Corsair/Spitfire hybrid

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Will Aldridge, Oct 16, 2010.

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  1. Jan 7, 2012 #321

    planebuilder

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    "I'm kinda excited. I found a gentleman with a 50 yd roll of BID he wanted to get rid of and it arrived today. After shipping costs were factored in I got it for about $4.60 a yd! Still a ways away from being able to use it but I'm excited to finally have something that will be in the actual plane! "

    Will, try Thayercraft Thayercraft Fiberglass Cloth Sales 800-218-1375 for Bid Cloth. You can buy uncertified Dacron covering material and that makes really nice and cheap peel ply. See if anyone in your area is covering a plane, they will have a ton of scrap. I am covering my robin right now, and I know I have a ton left over. It makes really good peel ply. One word of caution, do not use Dacron Cloth with 10% cotton, I still have some of that stuff stuck inside of a old fuselage I built. For slow cure epoxy resin, try these guys, they are the cheapest I have seen. Epoxy :*Epoxy Resins and Hardeners

    Mark
     
  2. Jan 9, 2012 #322

    Will Aldridge

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    Thanks Mark for that link. Always glad to find good suppliers. Looking through their listings however does not show any of the Rutan fabrics(at least I haven't found them yet). Style 1543 8.6 oz per sq yd looks lie the rough equivalent of UNI and style 1581 is the equivalent of BID? More research is clearly in order.
     
  3. Jan 14, 2012 #323

    Will Aldridge

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    Here is a link to Mark Langfords page where he discusses his third crank failure which finally damaged his plane to the point of requiring a lot of repair. Long story short this has shaken the Corvair movement pretty good. The consensus that seems to be emerging is that the Corvair is okay for low end applications like Pietenpols but faster higher revving motors on faster planes (like mine) are destined to break. The 45 year old cranks even with magnafluxing are just too risky.

    There is a group working on developing a billetted steel crank, but it will be several years before we know if that is working out. Yesterday I picked up two engine cores from one of the guys jumping the Corvair ship and he told me about rotary engines (I originally wanted one for my plane) and got me really interested.

    Looking at the mazda rotary I have a few questions. First my desired hp range is 120-150. From what i have read mazdas put out about 200 which I think would be way overpowered for my plane. Engine weight alone of the Corvair is about 250 lbs which is what I have designed for, and the Mazda weighs better than 300 ready to fly so that's an issue. So are there rotaries out there in the hp and weight range I listed?
     
    Last edited: Jan 14, 2012
  4. Jan 14, 2012 #324

    orion

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    Yes - the older and smaller 12A engines did output about 120 hp but I don't know if anyone is doing a flight version nor do I know how easy it is to get the parts - the engines have been discontinued for some time. Most folks seem to be concentrating on the 13B engines, and up. There however are single rotor 13B engines available that you may want to look into.
     
  5. Jan 14, 2012 #325

    orion

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    Looking at that page of materials, I don't see too many that I would really recommend for aircraft applications. The ideal materials for aircraft are those that maximize yarn properties. This requires materials whose weave results in fibers remaining fairly flat. This means either a thin yarn or a smoother weave. If you look at the lighter fabrics, Style 120 and 220 (which the site does have) are commonly used and applicable structural data does exist from several sources. One of the better and most commonly used materials in aerospace is 7781, an 8-harness satin. This drapes extremely well and has some of the better structural properties of the woven fabrics. There is an 8-harness satin weave at the site (1581) but I don't recognize the style number so am not sure if it's equivalent.
     
  6. Jan 14, 2012 #326

    Vigilant1

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    Here's a quick-and-dirty on the main Mazdas for flight (from memory--please verify)
    1) Stock iron end and center housing 13B engines with standard ports: A proven path, weighs about 300-325 with everything (coolant, rads, PSRU, muffler (required) etc) and good for about 160-180 HP.
    2) As above, but with peripheral porting (a relatively easy mod): Same weight (maybe a bit less due to simpler manifolds), good for 230-250 HP. Simple carbs work and save money, or spend more for EFI. In cars the P-port makes for very high/rough idling, but that's usually seen as an acceptable tradeoff for aircraft use.
    3) Turbos for above: The Mazdas respond well to boost, and the weight doesn't change much because you can eliminate the muffler. There were some problems getting the turbines matched to the compressors for aircraft use, and the very hot Mazda exhaust is tough on turbines. I think there are some successful installations out there.
    4) Single-rotor 13B and 12A engines: If you use the stock iron end housings, then you only save about 40-60 lbs from the weights given above (you lose the center housing, one rotor, and can cut down on the size of the cooling system and go with a less robust PSRU--but you need to add a counterweight for the rotor). HPs will be about 1/2 of the numbers above.
    5) Aluminum housings: Available from Racing Beat, these cut down weight considerably. Bring money (about $1500 each, 2 required). But the FWF weight for a twin-rotor 13B would be about 275 lbs and you could get about 250 HP with the peripheral ports, absolutely no problem getting the 150 HP you need for your plane--up to a considerable altitude. Or, go lightweight with a single-rotor and get about 120 HP (the lower end of your required range) and the whole thing will weigh about 210 lbs or so.
    6) Al end housings with iron inserts: Richard Sohn has been working on a single-rotor 12A peripheral port with his custom-made AL/Iron end housings for many years, he's reportedly nearly ready to fly it. He's expecting a FWF weight of about 175 lbs and about 100 HP (I'm not sure if he included EVERYTHING in this weight). I think it may be possible to use his end housings for a single-rotor 13b (the difference is the width of the rotor, so his end housings might still work) and that would be good for about 120 HP at a weight of about 200-210 lbs (with cooling system, PSRU, etc). That would be a great LSA engine. Also, a light (AL) single-rotor 13B that was turbo normalized would be a great engine for the light-plane market. It would be great to be able to get 110-120 HP at 9000' MSL.

