Dustin,

I don't know your goals or motivation for 300 hp, but there are usually two reasons for lots of HP in a Bearhawk, floats and/or speed.  

Using some rather loose math here's how I think the Bearhawk works.  The cruise speeds posted by Pat Fagan and others using the O-540 are based on a 250 HP O-540.  They're flying at 65% so using simple math that's 162 HP in cruise to get 165 MPH or almost 1 to 1 ratio of HP to MPH.  A 180 HP engine running at 65% is producing around 117 HP and is getting around 135 MPH or about a 1.15 ratio.   I don't recall the exact numbers but someone also posted cruise speeds at 75% and 85% as well.  When charting everything together, what's interesting is that as you increase HP beyond 162 there is a rapid decrease in the MPH returned per HP, mostly due to the draggy nature of the airplane.  My observation here is that reducing drag will yield a bigger pay back than increasing HP once we get beyond 162 HP.  

Now let's look at a rotary and see how it changes the game.  First, you'll need either a three rotor, a turbo two rotor or (hopefully) the new 16X to get a reasonable and reliable 162 HP in cruise.  Now assuming you put some wheel pants on the plane, the game changer in terms of drag is the cooling drag.  The rotary allows some design flexibility to reduce that.  Compare the slippery nose of a Cirrus or a Corvalis to the nose of traditional Bearhawk designs including the big square oil cooler hanging down.  There are some serious gains to be made there.  So assuming you take advantage of that, the same 162 HP produced by a rotary and an O-540 will result in a higher cruise speed for the rotary.

Now if we look at floats, it's a similar and much simpler story.  We want to add as much HP per weight as possible.  The three rotor solution comes in at about the same weight and slightly higher HP than an O-540.  BTW - I think the weight limit is 500 lbs on a Bearhawk for  the engine.  If you're open to rotary engines then the three rotor is the winner because of the higher HP.

Now on to your questions:

1a)  Bruce Turrentine comes highly rated as a builder but I haven't worked with him.  http://www.rotaryaviation.com/custom_mazda_engines.html

1b)  The all aluminum concept sure sounds appealing but what are we trying to achieve?  Is it more power for less weight?  Consider that in all likelihood, Mazda will release their 16X before you're ready for an engine.   http://www.mazda.com/mazdaspirit/rotary/16x/  One less rotor, less oil consumption, aluminum side housings, better fuel consumption and most importantly it theoretically delivers that O-540 level of 162 HP in cruise yet it weighs in at less than an IO-360.

2) I'd be careful regarding redrives and get as much info as possible.  I'm no expert but I found Tracy's "design philosophy" part 1, 2 and 3 very interesting info.  http://www.rotaryaviation.com/psru_development.htm  You've probably already read it, but at the very least, other manufacturers ought to speak to the same points of concern before their parts get the privilege of becoming a critical component of your airplane.  

3) Regarding reliability, my concern would be focused less on the engine and more on the fact that experimental airplane crashes are most often caused by fuel system and cooling failures.  Fuel system and cooling are common topics of discussion here for a reason.  Draw your own conclusions, but if you're going with an experimental engine I'd be very very diligent with these two areas. 

Finally two other things:

1)  As a fellow Bearhawk builder, I'd like to officially invite you to the Upper Midwest Bearhawk BBQ and Cheese Extravaganza.  It's just a get together of builders and flying Bearhawks here in the Upper Midwest.  It's in Medford, WI at KMDZ.  The official time and date will get posted on the Bearhawk group.  I host it usually the first week of October because the leaves are turning and the weather is still good, but I had to delay it this year due to my wife's pregnancy and some complications.  Look for the new date soon!    http://groups.yahoo.com/group/Bearhawk/  

2)  Whacha gonna Tig weld?  Most builders are using gas for the reasons specified here:  http://www.tinmantech.com/html/faq__why_gas_over_tig_.php  If you want to use TIG it's up to you.  I was just curious.

Best of luck.  Feel free to e-mail me off the list for any Bearhawk stuff not related to the Mazda engine.

Dwayne

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From: Dustin Lobner <dmlobner@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Mon, November 8, 2010 7:52:42 AM

Subject: [FlyRotary] Re: Current "state of the art" in rotaries - potential Bearhawk install

Barnstormers and trade-a-plane.  By "decent" I mean "still has about 500 hours before TBO"...  I've also been looking into Continental O-470s because 540s are harder to find as that's what the RV-10 crowd uses.

