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Ribs: Varnish vs Urethane vs Polyurethane

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roncarolnikko(at)hotmail.
Guest

Posted: Thu Feb 02, 2006 8:58 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

I need to preserve my ribs befor covering and was wondering what has been 

used by some who have gone before me.  My manual says varnish in the 

materials required section, but says polyurethane varnish in the chapter.  

In the store I find Minwax polyurethane for indoor use and Minwax Helmsman 

urethane for outdoor use. Neither say varnish anywhere and neither mention 

spraying them.  Do I need to find a bigger store?  Can I spray these?

          Sheesh!       not a chemist Ron Nb Ore

vadert(at)telusplanet.net
Guest

Posted: Thu Feb 02, 2006 9:35 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

Ron

    I used a clear epoxy varnish. You are protecting the wood from moisture 

entering it.  It may be prudent to use something sandable and lightly sand 

before covering so that the fabric adheres better to it.  I think it is 

important to pay special attention to the trailing edge nooks and crannys of 

the ribs where moisture will gather. Your wings will have drain grommets 

where air (moist or otherwise) will enter and exit depending on weather 

conditions and leave moisture (humidity) inside the wing.  The trailing edge 

(lowest point) is where that moisture will pool as the aircraft sits.



Tim Vader



---

Ceashman(at)aol.com
Guest

Posted: Fri Feb 03, 2006 3:54 am Post subject: Ribs: Varnish vs Urethane vs Polyurethane

 	  Quote: 	
		  >I need to preserve my ribs before covering and was wondering what has been 

>used by some who have gone before me. 


	


Hello Ron. 



It is important to varnish the wood bits to keep moisture and decay out.

When varnishing, brush is better than spray because of all the tight corners, 

90 degree angles and things the spray will just bounce back. Slop lots on to 

penetrate the wood but avoid flooding and runs too much. Take your time and 

enjoy, it is a no brainer but requires patience to make sure all angles are 

covered.

When dry use a soft rubber sanding block and sand the areas that fabric will 

contact. This smoothes any dirt or any wood fibers that spring out. If it 

feels rough, it will look rough under the fabric. When lightly sanding, you break 

through. re-coat these areas.



Important!!! Use the epoxy varnish that was supplied with the kit (Polyfiber) 

and do not use anything from the hardware store. 

If you look at the Polyfiber instruction manual (I think) The boat Spar 

varnishes or polyurethane varnishes will not hold up to MEK or the Polybrush that 

you will use to stick the fabric down with. It will soften and start to break 

down the so called Spar and polyurethane varnishes and the tensile and peel 

strength will be much lower.

There are a number of people on this list you can get the Polyfiber Epoxy 

varnish from, or from Aircraft Spruce.

Do not use anything but this stuff. One day when flying along and going 

through some bouncy sky, you look across the lower wings and see the slight 

billowing of the fabric and then you craft drops again. You will think to yourself 

"man, am I glad I used the correct epoxy and I am glad I stitched the wings" Not 

only that, rib stitching looks very cool.



Happy brushing. Eric.

dan(at)azshowersolutions.
Guest

Posted: Fri Feb 03, 2006 6:02 am Post subject: Ribs: Varnish vs Urethane vs Polyurethane

Hi Ron,

  I had the same question a while back and I went to John McBean w/ the question. John's direction made sense...He said if I want to be ensured there won't be a problem in compatibility (chemically) with covering materials, I should go with proven varnish. I was directed to use EV-400 Epoxy Varnish which is a two part epoxy and comes in a kit you can get from Aircraft Spruce. 

  Hope that helps,

  Dan B

  Mesa, AZ



ron schick <roncarolnikko(at)hotmail.com> wrote:

  



I need to preserve my ribs befor covering and was wondering what has been 

used by some who have gone before me. My manual says varnish in the 

materials required section, but says polyurethane varnish in the chapter. 