    Sorry to hear about the developments in the Corvair world. There's a lot of talent over there, hopefully they'll fix the crank issues.

    The Mazdas will burn a bit more fuel than you could have expected with a Corvair, but will be about the same per HP as present air cooled certified aircraft engines.

    Mark W.
     
    Last edited: Jan 14, 2012
  7. Jan 14, 2012 #327

    autoreply

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    Just an uninformed question, can you easily throttle back a lot (say 50% power), or don't they run that well on those settings, given their "RPM-hungry" reputation?
     
  8. Jan 14, 2012 #328

    Vigilant1

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    The Mazda 13B's best fuel efficiency occurs at right about the peak torque level (approx 5600 RPM), but I don't know how much the BSFC changes at lower RPM/power levels. The peripheral port BSFC will be a little better than the "standard" porting due to slightly reduced pumping losses.
    I think the "RPM-hungry reputation" comes from the fact that what sounds like a high RPM to folks used to piston engines really isn't high to a Wankel. The bearing loads on the 13B are lowest at about 6000 RPM and it is content to run there all day. It's true the engines don't have a lot of torque at low RPMs (compared to a piston engine), but with a PSRU the user can change the torque available at the prop to anything desired at a given engine or prop RPM.
     
  9. Jan 14, 2012 #329

    Will Aldridge

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    Thank you all for your replies.

    At present I only have 18 gallons of fuel capacity designed into my plane and I was aware of the rotaries thirsty reputation. That was one of the reasons for the hp range, I don't want to suck the tanks dry in less than an hour. This is however an around the patch plane not xc so I'm not too concerned with range (except for taking it to Oshkosh).

    Given the aerodynamic cleanliness of my plane, large wing area, and utility category rating as mentioned earlier I think I will easily be able to exceed Va in level flight so I am not concerned about long periods at high power but I do live at 5000 ft msl and wouldn't mind a lot better climb performance. I do have some cg issues to contend with. The pilot sits so far back that there is going to have to be some weight out front to balance things out (and I have put on 10 lbs in the last year). So 2 rotors seems a little heavy (and way overpowered) and 1 rotor is a little too light.
     
  10. Jan 14, 2012 #330

    Vigilant1

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    (Not trying to beat a dead horse, but just wanting to be sure I communicated well)
    Okay, but if you went with a one rotor p-port 13B and the factory cast-iron end housings you'd be at about 240-270 lbs and 120 HP. That's at/close to the weight you said you wanted and the same HP you'd have gotten with turbo Corvair. But you'd still have the option of adding a turbo if you wanted more HP at altitude for a few more pounds.

    Water cooling means you could also move the radiators (for oil and water) aft to fix your CG woes (at the expense of a bit more plumbing). That might make a twin-rotor AL engine work out for you: plenty of power and maybe 250 lbs FWF with another 20-30 lbs put aft of the CG No need to turbocharge with this setup, even at your field altitude. Your power loading would be very favorable.

    All this assumes you can't/won'/'don't want to change the distance from the firewall to the engine. A "too light" 200 lb AL single rotor might be just right for your CG issues if scooted forward a few inches, and you'd save weight (= better performance and lower power reqmts). In addition, with a "first of it's kind" airplane and potential weight/CG variability, I'd think having the ability to alter CG by moving a light engine forward is a big plus. If you've shoehorned in the heaviest engine the design will accommodate, there are fewer options for getting the CG right.
     
    Last edited: Jan 14, 2012
  11. Jan 14, 2012 #331

    Will Aldridge

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    Thanks Vigilant, I was a tad unclear on the weight of the 1 rotor 13B. Aparently I was a little unclear on my end as well. My cg at the moment is in danger of being too far aft since I am getting fat. I already have my engine mount designed kind of long to balance that out. I was just thinking that the 13B might be way too light and i'd have the aerial equivalent of Pinocchio.
     
  12. Jan 14, 2012 #332

    Will Aldridge

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    Okay I'm getting to the point where I'm seriously considering ditching the Corvair. There 2 major factors that must be addressed first.

    The most important is that I need a reliable engine coming out of the gate. I've always heard that you never want to have a brand new engine design in a newly designed airframe. I chose the Corvair because it looked like the conversion had matured to the point that all the major gremlins were known and accounted for. Is the Rotary conversion mature?

    Second issue is cost. I will not compromise my safety just to save a few bucks, but I need an affordable engine. This question is somewhat related to the first. I want to know what I'm getting into and not have issue after issue keep popping up that requires more and more money.
     
