Corsair/Spitfire hybrid

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

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  1. Jan 22, 2013 #381

    Hot Wings

    Hot Wings

    Hot Wings

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    You have just reached that awkward stage between idea/concept development and having enough detailed design work finalized to start making parts. At this stage there just isn't all that much progress that can be shown in a post. I'm pretty sure I'm not the only one that likes the look of your project and is looking forward to seeing the kind of progress that can be put into pictures! So even though your thread may remain dormant for a while please don't let it die.


    There are a few more of us that are interested in doing some worthwhile model testing. I found some threads here on HBA that are related. I haven't read them, or their links in detail but I intend to as time permits.

    http://www.homebuiltairplanes.com/f...s-new-technology/5459-dynamic-similarity.html

    http://www.homebuiltairplanes.com/f...ls-accuarely-predict-full-scale-behavior.html

    http://www.homebuiltairplanes.com/f...ns/4953-r-c-model-prototype-test-methods.html

    I'd like to see one of these threads revived for more discussion about using scale models as development tools.
     
  2. Jan 23, 2013 #382

    starbird

    starbird

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    Lots of good info in those threads. I think Orion summed up the idea in this post https://www.homebuiltairplanes.com/...c-model-prototype-test-methods.html#post36087

    I would argue that with the cheap sensors and off the shelf data loggers we have today, they may be good enough to get some quantitative feedback. Its definitely worth trying, especially if you are already building a scale model for testing.

    Yes, the distribution of mass is as important as the overall mass of the model if you are going to test dynamic stability. The scale mass may be too large to safely fly the model tho, so some compromise may have to be made.

    It does take some time to get everything up and running, but it does work.

    Unfortunately I don't have an instrumented aircraft right now. I was hoping to be able to build something and test these ideas last summer, but other things got in the way.

    If Will does go with an instrumented aircraft I would love to see the data. Be sure to take plenty of video too. :)
     
  3. Jan 23, 2013 #383

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    I'm getting really excited about this project again. It's never far from my thoughts but there are times when it just doesn't progress fast enough. Now is not one of those times. I thank you all for the help you are willing to give, it really motivates me.

    It also really motivates me to see my baby starting to exist in the physical world. As you can see the right side is taking shape. The front of the cowl is still missing. I'm going to turn some foam on the lathe to finish it off. Still trying to decide weather to go electric or gas engine.

    Definitely going to have to buy a FPV camera when I get this done so I can see from the cockpit when i fly it.
     

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  4. Jan 23, 2013 #384

    billyvray

    billyvray

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    What kind of foam cutter are you using? sorry if I missed that in the thread.


    ~Bill
     
  5. Jan 23, 2013 #385

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    2 inch thick blue insulation foam. Not sure what brand.
     
  6. Jan 23, 2013 #386

    Hot Wings

    Hot Wings

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    I think what he was asking is if you are using the little CNC thing in the background or this:
    hotwire.JPG
     
  7. Jan 23, 2013 #387

    billyvray

    billyvray

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    Yep, curious if you are doing the cutting by hand or what I thought I saw was a little CNC.


    ~Bill
     
  8. Jan 24, 2013 #388

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    Sorry my mind just edited the word "cutter" right out of your sentence. Yeah that is a woodland scenic hotwire cutter which I have used exclusively on this project. The CNC cutter sitting on the back of the table shown in the pic below has reached a semi operational status. I built it from scratch using the basic design from this site and bought their motor and circuit board combo. I bought the Mach3 software and got the thing to move using commands from the computer but one side was binding a little and I decided to try a different design (which failed) and so I've still got this one but no power supply or wire to actually cut anything. I also don't have any software to tell the Mach 3 software what to do.

    The X axis was made using 3 ft 100 lb drawer slides and the y axis uses 2 foot Home Depot slides. Still some more work needed but they are close to being functional if I just gave them the time.
     

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  9. Apr 15, 2013 #389

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    I think I finally settled on a paint scheme for my plane. It looks really cool and it won't have problems with the skin temp climbing too high in the sun.
    tan and grey paintjob.jpg

    And just for grins I put a smiley face on it.

    sharkmouth.jpg


    Now that the all important task of choosing colors has been completed I can get on with the minor tasks of design and building.
     