In the store I find Minwax polyurethane for indoor use and Minwax Helmsman 

urethane for outdoor use. Neither say varnish anywhere and neither mention 

spraying them. Do I need to find a bigger store? Can I spray these?

Sheesh! not a chemist Ron Nb Ore

rkstevens(at)verizon.net
Guest

Posted: Fri Feb 03, 2006 7:02 am Post subject: Ribs: Varnish vs Urethane vs Polyurethane

It's ** important ** to use an epoxy varnish (2 part epoxy - as sold by PolyFiber for example).  Otherwise, the MEK in the fabric finishing steps will melt right through "standard" varnishes.    The Poly Fiber finishing systems specify which varnishes are acceptable.



The best solution is to use an epoxy varnish - it's a little more expensive, but WAY better.



Ron

 	  Quote: 	
		  From: Tim Vader <vadert(at)telusplanet.net>

Date: Thu Feb 02 23:33:04 CST 2006

To: kitfox-list(at)matronics.com

Subject: Re: Ribs:  Varnish vs Urethane vs Polyurethane


	


[quote]



Ron

    I used a clear epoxy varnish. You are protecting the wood from moisture 

entering it.  It may be prudent to use something sandable and lightly sand 

before covering so that the fabric adheres better to it.  I think it is 

important to pay special attention to the trailing edge nooks and crannys of 

the ribs where moisture will gather. Your wings will have drain grommets 

where air (moist or otherwise) will enter and exit depending on weather 

conditions and leave moisture (humidity) inside the wing.  The trailing edge 

(lowest point) is where that moisture will pool as the aircraft sits.



Tim Vader



---

ddsyverson(at)comcast.net
Guest

Posted: Fri Feb 03, 2006 11:07 am Post subject: Ribs: Varnish vs Urethane vs Polyurethane

Ron,



This is pretty straightforward. If you do not want problems, the decision is 

easy.



Use only products which are known to be compatible. 



If you are using the polyfiber covering, this means use the polyfiber epoxy 

primer for any metal or fiberglass, use the polyfiber epoxy varnish for any 

wood, use the chemicals for the fabric recommended by the fabric manufacturer 

- if polyfiber - use polytack, polybrush and polyspray. When you are ready 

for a top coat, use polytone or aerothane.



I am not a polyfiber sales rep, I don't have any particular feelings that one 

covering system is necessarily better than another; but I know you need to 

stick to the items which are known to be compatible if you want to avoid 

problems.



Methyl Ethyl Ketone, which is used as a solvent in a lot of Polyfiber's 

products, will pretty much make lutefisk out of anything underneath which is 

not compatible and that may very well include minwax.

 

Sincerely,



Dave S (Chemist and autobody guy + model 7 trigear)



On Thursday 02 February 2006 10:54 pm, ron schick wrote:

 	  Quote: 	
		   



 I need to preserve my ribs befor covering and was wondering what has been

 used by some who have gone before me.  My manual says varnish in the

  

 
	


Do Not Archive

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Fri Feb 03, 2006 1:27 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

Dave-

lutefisk?



Lynn

do not archive

On Friday, February 3, 2006, at 01:57  PM, D& D Syverson wrote:



 	  Quote: 	
		   

 <ddsyverson(at)comcast.net>

 Methyl Ethyl Ketone, which is used as a solvent in a lot of Polyfiber's

 products, will pretty much make lutefisk out of anything underneath 

 which is

 not compatible and that may very well include minwax.



 Sincerely,



 Dave S (Chemist and autobody guy + model 7 trigear)

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Fri Feb 03, 2006 2:20 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

On Feb 3, 2006, at 10:25 PM, Lynn Matteson wrote:



 	  Quote: 	
		   lutefisk?


	


Lutefisk is Norwegian cod marinated in caustic soda. It becomes a jelly 

mass that tastes nothing. Of course, you have to wash it a lot to 

remove the caustic soda and it is served with bacon, beans and ... a 

lot of aquavit, which is a strong alcohol made from potatoes.