  13. Jan 15, 2012 #333

    highspeed

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    What is the minimum installed power you can have and still meet your performance requirements?
     
  14. Jan 15, 2012 #334

    Vigilant1

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    IMO, the 13B with the factory iron rotor housings and using Tracy Crook's PSRU and his peripherals or carbs, is well sorted out and reliable. It's also relatively affordable (maybe $5K in parts?) if you want to do the work yourself. But, that's the 300-325 lb answer.

    If you ponied up $5K more for the Racing Beat housings, you'd save some weight and could have 160-250 HP (depending on whether you went with a P-Port or not). All the ancillaries (PSRU, generator, cooling, etc) would be the same as the well-proven engines above, but your weight would be at about 275 lbs. I've heard folks are flying with the Racing Beat housings and I know folks race cars with them in 'em. Here's a link to the Racing Beat page with these aluminum housings. (Racing Beat AL 13B Housings). I wouldn't put this in the "mature" phase (for acft use), but I think it's relatively low risk.

    1 rotor: Nope, as far as I can telll, there aren't scores of these out there running right now accumulating thousands of trouble-free hours. If you want a bolt-in "here's the way we know it always works" engine, I don;t think we're there yet. Maybe in a couple of years (how long is your build going to take?) things will be at this stage.

    Could you make-do with a mid-time O-235? A bit below your stated HP reqmt and probably a bit heavy after all the real stuff is bolted on, but it's going to be reliable.
     
  15. Jan 15, 2012 #335

    Will Aldridge

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    100 hp is minimum requirement.

    I'm not close to completing the design yet let alone building it. So I think I have a few years. I'm just itching to do something on it and getting started on the engine was one thing I could do that supposedly wasn't going to change.

    It's funny, I'm calling this plane the WA-1.2. Version 1.0 was a 200 hp hot rod with retracts and a top speed over 300 mph. Common sense kicked in and I realized I never would be able to afford the $30,000 dollar engine I wanted at the time so I decided to look for a more modest alternative and found the Corvair(version 1.1 and it still had retracts). Version 1.2 is what you see now(no retracts). Now here you offer me an engine that supposedly costs less than the Corvair and puts out twice the hp. That's just not fair. I don't think I'll go back to version 1.0 though because I want something that is not quite as demanding to fly.
     
  16. Jan 15, 2012 #336

    4trade

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  17. Jan 15, 2012 #337

    Will Aldridge

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    Thanks for the link 4Trade. I must admit though that the more i think about more horsepower the more infatuated I become with the idea of a 2 rotor. Considering that the redrive is fairly long it sets the heaviest part of the engine back quite a bit further than the Corvair and if I have to I can mount a scoop on the belly for the radiators if I need to move the cg further back.

    Thank you Vigilant for suggesting contacting Paul Lamar. He was kind enough to send a model of the 13B which is shown inserted in my model set back from the back of the prop the same distance as if a RWS redrive were mounted on it. There is 7.5 inches between the aft face of the engine and the firewall(3.6" between the end of the shaft and firewall). I left the Corvair engine mount in place just to have a mount shown. It's amazing that the base of both engines are about the same distance from the center of their respective cranks.

    I think I've pretty much made up my mind to start selling off the Corvair parts and aquiring 13B parts.
     

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  18. Jan 15, 2012 #338

    Vigilant1

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    Will,
    Yes, the Mazda is really nice--compact, three moving parts, no valves to burn, stout enough to produce 900 hp in race form, a very short crank (eccentric) shaft that is virtually unbreakable, smooth running, and it fails fairly gracefully--will reportedly keep running for several minutes even with total loss of coolant. If only we could get appreciable HP at direct-drive RPMs so we could eliminate the PSRU, it would be perfect. The two-rotor is going to be heavy for your application if you go with the stock iron housings, but the plane would climb like a BOH. And if you want to save 50 lbs you can pay for the aluminum housings ($100 per pound saved sounds like a lot . . . I think I'll lose weight instead!)

    Paul Lamar and other "rival" tribes are always working to improve components. His project now is a lighter PSRU. Maybe by the time you're ready there will be a larger number of choices with some hours behind them.

    I'd recommend Tracy Crook's conversion manual http://www.rotaryaviation.com/book.html and spending some time poking around at his site (Real World Solutions) for more info. There's nobody who has done more to get real Mazda-based hardware in the air in large numbers.

    Good luck!

    Mark W.
     
  19. Jan 15, 2012 #339

    4trade

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    I was hoping that you start to warm up for two rotor. Your design is too good looking for moderate power....
     
  20. Jan 16, 2012 #340

    Will Aldridge

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    Mark,

    I have looked at rotaryaviation.com quite a bit. 1 thing I noticed is that it seems to be 5-6 years out of date. The cost of the conversion was listed as $6000. I bet inflation etc has bumped that price up. Do you know what the current cost of converting a 13B is?

    I'll be ordering the conversion manual in the next few days. Kinda bums me out as I had just bought enough Corvair parts to really have something to work on. I knew this would be a learning experience so now i get to learn about rotaries.
     

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