help understanding the best way to seal

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help understanding the best way to seal

Postby fuelfox4949 » Wed Apr 29, 2020 6:02 pm

i am just about finished with my first teardrop build, i took on this challenge because i wanted to learn about carpentry. i know about being a mechanic and welding however the woodworking has alluded me.
i camp every other weekend in northern Minnesota and wanted something stronger then a tent. anyway i'm having trouble learning the sealing part of it.
after searching and reading all sorts of articles i am still a bit confused as i prefer hands on learning so here i am finally asking for help so i can get this right the first time.

so i built a simply 4*8 teardrop with birch wood plywood sides, pine bcx plywood for the roof.
the floor was sealed and covered in henrys roof tar undercoat and rubber auto undercoat.
now for the sides and roof i want to seal the wood as best i can then use a exterior paint like behr marquee to paint it red and black to match my truck and jeep.

my plan is to get a gallon of minwax polyurethane semi gloss oil based 1 gallon and mix it with mineral spirits. i was going to do 50/50 mix and apply 2 to 3 coats.
in between coats i was going to lightly sand with 220 sandpaper to scuff a little.
after that i was going to use a 100 percent coat of minwax. let dry for a few days then paint over it with the behr marquee paint and primer in 1.
i get most my supplies from home depot or menards.

if this is wrong please direct me in a better way. if there is something better to use please provide a link or pictures so i can see it.
thanks for any and all help.
so far i have loved every moment of this project.
if you need more info on my project let me know and i'll get the details as fast as i can
p.s this trailer will be stored outside during the summer and inside during the winter.
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Re: help understanding the best way to seal

Postby tony.latham » Wed Apr 29, 2020 7:04 pm

my plan is to get a gallon of minwax polyurethane semi gloss oil based 1 gallon and mix it with mineral spirits. i was going to do 50/50 mix and apply 2 to 3 coats.
in between coats i was going to lightly sand with 220 sandpaper to scuff a little.


I think you've got a good plan but here are my tweaks:

First, buy gloss poly. All the other polyurethanes have a bit of wax in it that doesn't make for a good choice as a paint primer. Secondly, put two or three coats on, one after the other, and then let it dry for several days -mineral spirits isn't very volatile. You could put a topcoat on after that of uncut poly to really seal the deal.

There is no benefit of allowing one coat to dry. You can then do a 220 smoothing sand before you paint.

:thinking:

Tony
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Re: help understanding the best way to seal

Postby fuelfox4949 » Thu Apr 30, 2020 8:03 pm

thanks for the advice.
however i was just shopping on homedepot.com and it says that polyurethane is for indoor use.
so should i get the Varathane spar URETHANE oil based in gloss?
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Re: help understanding the best way to seal

Postby tony.latham » Thu Apr 30, 2020 8:32 pm

homedepot.com and it says that polyurethane is for indoor use.
so should i get the Varathane spar URETHANE oil based in gloss?


The problem with all non-spar varnishes is that UV light eats it up like a dog with a bowl of warm stew. But you're painting over it to the UV issue is gone.

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Re: help understanding the best way to seal

Postby twisted lines » Fri May 01, 2020 12:23 pm

I really like this under my clear exterior poly;
Never seen anything that after a long cure that could be sanded so well. (Except body filler)
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Re: help understanding the best way to seal

Postby Tomterrific » Sat May 02, 2020 6:01 am

I don't like Berh paint. My wife painted a wood canoe with it and it soon rotted under the paint. This was some years ago so the formula might have changed.
One thing that may help is to use a bonding primer over the poly. I'm certain the paint and primer in one doesn't have as good of bond as a true bonding primer.
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Re: help understanding the best way to seal

Postby swoody126 » Sat May 02, 2020 7:59 am

there is a process called HOT COATING that might help you thru your project faster

it involves consecutive coats being done prior to curing of the previous coat

a good quality oil based(not latex) UV inhibiting varnish can be hot coated up to and including a deep high gloss finish

the process when done correctly builds a layer of finish that is thicker due to constant chemical bonding not layering

for outdoor use always use high gloss varnished since the semis and satins don't inhibit the UV as well

1st coat is 25% varnish and 75% thinning agent recommended on the can(don't go substituting thinning agents)

rub gently w/ OOOO steel wool just before it cures to remove any wood fuzz(raised grain) and dirt

2nd coat is 50%/50% right after rubbing w/ steel wool and wiping w/ a tack rag

rub gently w/ OOOO steel wool just before it cures to remove any wood fuzz and dirt

3rd coat is 75% varnish and only 25% thinning agent right after rubbing w/ steel wool and wiping w/ a tack rag

rub gently w/ OOOO steel wool just before it cures to remove any wood fuzz and dirt

4th 5th and 6th coats are 100% varnish w/ a fine camel hair brush rubbing w/ steel wool and wiping w/ tack rag between each coat

i learned this process for doing bright work on sailboats many moons(over 50 years) ago and it usually stands up all summer in the sun

high gloss "spar varnish" is usually considered your best bet for outdoor service offering better UV protection than most of your options

remember... UV protection is not absolute it only slows down the effects of the sunight

as mentioned above the chemists who formulated the finish know way more than we do about the proper thinning agents for their products..DON'T SKIMP... the negative results are labor intensive

today's finishes are finicky and don't always play well w/ the old standby products

GOOD LUCK W/ YOUR FINISH

sw
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Re: help understanding the best way to seal

Postby twisted lines » Sun May 03, 2020 3:49 pm

Thanks for taking the time to share Swoddy!
I will use a little of that Technic resealing, after a little touch up with 60 grit :thumbsup:
First & only caulk going in the front seam under the Radi.
It also blends from 1/4" to 1/8"; This layer was sealed and cured for a few months before sanding.
I am wondering if I will know what it looks like in 10 year's,
Just like my time with boats; but I only want 1 more ft.
I certainly never built a wooden one! :beer:
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Re: help understanding the best way to seal

Postby fuelfox4949 » Sun May 03, 2020 7:30 pm

so i did the 5/75 mix put a coat down and boy did that ever soak right in, then i immediately followed with a 50/50 mix and then immediately the 75/25 mix.
i let it dry overnight as it was late, this morning i put a 100 pure coat on and 6 hours later another coat. looks great and works well... i hope.
I'm going to let it dry for 18 hours or more before i put the Behr marquee paint and primer in 1.
the saleslady said for best results put 2 coats on.

should i run a 220 grit sand paper lightly over everything before i paint over the spar urethane?
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Re: help understanding the best way to seal

Postby tony.latham » Sun May 03, 2020 9:19 pm

should i run a 220 grit sand paper lightly over everything before i paint over the spar urethane?


You certainly need to take the shine off of it.

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Re: help understanding the best way to seal

Postby Soderholm » Fri May 08, 2020 6:57 pm

I like to do a coat of epoxy to saturate all wood. Then, you can paint, varnish, whatever. You have to either paint or varnish UV will destroy the epoxy. The varnish or paint is sacrificial over time.
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