Hi team.
I've done the first coat of varnish on my strip canoe, left it for 24+ hours and just had a go at sanding it. What a nightmare!! The sandpaper (120/220 grit) just gums up after a few strokes. This is wet sandpaper, and I have to lie the paper flat and use a paint scraper to clean the paper off (i.e. it doesn't wash off)...
I can't face doing this 4+ times, especially because I have a limited supply of paper and NZ is in lockdown cos of covid so I can't buy any more.
Any tips?
Sanding varnish
Re: Sanding varnish
I lightly hand sand and remove dust with a tack cloth.
I like the Scotch brite pads, or reasonable fact simile. I don't really remove any varnish, but just scuff it, so the next coat has something to cling to.
I'm not an expert finisher, but this is what I do and it works for me .
Good Luck !
Jim
I like the Scotch brite pads, or reasonable fact simile. I don't really remove any varnish, but just scuff it, so the next coat has something to cling to.
I'm not an expert finisher, but this is what I do and it works for me .
Good Luck !
Jim
Keep your paddle wet and your seat dry!
Re: Sanding varnish
Sounds like you need to let the varnish cure longer. If it is an old fashioned oil/alkyd based spar varnish you may need to wait several days before sanding.
If you are using wet sanding paper make sure the hull surface is real wet. I use a spray bottle to mist the area ahead of the sanding. A light touch is all that is necessary. One sanding of 220 is all you need between coats. 120 would be removing all the varnish.
One trick I use for making sand paper last is cleaning it with a brass bristled brush. The brass won't dull the abrasive, but will get the gummy stuff out. Even with that I use a lot of paper. A quarter sheet of 220 will only efficiently sand 2 square feet of surface.
One question. How long did you let the epoxy cure before varnishing? Sometime varnishing over not-quite-totally-cured epoxy will mess with the varnish. Epoxy takes a week to be 100%, even after it feels hard and sands well.
If you are using wet sanding paper make sure the hull surface is real wet. I use a spray bottle to mist the area ahead of the sanding. A light touch is all that is necessary. One sanding of 220 is all you need between coats. 120 would be removing all the varnish.
One trick I use for making sand paper last is cleaning it with a brass bristled brush. The brass won't dull the abrasive, but will get the gummy stuff out. Even with that I use a lot of paper. A quarter sheet of 220 will only efficiently sand 2 square feet of surface.
One question. How long did you let the epoxy cure before varnishing? Sometime varnishing over not-quite-totally-cured epoxy will mess with the varnish. Epoxy takes a week to be 100%, even after it feels hard and sands well.
Re: Sanding varnish
The one thing you know is that if the varnish is gumming, it isn't ready to sand .... you tell that easily by taking a small piece of paper and lightly sanding a small area, it should produce a nice light powder..if it doesn't something is wrong.
Usual suspect is epoxy that is not fully cured, if this is so, it will prevent the varnish from oxidizing to form the hard finish .... this really sucks because if that is the cause, you just have to leave it to see if it hardens (try a week), if it doesn't you may be stripping it all back off.
I leave my epoxy for 2 weeks, just to be sure I have a full cure ... I rushed an epoxy set ONCE, the varnish took the season to finally harden, fortunately that was only a paddle, but the lesson was learned. It creates so much extra work, it is better to wait the full cure time. I usually plan to start the seats and trim in that time slot.
Amine Blush from the epoxy can also cause an issue, usually present if the cure environment is on the cooler/cold side of the rated curing range, this can be prevented by including a wash with light detergent after sanding the epoxy.
Final possibility is that you just haven't left the varnish long enough ... also consider that most varnishes cure better/faster with warmth and airflow .... what is your environment like? If you left it a day at cool temps and in a closed room, there is a good chance it just didn't have the time to cure properly. Solution would be to leave it longer and do a test patch by hand to check.
Brian
Usual suspect is epoxy that is not fully cured, if this is so, it will prevent the varnish from oxidizing to form the hard finish .... this really sucks because if that is the cause, you just have to leave it to see if it hardens (try a week), if it doesn't you may be stripping it all back off.
I leave my epoxy for 2 weeks, just to be sure I have a full cure ... I rushed an epoxy set ONCE, the varnish took the season to finally harden, fortunately that was only a paddle, but the lesson was learned. It creates so much extra work, it is better to wait the full cure time. I usually plan to start the seats and trim in that time slot.
Amine Blush from the epoxy can also cause an issue, usually present if the cure environment is on the cooler/cold side of the rated curing range, this can be prevented by including a wash with light detergent after sanding the epoxy.
Final possibility is that you just haven't left the varnish long enough ... also consider that most varnishes cure better/faster with warmth and airflow .... what is your environment like? If you left it a day at cool temps and in a closed room, there is a good chance it just didn't have the time to cure properly. Solution would be to leave it longer and do a test patch by hand to check.
