manolis

Fairing SC27 rudder

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I'm fairing the rudder on my dry-sailed SC27. The job was started with 3M premium Vinylester marine filler, sanding by hand with 80 grit on a longboard. It's slow going and after an afternoon I'm about 1/3 of the way through the job. Thinking through the process, I'd appreciate some recommendations.

 

What are the right tools to mix the filler? I used a popsicle stick, squeegee and a magazine. It was a mess and made it difficult to mix evenly.

What's the best process for applying filler? Squeegee it over the entire surface and block it down? Fair the leading edge, trailing edge, then apply a couple 'stripes' of filler from front to back, block those down and use them as guides to fill in the majority of the area? Trying to minimize the amount of improperly-applied and then cured filler that needs to get sanded off.

Is there a better way to block the filler down? An air file? Electric powered longboard? 40 grit paper? Angle grinder with a sanding pad? (yikes)

What's the best way to seal the surface? Can I use gel coat with surfacing wax? Roll it on? What kind of roller? Roll and tip, then block sand?

What grit paper should I get down to prior to gel coating?

Does sanded gel coat need to be 'sealed'? Or can I leave it sanded with 150 grit?

The trailing edge of the rudder is thick, and will get thicker as I fair (there's a fat spot in the foil about 3" in front of the trailing edge). To taper to a thin trailing edge, I'll need to add about 1/2" to the rudder chord. Can I use regular filler for this? Or does it need to be glass reinforced? What's the best way to apply it (tape one side, pack it in, flip, remove tape and repeat?)

Can I use polyester filler (bondo)? It's much cheaper ($30/gallon vs $150/gallon for the 3M stuff).

What's the best mask to use for this so I don't die? I bought a 3M OV/AG/P100 mask, but am still feeling it afterwards. Are there reasonable (positive pressure) fresh air supply masks available?

Can you recommend a place to buy all this stuff? The boat is in Los Angeles (San Pedro).

What other questions should I be asking?

 

Thanks!
Manolis

 

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Lot of questions, have you got a boatbuilder mate to ask. Someone at the club or yard? 

Dont use bondo, you'll need glassing skills to add a trailing edge, use epoxy filler and paint, avoid gelcoat.... Lots of methods to fair all work to a degree, a plane is good.

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Mix in a container like a quart yogurt container or a small ice cream pail for larger amounts.

Use a long squeegee, not the little Bondo spreaders - drywall trowels are good.

Don't use Bondo - it is polyester filled with talc and is very hygroscopic. I like talc filled epoxy I mix myself.

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What sloop said.  Squeegee it on with a long batton or similar tool.

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I like a plastic mixing board like this. Scoop out the filler onto the board, mix with the spreader on the board, and the use it to carry the filler while you apply.  No additional containers needed.  Dried filler will flake off, but I find it far more effective to clean promptly with a rag and denatured alcohol before it dries.

If you set on a scale it's possible to mix by weight.

13682_usc_37005_ppm-tif

 

 

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Thanks for the suggestions. I'll try a trowel, plane and the mixing boards.

Any tricks to laying down gelcoat without a gun?

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11 hours ago, xyzzy said:

I like a plastic mixing board like this. Scoop out the filler onto the board, mix with the spreader on the board, and the use it to carry the filler while you apply.  No additional containers needed.  Dried filler will flake off, but I find it far more effective to clean promptly with a rag and denatured alcohol before it dries.

If you set on a scale it's possible to mix by weight.

13682_usc_37005_ppm-tif

 

 

neat,  where do you get those?  i've haven't seen them around my area, not even the auto paint supply shops

 

 

pss. nevermind, found them...

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15 hours ago, manolis said:

I'm fairing the rudder on my dry-sailed SC27. The job was started with 3M premium Vinylester marine filler, sanding by hand with 80 grit on a longboard. It's slow going and after an afternoon I'm about 1/3 of the way through the job. Thinking through the process, I'd appreciate some recommendations.

 

 

Thanks!
Manolis

 

one afternoon, hah...  try sanding a full keel in 104* heat...    

I found the 3m premium fller pretty easy to sand..  Are you changing your sandpaper often enough? wearing the grit down to the backing?

