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What is "High Build Primer Surfacer?"

RV10Rob

RV10Rob

Well Known Member
Hi, all... I apparently had a can of SEM "High Build Primer Surfacer" mixed in with my cans of the standard self-etching primer, and I didn't notice until I sprayed my elevator spars with it. I have no idea what this stuff is. I found some Websites that describe what it's used for, but nothing about how it relates to the self-etching primer. A couple questions:

  • What is this stuff? Is it similar to self-etching primer? It seems slightly thicker and slightly lighter in color.
  • If it's okay to use, is it okay that I had already spread the part with the self-etching primer? I know you typically don't want to use two different kinds of primer on the same part.

For reference, the cans look almost identical:
148_a.jpg

139_a_1.jpg


Thanks...

-Rob
 
I think it is for filling surface imperfections before sanding and painting. I would send it back, or use it on fiberglass.
 
If you are using primer for corrosion control, don't use the "fill" primer. It will actually promote corrosion. A high fill primer is extremely porous and will hold moisture. It is meant to be sealed with a top coat.
 
Thanks for the quick responses, guys... would it be possible to sand it and spray the self-etching primer on top? I suppose I really should just remove the primer and spray the right stuff directly on the aluminum.

This is what I get for using rattle cans :)
 
RV10Rob said:
Thanks for the quick responses, guys... would it be possible to sand it and spray the self-etching primer on top? I suppose I really should just remove the primer and spray the right stuff directly on the aluminum.

This is what I get for using rattle cans :)
Click to expand...

Yes, if you want the self-etch to do its job, don't apply it over the high-build. Lacquer thinner will cut the high build. Hang on to the cans of surfacer, they will come in handy when you prep the plane for paint. It should do a pretty nice job of filling pinholes in epoxy.

Nothing wrong with rattle cans as long as the right stuff comes out the nozzle. :)
 
Rob,

I do not know where you would want to use high build primers on an RV except the fiberglass areas (where you don't need corrosion protection) Once you have the fiberglass parts glassed and contoured with an epoxy micro type product (DO NOT USE BONDO), you apply the high build primer to fill in all the pin holes (as stated above). Then apply final primer and paint.

Ryan
 
OK to etch over high build?

So is it OK to apply etching primer on top of high build primer? I used the high build primer on the windshield fairing.

Steve
 
The etching primer is used on bare metal as a bonding coat for all other top coats (primer and paint) and does not do what it is made to do if sprayed over other primers.
 
compatibility question

I have purchased, on a friend's recommendation, a quart of Duratec sandable primer, with the intention of using it on the composite parts of my -10 build and the feathered transitions between epoxy resin and bare aluminum.



Before I applied this to my windshield lower fairing, I had planned to pull the electrical (vinyl) tape off the plexiglass and apply a new masking strip just a millimeter or so away from the sanded edge of the fairing to allow the primer and paint to lap slightly onto the plexiglass and over the edge of the fiberglass layup. This means a very narrow band of contact between primer and plexi. Instructions on the fairing layup specifically call out epoxy resin (I used West) because polyester and vinylester resins are not compatible with the plexi.

I don't want to craze this windshield, obviously, so am wondering if I need to abandon this product in favor of an epoxy filler-primer.



If I don't use the Duratec near the plexi, can I still use it on the other fiberglass, such as canopy, wingtips, cowl? I'm not sure how to blend (or butt) this stuff with the epoxy primer I will one day use on the sheet metal prior to paint.

Even with a complete build under my belt 20 years ago, this is one area I'm really not feeling too confident about.

Thanks for suggestions.
 
Last edited:
Bill Boyd said:
I have purchased, on a friend's recommendation, a quart of Duratec sandable primer, with the intention of using it on the composite parts of my -10 build and the feathered transitions between epoxy resin and bare aluminum.
Click to expand...

Why was this product recommended?
 
az_gila said:
It seems to be the same as the Prestec primer product which is commonly used for surface filling and smoothing during refinishing and repairing the epoxy structures of sailplanes...
Click to expand...

Sailplanes commonly need refinishing because their polyester finishes shrink, crack, craze, and blister. There are even AD's prohibiting some polyesters.

The glider community puts up with that nonsense because it been part of the game for so long (Google "sailplane refinishing" or "glider refinishing"), but our goal here in the RV world is never require refinishing.

Gil, if you want to use a particular Prestec product, go for it. I'm sure it will be fine for a while. In the meantime, formulations vary, so there is no real basis to recommend a Duratec mold filler based on your Prestec experience.
 
DanH said:
Sailplanes commonly need refinishing because their polyester finishes shrink, crack, craze, and blister. There are even AD's prohibiting some polyesters.

The glider community puts up with that nonsense because it been part of the game for so long (Google "sailplane refinishing" or "glider refinishing"), but our goal here in the RV world is never require refinishing.

Gil, if you want to use a particular Prestec product, go for it. I'm sure it will be fine for a while. In the meantime, formulations vary, so there is no real basis to recommend a Duratec mold filler based on your Prestec experience.
Click to expand...

The Duratec is advertised as a high build primer as well as a mold surfacer, so I presume that was why the poster got it as a recommendation.

As far as durability goes, the Prestec finishes are usually used as a replacement for the original German gel coats. Those are the ones that created the need for refinishing.

My experience from refinishing my sailplane with Prestec products is the finish is still great and polished after 33 years.

As far as my plans for the interior of the RV-10 cabin top, I have purchased the JetFlex composite primer since I intend to use the one-part JetFlex WR polyurethane product. I'll report how well that works since the cabin top interior of my old green cabin top is pretty cra*py and will need a lot of smoothing work..
 
To answer DanH's question, it was recommended by some fellow -10 builders for ease of use and good results, at least short term, and above all availability in single quart qty from the supplier. I'm not sure how I'm going to like the relatively short pot life in the gun (15 min max, I'm told) and may end up rolling it on.

I have done extensive finish sanding of all my composite exterior surfaces with 400 wet over a squeegie coat of neat epoxy and feel like I probably have the surface trueness and pinhole filling I want, but I know those are famous last words. I'd feel better with a protective coat of something sandable on there before I move on to other aspects of the build in case some grease/oil contaminants find their way onto the composite pieces during the rest of the build.

The question remains - whether it's safe to let this stuff come in contact with even a 1mm wide strip of the windshield.
 
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