+ Reply to Thread
Page 2 of 4 FirstFirst 1234 LastLast
Results 16 to 30 of 52

Thread: All aluminum ultralight?

  1. #16
    BDD
    BDD is offline
    Registered User
    Join Date
    Apr 2005
    Location
    WI
    Posts
    388

    Re: All aluminum ultralight?

    I think there is an ultralight version of the Tornado. It's that one or another that looks exactly like it. I think the wings are also designed for a rather high G loading.

  2. #17
    Registered User
    Join Date
    Apr 2007
    Posts
    293

    Re: All aluminum ultralight?

    Although too fast to be classified as an ultralight, the Davis DA-11 weighs ~170 lbs. and cruises ~130 mph on an inexpensive 20 hp Briggs & Stratton lawn mower engine. It would go even faster with that same power if wing and V tail airfoil roots were filleted, wing tips faired, wheel pants added, etc.. YouTube for Davis DA-11 video.

    For a significantly lower takeoff and stall speed, increasing the wing chord would add very little weight but much lower the wing loading.

    Since planes are effectively priced by the pound, and the Davis planes are very light, inexpensive, and efficient, why not consider such designs?

    Compare DA-11's weight, cost, ease of construction, fuel consumption, and performance side-by-side with the CriCri.

  3. #18
    Registered User Dan Thomas's Avatar
    Join Date
    Sep 2008
    Posts
    2,994

    Re: All aluminum ultralight?

    Quote Originally Posted by Bart View Post
    Although too fast to be classified as an ultralight, the Davis DA-11 weighs ~170 lbs. and cruises ~130 mph on an inexpensive 20 hp Briggs & Stratton lawn mower engine. It would go even faster with that same power if wing and V tail airfoil roots were filleted, wing tips faired, wheel pants added, etc.. YouTube for Davis DA-11 video.

    For a significantly lower takeoff and stall speed, increasing the wing chord would add very little weight but much lower the wing loading.

    Since planes are effectively priced by the pound, and the Davis planes are very light, inexpensive, and efficient, why not consider such designs?

    Compare DA-11's weight, cost, ease of construction, fuel consumption, and performance side-by-side with the CriCri.
    Just try to buy the plans for it. They're not available.

    Leeon Davis was something of a master in designing light, fast airplanes. If he didn't use wheelpants and fairings, he probably judged them (more likely calculated them) to be not worth the extra weight. On a tiny, super-light airplane like the DA-11, every last ounce matters. Add a few pounds to such a light airplane and you increase wing loading and induced drag. Stall speed goes up. Maybe takeoff distance gets too long, or maybe it won't take off at all. In my Jodel, which grosses at 1200 pounds, the performance difference, between flying by myself and having a 150-pound passenger with me, is enormous. I can imagine how little extra weight a 170-pound airplane can tolerate.

    Dan

  4. #19
    Registered User
    Join Date
    Apr 2007
    Posts
    293

    Re: All aluminum ultralight?

    Quote Originally Posted by Dan Thomas View Post
    Just try to buy the plans for it. They're not available.

    Leeon Davis was something of a master in designing light, fast airplanes. If he didn't use wheelpants and fairings, he probably judged them (more likely calculated them) to be not worth the extra weight. On a tiny, super-light airplane like the DA-11, every last ounce matters. Add a few pounds to such a light airplane and you increase wing loading and induced drag. Stall speed goes up. Maybe takeoff distance gets too long, or maybe it won't take off at all. In my Jodel, which grosses at 1200 pounds, the performance difference, between flying by myself and having a 150-pound passenger with me, is enormous. I can imagine how little extra weight a 170-pound airplane can tolerate.

    Dan
    Yeah, but with just a few ounces of foam, shaped by a peanut butter jar* wrapped with sandpaper and then covered with aluminum foil adhesive tape, you could nicely fillet those wing and tail feather roots.

    *Some EAAer came up with this idea. Said ~4" diameter Skippy plastic peanut butter jar was perfect--good diameter, just a bit of give, priced right, recyleable. Protected the adjacent fuse and wing surfaces with duct tape while he sanded the foam, pealed off duct tape, and had perfect fillets. I'd bet you could do a DA-11 including wheel pants for <~5 lbs. additional weight.

    Leon's forte' was smart use of off the shelf sheet aluminum. That is great for simple curves, but not so good for compound curves. Maybe tweak his design by using light plastics for non-structural fairings such as wheel pants, wingtips, etc.?

  5. #20
    Registered User
    Join Date
    Nov 2009
    Location
    Virginia/United States
    Posts
    71

    Re: All aluminum ultralight?

    All this talk of making FAR-103 weight and nobodies mentioned the heaviest piece of every airplane...THE ENGINE

    The ultracruiser was designed around a 90lb. engine and that doesn't include the propeller(another 5lbs. or so)

    Just find a lighter engine

  6. #21
    Registered User catalysth2o's Avatar
    Join Date
    May 2010
    Location
    Wendell, NC/USA
    Posts
    12

    Re: All aluminum ultralight?

