Monday, November 17th still working on the cowling

I was off Friday and was able to spend a fair bit of time working on the cowling.  Ended up working on it 8 to 10 hours total between doing other stuff.

I'm pretty much following the plans and notes I've gleaned.  So far (knock on wood) it's been going pretty well and I'm pretty happy with the fit.

One thing I noticed I hadn't heard mentioned - the top hinges had a fair bit of slop in them after I drilled the first couple of holes (I started on the inboard side of the short hinge on the passenger side).  This is due to the fact they have you use a .90 stainless hinge pin instead of the provided (and larger) aluminum pin.  At this point I'm trying for the closest fit possible.  I know folks have said they are leaving as much as 1/16" gap for paint.  I'm polishing (although I'll probably paint the cowl) and for now want as close a fit as I can get.

First thing I did was finish fitting the hinges to the aft edge of the top cowl.  At first I was going to just try match drilling by marking the cowl and drilling both hinge and cowl at the same time.  The more I looked at that the more I didn't like it - too many variables - too much chance of not enough edge distance and I felt like I'd probably end up with a goofy rivet line.

I finally decided to drill the hinges first, then figure out how to match them to the cowl.  At first I thought I'd hold them tight and back drill a few placement holes from the inside, then remove and finish drilling.

I finally decided if I backlit the hinges I could drill from outside, and that ended up working really well.

To make sure I had the fit I wanted, I reached in and pulled the hinge tight before I drilled each hole.  Once I'd done a few the gap was pretty much closed.

From Finish Kit

Cowling backlit from the inside with a small battery powered trouble light.  Only missed one hole slightly.  The rest were perfect.  Worked great.

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Had to cut out the oil cooler door so I could install the hinge pins.  At first I thought I'd made the fit *way* too tight, cause I could hardly move the pins, much less put them all the way in.  I polished them some, beveled the pointy end a bit to make it slide in better, beveled the hinges themselves some, boelubed, and tried again.  After about the 3rd time they were actually pretty easy to do.

Having done this does give me pause regarding installing anything high up on the firewall.  Have to pay attention that nothing goes there that would interfere with installing the hinge pins.  You do need some room, and don't want anything sharp (like a forest of grounds similar to what B&C sells) that would rip your hand to shreds if you slipped.

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Top cowl match drilled and pins in place.

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  Pretty happy with the fit.

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There is one spot on the aft edge, pilot's side that is a bit proud of the skin.  I think this must be where they mention a .032 shim on the plans.  Easily addressed later before I rivet everything.

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Slid the bottom into place to see if it's level and looks reasonable.  Not bad.

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The inlets still don't match very well.  The next thing I did was trim these up some.  The lower cowl had a lot of extra material that was preventing a good fit at the outboard sides of the inlets.

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I played with everything quite a while and finally decided (as per the plans) that the next step was to trim just the bottom without touching the sides.  That would allow it to ride up to near where it will sit when finished.  Trimming the sides prior to that would result in either under or over cutting.

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Measuring the bottom of the cowl to cut it.  I just used 1 1/2" masking tape that was aligned with the edge of the skin, then measured from the exposed edge inward 1 1/2" (it was actually 1 7/16" - glad I checked it).  I under trimmed the line *very* slightly, then sanded to the line til it fit well.  There is a lot of putting on, measuring and marking, then taking it back off and sanding some more.

One other thing that might help folks if they are working on this alone.  As you can see I'm using a long cargo strap to secure it.  To be honest this was a real pain to horse around and try to hold everything in place by myself.

I had an ancient backless office chair that I've used for various things.  By adjusting the height with the screw, I was able to use it by sliding it up the snorkel after holding the cowl in place.  This ended up being *way* easier.  The chair is just woven, so there isn't any risk of scratching.  It would be worth creating something similar if you didn't have something like that.  Saved a ton of time once I decided to use it.

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Drilling the hinges to the lower firewall.

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Used the same backlighting technique to drill the hinges to the cowl.  Since this pin is full size, I didn't have the slop issue I had with the top.

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Once the bottom was done I started on the sides.  Again, measure, cut undersize, fit, measure some more, sand/trim, repeat.  I ended up using sheet metal shears on the side since I didn't want all the dust from my Dremel tool.  The shears cut very easily and pretty accurately.

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Working through some issues.  I think this bottom corner on the passenger side will have to be filled and sanded to fit correctly, but won't be a big deal.  Everything else fits really well.

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Starting on the side hinges.  Once these are done and it's nailed down, I'll trim the sides to length and fit the side hinges.

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Sunday, November 9th starting on Pete's favorite thing, the pink cowling

After finishing up the A/P servo & such, I decided it was time to work on the cowling.  I'd like to get that done so I can do the baffling and then start on doing all the engine wiring and installing the sensors.

This is another one of those areas where people seem to have some struggles at times.  I watched Pete spend several months on his trying to get it right.  Sounded like the front was really jayhawkered and he had to spend a lot of time altering it to get it to fit right.

