bare wood first, then lay on the new matting while still wet; or ly the matting on, then wet the epoxy? Thanks!
oldsaltoz
Well-Known Member
G'day Will (thalassa),
I think you need to have a very close look at your rudder, the leading or trailing edge may be have a fine crack caused water entering and swelling the timber, also check the hole by drilling it out at least 10 mm oversize, then fill it in with epoxy resin and Micro-fibres, let this cure fir 24 hours and re drill to the required size.
As for oiling the timber; not a good idea, epoxy will not stick and some of it may not cure near any trace of oil. Expose the area and when fully dry wash it with Acetone and let it dry, then do it again a couple of times as any oil will be washed off the surface and a little more drawn out.
When it's clean and dry; mix a small amount of resin then add around 40% by volume of methylated spirits, this will thin resin enough to penetrate the timber. if the glass is only to protect the timber I would use a light roving cloth, just paint on some fresh resin and lay the roving's over it then roll it till wet through, you may have add a tiny bit more resin to get it all wet.
Let this cure for 24 hours and wash it before sanding using a running hose and scotbrite plastic kitchen scourer till the water no longer forms beads. Now add 3 or more oats of resin wet on tacky, let this cure and wash as above, sand it with a 200 grit just enough to remove the high gloss and add a coat of epoxy primer.
After it has cured, another light sanding and you are ready to paint.
Avagoodweekend......
I think you need to have a very close look at your rudder, the leading or trailing edge may be have a fine crack caused water entering and swelling the timber, also check the hole by drilling it out at least 10 mm oversize, then fill it in with epoxy resin and Micro-fibres, let this cure fir 24 hours and re drill to the required size.
As for oiling the timber; not a good idea, epoxy will not stick and some of it may not cure near any trace of oil. Expose the area and when fully dry wash it with Acetone and let it dry, then do it again a couple of times as any oil will be washed off the surface and a little more drawn out.
When it's clean and dry; mix a small amount of resin then add around 40% by volume of methylated spirits, this will thin resin enough to penetrate the timber. if the glass is only to protect the timber I would use a light roving cloth, just paint on some fresh resin and lay the roving's over it then roll it till wet through, you may have add a tiny bit more resin to get it all wet.
Let this cure for 24 hours and wash it before sanding using a running hose and scotbrite plastic kitchen scourer till the water no longer forms beads. Now add 3 or more oats of resin wet on tacky, let this cure and wash as above, sand it with a 200 grit just enough to remove the high gloss and add a coat of epoxy primer.
After it has cured, another light sanding and you are ready to paint.
Avagoodweekend......
thalassa
Well-Known Member
Thanks Brian, I'll do as you recommend. The origin of the problem was all too apparent after removing the layers of glass. The SS pivot flanges were not completely epoxied in. Cheers!
bobm
Well-Known Member
Thanks for the comprehensive advice, I will save for later when the boat is out this winter.