    Good input from everyone, but not really interested in ones that are too heavy or too fast, that's moving away from what I wanted to do with the aircraft. I basically wanted to build an all-aluminum ultralight aircraft that is 103 legal or at least very close to it (I've read that they don't police it all that much) to get some seat time before I start working toward my pilot's license. Don't worry, I plan to get some instruction from a flight instructor at the local airfield before I try to fly it. Thanks for everyone's replies, it appears that the Ultracruiser is the best game in town; the Moni would be ok if the stall speed was lower and it wasn't too fast at cruise.

  7. #22
    Registered User
    Join Date
    Nov 2009
    Location
    Virginia/United States
    Posts
    71

    Re: All aluminum ultralight?

    Quote Originally Posted by catalysth2o View Post
    Good input from everyone, but not really interested in ones that are too heavy or too fast, that's moving away from what I wanted to do with the aircraft. I basically wanted to build an all-aluminum ultralight aircraft that is 103 legal or at least very close to it (I've read that they don't police it all that much) to get some seat time before I start working toward my pilot's license. Don't worry, I plan to get some instruction from a flight instructor at the local airfield before I try to fly it. Thanks for everyone's replies, it appears that the Ultracruiser is the best game in town; the Moni would be ok if the stall speed was lower and it wasn't too fast at cruise.
    I have a set of plans for the ultracruiser and let me tell you they are well worth the money. They are drawn on autocad and are very detailed. Their is also a well established community for that aircraft on the net if you need help with your build.

  8. #23
    BDD
    BDD is offline
    Registered User
    Join Date
    Apr 2005
    Location
    WI
    Posts
    388

    Re: All aluminum ultralight?

    Quote Originally Posted by travis1990 View Post
    All this talk of making FAR-103 weight and nobodies mentioned the heaviest piece of every airplane...THE ENGINE

    The ultracruiser was designed around a 90lb. engine and that doesn't include the propeller(another 5lbs. or so)

    Just find a lighter engine
    Use a Kawasaki 440 and you would have more h.p. and an extra 45 pounds of weight to play with. Or you could eat out more often. 45 pounds of weight judiciously added to the structure or crashworthiness would be a very good thing.

  9. #24
    Registered User Dan Thomas's Avatar
    Join Date
    Sep 2008
    Posts
    2,994

    Re: All aluminum ultralight?

    Quote Originally Posted by BDD View Post
    Use a Kawasaki 440 and you would have more h.p. and an extra 45 pounds of weight to play with. Or you could eat out more often. 45 pounds of weight judiciously added to the structure or crashworthiness would be a very good thing.
    Judicious, indeed. A light engine makes the tractor airplane tail-heavy. Any weight added will have to be substantial and all ahead of the CG, or the engine will have to move a long way forward to maintain the balance but screwing up stall/spin/slip safety.

    Adding stiffness in some areas can actually precipitate failure. Stiffness can simply transfer loads to some weaker area. We're seeing that in old Champs, where the plywood spar stiffeners at the strut attach points make the spar stiff through that area and caused compression failures in the wood at the ends of the stiffeners. There's an AD on it.

    Dan

  10. #25
    Registered User
    Join Date
    Apr 2007
    Posts
    293

    Re: All aluminum ultralight?

    Quote Originally Posted by Dan Thomas View Post
    Judicious, indeed. A light engine makes the tractor airplane tail-heavy. Any weight added will have to be substantial and all ahead of the CG, or the engine will have to move a long way forward to maintain the balance but screwing up stall/spin/slip safety.

    Adding stiffness in some areas can actually precipitate failure. Stiffness can simply transfer loads to some weaker area. We're seeing that in old Champs, where the plywood spar stiffeners at the strut attach points make the spar stiff through that area and caused compression failures in the wood at the ends of the stiffeners. There's an AD on it.

    Dan
    If a plane were built pod & boom like Alex Strojnik's Laminar Magic or a Janowski Marco J-5, the engine mass and consequent stresses would be amidships, with much less weight & balance issue, short stress paths, and lighter weight.

    The Davis DA-11 is about 75 lbs lighter than an Ultracruiser, an otherwise comparable aluminum single seat plane. Supposing the same powerplant were put into a Strojnik/Janowski pod and boom planform, such a plane might be even lighter than an Ultracruiser or even the 170 lb. DA-11. No heavy engine hanging out at the end of the fuselage, nor long and therefore heavy landing gear out in the slipstream.

  11. #26
    Registered User
    Join Date
    Apr 2007
    Location
    Northern California
    Posts
    328

    Re: All aluminum ultralight?

