Roee Kalinsky's RV-7A Project

2007.04.17: (10.0) Trimmed and fitted the rudder bottom fairing.  The fairing as it arrives from Van's is composed of two molded halves that have already been joined.  Unfortunately, the weren't joined quite symmetrically, and had some definite twist.  It was close enough to be usable, but just wasn't pretty if you sight it down very closely.  Having resigned to pick my battles with Van's, I decided to use it anyway and make the best of it by trimming such as to balance the twist fore and aft as much as possible.  I also found that the forward end fit better inside the flanges of the rudder's spar than outside.  So be it.

The rudder bottom fairing attaches to the rudder from the outside.  Or in other words, the aluminum flanges of the rudder go behind the fiberglass.  I decided to fasten the fairing to the rudder using platenuts and MS24693C2? #6 stainless steel sountersunk screws.  To better protect the fiberglass from the head of the screw, I'm also using countersunk finishing washers to spread the load.  I will likely use the same method to fasten other fairings that attach from the outside.

It seems that MS24693C screws are not so easy to find in certain sizes.  But between Aircraft Spruce and McMaster-Carr I was able to get a good assortment.  The stainless steel countersunk finishing washers also came from Aircraft Spruce (Spruce p/n 04-00397, Mfg ??? p/n A3236-SS-012).

2009.03.17: (0.0) Working on the elevator tips.  I had already drilled them way back when I built the elevators, but now there is still trimming to be done, and ultimately some kind of closure around the front where the lead weights are located.  For now, I just cut the clearances around the front so there's no interference with the lead weights.  And I bonded in some 0.020" aluminum backing strips to spread the pressure of the pop rivets that will hold the tips in place.

2009.04.06: (0.0) Working on the right elevator tip.  I filed down the lead counterweight around the sides to remove interference with the fairing, and around the front to match the curvature of the aluminum inboard of it, plus a few mils deeper to leave room for fiberglass.  I laid up fiberglass (one ply of RA7781) all around the part of the lead counterweight that resides inside the fairing.  I figured that doing this would give me the best possible adhesion over the largest possible surface area of the lead, and then provide a better bonding surface (fiberglass rather than lead) for the final installation of the fairing.

[these photos actually show the left elevator, which I did later]

I also laid up another layer of glass on the inside of the fairing for about 2" from the forward end to reinforce it (these molded parts from Van's are pretty crappy, and this one had massive voids and cracks in that area, which I fixed as well as I could).  With this added glass there was still a millimeter or two of clearance between the fairing and the lead weight.  I installed the fairing, using flox to fill that clearance.


I also used flox to bond the fairing along its length to supplement the pop-rivets and fill the seam.  Since the lead counterweight design forced me to bond the fairing in that area, making it a "permanent" installation, I figured I may as well bond the rest of it too and make it as strong as possible.  After this all cures, I'll sand down the forward end to a nice contour, and add a ply of glass to seal the deal.

Side note: For my next RV (just kidding!) I would consider another approach, and make the elevator tips removeable.  Van's sure didn't make that easy with the molded counterweight design, but by trimming back the counterweight even further, and capping the fairing around the front, it could be done.  That would make it possible to adjust the counterweight without drilling holes into it from the outside ("sub-optimal", to put it nicely), and would also eliminate the need to bond composites to metal (also "sub-optimal").

Working on the left elevator tip, same technique, just a few steps behind.  And I also started fitting the HS tips.

2009.04.16: (0.0) Elevator tips are now bonded closed, but more shaping and possibly some glassing will be required at the forward ends.

Started working on the HS tips.  Matched drilled the tips to the HS, and trimmed them to achieve the minimum 1/8" gap from the elevator counterweights.  Bonded 0.020" aluminum strips on the inside to reinforce the rivet line.  I decided to cap the aft end of the HS tips, and my technique of choice was to form an end rib and then bond it in place.  I fabricated the end rib by making a balsa core (2 plies of 1/8" balsa bonded together with their grains at 90° to each other), and then laying up fiberglass to encapsulate them all around.  The fiberglass along the edges then provides a good surface for bonding into the tip using flox.

2009.05.28: (0.0) I permanently installed the HS tips using CS4-4 pop rivets and epoxy/flox.

I fitted the top rudder tip.  This one was a bit of a challenge because it was molded complete at the factory, including the forward end cap, but was about 3/16" too short for a good fit.  Argh @#%$!!!  I know this is a common problem because I've seen completed RV's where the builder just attached the tip with this grossly poor fit (very noticeable!).  Anyway, I decided to fix this by building up material to extend the forward end cap.  This approach will add just a bit of extra weight, but it's actually in the ideal location to aid in counterbalancing the rudder, so I'll take it.  I did this by prepping the surface of the forward end cap, taping a "dam" of 4 mil plastic sheeting to extend the contour of the fairing as an ad-hoc female mold, and then pouring in flox about 1/4" deep.  I should elaborate just a bit further on the flox.  I actually poured it in in several stages, starting with neat epoxy and moving gradually to increasingly thick mixtures.  I did this to ensure that I didn't get any voids around the sides where a viscous mixture would have a hard time penetrating.


After it cured, I then shaped the flox using abrasives and files, first the bottom part to fit into the rudder counterbalance arm, and then the top part to match the exterior contours.

Note also that I elected to make the rudder top tip removable using screws and nutplates rather than to permanently install it.  I made this decision early on when I built the rudder, the reason being to provide access to add counterbalance weight if necessary using a couple of extra nutplates that I installed on the top of the counterbalance arm.  Not sure if this will be necessary or not.  I'm told that rudder doesn't need to be quite neutrally balanced.  But anyway, the provision is there.

Finally, I fitted the VS tip using the same methods I used for the HS tips.

All that remains now is a bit of sanding to shape the forward end caps of the elevators and rudder, and surface finishing, i.e. fill, sand, fill, sand... on all the emp tips.  I'll put that off for now.  I need a break from composites work.

2010.11.14: (0.0) Fitting the empennage fairing...  Like most of the fiberglass components in the kit, it fits just well enough to make me not want to throw it away and start from scratch, but poorly enough that it'll take a week or two to massage it into a good fit.  I'm now a few days into that drudgery, but it's starting to shape up.



I'm also making some mods in the attachment of the bottom gap fairing.  In the plans, this aluminum strip is attached to the fuselage using #6 screws (into tapped holes in the longeron) and a rubber channel closes the gap between the top of the strip and the bottom skin of the HS.  Several details of this attachment are clunky at best.  Given that, and the fact that there is no good reason for the bottom gap fairing to be removable, I've decided to simply rivet it to the fuselage, and use proseal to fillet the intersection between the top of the gap strip and the bottom of the HS.  Not done yet, but that's the plan.


I just noticed that I hadn't taken any pictures of the installed HS and VS tips (done last year), so here are some pics: