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snip
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

  OK, now I'm bummed all over again about the weight of my airplane. I'd
  forgotten just how cool those Superlights were. I saw Alan and Everett at
  the Copperstate fly-in in the mid 90s. They were there with Alan's RV-3.
  That was an awesome airplane. Sure would be great to see that engine
  technology applied to my airplane.

  Mike Wills

  Airplanes like the RV4 are marginal for a stock 13B weight wise. Where
  the rotary really pays off is power to weight ratio in P-port
  form with a 2.85:1 gear box. Then you are looking at 250 HP which takes
  a heavier six cylinder to equal. If you have 250 HP in an RV4 you have a
  good single place hot rod with baggage room :)

  To get the speed however it takes a lot of work on the detail aerodynamics.
  Dave Anders and Tracy Saylor used to hang out on our taxi way with
  Klause Savier. Dave's RV4 airplane went over 250 MPH and Tracy Saylor's
  RV6 238 MPH. Allan Tolle's rotary RV3 also went 235 MPH as I recall in
  the Sun 100 with a Mazda based engine. Not the ultra light.

  All three piston engines were souped up with reduced TBO to roughly 500
  hours. Remember, top speed is the cube root of HP so it was mostly
  reduced drag. I would say Dave's IO-360 engine was roughly 250 HP.
  Tracy Saylors somewhat less. Both Dave and Tracy had special CS metal
  props.

  The Nemesis Nxt fusleage mold was also built on our taxi way so we
  arguably had the fastest light kit aircraft taxi way in the world
  there for awhile :)

  Paul Lamar


  Paul,

  I'm not sure what you mean when saying the RV-4 is marginal for a stock
  13B?
  My airplane is heavier than the typical RV-4, but my performance is
  slightly
  better than what my old RV-6A would do with a 160HP Lyc. My overweight
  issues (and I'm sure Brian's as well) are due entirely to engineering
  issues. If there was any doubt, make it beefier. Cost was also a factor in
  the weight. I have no doubt that with a careful weight loss program I could
  remove 50 - 70 pounds. Which would make it comparable in weight to a
  typical -4. Now if what you meant is that the RV-4 is a marginal 2 place
  cross country airplane, I'd agree.

  I've toyed with the idea of building a Harmon Rocket (Lyc powered) for
  several years now. But you've got me thinking about going the same route as
  Mark Steitle and building up a spare PP engine for my current plane while
  flying the current engine. Building a PP engine with aluminum intermediate
  housings is particularly appealing. Rocket performance in an airplane that
  cost less than a new IO-540! Lots cheaper and less work than building a
  whole new airplane. I'm looking forward to hearing from Mark on how much
  his
  performance improves with the new engine.

  Mike Wills

  What I meant was weight of engine allowed.
  An airplane with a higher empty weight or gross weight has a
  little more margin of error on engine weight.

  While you are at it I like the idea of air racing.
  The Dayton to OSH 500 mile race requires more fuel than the
  stock RV4 or RV3 can handle. Steve Beckham and I had a long
  discussion on what to do about that and Steve is implementing
  tip tanks on the RV3 racer.

  The news letter Everett Hatch Memorial still has a $1000 prize for any
  rotary
  powered airplane exceeding an average 220 MPH in that race.
  A P-port PS 13B Velocity came close in 2007 at 214 MPH.


  Paul Lamar

  I have to agree with Mike- anytime there was doubt about strength, I over
  engineered. My
  plane still has lower wing loading than the RV-8, even if I were to use
  1700lbs as gross
  weight. That's not to say that I am content with 1091 lbs as an empty
  weight. I'm not. I
  just look at what Everett, Steve, and Allan have done - a rotary powered
  RV-4 at under 900
  lbs- that's almost 200 lbs less than mine. Everything being equal, I'd
  prefer superior
  lightness to superior power. I might have more power, but the airplane
  won't glide so well.

  It cost about $6000 for my firewall forward installation- that includes the
   redrive,
  EC2 and EM2. Compare that with even a used lycoming 0-320. At that price,
  it's not
  unreasonable to think about an extra $3000 for aluminum side and
  intermediate housings in
  order to lose a goodly amount of weight.

  I'm definitely going to think about building up an all-aluminum P-port
  engine in the
  future. It's always good to have a spare, right?

  Brian Trubee

  Weight is unrelated to gliding performance. The airplane sinks faster, but
  it
  also moves forward faster; the glide angles remain the same. If only the
  same
  were true of climb!

  Peter Garrison


  Thanks Peter,

  I learned something today. So my glide radius at any given altitude would
  remain the same, I'd just be traveling and descending faster, yes? Well,
  that's not too troubling,   I thought I'd also have a steeper glide angle,
  and a shorter glide radius.

  But, I'd like a steeper climb also. There, weight is an issue.

  Brian Trubee


Yes, glide ratio and gliding radius are functions of aerodynamic shape, not
of weight or wing loading. Airliners make quite good gliders.

Peter Garrison