Brian
Re: Sanding varnish
Thanks for the replies team
It's definitely not uncured epoxy as that was done about a month ago. It's not an old fashioned varnish - pretty standard one. And I live in a very temperate climate so cure times shouldn't be abnormal. Sedges, I think you have the answer - more water (any father Ted fans out there??). This makes it manageable (but not easy!). I think patience is the key. It's been 9 months in the making now, so what's the hurry in the final steps...
Stay safe team, be kind.
It's definitely not uncured epoxy as that was done about a month ago. It's not an old fashioned varnish - pretty standard one. And I live in a very temperate climate so cure times shouldn't be abnormal. Sedges, I think you have the answer - more water (any father Ted fans out there??). This makes it manageable (but not easy!). I think patience is the key. It's been 9 months in the making now, so what's the hurry in the final steps...
Stay safe team, be kind.
Last edited by Phildub on Sat Apr 04, 2020 3:57 am, edited 1 time in total.
Re: Sanding varnish
Brian brought up a good point ! If it's blushing, you'll need to strip the varnish.
What epoxy did you use. I can sand my varnish easily within a day or two.
Jim
What epoxy did you use. I can sand my varnish easily within a day or two.
Jim
Keep your paddle wet and your seat dry!
Re: Sanding varnish
No it's not blushing, just an inpatient boat builder. I used the usual Wests Epoxy. I'm using Bondall Marine grade monocel varnish (satin finish). Seems pretty good so far. Goes on thicker than I expected and starts curing fairly quickly so haven't had issues with runs. The tin says 6hrs cure minimum, but I'd say it needs the best part of a day to cure enough to sand.
I'm reading lots of differing numbers on how many coats. How do you all know when enough is enough?
I'm reading lots of differing numbers on how many coats. How do you all know when enough is enough?
Re: Sanding varnish
If it seems to go thick and your shop is not real warm and dry it may take a lot longer to harden than the specs say.
I have never applied more than 3 coats on the outside and 2 on the inside. Applying 6 or 7 coats might be important over bare wood, but not over epoxy. You just want a pretty finish with UV protection. I only put 1 coat on the floor on the inside and put in a non-skid additive.
I have never applied more than 3 coats on the outside and 2 on the inside. Applying 6 or 7 coats might be important over bare wood, but not over epoxy. You just want a pretty finish with UV protection. I only put 1 coat on the floor on the inside and put in a non-skid additive.
Re: Sanding varnish
Three and two coats like Sedges. Usually about a quart, give or take by the canoe size.
You can finish, for show, but mine get used so it's more about UV protection, to me any way !
Jim
You can finish, for show, but mine get used so it's more about UV protection, to me any way !
Jim
Keep your paddle wet and your seat dry!
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cedarphile
- Posts: 18
- Joined: Sun Jan 22, 2017 11:41 am
Never sand spar varnish
There's no need to sand soft spar varnish on a cedarstrip hull....because you should never use it there.
This post is going to be a little long as it's going to save savvy builderrs hours and hours of uncomfortable agony in a sweaty sanding mask.
Take your epoxy-coated and 220-sanded hull to your local auto body shop and have them spray 3 coats of automotive clearcoat on the hull in one hour for about 100 bucks (about the same as 3 quarts of top-quality spar varnish). Then take the canoe home realizing you'll never have to do anything to the outside hull again–EVER.
Years ago,I also wet-sanded, varnished; wet-sanded, varnished; wet-sanded, varnished, wet-sanded, varnished my cedarstrip hulls. An expert builder from Chicago, Jim Miller told me about sprayed automotive clearcoat several years ago, but warned me,"Don't mention clearcoat on builder forums as you'll be soundly trashed as a spar-varnish hater, untraditional, heretical, and just plain wrong "
Well here's the deal–––from 50 years of cedarstrip-building experience.
Spar varnish is made for sun-baked surfaces like paddles or thwarts or decks that you're going to handlle frequently, so you want a soft hand feel with pretty good UV resistance.
Spar varnish is made to be soft, automotive clearcoat was created to be super-hard. I often use my cedarstrips in Class I-II whitewater and inevitably scratch up the bottom. Why would I put the softest material available–spar varnish–on the outside of that often-abused hull? At the end of 2-3 seasons with some bottom scrathes, I wet-sand out the scratches and take it back to the body shop. He leaves it handy on a nearby sawhorse waiting, then hits the hull with a couple coats when he's' clear-coating a car anyway and he's waiting for the car's sprayed clearcoat to flash dry. He charges me $25 for these biennial or triennial refresher coats.
3-4 coats of Epiphanes or other premium spar varnish has UV protection of 4 mils and protects for maybe three years; then you have to repeat the whole process of varnish, wet-sand, varnish.... ad infinitum––forever
Three coats of of sprayed clearcoat leaves 8-9 mils of UV protection and lasts virtually forever, protecting what's underneath from sun damage. All modern car finishes are two layers, color coat then clearcoat. Ever see a modern car with faded paint? There's a lesson here for us canoebuilders.