  10. Apr 15, 2013 #390
    To quote dougas adams :)
     
  11. Apr 23, 2013 #391

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    I've been drawing in and modifying the components of the WAR replica Corsair. As I anticipated the root chord was very close, within 1/8" in fact. I don't know what airfoil the replica uses but it reaches max thickness by about 25% chord and that is where the front spar is located. It also stays relatively thick until about 75% chord. There were certain constraints that limited the replicas main spar depth to 7 inches. I was able to make mine 8 inches deep. The spar caps are 2 inches thick x 2inches wide built up from 3/16" strips laminated together. Although my main spar is deeper the aft spar is a couple inches shallower. One other advantage I have is that I don't have a notch in my bottom spar cap so the gear can retract.

    The main gear on the replica hangs on a bracket mounted to the front spar, but since the front spar is at about 25% chord the distance from the face of the spar to the gear leg is only about 4 inches. Since my spar is located at 40% chord my gear leg is about 15 inches from the face of the spar. The idea I have come up with for mounting the gear leg is shown below. Basically a steel tube truss mounted to straps that join the inboard spar to the outboard spar. Sine i already had them drawn in I used engine mount spools. This is of course a very quick and dirty concept drawing just so you could see what I was thinking and provide feedback.
    maingearmount.jpg

    I am considering adding a plate inbetween the truss and the gear leg and have the gear bolt to the plate that way it would be easier to remove for maintenance. Also I remember when Mike Arnold had his engine failure and bent his gear. He designed his main gear so they would bend backwards in a crash instead of ripping out the mounts in the wing. I would like to do something similar, so if you know what considerations are needed I'd appreciate hearing about them.
     
  12. Aug 17, 2013 #392

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    Been working on the airbrakes. The attached screen cap shows the aft spar looking forward from behind the wing. The diamond shaped purple brackets are the seatbelt attachments, the purple tube coming out perpendicular to the spar is the elevator pushrod and the tube running parallel to the spar is the speedbrake torque tube. The pushrods and control arms to the speed brakes have obviously not yet been draw in.

    I've been thinking about having a manual or an electric actuation of the speed brakes. In case of a go around I don't want the brakes on so I'm leaning heavily in favor of an electric system that when the throttle is firewalled it automatically retracts the brakes, that way I don't have to worry about grabbing a lever and moving it, letting go and grabbing the throttle. Also the shape of the fuselage, how it is rounded on the bottom will make installing a manual lever much more difficult.

    Downsides of the electrical actuation would be failure of said system with brakes extended and accidental or uncommanded actuation. I vividly recall a video of a long eze doing a go around and for some reason the speed brake deployed and dropped the plane like rock right on the runway from about 20 ft up. Wether that was a mechanical or servo controlled I don't know. But your comments are welcomed.
     

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  13. Aug 18, 2013 #393

    autoreply

    autoreply

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    I have a strong preference for manual controls. Simple, reliable, light.

    Imagine the lever in the cockpit, pus hrod to the rear, which attaches to a torque tube, where a push rod goes to each "drag flap".

    Automatic retraction is done in many sailplane (Hänle tuten). Have the power and flap lever next to eachother, but give the flap handle half the travel. Then have a small tube on the side of the flap lever such that it's impossible to have it behind the throttle and have the locking mechanism of the flaps unlock when the throttle lever touches the flap lever tube. Applying over 50% throttle and your flaps are automatically retracted.

    Sounds complex, but it's pretty easy to do mechanically and probably as few parts as electric flaps.
     
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  14. Aug 18, 2013 #394

    rtfm

    rtfm

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    Hi,
    Got a picture? Sketch? It would be very helpful to see it.

    Sounds simple though.

    Regards,
    Duncan
     
  15. Aug 19, 2013 #395

    Will Aldridge

    Will Aldridge

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    Thanks that makes a lot of sense. I would also like to see a pic or diagram if you have one.

    Is the drag flap lever usually placed inboard or outboard of the throttle?
     
  16. Nov 30, 2013 #396

    Will Aldridge

    Will Aldridge

    Will Aldridge

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    I thought I had made the decision on the type of canopy I was going to put on my plane a long time ago. It was going to be a single piece that hinged on the right side.
    instrument panel.jpg

    Then I came across Mark Langfords page about the Kr-2 he bought that he was converting from side hinged to front hinged canopy and why he was doing it that way. The salient point in my mind is what if the canopy came unlatched when it wasn't supposed to. The lift on that side of the plane is immediately killed and tremendous drag added. He mentions one Kr owner by name who had that happen to him. Fortunately it was on takeoff and although it did substantial damage to the aircraft by causing it to veer suddenly off the runway the pilot lived to tell about it. In a front hinged canopy if it comes unlatched it might lift up a bit and be disconcerting but it's not going to do really bad stuff to the aerodynamics of the aircraft.

