RV-3B Dave's in Colorado

[David Paule]

Thanks!

Rick and Larry did the hard stuff. For me, mostly this just opens the gate to a lot more work... as you know. Kinda looking forward to it.

Dave

[BoydBirchler]

Cadmium plating ? On the engine mount? I doubt that Vans would do that on a tubular mount because of the danger's of entrapment of the plating solution in closed areas of tubing and because of hydrogen embritlement.

[David Paule]

The cad plating was done by an aerospace plating company, which unfortunately is no longer in business. The engine mount was masked beforehand and baked afterwards, to prevent those issues. It was done per the relevant specs.

While I was there, I saw a number of other aerospace parts in for similar plating.

Dave

[David Paule]

I decided to install the stainless steel fuel line from the firewall to the gascolator, only to find that it didn’t come close to fitting. That was one of the parts I’d made a pattern for while the dummy acrylic firewall was in place. In theory it should fit, but in practice it doesn’t. And that my friends, is the difference between theory and practice. However, other things which I fit the same way, fit just fine. It’s only this one part.

Incidentally, if you haven’t already installed the tiny screws for the tube fittings on an Andair device, do it before you install the device. You’ll be happier. I removed the gascolator, put in the screws and reinstalled it. Andair says to stake the screws and I didn’t do that - I used Permatex Threadlocker Blue instead.

You may have heard that there’s not much room between an RV-3 firewall and the engine. That’s entirely correct.

David Howe’s cowl tool is virtually essential for aligning the cowl. Wirejock, aka Larry Larson, made the necessary disc to replace the spinner. I shortened the length of the tool because my shop is too small for its full length. Here, you can see the full length tool without the disc. I later installed three length adjustment bolts in the empty hub holes - these control the cowl position so that the prop and spinner will fit (I have not ordered these yet).



Even with a heavy book and a water jug resting on the top cowl, it would not lay fair to the fuselage.



I copied Jack Nystrom’s work here on his RV-3, Hack Job, and made several slits in the inner skin. The slits are 10” long. This worked but I’ll need to fill and seal the slits later.



The top cowl fits reasonably well. The bottom cowl was more difficult, mostly because it needed the top cowl to hold it up. At this point, the lower quarter-turn fastener locations are not in, also the cheeks aren’t trimmed to length. But you can see the disk and the shorter length tool.



In that photo, the wide angle lens (did I mention that I have a small shop?) causes distortion in the fuselage.

Under the small potatoes category is the burning question: do the cowl cheek bulkhead flanges face forward or aft? I have 11 photos showing them. Five said flanges aft, and six said flanges forward, which was my inclination anyway. The plans don’t show it, no surprise, and the SK sketches sort of illustrate that either the person drawing it was lazy or the flanges face forward; it could be interpreted either way. On mine, forward they will point. The actual parts are labeled R and L, and if I followed that, they’d point aft.

Dave

[wcalvert]

You have discovered the magic of David's cowl fitting jig! It made that part of my build the 'knees ...

"In theory, practice and theory are the same. In practice, they are not" Benjamin Brewster 1882

Words to live by!

[David Paule]

Thanks - I hadn't known the origin of the quote.

Incidentally, here's a look at SK-82, which shows the firewall and cowl. You can see why I commented about either the flange direction or the or the person drawing it.



Dave

[David Paule]

Along with the cowl cheek bulkhead flange orientation, there’s another burning question. Do the cowl cheek extensions end at the spar bulkhead as shown in SK-86 or do they extend aft a bit?



I went back into my photo collection and found 15 RV-3s with the cheek extensions ending at or close to the spar bulkhead, 11 ending a short distance aft of that, and 21 ending a long distance aft. Now, without a lot of measuring and calculating, “short” and “long,” as I’m using it here, are probably around 3” and around 6” more or less. And I mean in its most approximate sense. I measured my F-364 pieces and they’d extend aft around a foot, if I didn’t trim them. The front matches the bulkhead curve nicely but the aft end is relatively poorly formed. If I did any trimming, I’d need to rebend the entire part. And if I used them at their current length, I’d need to reform the aft end. You may remember the fun I had bending the bottom aft fuselage skin. Well, these are thinner, a plus, but a much tighter bend, too, which makes it more difficult.

Alternatives are using the RV-4 part, a fiberglass section, which needs to be extended in the front, as a few RV-3s have done or making my own from scratch of fiberglass, as John Nystrom did on his excellent plane. I thought about it and ordered the RV-4 parts from Van’s. These are subject to their wait and ship mode right now and should be in this coming week, but I won’t need to put them on just yet.

I’m supporting the lower cowl with bungees in the back, attached to the cowl by clecoed tabs, and the cowling tool and clamps up front. Here’s the back.



The forward lower cowling has spacers in the cowl tool for spacing.



Dave