Like most builders, I get off on the sensual process of lovingly varnishing wood: the smell of linseed oil, the smooth, ripple-free smoothness you see in the low-angle light as the varnish flows and brush strokes disappear, putting on a perfectly even coat by feeling the brush drag, rather than watching with the eyes. I still get that spar-varnish pleasure with my paddles, thwarts, decks, etc, But never on the outside of my hulls.
I never liked the sight of a high-gloss hull, preferring a satin finish to hide small boogles. My auto body sprayer added a little powdered flatting agent to the clearcoat. Bingo, a perfect satin finish.
After 50 years of building these things, I can't think of a single reason to put spar varnish on the outside of my cedarstrips.
AND: I glued up a 3/4" thick "cherrystrip" end gate for my utility trailer, fiberglassed it using epoxy, then had my local body shop clearcoat it. As the acid test, I intentionally park the trailer with the tailgate facing south. After 10 years, it's as shiny and perfect as the day I had it sprayed.
And if someone can tell me how to post a picture, I'll do it.
This post is going to be a little long as it's going to save savvy builderrs hours and hours of uncomfortable agony in a sweaty sanding mask.
Take your epoxy-coated and 220-sanded hull to your local auto body shop and have them spray 3 coats of automotive clearcoat on the hull in one hour for about 100 bucks (about the same as 3 quarts of top-quality spar varnish). Then take the canoe home realizing you'll never have to do anything to the outside hull again–EVER.
Years ago,I also wet-sanded, varnished; wet-sanded, varnished; wet-sanded, varnished, wet-sanded, varnished my cedarstrip hulls. An expert builder from Chicago, Jim Miller told me about sprayed automotive clearcoat several years ago, but warned me,"Don't mention clearcoat on builder forums as you'll be soundly trashed as a spar-varnish hater, untraditional, heretical, and just plain wrong "
Well here's the deal–––from 50 years of cedarstrip-building experience.
Spar varnish is made for sun-baked surfaces like paddles or thwarts or decks that you're going to handlle frequently, so you want a soft hand feel with pretty good UV resistance.
Spar varnish is made to be soft, automotive clearcoat was created to be super-hard. I often use my cedarstrips in Class I-II whitewater and inevitably scratch up the bottom. Why would I put the softest material available–spar varnish–on the outside of that often-abused hull? At the end of 2-3 seasons with some bottom scrathes, I wet-sand out the scratches and take it back to the body shop. He leaves it handy on a nearby sawhorse waiting, then hits the hull with a couple coats when he's' clear-coating a car anyway and he's waiting for the car's sprayed clearcoat to flash dry. He charges me $25 for these biennial or triennial refresher coats.
3-4 coats of Epiphanes or other premium spar varnish has UV protection of 4 mils and protects for maybe three years; then you have to repeat the whole process of varnish, wet-sand, varnish.... ad infinitum––forever
Three coats of of sprayed clearcoat leaves 8-9 mils of UV protection and lasts virtually forever, protecting what's underneath from sun damage. All modern car finishes are two layers, color coat then clearcoat. Ever see a modern car with faded paint? There's a lesson here for us canoebuilders.
Like most builders, I get off on the sensual process of lovingly varnishing wood: the smell of linseed oil, the smooth, ripple-free smoothness you see in the low-angle light as the varnish flows and brush strokes disappear, putting on a perfectly even coat by feeling the brush drag, rather than watching with the eyes. I still get that spar-varnish pleasure with my paddles, thwarts, decks, etc, But never on the outside of my hulls.
I never liked the sight of a high-gloss hull, preferring a satin finish to hide small boogles. My auto body sprayer added a little powdered flatting agent to the clearcoat. Bingo, a perfect satin finish.
After 50 years of building these things, I can't think of a single reason to put spar varnish on the outside of my cedarstrips.
AND: I glued up a 3/4" thick "cherrystrip" end gate for my utility trailer, fiberglassed it using epoxy, then had my local body shop clearcoat it. As the acid test, I intentionally park the trailer with the tailgate facing south. After 10 years, it's as shiny and perfect as the day I had it sprayed.
And if someone can tell me how to post a picture, I'll do it.
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Patricks Dad
- Posts: 1476
- Joined: Wed Oct 13, 2004 1:11 pm
- Location: Warrenville, Illinois
Re: Sanding varnish
I had the first canoe I built clearcoated. It looks awesome. scratches just as easily as anything else and isn't easily "touched-up" as varnish but your approach of periodically clearcoating makes the touch-up problem moot.
As for posting a picture. Look at the series of icons above your window you type in when making a post... The 9th icon from the left is a picture button. click it and some text will be automatically added to your post. between the ][ in that string of text insert a link to your picture (you can't upload pictures but only put a url to a picture stored somewhere else on the internet).
Thanks
As for posting a picture. Look at the series of icons above your window you type in when making a post... The 9th icon from the left is a picture button. click it and some text will be automatically added to your post. between the ][ in that string of text insert a link to your picture (you can't upload pictures but only put a url to a picture stored somewhere else on the internet).
Thanks