Lutefisk is a traditional dish mostly eaten during Christmas time. Some 

people nearly makes it a cult. It doesn't taste bad, it tastes ... 

nothing.



Its origin is said to come from the big fire of the town of Bergen, a 

few centuries ago. Bergen was the hanseatic center where ships came all 

over Europe to buy stock-fish, the Norwegian dried cod. During the 

fire, many warehouses on the quays were burnt down, with the fish still 

inside. Later, poor people from the town, came to salvage what they 

could from the ruins. But wood ashes and water was very basic and the 

fish became jelly-like, pretty much the way it is done now with caustic 

soda.



.. now, aren't we off-topic? 



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

aldaniels(at)fmtc.com
Guest

Posted: Fri Feb 03, 2006 4:03 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

I have sealed the wood with a good spray coat of polybrush. That way 

everything is compatible. It seems to hold up better that the varnish. 

Cost is about the same.

 	  Quote:

flier(at)sbcglobal.net
Guest

Posted: Fri Feb 03, 2006 5:59 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

Polybrush won't seal wood.  Polybrush is a structural adhesive only for

fabric.  Epoxy varnish is the only recommended / approved wood sealer for

the Stits Polyfiber process.



--

aldaniels(at)fmtc.com
Guest

Posted: Fri Feb 03, 2006 7:48 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

It might be, but wood I treated with Polyfiber epoxy varnish when left 

in a harsh environment for several years went to heck and the stuff 

sprayed with polybrush stayed like new. What I did on my plane that was 

destine for a harsh environment was brush epoxy varnish and then when 

dry spray everything on the wing before covering with polybrush. It 

sealed everything very well.  Rivets and metal structural joints now can 

not hold moisture as they are sealed. It is the same vinyl base as the 

polytone paint.



flier wrote:



[quote]



Polybrush won't seal wood.  Polybrush is a structural adhesive only for

fabric.  Epoxy varnish is the only recommended / approved wood sealer for

the Stits Polyfiber process.



--

flier(at)sbcglobal.net
Guest

Posted: Sat Feb 04, 2006 12:31 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

I misunderstood Alan.  Sorry.  The only issue with Polybrush is that it

doesn't adhere well to things other than fabric and itself.  If sprayed

thick enough over hard surfaces you can peel it like a film from the

surface.  My understanding is that it was formulated to fill weave, provide

bulk/level, and act as a base for the other coatings (MEK based) in the

system.  Properly applied epoxy primer & epoxy varnish are the best ways to

go for weather proofing.



Regards,



Ted



--

Ceashman(at)aol.com
Guest

Posted: Sat Feb 04, 2006 12:41 pm Post subject: Ribs: Varnish vs Urethane vs Polyurethane

-->It might be, but wood I treated with Polyfiber epoxy varnish when left 

-->in a harsh environment for several years went to heck and the stuff 

-->sprayed with polybrush stayed like new.



Hi Alan.

I think you are correct by saying an epoxy varnish when left in a harsh 

environment goes to heck.

2 component  epoxy paints do not like sunlight, ultra violet will break down 

the paint structure. Normally you will start to notice powdering (chalky). 

Then later the paint film will start to show fine cracks. After that water / 

moisture creeps through the micro cracks and the wood absorbs this like a wick. 

Not long before the epoxy varnish starts crumbling off the rotting wood.

But I think if the wood has adequate film thickness of epoxy and never left 

exposed to sun, it should be a sound system.



Eric.

jlfernan

Joined: 10 Jun 2006
Posts: 51
Location: MIAMI

Posted: Tue Oct 07, 2008 6:08 pm Post subject: Re: Ribs: Varnish vs Urethane vs Polyurethane

I used two part epoxy varnish, very tedious. How many coats is recommended for wing ribs?

_________________
Jorge Fernandez
Supersport
Fuselage/Forward Controls
http://websites.expercraft.com/jlfernan/

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