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When I fared my rudder and added a better trailing edge I used
Q-cel and AeroSil about 50/50 mixing it to almost peanut butter consistency for filler and fairing. easier to sand than the 3m vinylester  filler.
Some glass tape about 6" for trailing edge structure.sand, fair and coat.

We have an FGH near by so tons of cool stuff to get hold of.
https://www.fiberglasshawaii.com/shop/resin-fillers-gel-coat/fillers/

 

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Cardboard (sealed) makes a reasonable palette, scraped clean each time. Vinylester is good but stay cool. If going to gelcoat why not just fair with that, how much build are you looking for? If you can afford a 1/2 sheet sander that's a reasonable sub for a handboard, checking with batten or longboard as you go. Think indicator coats. Using templates or eyeballing? Changing section? What's goal?

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About the only speed tip, is don't long board in 80 if you can find 60. 80 is on the edge of smoothing, 60 you are still fairing, and 40 you are shaping. 

I use 3M dry guide coat or west systems graphite smeared on the surface.  Once you are in primer, denatured alcohol and a dash of green food coloring works well. 

Once you have template good, pattern good areas put some tape over them or prime them with interlux interprotect and lock them down as good.  A lot of folks will chase their own tail by not working in station lines and going over and over, sanding outside the lines things that are already fixed and good.  That takes a lot of extra effort.  Fairing just means getting things flat, and in the right plane.  If it is curved, it means wasting down to the fairest curve you can get and building up the lows...  And has nothing to do with sanding until you end up with a smooth surface. 

Only two camps, screeding on the putty with a trowel or metal bar wide enough to span onto good station lines, or over-filling every low spot so it is a bleeding high spot and knocking it down flush the the surrounding area.  One, you scuff with 80 grit and prime... The other you rock out with 40 grit until it is fair.  If you over fill and sand with 80 grit, you don't get fair except by accident.

A foot and a half sheet rock trowel pulls a slight curve to it that feathers in the edges.  That is what it is made to do.  It is meant to go over the top of a lump, and pull a tapered fill to each side of the tape on a sheet rock joint on a wall no one gives a shit about if it is flat or not in egg shell paint.

 A piece of angle iron or 3 inch wide 1/4 inch aluminum flat bar is fucking flat as a screed.  Most people use a sheet rock trowel, flexible knife, and pull a slick...  The slick ends up low in the middle, unless you over fill it so the edges so they are bleeding high spots that you have to work your ass off to feather in.  Otherwise you end up with a low hollow in the middle of the low spot and a taper in that needs filling.  Using a flat bar wide enough to span the whole shooting match to pull means you can't put any more into the hole than what it takes to fill it.  Wider is better, until you are fixing holidays, finger prints, and drag marks. Then just big enough to cover the holiday and a big blob on top to account for shrink back rules the day. 

If you go finer than what you are boarding with on a DA, you can DA until the board scratches disappear and get a fresh look at things.  With fresh paper, a 2 foot by 2 foot area doesn't take long to get a clean canvas as you aren't sanding a flat surface but one that is already heavily grooved. Most folks can work until they kill themselves pushing a board, and if things are too rough folks can't feel the difference between a low spot, and a textured spot that the board kisses only one direction.  Unless you have an orbital air file, almost no one board sands without throwing power at it, heavily, at alternating intervals when fairing.  World is split when you get past 180 grit...  Some folks board sand to completion, but almost nobody does 40 grit work purely by hand.  

Gist is, if the 80 grit paper cuts a scratch depth and 40 grit cuts a scratch depth.  You remove the depth of the 40 grit scratches when you sand them off...  But that means you can in effect "measure" how low your lows are.  If you don't have many lows, or many highs, and you are trying to work out the surface and get it flat, going coarser does the job better if you have more than one material visible.  Soft stuff doesn't sand the same as hard stuff, and you can't sand hard and soft stuff with fine sand paper without, never, finishing until you eventually put a glaze over the surface thick enough just to scuff and prime and sand out as one material.  Primer is a surfacing agent.  Interlux Interprotect in grey is self guide coating. 

