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Mike Arndt IE

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About Mike Arndt IE

  • Rank
    New Member

Personal Information

  • Real Name (Public)
    Mike
  • Location (Public)
    United States

Project/Build Information

  • Plane
    Cozy Mark IV
  1. Mike Arndt IE

    Cozy weight and balance

    Mark, Thank you for the insight, I hadn't considered that weight might induce a flutter issue, and I have no desire to go the way of Zubair Khan. The wing area is 88.7 sq ft, and the canard is 14.7 sq ft, with a span of 12.6ft. At a guess, say 2 of those 12.6 ft are in the nose, so if I read this right, the lifting surface of the canard is 14.7 sq ft - 10.6 ft long and 1.38 ft wide. The max weight is 2050 lbs, and if the canard is lifting 25%, then the wing loading is about 34.7 lbs per square ft. If we lengthen the canard by 3 inches per side (keeping the original size : ), that adds 0.6 ft X1.38 ft = 0.828 sq ft or 28.7 lbs more lift on the canard. The canard CG or center of lift is about station 20, so a delta of 60 to ideal CG. 28.7 lbs x 60 inches = 1724 inch lbs. The front seats are at station 59 or 41 inches delta to ideal CG. Y new lbs in the front seat X 41inches = 1724 inch lbs so Y = 42 lbs additional front seat weight. All with no mad science . Thanks for the tip! Kent, While the Bearhawk is certainly built for the weight, I don't normally use off airport runways, and the shorter range, slower top speed, and high kit purchase price don't fit our family goals of fast long distance flight. There are faster planes, but a stone will fly if you strap on a big enough engine (I wouldn't want to pay the fuel bill though). I just don't know of any other four place experimental that can match the cozy for range and speed in the 180 to 200 hp range.
  2. Mike Arndt IE

    Cozy weight and balance

    Made some headway on the calculation: Moving the engine doesn't help (or hurt) as much as you might think. Compared to the ideal CG of 100 (where smaller numbers are inches forward of 100 and larger numbers are inches aft) the front seats and engine are equal distances from the CG, so one more lb of engine balances one lb of front seat pilot or passenger. If anyone else is out there looking at the front seat weight question, here's what I used: All values in inches Nose Ballast = -3 Front seat/pilot = 59 Forward FG limit = 97.5 Ideal CG = 100 Back seat/baggage = 101 inches Aft CG limit = 102 Fuel tank = 103 Firewall = 123.3 Engine = 142 So the engine at 42 aft is just about the same as the front seat at 41 inches forward of ideal CG. So moving the engine around is a major tech mess, and more to the point, its not very productive. At this point, the only solution that still makes sense would be to use the same 'fiberglass pipe with lead ended counterweight' and mount them out on the wings, outboard of the ailerons. If I glassed in just the mount on each side, and made to pipes about 3 ft long weighing 15lbs each with a cg about a foot aft of the wing tip, then 30 lbs ballast counters 60 lbs of front seat weight plus the ballast probes could be removed to return the CG to normal when not flying with a heavy front seat. The wings already produce the vast majority of the lifting force (duh), so in flight 15 lbs of weight/twist per wing probably wouldn't be enough to matter. What do you think? Mad science , or better to just chance it and fly past the forward CG as some are doing today?
  3. Mike Arndt IE

    Cozy weight and balance

    Wow, thanks for the info : )
  4. Mike Arndt IE

    Cozy weight and balance

    Agreed, I was thinking the same thing about the ballast when empty, but I had a work around for that... Admittedly its a little different, but the moment is (weight in lbs X lever arm in inches), so if the ballast was in the form of a long iron rod that locked into the nose and stuck out like this, that would give a lot of extra inches without so much unwanted weight. Parking it would be fun, but if I manage to build a aircraft, I'll bet I can figure out some way to push it around on the ground without tipping over. Thank you for the link to the POH, but I couldn't get the measurements I needed from that (at least, I didn't see them when I downloaded it and looked around pages 30 - 35). Ultimately this idea needs to be settled by calculation - if the engine needs to move 3 ft back to make this work then the idea is impractical and no good. If it needs to go back 6 to 8 inches then maybe it could be done. I just need those aircraft dimensions to run the calculation and see where reality stands vs my dreams of grandeur : ). Nose tip to front wheel = Front wheel to rear wheel = Rear wheel to CG = ( not sure if target CG is before or aft of rear wheel) Rear wheel to firewall = Thanks for your reply!
  5. Mike Arndt IE

    Cozy weight and balance

    Hey everyone : ) I've been learning about the Cozy Mark IV for years now, and I'm trying to make a CG/ weight and balance calculation but having a hard time. I've found various spread sheets that compute it for a complete aircraft, but I'm trying to find out the distances (X axis only) between the tip of the nose, the front wheel, the rear wheel, the CG and the fire wall. I've read up on the details of engine weight vs position to attain the original cg, (Link) but I'm trying to calculate a ratio, specifically, "Shifting the engine X inches back will add Y lbs weight capacity to the front seat". Understandably, shifting the engine back will necessitate more nose ballast when flying solo, but as long as the total CG/weight and balance remains in the stable range everything should work. Yes, shifting really far back will make takeoffs/landings more difficult by decreasing the distance between prop and runway on rotation, but to me its worth the trade off. My wife and I together are about 450 to 475 lbs, and we do everything together, so no way is she taking the back seat on this. Can anyone here provide these dimensions? Nose tip to front wheel = Front wheel to rear wheel = Rear wheel to CG = ( not sure if target CG is before or aft of rear wheel) Rear wheel to firewall = Any help would be appreciated...
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