    I didn't like the forward hinge so I decided to do a sliding canopy as shown. I have always had it in the back of my mind that I was going to be roasting in the cockpit any time the sun was out and i was taxiing. I don't really like the idea of having the canopy bows obstructing the view but I gotta admit that it looks pretty sweet. You can definitely see the Fw-190 DNA in the plane more clearly now.
    Fw-190 style.jpg
     
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  17. Dec 1, 2013 #397

    Toobuilder

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    Couple of comments:

    Having flown flown both a slider canopy (RV-8) and a side hinge (Rocket), I much prefer the side hinge. The slider seems to encroach too much on the shoulder area due to the rails remaining parallel. There are more options for a single seater like yours however. Also, when a side hinge canopy does come off in flight, it generally departs the aircraft. Not much comfort perhaps, but at least the aircraft will remain symmetrical. All that said, I'm planning a change to a separate windscreen for the Rocket, but I'm remaining with the side hinge for the canopy (think F-104 or U-2). I want the impact protection of a thick flat wrap windscreen and the simplicity of the side hinged canopy.

    I also read your speed brake comment above. You might just consider leaving that completely off. I once thought they would be nice to have on the RV, but it has proven to be uneccessary. Even the 200+knot Rocket is easy to get slowed down with a little planning. Remember, equipment not installed is weightless and 100% reliable.
     
  18. Dec 1, 2013 #398

    DangerZone

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    A guy I know has built his Spitfire with a side hinge, it's much less complicated, simpler and stronger than a sliding canopy. Maybe some of these pics might help:

    sajam06.jpg spit1.jpg

    It was a half scale Spitfire and the builder flew with it around 300km/h with a two stroke Rotax, the structure was similar to the KR-1 yet much lighter, only 176kg empty weight. These might give you an idea or two.
     
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  19. Dec 1, 2013 #399

    autoreply

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    Side-hinged canopies aren't a big deal when opened (and none when they depart). Have seen several gliders land with them, the only one that didn't end well spun it (panic..) A nightmare on the ground though, a bit of wind and it'll blow itself apart if forgotten to latch.

    Front-hinged canopies IMHO should be done sailplane-style. Hinge the instrument panel, for perfect ingress/egress and attach the canopy to the instrument panel. Lock in the very rear. When you want to jump, unlock the instrument panel/canopy joint and it'll come off cleanly. Have a cord running to the rear and a knot halfway such that you can have it halfway-opened for taxiing. Slightly awkward for looks on the instrument panel, but otherwise great.

    If memory serves me well, the speed brakes were required because Will is going for flaperons? If so, I'd think they're almost a necessity; you can't deploy flaperons sufficiently for a reasonably steep approach.
     
  20. Dec 1, 2013 #400

    Will Aldridge

    Will Aldridge

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    Well my first design run on the sliders have them mounted on the aft deck so there is no appreciable reduction in width in the cockpit.

    And I did have the same thought regarding bird strikes and making the windscreen thicker to provide some protection. If I go with the windscreen What thickness should it be?



    "I have a few basic problems with the side-hinging canopy detailed in the original KR2 plans. The biggest one is safety. If the canopy is left (or becomes) unlatched in flight, it will immediately open fully and out onto the wing, and will then either rip off, or kill the lift on the inboard section of the wing. I know at least one KR builder/pilot who totalled his plane (and almost himself) when his canopy opened on takeoff, and the plane stalled and rolled off to the right and hit the ground. Not a pretty sight."

    The above is direct quotation from Mark Langfords website. So I'm not quite sure I believe there is no safety issue other than the distraction aspect. I do concede that my canopy is half the width of a Kr canopy and might therefore be less catastrophic if it were to open inadvertently. Making a separate windscreen would add some protection to the pilot and further reduce the size and resultant interference if it were to open.

    Yes I'm going to be using flaperons since adding flaps would be an awful lot of complexity on the bent wing. And as per your suggestion above I have a mechanical system in mind that would rectract the brakes when the throttle is advanced.

    AR you posted a link to a sailplane that uses flaperons (although maybe on the inboard sections only outboard are pure ailerons?) and I think they had 30 deg deflection on the flaperons and still used them as ailerons(if I read the graph right). Can sufficient control be maintained with the flaperons deflected that much? If so maybe I don't need the speed brakes since the 172's I have flown only have 30 deg of flaps and it works just fine for them. But they do have fowler flaps and have significantly more drag than my bird will so maybe it's not a good comparison.

    While we are on the subject of flaperons, I was watching that video you posted AR about the Sparrowhawk and Duckhawk. There was a notation on one of the slides about flaperons having different balancing requirements than ailerons. Could you point me to some references?
     

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