Dustin

On Mon, Nov 8, 2010 at 12:45 AM, Jeff Luckey <JLuckey@pacbell.net> wrote:

Dustin,

 

Where did you find a decent O-540 for $15k?  I have not looked in a while but you may find a decent O-360 in that price range, but an O-540 will probably be twice that???

 

 

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From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy
Sent: Sunday, November 07, 2010 11:13
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Current "state of the art" in rotaries - potential Bearhawk install

 

Hi Dustin,
   Answering the broad  "what should I do " question is always a tall order.   But in general, if you want a reliable 300HP your only option is a 20B.  The 'all aluminum' version would be great (if it's real) but I doubt you could hit your target of  $15K with that.  Forget about 90+% of the car racer mods and just go with mild street porting.   The peak loads we place on the engine are way less than a drag race application so the extra dowels are not necessary.   The 20B in my RV-8 was built from mostly 13B parts except for the 20B center housing, crank and tension bolts.  No other significant mods other than mild street port.  Ceramic coating of the rotors is fine if done right but it has nothing to do with avoiding detonation.   Use the 89 - 91 13B  9.7 : 1 CR rotors if possible.

Tracy

On Sun, Nov 7, 2010 at 1:15 PM, Dustin Lobner <dmlobner@gmail.com> wrote:

Hi everyone!

This is my first message here.  My name is Dustin, I live in the Rockford area in Illinois.  I'm going to be starting a Bearhawk in the next couple of months and am strongly considering a rotary conversion for it...it'll be a few years before I'm at the "need an engine" point, but I want to know what I want to do before I get there, hence research now.  The three sentence background on the Bearhawk: It's a 4-place utility/STOL aircraft that's pretty much my dream plane.  Typical engine installs are O-360s and O-540, max HP set at 260HP due to the weight of a 300 HP Lycoming.  I'd be comfortable running about 300HP on it, with a max complete engine weight of 400 pounds.

I'm a metallurgical engineer at an aerospace company here in town.  This, along with family, keep me very busy.  As such, I'm interested in as close to a "turnkey" option that I can get (without forking over $+60k for something like a Mistral).  I have extensive experience working on cars and motorcycles (and several friends who have a lot more), none working on a rotary though.  I also have welding experience and will be buying a TIG welder as part of this project.

With all that in mind, how I want this to work out is to buy the big pieces and bolt them together and work out things like intake, exhaust, etc.  I'm an engineer, I do like figuring out how to do stuff and engineering solutions to problems...but I worry about never finishing, hence wanting people who know what they are doing to make the big parts.

On with the questions...

#1a) I'd like to have an engine builder build me a "core engine", minus EFI, intake, exhaust, etc.  Any recommended builders out there?
#1b) I emailed the folks at www.rotaryengine.com.  I laid out my requirements and asked "what do you think I should do?"  They aren't an aviation engine builder, so it'll be interesting to see what they come back with.  In particular, they have all-aluminum engines (they bill themselves as the "home of the 3 rotor all-aluminum engine").  Any thoughts on them as a company or on the all-aluminum concept?
#2) I was planning on using Tracy's ECI3/EMS3/RD-1C reduction drive.  I see that Tracy is active here, which is awesome.  (Tracy, you seem like a nice guy, so no offense intended on the next statement here): Are there any other viable options for a rotary reduction or ECI/EMS system out there?
#3) Are there any recommended modifications to the engine to make it more reliable?  There are a ton of things recommended by www.rotarengine.com (who sells the stuff, so take it with a pound of salt).  These things include ceramic coatings of rotors to prevent detonation, various porting mods, oil-flow enhancement, cooling flow enhancement, installation of more dowel pins, etc.

I had (somewhat arbitrarily) set the cost I was willing to spend at $15k, about the cost of a decent used Lycoming O-540.  If the cost of this can stay below that, awesome.  I'd rather spend a bit more and get something "done right" than skimp and then have an engine or redrive blow up on me.

Tracy, I sent you an email with most of the above laid out.  Feel free to ignore it, reply here if you wish.

Thanks in advance for any replies!

Dustin