Primer Decision

I was running out of the SEM self etching primer and after thinking long and hard about it I decided to switch to a two-part epoxy primer.  This was due to a number of reasons, but primarily because I was having issues with the SEM primer not adhering consistently.  No matter how well I prepared some parts, it seemed I frequently had small spots that didn’t stick.  I’m not sure whether this was due to the age of the primer (it is at least several years old, as it was included with the empennage kit that I bought, and the previous owner had it for some time before that).  I am certain the metal was prepared well.

When the SEM primer stuck well it appeared to be quite robust.  It is difficult to scratch when properly adhered.  I just couldn’t get it to be consistent, whether that was due to age or some other unknown factor.

So I decided I was going to go with a spray-gun applied primer and after some searching around and talking to people, I decided on the Sherwin-Williams CM-0724400 chromate primer.  I wanted a few things in a primer:

  • Superior corrosion protection
  • Adhesion
  • Flexibility (physical)
  • Epoxy base
  • Light color

The first three are rather self explanatory.  I wanted the light color because I think inspecting the aircraft will be easier if the internal parts are lighter in color.  I think it will be more likely to show (or at least easier to see) cracks, imperfections, dirt, and leaks against the background of a light color primer.  In addition, the lighter color will make it easier to light up the inside of a wing during inspections than a more absorptive shade.

I talked to a Sherwin-Williams technical support guy and even though I’m just a homebuilder, they treated me well and were willing to spend time talking about their products’ features and compatibility.   The only disappointment I had was finding out that S-W will not ship aircraft paints to their local retail paint stores.  I was hoping to reduce the hazmat fee associated with my order by having them ship it to a local store along with other stuff, but the paint store, while very helpful, finally had to tell me they couldn’t do it.  I ended up buying the primer from Aircraft Paint Supply in Ohio.  The rep from APS was very helpful, and I received the paint two days after my order.  The Sherwin-Williams primer meets all of those criteria and it is a rather bright shade of yellow.  I haven’t shot a coat of it yet, but I will be doing so soon once I finish a number of small parts for a painting batch.

I Knew Better, but I Wasn’t Thinking

I spent a hell of a lot of time preparing the left wing ribs.  Finally all the deburring was complete, and I prepared to prime them.  By the time I got all the roadblocks out of the way, it was dusk when I began spraying.  Outside.  I think what happened is that the relative humidity skyrocketed right as I was priming and caused this failure:

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Catch-up on Wing Progress

Over the last few weeks, I’ve completed a number of steps and logged in my paper log, but haven’t really updated the progress here.

So, in the interest of completeness, and while some primer dries, here’s an update.

4/23/2016

RHS Main spar countersinking–finished the rib/skin attach countersinks; need to complete nutplate holes.
3 hours.

4/26/2016

Received confirmation that J stiffeners can be extended with no negative (from Van’s Aircraft). Misalignment of spars and J channels required either re-making the channels or extending them.
Made Four J-Stiffener extensions approximately 9-1/8″ long each. This allows overlap of 3 rivets in the splice joint.
0.5 hour

4/27/2016

LH Spar bottom countersink complete. Top remains.
1.5 hours

4/30/2016

Machine countersank all lower fuel tank attach screw holes after installing the nutplates on the LH main spar
5 hours.

5/11/2016

Countersank RH main spar top tank attach screw holes
1 hour.

5/14/2016

“Completed Page 13-3 – Finished RH and LH main spar countersinks, installed inspection plate nutplates and countersank.
Spot primed. Widened hole in LH Spar–all per plans. Also primed spar web extensions and doublers.
5 hours

5/15/2016

“Completed page 13-2 step 4 – Web extension riveting, both wings.
Page 13-4, steps 1,2,3,4,5,7 completed L&R. 8&9 completed RH only.”
7 hours.

Total hours to date: 85.75

RV-10 SB 16-03-28 Kit

Yesterday I received the kit for the Van’s Service Bulletin 16-03-28. I had placed an order as soon as the kit became available. It was delivered in only a few days. Van’s charged $25.00, which they said is their production cost, plus shipping.

The kit is for both the RV-10 and RV-14, came in a padded envelope, and includes the following:

SB-16-03-28 Contents
SB-16-03-28 Contents
SB-16-03-28 Unpacked
SB-16-03-28 Unpacked

1. Paper copy of the Service Bulletin
2. W-00007CD (to be separated into parts)
3. A piece of pre-drilled angle (part number printed on a label but I forgot what it was) to be cut into parts.
4. W-1013D-R
5. W-1013D-L
6. W-1013E-R
7. W-1013E-L
8. Bag 2751 containing AN470AD4-7 Rivets
9. Bag 1320
10. Bag 1978 containing AN470AD4-5 Rivets
11. Bag 1166 containing AN470AD4-11 Rivets
12. Bag 2412 containing AN426AD4-7 Rivets
13. Bag 1121

There are no specific instructions for installing these parts as an initial construction–the instructions focus on retrofit of completed wings. It should be relatively straightforward, however. The flat parts appear to be thicker and “beefier” replacements for existing aileron bracket parts. In addition, instead of a sandwich of three parts making up the bracket, there are only two parts per bracket, with increased thickness.

There are two bracket pieces that are to be separated into multiple parts and installed on the forward and aft sides of the rear wing spar to provide additional resistance to flexing in the spar web.

Well, That Was A Productive Five Hours :|

Just about 5 hours (including a few short breaks) to countersink the holes on the top flange of the right hand main spar. About 308 holes, so roughly 1 per minute. Only about 930 left to go…I’m beginning to see why it takes people over 2,000 hours to build an RV-10!

Spar Confusion: Page 13-3, Steps 2 and 3. VAF to the Rescue!

Steps 2 and 3 on Page 13-3 of the RV-10 Wing plans can be rather confusing as to which holes to countersink. The language seems to be rather precise, and if taken literally, has you looking for holes that aren’t there.

The confusing sentence in Step 2 is

“Machine countersink those rib to spar flange attach rivet holes that are in line with the nutplate attach rivet holes and are inboard of the most outboard fuel tank attach nutplate.”

It’s not a difficult sentence to parse, particularly, and the latter third is quite clear. The first half, however, indicates that there should be some (rib to spar flange attach) holes IN LINE with the nutplate rivet holes. Well, if taken literally, there are NO SUCH HOLES. There are some holes that partially fit the description, but they are not exactly in line with the nutplate rivet holes–but their centerlines are about 1/16″ of an inch aft of the nutplate rivet holes’ centerlines. To someone like me who tends to read things very literally, this sentence has the potential to introduce significant confusion and frustration.

I had read aloud and thought about these steps for FAR too long, and finally decided that someone else surely has had the same confusion. So a simple search on Van’s Air Force Forums produced this gem of a thread, which I recommend to anyone as confused as I was.

A link from that thread, provided by Mike Jimenez, contains some helpful photos.