Work has been light the past couple of days, so I finally got off my ass and finished the wheel pants today. My goal was to try to get 'em done before the weekend, because there's some formation practice happening on Saturday. And, I really want to get a fair amount of flight time on the plane with the wheel pants on during the next week before the big trip. If there's gonna be an issue with 'em, let's let it happen now while I'm home.
Here you can see the result of adding many plies of fiberglass to the mounting bracket areas. This serves both to reinforce the area in general, and also to provide enough thickness so that when I countersink for tinnerman washers there's plenty of material there.
Long story short, they're on. Again, just follow the plans. It's simple enough.
There has been some talk about how to fasten the outboard hat section mounting bracket to the aft wheel pant half. The plans call for AN426 rivets, and that's what I went with. People have complained about these rivets pulling through the fiberglass after many hours of flying, and I can definitely see and understand why that would happen. Some people have used screws and tinnerman washers instead of rivets. I've seen that setup, and I want to avoid it if possible due to the sheer number of visible screws and washers. My solution is to follow the plans by using the rivets, which will be cosmetically ideal, but also to glass the crap out of the brackets to the aft wheel pant half. Basically, the bracket flanges will get sandwiched between glass layers and the pant. The rivets will do most of the tensile work, but the glass will ensure that the bracket won't pull away from the pant and pull the rivets through. I'll take some photos of this when I do this.
Here's a shot of the inboard side. Pretty straightforward. I still have yet to mold up the lower intersection fairings. The opening in the aft wheel pant half for the axle is about as small as it can be, but sealing it and fairing that area should produce less drag.
Ok, now I hope you're sitting down, and I hope you aren't the jealous type. If you are, stop reading now. Hehehhhe...
After getting these wheel pants on, I decided to go fly and do a 4-way speed run. I was on the ready during taxi and on takeoff for anything unusual. You never know...I did my best to ensure that there was enough clearance around the tire, and that the wheel pants are on there good, but you know the routine. New stuff, homebuilt plane, who knows. Everything went fine, and after takeoff I couldn't feel any difference. I climbed up to 7500'. It was a little choppy on the north side of the ridge line running from Corona down to Lake Elsinore, so I crossed the ridge line and headed toward the Orange County coast. As soon as I crossed the ridge the air was smooth.
Now let me just say that I've been running with the assumption that the wheel pants were only gonna be good for another 3-4 mph gain. I was told that the leg fairings are the big win, fairing that horrible round cross section of the gear leg out of the slipstream. I originally saw a 9-knot increase in maximum true airspeed when adding just the leg fairings. From what I had heard, I was figuring on another 3 knots or so from the wheel pants.
I pushed the prop in for 2660 RPM (that's the max I can get...I need to adjust my governor to get 2700 one of these days), and I set up the power for maximum speed. I had the throttle and ram air wide open, and I was getting 23.2" of manifold pressure. I leaned past peak, then peaked it as I enriched the mixture. I kept going rich to about 84 degrees ROP (rich of peak). This seemed like the magic spot for getting the best indicated airspeed and highest groundspeed on whatever heading that was that I was flying at the time.
I turned due south and began my 4-way speed run. Here are my groundspeeds, as read off the GX60:
| Heading | Groundspeed |
|---|---|
| South | 182 knots |
| East | 196 knots |
| North | 189 knots |
| West | 177 knots |
| Average | 186 knots |
Wait a second...I had to repeat the circuit a few times to make sure I wasn't hallucinating. Jen, pinch me. Wake my ass up to the reality that the wheel pants aren't even finished yet. There's no place like home, there's no place like home... I'm not dreaming? YES!!!!!
186 knots true airspeed, wow! That's 214 mph. Muaahahahahaha. That's 7 mph faster than the factory specs Van's provides for the 200hp RV-7 (207 mph, or 180 knots). Read it and weep. And this was done at a density altitude of about 9600' (7500' MSL, 62F, 28.89" Hg). I suspect that if I went down to 8000' density altitude I could work another knot out of this puppy.
My goal since day one was to be able to do 180 knots true at whatever power setting, altitude, and configuration was necessary. I didn't care about fuel flow, or how impractical it would be. I just wanted to hit that magic 180 knot number. Now I've blown right past it. This rocks!
Yesterday I had 99.9 hours on this plane. Today I have 100.7. What better way to blast through the 100-hour mark than by blasting through my speed goal?
I'm very, very happy. If I never see another knot out of this thing, 186 KTAS will keep me content for a good long time. But there's still plenty of room for improvement. I need to mold those lower intersection fairings, seal the canopy, finish the wrap-under of the empennage fairing, fair the tailwheel, increase the radius on the lip of the ram air inlet, etc. Lots of room for improvement. We'll see what I can get out of this puppy.
So, why am I seeing better performance than the factory specs? That's an interesting question. I would theorize that it's a combination of electronic ignition, Airflow Performance fuel injection, and a very slight ram air boost. Maybe it has something to do with the AeroSport Power overhauled engine (new cylinders, crank, etc.) being built to tigher specs than a factory new Lycoming? Possibly contributing might be the Rocket Steering Link, and generally clean rigging? Who knows, who cares?! Heheheh...
Catch me if you can!!!