If you have enough material on to not cut through to the base material, you can cut with the hand board and see the surface of what the board touches and does not touch, and DA around where you aren't making contact to lower the whole area.  Until you get squeedgee fair, where you are pulling the final skim with a 6 inch squeedgee and just putting a glaze on to smooth out before priming...  You don't lose much ground by slicking out to take a look at things.   

The worst of your low spots will still have hand board marks, as the DA can't fit the low spots that are that low either.  If you have places like that, keep on sanding with coarse grits until you get shape...  Then putty the whole damn thing up in a thin skim and smooth it out. with fine grits.  

The Hand board cuts grooves, and unless you cross off the surface, more grooving the same direction as the rest of the grooves doesn't cut material very quickly.  A DA cutting a harshly grooved surface, makes quick work of smoothing.  You can speed up hand boarding small knots and high spots by using a 40 grit block and rough scuffing vertical and horizontal over them, and hand boarding the 45's until the 40 grit scratches are off...  But if you find that useful, you really shouldn't be in 80 grit yet.  Most folks are well served by not trying to 80 grit to get shape, until they are ready to mix primer.  Even if you back up and punt on a few places, it is faster not to try to jump ahead in grits and get smooth before you are straight.  Stuff that doesn't cut down high knots, smooths them out but you have to kill yourself to get them gone. 

About a third of the time you spend hand with a 16 inch board, ought to be vertical work instead of just working your crosses.  Verify that you've got a consistent thickness, by working the vertical and if you don't have kiss-contact around the areas you've been pkcing on to get shape...  You've got shape, but that shape is low.

I use a silcone 3M half mask and P100 pink cartridges for general grinding and the activated carbon ones for working in fresh material.  Thickster latex or vinyl gloves make a big difference in getting out of the fiberglass itch as grinders throw glass at high speed into the back of your hands... 

 

 

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7 hours ago, Zach said:

About the only speed tip, is don't long board in 80 if you can find 60. 80 is on the edge of smoothing, 60 you are still fairing, and 40 you are shaping. 

I use 3M dry guide coat or west systems graphite smeared on the surface.  Once you are in primer, denatured alcohol and a dash of green food coloring works well. 

Once you have template good, pattern good areas put some tape over them or prime them with interlux interprotect and lock them down as good.  A lot of folks will chase their own tail by not working in station lines and going over and over, sanding outside the lines things that are already fixed and good.  That takes a lot of extra effort.  Fairing just means getting things flat, and in the right plane.  If it is curved, it means wasting down to the fairest curve you can get and building up the lows...  And has nothing to do with sanding until you end up with a smooth surface. 

Only two camps, screeding on the putty with a trowel or metal bar wide enough to span onto good station lines, or over-filling every low spot so it is a bleeding high spot and knocking it down flush the the surrounding area.  One, you scuff with 80 grit and prime... The other you rock out with 40 grit until it is fair.  If you over fill and sand with 80 grit, you don't get fair except by accident.

A foot and a half sheet rock trowel pulls a slight curve to it that feathers in the edges.  That is what it is made to do.  It is meant to go over the top of a lump, and pull a tapered fill to each side of the tape on a sheet rock joint on a wall no one gives a shit about if it is flat or not in egg shell paint.

 A piece of angle iron or 3 inch wide 1/4 inch aluminum flat bar is fucking flat as a screed.  Most people use a sheet rock trowel, flexible knife, and pull a slick...  The slick ends up low in the middle, unless you over fill it so the edges so they are bleeding high spots that you have to work your ass off to feather in.  Otherwise you end up with a low hollow in the middle of the low spot and a taper in that needs filling.  Using a flat bar wide enough to span the whole shooting match to pull means you can't put any more into the hole than what it takes to fill it.  Wider is better, until you are fixing holidays, finger prints, and drag marks. Then just big enough to cover the holiday and a big blob on top to account for shrink back rules the day. 

