Sam Buchanan's RV6
To the Airport!
There is considerable effort involved in getting all the airplane parts into one large chunk. The major operation involves the attachment of the wings. A trial fitting is part of the fuse assembly, but the final attachment involves over seventy fasteners. I was fortunate in that most of the bolts fit their respective holes fairly well with only minor tweaking required. I suggest that the 3/8" bolts on the bottom row be fitted first, followed by the upper large bolts, then the outboard 1/4" bolts, and finally the multitude of 3/16" bolts. Getting all the bolts in place is not necessarily difficult, but quite time-consuming. I spent about seven hours and a couple of minor cuts on the process. A helper is necessary to get the large bolts in place. I used several old wing bolts with rounded ends as drift pins to get everything aligned.
Here is a punch list of some other items that have to be addressed:
* Installation of aileron pushrod tubes.
All of this takes more time than you will anticipate. While most of these components have been trial fitted at some point, a lot of assembly is required.
By the way, this is how the upper gear intersection fairings are attached. Hook latches around one of the engine mount tubes.
Here is the method used to connect the fuel tanks to the fuselage fuel lines.
The plans call for aluminum lines from the tank fittings to the fuel valve. It seemed to me that getting the proper bends in the aluminum line and installing the flared fittings in the confines of the wing root was going to be a pain! I used flexible lines for the fuel and vent connections as shown and the installation was very easy.
This is all pointing toward getting the plane ready for finding out how successfully the builder has been able to keep the project from fattening up as the construction proceeded. When oil is in the engine and all the bits and pieces are attached, the weighing process can begin.
I used two bathroom scales to weigh each wheel individually. Having three calibrated scales would certainly be the preferred scenario, but the bathroom units seemed to work well for me. Unfortunately, I know about what my weight is, so I served as the calibration weight (many say dead weight....) to sync the scales. The airplane was carefully leveled by using a lot of wood blocks and props. The jacking doo-hickey that fits in the axle was used to hoist the wheels up on the scales. By the time the scales are placed under a main wheel, the tail will have to be nearly four feet off the floor. Great care, good chocks, and a trusted assistant (Thanks Bob! (RV-6A, N413BB)) is called for to prevent a disastrous crash before the plane even leaves the hangar. The above photo shows the canopy open and the flaps down, but both need to be in operational position for the weigh-in. Be sure the weight of any platforms or blocks on the scales is deducted from the numbers.
The first attempt yielded numbers that were way too good to be true! Man, the power to weight ratio of this puppy was going to be impressive. However, it was obvious something was wrong since we came in over two hundred pounds too light. The problem was solved when we noticed that one of the scales had started around the indicator an additional time and was actually depressed a hundred pounds more than indicated.
M399SB came in at 1010 pounds. This is close to what I was hoping to see since my intention all along was to build light and simple. The sample figures in the instructions show a 965 lb RV-6, but I have no idea how you could achieve that weight without omitting some control surfaces, unless my scales are indicating high. Actually , I am confident that the 1010 figure is pretty close, even allowing for some minor inaccuracies in the scales.
Even more important is that the CG calculations showed the plane to be in the envelope in all but the most extreme conditions (200 lb pilot. 250 lb passenger, 100 baggage, five gallons of gas!). This no doubt is aided by the ridiculously porky Prestolite starter, but even if a lightweight unit is installed, we are still in good shape.
Next hurdle to jump was to see if the tanks held fuel! In conjunction with loading the tanks, the really neat Electronics International fuel gauge had to be calibrated. This is a fairly straightforward process which involved filling each tank in increments of two gallons with the plane in level flight attitude.
Man, it was so hot the day we filled the tanks you couldn't even touch the plane without getting burned! We put 18 gallons per side, but since the sender floats hit the top of the tanks before the tank is full, the highest reading I get on the gauge is 15 gallons per side. This just means that three gallons will burn off before the gauge begins to show the actual fuel remaining.
