Hurricane Mk103

Discussion in 'The light stuff area' started by pictsidhe, Aug 6, 2018.

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  1. Aug 22, 2018 #101

    pictsidhe

    pictsidhe

    pictsidhe

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    I'm thinking of the 627 at 77lb out of the box. 23hp standard. I believe Colomban gets 40hp from his. It's feasible at 5000rpm. I was wincing at the weight of 503s not far back...
    I have Legal Eagle and Minimax plans to plagiarise for ideas.
     
  2. Aug 22, 2018 #102

    radfordc

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    A 503 with B box and prop is under 100 lbs. How much is the Briggs with redrive and prop? A 50 hp Hirth is about 80 lbs.
     
  3. Aug 22, 2018 #103

    pictsidhe

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    503 + B box =96lb, according to Rotax. I think that I can do a briggs at around 80lbs with redrive. My most recent redrive maths suggests that I 'only' need a 10lb flywheel, instead of the stock 19lb one. I am tempted by Rotax or Russian clone, but the weight is offputting. I'd also much prefer the 6lb heavier C box to swing a big prop.
     
  4. Sep 9, 2018 #104

    pictsidhe

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    My A. L. Bentley drawings turned up. Purportedly the best set around. They look excellent. I was wondering why the tube weighed 2lb. There were a few dozen unrequested copies of original Hawker drawings of various legibilities. One of them has wing airfoil ordinates :). The tail airfoils have much smaller nose radii than the regular 00 sections. Possibly thin nose 00. The few in TOWS have 6 series like drag buckets. I'm a little dubious if there will be much laminar flow in the propwash, but can't see an issue with using 6 series foils there.
    Now I have these drawings, I can start on detail design. I also ought to make a cardboard cockpit before fixing the fuselage dimensions... I went through FAR23 landing gear design the other night and unsprung gear with 4.80/4.00-8 tires almost meets it.
     
  5. Sep 9, 2018 #105

    Basil

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    The lightest Briggs is the 810cc vertical shaft but it needs more converting. See http://www.sdplanes.com/new/engine-kits/. SE33.
     
  6. Sep 9, 2018 #106

    pictsidhe

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    627cc vanguards are 77lb. 810cc Briggs are 87lb. Both of those have heavy flywheels that can be removed for DD. The 627 flywheel is 19lbs. There are lighter ways to make sparks...
     
  7. Sep 12, 2018 #107

    pictsidhe

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    No work tonight, so I had some extra time on this. i just fed the production Hurricane wing ordinates in XFLR5, and it likes them, They are very slightly different from a scaled clark YH, but the performnce is way, way better. More lift, less drag, less Cm. Works pretty well at 103 Re, too.
     
  8. Sep 13, 2018 #108

    larr

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    I always wondered if there was a place in ultralight construction for Alucabond or Dibond - stiff and light stuff. It can't be bent much but that is sort of the point. Maybe good for a box type fuselage with coroplast to get the outside shape (sort of like the real thing.)

    Engine-wise what about the Valley Engineering Big Twin? 40 H.P. takeoff, 32 H.P. continuous, 120 lbs everything including prop.
     
  9. Sep 13, 2018 #109

    samyguy

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    You know when comparing the Briggs to the Rotax. The 2-stroke motor mount weights 2 or 3 times more than the 4-stroke mount.
    A flat piece of Al. My 503 weighs the same as my Generac and redrive. It's the mount!
     
  10. Sep 14, 2018 #110

    addicted2climbing

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    Are these numbers correct?

    Briggs.JPG

    32KG does that include the Prop and motor mount?
     
  11. Sep 14, 2018 #111

    Basil

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    Can't answer that directly but the UK dealers SD1 with this engine is a few kg lighter than mine with a Hirth F23 50hp two stroke.
     
  12. Sep 14, 2018 #112

    pictsidhe

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    They are very similar to parazoom's Briggs conversions.
     
  13. Sep 16, 2018 #113

    Basil

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    But direct drive 810cc rather than reduction drive 627cc.
     
  14. Sep 17, 2018 #114

    lr27

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    The only suitable use for Coroplast ballast is for a mockup. It's going to be mostly dead weight, because it's about one step up from bubble gum. If you're serious about part 103, drop it right now. If you're not serious about part 103, the plane will be faster and there will be even more need to back up the Coroplast with something that has actual structural properties. I really think that if you want this to be part 103, you need to make weight savings the first priority. That probably means no retracts or else carbon everything, I'd guess.

    If you go for 3/4 scale, that gives you a 30 foot wingspan. That means you'll need less power than a shorter span ultralight. 20 hp is the suggested MAX horsepower for the 32 foot Sky Pup, though of course the aircraft is only for average or lighter pilots. The Sky Pup has shown that it's possible to make a good airframe out of foam and wood at significantly less than the prescribed weight, though I think a scale appearance will probably increase the weight somewhat. If you're going to use a 19 inch thick airfoil, then I expect the same wood sizes the SP uses will be strong enough for a 250 lb ultralight.
    ---------
    Unfortunately, the computer ate part of my response, so I'll try to reconstruct it here.