If you go finer than what you are boarding with on a DA, you can DA until the board scratches disappear and get a fresh look at things.  With fresh paper, a 2 foot by 2 foot area doesn't take long to get a clean canvas as you aren't sanding a flat surface but one that is already heavily grooved. Most folks can work until they kill themselves pushing a board, and if things are too rough folks can't feel the difference between a low spot, and a textured spot that the board kisses only one direction.  Unless you have an orbital air file, almost no one board sands without throwing power at it, heavily, at alternating intervals when fairing.  World is split when you get past 180 grit...  Some folks board sand to completion, but almost nobody does 40 grit work purely by hand.  

Gist is, if the 80 grit paper cuts a scratch depth and 40 grit cuts a scratch depth.  You remove the depth of the 40 grit scratches when you sand them off...  But that means you can in effect "measure" how low your lows are.  If you don't have many lows, or many highs, and you are trying to work out the surface and get it flat, going coarser does the job better if you have more than one material visible.  Soft stuff doesn't sand the same as hard stuff, and you can't sand hard and soft stuff with fine sand paper without, never, finishing until you eventually put a glaze over the surface thick enough just to scuff and prime and sand out as one material.  Primer is a surfacing agent.  Interlux Interprotect in grey is self guide coating. 

If you have enough material on to not cut through to the base material, you can cut with the hand board and see the surface of what the board touches and does not touch, and DA around where you aren't making contact to lower the whole area.  Until you get squeedgee fair, where you are pulling the final skim with a 6 inch squeedgee and just putting a glaze on to smooth out before priming...  You don't lose much ground by slicking out to take a look at things.   

The worst of your low spots will still have hand board marks, as the DA can't fit the low spots that are that low either.  If you have places like that, keep on sanding with coarse grits until you get shape...  Then putty the whole damn thing up in a thin skim and smooth it out. with fine grits.  

The Hand board cuts grooves, and unless you cross off the surface, more grooving the same direction as the rest of the grooves doesn't cut material very quickly.  A DA cutting a harshly grooved surface, makes quick work of smoothing.  You can speed up hand boarding small knots and high spots by using a 40 grit block and rough scuffing vertical and horizontal over them, and hand boarding the 45's until the 40 grit scratches are off...  But if you find that useful, you really shouldn't be in 80 grit yet.  Most folks are well served by not trying to 80 grit to get shape, until they are ready to mix primer.  Even if you back up and punt on a few places, it is faster not to try to jump ahead in grits and get smooth before you are straight.  Stuff that doesn't cut down high knots, smooths them out but you have to kill yourself to get them gone. 

About a third of the time you spend hand with a 16 inch board, ought to be vertical work instead of just working your crosses.  Verify that you've got a consistent thickness, by working the vertical and if you don't have kiss-contact around the areas you've been pkcing on to get shape...  You've got shape, but that shape is low.

I use a silcone 3M half mask and P100 pink cartridges for general grinding and the activated carbon ones for working in fresh material.  Thickster latex or vinyl gloves make a big difference in getting out of the fiberglass itch as grinders throw glass at high speed into the back of your hands... 

 

 

I'm going to print this post out for careful study. I've done my share of fairing, but there's gold here. Thanks for the effort.

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9 hours ago, Zach said:

About the only speed tip, is don't long board in 80 if you can find 60. 80 is on the edge of smoothing, 60 you are still fairing, and 40 you are shaping. 

I use 3M dry guide coat or west systems graphite smeared on the surface.  Once you are in primer, denatured alcohol and a dash of green food coloring works well. 

Once you have template good, pattern good areas put some tape over them or prime them with interlux interprotect and lock them down as good.  A lot of folks will chase their own tail by not working in station lines and going over and over, sanding outside the lines things that are already fixed and good.  That takes a lot of extra effort.  Fairing just means getting things flat, and in the right plane.  If it is curved, it means wasting down to the fairest curve you can get and building up the lows...  And has nothing to do with sanding until you end up with a smooth surface. 

Only two camps, screeding on the putty with a trowel or metal bar wide enough to span onto good station lines, or over-filling every low spot so it is a bleeding high spot and knocking it down flush the the surrounding area.  One, you scuff with 80 grit and prime... The other you rock out with 40 grit until it is fair.  If you over fill and sand with 80 grit, you don't get fair except by accident.