    Quote Originally Posted by Bart View Post
    If a plane were built pod & boom like Alex Strojnik's Laminar Magic or a Janowski Marco J-5, the engine mass and consequent stresses would be amidships, with much less weight & balance issue, short stress paths, and lighter weight.
    Not necessarily, The pod a boom results in a rather small diameter member (the boom) that has to transfer all the stresses from the tail to the fuselage. Stiffness and buckling resistance goes up significantly with increase diameter and can result in reduced weight with increased size.

  12. #27
    Registered User
    Join Date
    Apr 2007
    Posts
    293

    Re: All aluminum ultralight?

    Quote Originally Posted by DaveK View Post
    Not necessarily, The pod a boom results in a rather small diameter member (the boom) that has to transfer all the stresses from the tail to the fuselage. Stiffness and buckling resistance goes up significantly with increase diameter and can result in reduced weight with increased size.

    While I agree with your "not necessarily" comment above, as a practical matter the Strojnik S-2 with 49' wingspan handled all its tail stresses with a 4" square tube boom that weighs 2.2 lbs per linear foot. A 14' long ultralight would have a tail boom of maybe 7-10 foot length, max, or 15-22 lbs. unless made lighter by drilling holes in it. So, to compare with Ultracruiser, is its tail cone total weight 15-22 lbs.? Somehow, I don't think so.

    So, that 4" tail boom planform winds up saving lots of landing gear weight since the prop disk is up out of the dirt without resort to long spindly and heavy landing gear, yet that 4" diameter tail boom handles tail stresses just fine: If it works on a 49' span sailplane of several times the weight of an ultralight, it will damn sure handle the stresses of a smaller, much lighter ultralight.

  13. #28
    BDD
    BDD is offline
    Registered User
    Join Date
    Apr 2005
    Location
    WI
    Posts
    388

    Re: All aluminum ultralight?

    I'm thinking that for an ultralight the loads from the tail are not all that large and that a tail boom might actually be the way to get a larger tail moment with less weight. This is also one place where carbon fiber could be very useful.

    With a conventional fuselage to hold carry the tail, it could be heavier and stronger than you need and to maintain weight it might have to be reduced in length resulting in a relatively speaking shorter coupled configuration.

    The tail adds a lot of weight that has to be balanced by the engine and I always assume some minimum sort of tail or fuselage structure to have a chance to be within Part 103 weight limits. Meeting those weight limits isn't really easy while providing sufficient structure. I woul like more than an absolute minimum plane while still meeting part 103 and being completely legal. Engine weight is a big factor in this. Also, if you configure a strong light plane that is very efficient structurally, you will have more powerplant options and could maybe "afford" a more reliable 4-stroke. I am interested in what other people think about this and efficient configurations for light weight.

  14. #29
    Registered User BBerson's Avatar
    Join Date
    Dec 2007
    Location
    Port Townsend WA
    Posts
    4,217

    Re: All aluminum ultralight?

    Sure, the tailboom is good idea for tractor ultralights, not just for pushers only. But the boom needs to be large enough to avoid flutter. Stan Hall reported flutter problems he had with a small boom, I think it was 5". The 2.2 lbs. per linear foot tailboom mentioned by Bart is too heavy for an ultralight, in my opinion. The boom needs to about 14-15' long to extend to the engine.
    A highly engineered lightweight structure does allow for a heavier engine. You are on the right track.
    This is the future of affordable aviation.

  15. #30
    Moderator Dana's Avatar
    Join Date
    Apr 2007
    Posts
    5,250

    Re: All aluminum ultralight?

    FWIW, all the Kolbs up through the Firestar had 5" diameter X .058 6063 aluminum tailbooms and wing spars (with about 24" of internal steel reinforcement at the wing strut and rear fuselage cage attachment points).

    Back to the original subject, I was admiring a gorgeous Ultracruiser at a fly-in last summer. It had a 1/2 VW, and the owner/builder said it was under the 254# limit... but with no brakes and minimal instrumentation. He was scrupulous about keeping it legal, because it doesn't look like an ultralight, and he was afraid of getting ramp checked.

    -Dana

    Gun control: The theory that 110lb. women should have to fistfight with 210lb. rapists.

+ Reply to Thread
Page 2 of 4 FirstFirst 1234 LastLast

Similar Threads

  1. New design project: Aerobatic ultralight biplane
    By Dana in forum The light stuff area
    Replies: 136
    Last Post: September 25th, 2013, 01:53 PM
  2. Bonding Aluminum to Foam Ribs
    By GESchwarz in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 45
    Last Post: October 26th, 2011, 09:40 AM
  3. Homebuilt metal forming tools
    By Othman in forum Workshop Tips and Secrets / Tools
    Replies: 51
    Last Post: May 29th, 2011, 10:35 PM
  4. [Wanted] Aluminum honeycomb flat stock
    By Holden in forum For Sale / Wanted
    Replies: 14
    Last Post: July 7th, 2010, 09:11 AM
  5. Aluminum rib design options
    By handprop in forum Aircraft Design / Aerodynamics / New Technology
    Replies: 3
    Last Post: May 18th, 2009, 11:49 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts