Today was the day of judgement, the measure of my building
 prowness- no, not the first flight, but the weight and
 balance.  My plane weighs 1091 lbs, weighed as it should
 be- no usable fuel, full oil and coolant.  I for one would
 go with the aluminum housings if they cost me up to $1500
 more than the cast iron ones.  If they saved 70 lbs total,
 that would be around $21 for each pound saved, to get my
 plane down to a more svelte 1021 lbs.  I'm sure I could
 probably get another 15 lbs off if I did some weight
 reduction on my Shertz beam front mount, along with other
 things.  I also went a bit heavy on my engine mount- 1"
 dia x .049 thick tubes on some of the mount.  I at least
 have confidence that my mount should hold up.  The CGs all
 work out OK- design range is between 6 8.7 -77.7 inches
 aft of datum.  Here is how it works out:


 Vans states that most RV-4s come in around 950 lbs.
 Gross recommended is 1500 lbs.

 Mine:
 Empty 66.2, wt.1021 lbs  with 180 lb pilot, but no
 fuel-68.51, just a bit out of CG by .2 inches, total wt.
 1271 with 180 lb pilot and full fuel 68.8, total wt.  1465-
 with 35 lbs baggage- cg-70.38 total 1500

 If I want to take a passenger with full fuel and baggage,
 they'd better not weigh a thing, or I'll be flying over
 gross recommended weight.

 Brian Trubee

 Jeff's motor plate will help as it in effect
 eliminates the 9 pound weight of
 the Scheretz beam. It weighs about the same as Tracy's plate but
 the motor mounts are built in. Not helpful for Brian as he is too far
 gone for a new motor mount.

 One inch .049" tubing weighs about .0462 pounds per inch. Four pieces
 30 inches long therefore  weighs 5.5 pounds. 3/4 OD .049 4130 tubing
 weighs .0346 pounds per inch  so if you replaced just the top two tubes
 with 3/4 you would save 2 pounds. Careful design is important with
 no tubes in bending.

 I think 10 pounds can be gotten out of Tracy's gear box with out too much
 trouble. See the attached PSRU parts weights.

 Aluminum end housings are $1500 each. I am not sure about the TBO however.

 If you are 100 pounds over gross your climb rate assuming the
 same power will be down 1500/1600  or .9375%. Top speed will hardly
 be affected. If the climb rate is given as 1500 FPM with a 150 HP
 O-360 than a P-port rotary would be about 2500 FPM. I suspect a
 few pounds would be saved in the intake manifold with a p-port
 slide throttle setup.

 --------------------------------------------------
 Correction on the tube savings. 30 inch 1 inch OD tubes
 weigh 1.375 pounds each for a total of 5.5 pounds.
 So you would only save about a pound and not two pounds.

 If a tube is in tension or real short use 3/4.

 Also 2500 FPM P-port estimate is a bit high. More like 2000 FPM.

 Paul Lamar


 I was reading a reply to my posting "weighty matters" and saw
 that I had mis stated the weight of the airplane. It is not
 1021 lbs, its 1091 lbs, EMPTY. That's 140 lbs over what they
 generally come in at. Not something that would sell a rotary
 engine conversion. Obviousy, this is much more than I wanted
 to end up with, but I'll fly it and then start a Jenny Craig
 program for this airplane.

 Brian Trubee

 Brian, What does the aluminum cowl weigh and how does
 that compare to the stock cowl?  How thick is it?

 Mike Wills, What does your RV4 weigh?

 Paul Lamar

 The cowl weight is 28 Lbs., if I remember correctly. It's
 .050 thick. Pretty much comparable to a fiberglass one,
 maybe even a bit lighter. The Prop is wood.

 My front motor mount is a massive piece of aluminum
 extrusion, I could probably cut the weight down on that by
 half. It's a 1/2 inch thick 4x4 aluminum angle. I do have
 access to a very nice mill, so a future project for a rainy
 winter day or three up here would be to lighten that. Same
 with the redrive mount plate and one of the spacer pieces.
 I don't know about the body of the redrive, I'll have to
 see how thick that is. Maybe fluting the body of the
 redrive would be an option, if there is enough thickness to
 it.

 My batteries are two powersonic PS 12180  batteries-
 12.6 lbs each, 18 amp-hour. My water pump is a pretty heavy
 hunk of metal, I should be able to lighten it up a bit. My
 fuel filter/moisture separator is a big thing- it's the
 size and weight of a larger oil filter, and the mount is a
 remote mount, pretty chunky, and so is the adapter plate
 that mounts on the oil filter mount point on the engine
 block.

 A peripheral port engine would
  be nice, since I'd have half the intake runners that I
 have now, so there's about 7-10 lbs, plus a bit more power.
 Not a bad trade off.  If I can fly this plane this summer
 and get the hours flown off, I'll be happy. I'd be a lot
 happier to have this plane somewhere under 1030 lbs. I
 think it's kind of a deal killer to tell people about this
 conversion being as heavy as it is.

 How was Everett Hatch and Allan Tolle's Superlight engine
 constructed? They made their own end plates, right?  How
 did they hold up, and how did they deal with wear
 considerations?


 Brian Trubee


 .050" aluminum weighs .72  of a pound per square foot. An RV cowl is
 1/4 inch honeycomb fiberglass which is much lighter than that.

 Two layers of ten oz cloth weighs .12 pounds per square foot.
 Add or .26 pounds per square foot for hand layup resin.
 The 1/4" honeycomb weighs next to nothing. Give it .05 pound
 per square foot for a total 0f .39 pound. Near half the weight.
 This is boat tech.

 Way back in the late 1960's I did a study on vac bagged
 1/4 inch thick PVC foam sandwich with 4 oz fiberglass cloth and
 epoxy resin compared to the panel stiffness of .032 aluminum.
 The foam sandwich was much stiffer and about 1/3 the weight.

 Because of that study the body of this car was made
 from that material. It was so light it became twice as
 heavy when it was painted :) Of course you would have
 to insulated it from the exhaust heat with .016" thick SS
 sheet and fiberfrax.

 A 4 by 4 by .5" thick Schertz beam 30 inches long
 would be about 12 pounds. Jeff's adapter plate with MM
 weighs about 8 pounds about the same as Tracy's adapter
 plate so if the aluminum Scheretz beam is replaced
 by Jeff's adapter plate you would save 12 pounds
 there. No need of the Schertz beam.

 Steve Beckham might be able to fill us in on the PS end plates.

 With Racing Beat end plates, center housing and RX8 front
 cover water pump the bare engine weighs 109 pounds.

 Paul Lamar

Steve Beckham sent a long reply so I converted it into
a pdf and included some photos.

Here it is.

Paul Lamar