    You might consider aircraft with bigger canopies, such as the P-35, or the Brewster Buffalo.

    Or you could consider fighters that don't have to be shrunk, such as the diminutive Caudron CR-714, with less than 30 feet of span. You might actually want to enlarge it!
    https://en.wikipedia.org/wiki/Caudron_C.714#/media/File:Caudron_760.svg

    The Miles M.20 would be very cool, and the span is less than 35 feet. However, if you shrunk it at all, you'd probably have to use a larger than scale canopy.
    https://en.wikipedia.org/wiki/Miles_M.20#/media/File:Miles_M.20_3-view.svg

    My own taste would run to 1930's racing aircraft that would have to be enlarged, such as the Miles Hobby:
    https://en.wikipedia.org/wiki/Miles_Hobby#/media/File:Hobby_3V.png

    Someone mentioned the caricature route. Certainly, that can be made to work. Presumably, if it can work in model size, it can work full scale.
    http://www.stickandtissue.com/yabbfiles/Attachments/finished_B-51_left_front_quarter_001.jpg
    https://www.youtube.com/watch?v=dEkQpTN7HZM
     
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  15. Sep 17, 2018 #115

    lr27

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    BTW, if you're really concerned about low stick forces, you might consider an anti servo tab. However, I doubt you'll need that, and it's extra work and a tiny bit of extra weight.
     
  16. Sep 17, 2018 #116

    pictsidhe

    pictsidhe

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    I'll ditch the coro if the numbers tell me to. Right now, they are suggesting the empennage may be best in fabric, though I have more numbers to run there. The ballparking numbers on the fuselage are more optimistic. Aft of the pilot, it's one huge beam and it is looking like coro may well make a lot sense there.
    I'm set on the Hurricane. It has a lot going for it. One of the easiest WWII fighters to fly, the pilot in a 2/3 version is going to be very close to the cg unlike most others. Oh yes, I like them!
    Retracts will add little weight, it's mostly a few hinges on top of a fixed gear. Oleos would be heavier. If I have to, the gear will be 'seized' and 'stuck down'. The lightweight option on oleos is mountain bike air shocks (~9oz) But they usually only have 2" travel, which is hardly worth bothering with. 4.80/4.00-8 barrow tires are 2 1/2 lb and close to scale, but wheels are an issue. I'd like to spin some, but lack a lathe here, so may have to make carbon ones.
    I've been doing some numbers and a lot of pondering, reading and looking for possible parts. It took a while for some accurate drawings to show up so I could start on detail design. Progress is being slowly made. Hopefully I'll try out painting options (camouflage is compulsory) this month and get some finished coro weights.
     
  17. Sep 18, 2018 #117

    pictsidhe

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    I think the tail is not as heavily loaded as I thought above. I think the g and safety factors went in twice. Oopsie. I am only partway through the numbers anyway and was going on what I have worked out.
     
  18. Sep 18, 2018 #118

    cluttonfred

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    +1 for the Miles M.20, or almost any of the thick wing, relatively low aspect ratio Miles designs. The M.20 is neat because you have the option of a couple of WWII camo schemes but it's unusual enough that the same airframe would not look out of place with a flat engine and swoopy cowling.
     
  19. Sep 18, 2018 #119

    lr27

    lr27

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    Here are some specs for the resin Coroplast is made with:
    https://www.coroplast.com/technicalinfo/resinspecs.htm

    Note the specific gravity of 0.9, compared to maybe 0.45 for Sitka Spruce or 0.1 for light balsa. The tensile strength is given as 4,000 lbs, or about 2/3 that of Sitka Spruce, according to ANC-18. The elongation at yield is given as 10 percent, but I don't believe that, because it implies an elastic modulus of only 40,000. I've seen figures for polypropylene elsewhere as 220,000 to 290,000. As I vaguely recall from my own tests, a good piece of 6 lb balsa would be around 200,000! (or was that a good piece of 5 lb??) So, let's say the same as 8 lb balsa wood, which has a s.g. of about .13. So the polypropylene is about 7 times as heavy as balsa of the same stiffness, and twice as heavy as spruce that's 5 times as stiff.
     
  20. Sep 18, 2018 #120

    pictsidhe

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    Ther are better spar materials. that's why I have no intention of using it for a spar.
    Take a piece of coro and piece of ply of the same weight and see which has the greater bending stiffness.
    Modulus is ~180,000. Don't forget that coro is hollow section. I have misc scraps of unknown manufacture, but the webs in 4mm are about 1/4 of the total weight if you want to check the math. Once you factor the hollow core in, it's stiffer in bending than solid carbon of the same areal weight let alone balsa. That means less supporting structure is needed. Yes, I could make a superior sandwich skin from carbon and 1/8 divinylcel, but that would be a lot trickier and way, way more expensive. Have you seen the price of 3k carbon fabric? I also suspect hangar rash would be an issue. The give in coro means that it spreads loads and is very tough stuff.

    At least one brand of corrugated plastic is made from this resin
     

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