I have ordered the Cruzer  kit to be delivered first part of March.  

Having built an RV9A years ago and using pro seal liberally throughout construction where skins join ribs I wondered if builders are doing anything similar in building their Zenith aircraft.  I had attended a builder workshop for 3 days taught by a former Lockheed employee who advocated the use of pro seal in addition to fuel tank sealing in construction of all types of aluminum skinned aircraft.  It seemed to work fine on my RV.

Is that a reasonable strategy or a waste of time for my Cruzer?


Lance Sorensen

Views: 243

Reply to This

Replies to This Discussion

Hey Lance, pro-seal isn't typically used, so if it isn't broke don't fix it. Don't see any real advantage, and if you ever need to repair it for any reason you'll have a hard time getting it apart. One of the amazing benefits of owning a Zenith is the simplicity of build AND repair. -Alissa

Having built a RV9A, you've likely got the Proseal application down pat, but seems to me it would be relatively expensive, messy, and unnecessary!  The 6061T6 aluminum Zenith uses is naturally corrosion-resistant, but a lot of builders at least apply corrosion protection to mating surfaces such as ribs/skin, etc.  Zenith sells and recommends Cortec, a non-toxic corrosion preventative.  Normally, Cortec is only available in very expensive, industrial quantities (I think 5 gallons is the smallest amount available?), but Zenith re-packages it in quart containers - one quart will be more than enough for all the mating surfaces on the Cruzer.

I thin Cortec in small disposable lab sample cups with lids and apply it with disposable foam brushes.  An engineer at Zenith told me to thin it (with water) to a consistency so that it would leave a thin film and spread easily.  If you keep the film thin, it dries quickly.  You can assemble parts with it still wet, but when it dries it acts like a glue, so only assemble parts with wet Cortec that are a final assembly.



Hi Lance,

I’m very curious what advantage might be achieved using proseal.  I have built an 801, and I’m currently working on a RV-14A. As John pointed out, I think there are easier and lighter ways to protect against corrosion if that is the goal.  But maybe I’m missing something....   what’s the goal you are looking to a achieve?

I agree w John...Cortec is the way to go.  I think you'd also be adding unnecessary weight applying proseal everywhere aluminum meets.  On a previous build I used a polyurethane sealant (like a silicone) between the aluminum (more as a waterproffing feature than anything else) and I did have to do some repairs...I essentially had to replace some parts because I could not get them apart...so I do not recommend it.

Hi Lance,

For my part, is something I found overkill vs adding little strengthening to the wing:

1) Not pleasant to applyed, dirty and messy the construction;

2) Add weight

3) If you have to rebuild or re-assembly some part, hard to remove pieces to made repairs, this is not funny. You cannot retired .0025 sheet without scrapt the sheet.

I prefer apply an epoxy primer like Dupond formula. Help again corrosion. Better time investment.

My humble opinion

Christian Tremblay
CH640 -0059 from plan.

hello having been a a and p for 15 plus years the main reason. why certified aircraft use proseal is for two reasons
1. corrosion/moisture barrier in dry areas(non fuel )
2. fuel proof barrier in wet areas.
if you know what your doing and use the right sealant such as A-2 or c-12 and roll it on in a moderate manner its not that messy and won't add as much weight . also make sure you clean the squeeze out (i currently use it every day of the week).

3. a third option for sealant use is to provide a contour pad (almost like liquid shim) so that the sealant can fill the inconsistencies and gaps of matting surfaces. I know in production no spar or skin is exactly perfect and one can have gaps between mating parts, which can lead to long term issues down the line
in all of.my experience i would never assemble anything that is a part of fuel tank with out sealant. I would fay seal surfaces that make up fuel tank spars skins etc. and wet install evey sing fastner Penetrating the fuel tank. I imagine over time your joints and fastners will begin to leak. now their exceptions In that there are actually special rivets that are designed to be fluid tight (ex. briles rivets). in a typical wing construction your size you may need 5 to 6 tubes per wing each tube is around 6 oz keep in mind your going to squeeze out the excess and if you clean the excess you only be using 80 to 90 % of sealant applied. you will also need a sealant gun and plastic spatula so you can evenly apply a thin coat and take off extra

I think some confusion arise about this topic and discussion following responds.

In the original post from Lance, he don't mention in his question that he was tinking about use pro-seal for ribs-skin gas tank sealer, if it was his question, sure, we should use kind of pro-seal stuff for that kind of joints.


Christian has hit the nail on the head.  We need to know the goal being pursued to provide meaningful advice.


New from Zenith:

Zenith Planes For Sale 

Classified listing for buying or selling your Zenith building or flying related stuff...

Custom Instrument Panels
for your Zenith

Custom instrument panels are now available directly from Zenith Aircraft Company exclusively for Zenith builders and owners. Pre-cut panel, Dynon and Garmin avionics, and more.

Custom Upholstery Kits for your Zenith Aircraft:

Zenith Vinyl Upholstery Kits

Zenith Apparel from EAA:

Zenair Floats

Flying On Your Own Wings:
A Complete Guide to Understanding Light Airplane Design, by Chris Heintz

Builder & Pilot Supplies:

How to videos from HomebuiltHELP.com

Developed specifically for Zenith builders (by a builder) these videos on DVD are a great help in building your own kit plane by providing practical hands-on construction information. Visit HomebuiltHelp.com for the latest DVD titles.

Aircraft Insurance:


West Coast USA:

Pro Builder Assistance:


Transition training:

Golden Eagle Aviation

Pianosa Flying Farm

Aircraft Spruce & Specialty for all your building and pilot supplies!

© 2022   Created by Zenith.Aero.   Powered by

Badges  |  Report an Issue  |  Terms of Service