I read over a bunch of posts on VAF (Brantel's in particular was really good), re-read the instructions, watched the Orndorff video a couple of times and then went over the plans pages very carefully with a highlighter.  I think I finally get the procedure at this point.


Started off by measuring the distance to find the centerline since the middle rib is offset (used a piece of tape), then put a piece of tape across the top to use as a reference to begin trimming back the upper cowl.

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Decided to try the stack of books method to shim the cowl up to the back plate rather than try something else.  Not sure if I'll stay with this or not, but it works well for initial fitting anyway.

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The engine is offset to counteract turning tendencies and p-factor, and it shows in the way the cowl fits.  It's quite parallel with the back plate.  I ended up measuring the offset - turns out the engine is offset 1/2" left.  Apparently as part of the engine mount.

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I then drew a center line down the cowling just so I had a good reference.  I later extended it all the way forward.

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Trying a test alignment.  Nothing has been cut at this point.

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Later I trimmed 1/2" to 3/4" off the back after triple measuring to make sure it wasn't too much.  Still have at least 1/2" to go, and I was measuring with the cowl hard against the back plate.  I needs to be between 1/8" and 1/4" aft, so that leaves me about 5/8" to 3/4" still to work with.

I had to do a lot of sanding inside the nose on the flanges to get anything remotely like a decent fit.  The openings to either side are way off.  Once I trim up the outboard flanges they should sit much better.  Won't do that til later.

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Checking everything to see how it fits before I drill the inboard holes for clecos.

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Drilled the inboard flanges.

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Next step is to mount the hinges around the aft top.  Last thing for the day was to match drill the upper firewall to the top skin.  Then I can match drill the hinges to the firewall and start working on fitting the upper cowl.

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Sunday, November 1st adahrs tray, a/p servo, adahrs

I forgot to finish my last post.  After more or less finishing the canopy (still need to do a couple of things and then rivet it) I decided to do the Van's ADAHRS tray, the ELT and the pitch A/P servo.

I picked up the Van's ADAHRS tray last summer thinking that would be perfect for the transponder, ads/b and/or the ELT.  At the time I was sure I was going to go with the Garmin G3X.  Their AHRS unit doesn't have the magnetometer built it, and can be mounted literally anywhere, so I knew I wouldn't use the tray for that.

After SNF and spending 3 days playing with all the glass panels, I was really impressed with the Dynon, and knew I really didn't like the Garmin Touch.

At any rate, I decided to go Dynon.  Their ADAHRS unit *does* have the magnetometer built into it, so it *cannot* be near any mag interference.  Since the pitch servo is mounted on the elevator bellcrank rib which is right next to the Van's ADAHRS tray, I knew I couldn't put it there.  I ended up just putting the ELT on it.  The ADAHRS ended up on the aft elevator deck.

Here's what the ADAHRS tray looks like.  The narrow end goes aft.  It's upside down in this shot.

From Finish Kit

There is a second rib that runs fore and aft between the two bulkheads just aft of the baggage compartment, then a tray that ties the rib back over to the elevator bellcrank rib.

It comes pre-drilled for a bunch of ADAHRS units (GRT, etc).  I just added some more holes to fit my AK ELT unit.  The aluminum tray is the mounting tray for the ELT.

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This is the Dynon pitch servo kit.  The servo itself is generic.  The kit part is specific for the RV series.   The pushrod, doubler and most of the mounting hardware comes with the kit.  Instructions are very clear and the install is pretty simple.

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Working on mounting the doubler.  It gets drilled to the elevator bellcrank bulkhead.

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Finished installing the servo and the ELT test fitted.  Everything still needs to be wired.

I've seen notes from folks that said the pushrod interfered with the elevator pushrod.  In my case it is close, but there is no point in the travel (except *way* beyond the stops) that it hits the pushrod.  I'll still have to check it once everything is hooked up.

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Working on mounting the Dynon ADAHRS (Air Data, Attitude, Heading Reference System).  Basically a digital equivalent of a six pack - altimeter, air speed, vertical speed, directional gyro, digital compass, and attitude indicator, and AOA).  I looked at a whole slew of locations, and at the end of the day I just wasn't comfortable with anything in the mid fuse - didn't want the seat belt cables wearing against it or possible chafing from something.

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Has to be level and aligned fore and aft within one degree.  I needed some non-magnetic fasteners to mount it.  Couldn't find any good supplies, and oddly enough ACS didn't seem to have anything suitable, so I got them from McMaster Carr.  What an awesome hardware supplier.  http://www.mcmaster.com/

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While I was waiting for the brass bolts and locknuts, I went ahead and fabbed up the copper bus bar jumper between the master and starter solenoids.

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Got the brass hardware the next day, so I finished mounting the unit.  Again, still need to cable.  Once I get the cowling done I think it will be time to start wiring.

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