Engine start came next. My engine was purchased used from Wentworth Salvage in Minneapolis. I had not started the engine prior to taking the plane to the airport since I only had the wings in place in the shop at home. Things would have been a bit too exciting in the shop for an engine start in a 24'x24' area! The engine fired right up, ran for a few seconds, then stopped as fuel began streaming out the airbox. Hmmmmmmm, maybe a stuck float? Since I hadn't opened the carb, I decided to open it and make sure the proper venturi and float were installed along with checking the general condition of the carb. Inspection showed that all was well, so another attempt was made with the same results. However, on one of the attempts, the engine was started with the fuel valve closed. The engine ran fine until the float bowl emptied. Hmmmmmmmm...... The needle valve works fine with just the boost pump on, but floods like a river when the engine is running........
My dealing with Wentworth was a hot and cold affair. The salesman was eager to help me with the sale, but attempts to close the loop on a couple of details following the sale were problematic. One of the issues that was unresolved was the shipment of the fuel pump. After numerous calls (and finally the ultimatum that the charge card purchase was going to be put under dispute if I didn't have a pump tomorrow), a fuel pump arrived three weeks after the arrival of the engine. There were no markings on the pump, but it fit the accessory case.
It appears that I was provided with a high-pressure pump! The flow of fuel at over thirty pounds of pressure is sufficient to overpower the poor float needle, and results in fuel pouring out the carb with the engine running. Of course the engine will only run a few seconds before it drowns in fuel. As soon as a new pump is installed we will be ready for a restart. The engine did develop nearly eighty pounds of oil pressure, so that is an encouraging beginning.
8/24/99; The new fuel pump arrived and was installed. The engine fired readily and ran exactly as it should! Wentworth's goof cost me three days of testing. The plane was tied down and the engine run in several rpm ranges. Everything appeared to be working well with the exception of the alternator. Some troubleshooting revealed that field voltage wasn't getting to the alternator due to a blown fuse. Not sure why (or when) the fuse blew, but further testing should turn up any remaining glitches.
Man, this plane wants to fly! I can't tell you how tempting it was while taxing to the runup area to just open the throttle and let 399SB rip into the sky. Inspection is scheduled for September 1, and hopefully all ground testing will be complete at that time so first flight can occur shortly afterward.
Today was the first time I had ever been in an RV-6 with the tip-up canopy. The visibility is awesome without the windshield bow in your face, and gives you a pseudo open cockpit feeling.
8/28/99; I spent a little time taxi-testing this morning to get the feel of the tailwheel. The plane is solid with no peculiar quirks, and doesn't require much rudder input to generate necessary steering actions. However, I wish I had set up the brake pedals with more forward slant so my big feet would stay off them during taxi ops. I may add some rubber tubing to the rudder pedals to give the brake pedals more clearance.
Since the low speed taxi test was uneventful, I decided to do a couple of high speed taxi passes down the 5000' runway. One pass with the tail in the air was enough to convince me that no more high speed taxi test will be conducted until the airworthiness certificate is in hand. It appears that if the throttle is not reduced soon after the tail is lifted off the ground, that is would be possible to exceed lift-off speed, which would probably be around 58 mph. If this happened, one supposes that it might be possible for the plane to begin to "skip" along the surface of the runway. It is not too hard to imagine a scenario where the skipping would progress to actual flight a foot or so above the runway, especially if the particular RV6 was fairly light. If this was to happen, returning the plane smoothly to the runway could get a little tricky since the plane wouldn't be in the normal landing configuration. It might be possible to create a series of pilot induced oscillations as attempts are made to pin the wheels back on the runway.
Anyway, because of the possibility of something like the above situation arising, I will postpone further high speed tests until the FAA gives the plane their blessings. At that time, only one high speed attempt will be made, and the throttle will not be reduced! Temps seem to be in range, the alternator is alternating, the carb is carbing, and the pistons are, uh, working, so all looks good for a flight soon after inspection on 9/1/99.
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The Finish Kit