A foot and a half sheet rock trowel pulls a slight curve to it that feathers in the edges.  That is what it is made to do.  It is meant to go over the top of a lump, and pull a tapered fill to each side of the tape on a sheet rock joint on a wall no one gives a shit about if it is flat or not in egg shell paint.

 A piece of angle iron or 3 inch wide 1/4 inch aluminum flat bar is fucking flat as a screed.  Most people use a sheet rock trowel, flexible knife, and pull a slick...  The slick ends up low in the middle, unless you over fill it so the edges so they are bleeding high spots that you have to work your ass off to feather in.  Otherwise you end up with a low hollow in the middle of the low spot and a taper in that needs filling.  Using a flat bar wide enough to span the whole shooting match to pull means you can't put any more into the hole than what it takes to fill it.  Wider is better, until you are fixing holidays, finger prints, and drag marks. Then just big enough to cover the holiday and a big blob on top to account for shrink back rules the day. 

If you go finer than what you are boarding with on a DA, you can DA until the board scratches disappear and get a fresh look at things.  With fresh paper, a 2 foot by 2 foot area doesn't take long to get a clean canvas as you aren't sanding a flat surface but one that is already heavily grooved. Most folks can work until they kill themselves pushing a board, and if things are too rough folks can't feel the difference between a low spot, and a textured spot that the board kisses only one direction.  Unless you have an orbital air file, almost no one board sands without throwing power at it, heavily, at alternating intervals when fairing.  World is split when you get past 180 grit...  Some folks board sand to completion, but almost nobody does 40 grit work purely by hand.  

Gist is, if the 80 grit paper cuts a scratch depth and 40 grit cuts a scratch depth.  You remove the depth of the 40 grit scratches when you sand them off...  But that means you can in effect "measure" how low your lows are.  If you don't have many lows, or many highs, and you are trying to work out the surface and get it flat, going coarser does the job better if you have more than one material visible.  Soft stuff doesn't sand the same as hard stuff, and you can't sand hard and soft stuff with fine sand paper without, never, finishing until you eventually put a glaze over the surface thick enough just to scuff and prime and sand out as one material.  Primer is a surfacing agent.  Interlux Interprotect in grey is self guide coating. 

If you have enough material on to not cut through to the base material, you can cut with the hand board and see the surface of what the board touches and does not touch, and DA around where you aren't making contact to lower the whole area.  Until you get squeedgee fair, where you are pulling the final skim with a 6 inch squeedgee and just putting a glaze on to smooth out before priming...  You don't lose much ground by slicking out to take a look at things.   

The worst of your low spots will still have hand board marks, as the DA can't fit the low spots that are that low either.  If you have places like that, keep on sanding with coarse grits until you get shape...  Then putty the whole damn thing up in a thin skim and smooth it out. with fine grits.  

The Hand board cuts grooves, and unless you cross off the surface, more grooving the same direction as the rest of the grooves doesn't cut material very quickly.  A DA cutting a harshly grooved surface, makes quick work of smoothing.  You can speed up hand boarding small knots and high spots by using a 40 grit block and rough scuffing vertical and horizontal over them, and hand boarding the 45's until the 40 grit scratches are off...  But if you find that useful, you really shouldn't be in 80 grit yet.  Most folks are well served by not trying to 80 grit to get shape, until they are ready to mix primer.  Even if you back up and punt on a few places, it is faster not to try to jump ahead in grits and get smooth before you are straight.  Stuff that doesn't cut down high knots, smooths them out but you have to kill yourself to get them gone. 

About a third of the time you spend hand with a 16 inch board, ought to be vertical work instead of just working your crosses.  Verify that you've got a consistent thickness, by working the vertical and if you don't have kiss-contact around the areas you've been pkcing on to get shape...  You've got shape, but that shape is low.

I use a silcone 3M half mask and P100 pink cartridges for general grinding and the activated carbon ones for working in fresh material.  Thickster latex or vinyl gloves make a big difference in getting out of the fiberglass itch as grinders throw glass at high speed into the back of your hands... 

 

 

This is dynamite. I pulled a ton of great notes here; Thank you!

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