main spar primer

[Dave S]

Your build manual provides instructions for prepping the spars and similar before bonding ribs and other parts with the hysol - that means prepped metal to hysol to ribs - I'd follow the instructions......

Dave S

[szicree]

I appreciate the advice. I have been flipping through the manual while waiting for my kit and am unclear about the use of Hysol. I understand the tail feathers are powder coated but need to have their ribs glued in. The manual says to scuff with Scotchbrite and I assume they mean scuff the powder coat. This would mean that Hysol sticks well to paint. So...couldn't I prime my spar inside and out before gluing the wing ribs in place? If this is not the way, then can I assume that the spar is primed after all the ribs, stringers and drag/antidrag tubes are in place? Seems like a major masking headache. The manual seems to indicate that many slosh the inside of the spar but makes no direct mention of protecting its exterior. Seems awful silly to slosh the inside and leave the outside naked to the world. Any thoughts/experience is greatly appreciated.

[Tom Waid]

The manual seems to indicate that many slosh the inside of the spar but makes no direct mention of protecting its exterior. Seems awful silly to slosh the inside and leave the outside naked to the world. Any thoughts/experience is greatly appreciated.

About the inside of the spars. My plan is to wait until the airplane is assembled and do not anticipate any more gluing and painting. At that time I'll treat the spar interiors with Corrosion X or similar product.

[GT280flyer]

E-mailed Stewart systems this morning about using other products with theirs. I have poly fiber epoxy primer that came with the kit, Stewart systems said they have no incompatibility problems with other products. I am NOT endorsing the use of differing products and it is at the builders own RISK if they chose to do so. This post is only for discussion and future reference. To answer a earlier post I am not in to chemicals nor do I have a lab. Just a garage with a beautiful kitfox under construction in it

[Dave S]

Hi Steve,

Just wanted to try to answer a couple of your questions. I do want to be clear that every one of us probably has some personal ways we prefer to do at task - but here is my reasoning on the wings/tailfeathers/ribs/hysol/primer deal. Certainly others may look at it differently. In the end - if a person follows the manual they will be fine - it's good.

1) Bonding the wing ribs to the spars is more structurally significant in my opinion - the ribs and the drag braces are what hold the spars in the proper place - for that reason - I wanted the best possible bond between the ribs and wing spars.

2) Powder coat is not the same as epoxy primer or any other paint

3) For the tail feathers - the horizontal stab, elevator, vertical stab and rudder are all structurally accounted for with the steel tube frames/spars and and ribs welded together - the wood ribs we bond into these parts pretty much serve only to define the airfoil shape and hold the fabric - consequently, I feel that the process of bonding the tail feather ribs to the steel structure is way more than adequate if a person scotchbrites the powder coat/cleans up and bonds the wood ribs into the tail parts right on the powdercoat.

4) masking and painting spars.....I have attached a photo - basically I did not concern myself with masking anything - reasoning I am not going to be inside the wing looking at it anyway; and, overlap/overspray is a good way to seal up between layers of epoxy varnish on the ribs, the hysol and cover the spars & drag tubes with primer - sealing is what this is all about anyway - overspray was not actually all that bad - you guys be the judge. The polyfiber tech guy said the epoxy varnish and epoxy primer & hysol are all 100% compatible in any case (there is some epoxy superfil in places too.)

Sincerely,

Dave S
KF 7 Trigear

[szicree]

Dave,

Very clear info and very much appreciated. Looks like a good plan. So, I gotta ask what all those hemostats are for. You doing surgery in the shop?

[Dave S]

Steve,

Ah..yes....the artery clamps...... I found that they were very useful when doing the rib lacing (which was going on with another part of the tail at the time of the photo) - actually - found them useful for lots of stuff during the build - holding washers, wires, rivets, small nuts and lots of small parts during fitting and assembly. Buried with the artery clamps in the photo is my pinking shears and a large tweezers - also used during covering & rib lacing. Guess I left a few things laying out in the shop....

Dave S

[flypdx]

Dave-

Why couldn't a person just spray seal the entire wing (including the spars) when finished and prior to covering? Just like you did but hit the spars also.

Or are the wood portions better off varnished? I guess it could add quite a bit of weight maybe?

[Dave S]

Hi Jeff,

The intended use for the varnish is to use it on wood parts - whereas the epoxy is pretty much intended for everything else - my angle on this had more to do with compatibility between the two as advised by the polyfiber rep. and therefore seeing no need to mask off the two when painting the spars. I think the fact that varnish is transparent also gives a person a chance to see the condition of the underlying wood during inspections and eventually when recovering.

Sincerely,

Dave S

[flypdx]

Yep, seems like primering everything would be overkill. I think I'll plan to do it the same way you did.