Issues and Solutions for kit- and plans-based sailplanes and motorgliders

Discussion in 'Soaring' started by TerryM76, Sep 3, 2019.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Sep 7, 2019 #141

    TerryM76

    TerryM76

    TerryM76

    Well-Known Member HBA Supporter

    Joined:
    Sep 8, 2012
    Messages:
    491
    Likes Received:
    186
    Location:
    Tempe, AZ
    Cygnet or Pottier P130?
     
  2. Sep 7, 2019 #142

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,702
    Likes Received:
    962
    Location:
    Warren, VT USA
    Cause you live on a live in airport and you have a hangar connected to your house? You might not be the audience...

    The Phoenix is about as close as you can get currently. Span is span. It is needed to accomplish the mission.
     
  3. Sep 7, 2019 #143

    Topaz

    Topaz

    Topaz

    Super Moderator Staff Member

    Joined:
    Jul 30, 2005
    Messages:
    13,873
    Likes Received:
    5,482
    Location:
    Orange County, California
    Visibility in thermals was exactly the strongest objection raised to Neil Pfieffer's concept of starting with a Wittman Tailwind for a core fuselage, and adding longer wings. And yeah, I wouldn't want to thermal in something like that, either. Anything like a stretched Cygnet, the older BA-7 (below), or SAAB MFI-9 would resolve the visibility issue, but they tend to be a little hard to get into and out of, without some kind of step. The Nord NC.850 (bottom) manages to get a side-door in the concept, but that one might be getting to be a rather large airplane for a motorglider.

    The only issue with these configurations, assuming you're either willing to put up with the nose-mounted engine drag or can find a way to shut off the cooling air, is that they generally require a more-than-normal amount of forward sweep. A little less of a problem for a long-winged sailplane version, in that the long wings reduce the necessary forward sweep angle, but it's still a consideration.

    4824374800_97a09d32f5_z.png
    NC854.png
     
    Last edited: Sep 7, 2019
  4. Sep 7, 2019 #144

    BJC

    BJC

    BJC

    Well-Known Member HBA Supporter

    Joined:
    Oct 7, 2013
    Messages:
    9,739
    Likes Received:
    6,526
    Location:
    97FL, Florida, USA
    I do live on an airpark, and my hangar / workshop is 40 feet away.
    Perhaps not, but I have the interest and the means to purchase a motor glider that meets my wants.

    Yes, and that is why I didn’t buy. Why are others not buying, and are there enough of them, without people like me (and there are several more right here) to meet the needs being discussed in this thread?


    BJC
     
  5. Sep 7, 2019 #145

    mm4440

    mm4440

    mm4440

    Well-Known Member

    Joined:
    Jan 14, 2012
    Messages:
    180
    Likes Received:
    38
    Location:
    LA area, CA
    Some interesting progress on the e soaring thread. An e Phoenix.
    Most current motor gliders have span breaks at ~36 feet to deal with hangar and taxiing problems.
     
    John.Roo likes this.
  6. Sep 7, 2019 #146

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,201
    Likes Received:
    2,401
    Location:
    Port Townsend WA
    Yes, significant operational limitations. The Phoenix website shows tips can be removed in 60 seconds for the hangar. Is that a problem?
    That still leaves problems with runway lights and signs, etc. Always a problem, one time the runway cones were moved close together and I had to go out and move all of them... after calling the airport owner.
    Consider a single seater. Passengers are not always thrilled about motorglider cross country rough rides.
    A single seater could be a lot smaller with less operation issues. I wish I could trade to a single seat, for trailering convenience and the nice view from both sides.
     
  7. Sep 7, 2019 #147

    Jay Kempf

    Jay Kempf

    Jay Kempf

    Well-Known Member Lifetime Supporter

    Joined:
    Apr 13, 2009
    Messages:
    3,702
    Likes Received:
    962
    Location:
    Warren, VT USA
    Are there enough out there that aren't buying for one or another reason? Hard to tell. If a 40' t hangar is a restriction then this ain't gonna work. Span is needed. If a trailer that can be used in say 30 minutes of time once a week is a problem this isn't gonna work. If tips can be remove in minutes and or folded to get in that T hangar then this isn't gonna work. Cause 15 meters is probably the minimum span to make it work. Surprisingly it isn't about wing area as much as it is span loading and aspect ration. I guess that is all the same optimization subject matter in the end. Wing loading can be quite high for this sort of craft and it can still have adequate soaring performance and that helps cross country flights. Sink rate suffers so marginal conditions are sacrificed. For me that matters not up to a point.

    So would you consider folding tips or removable as a compromise?
     
    Topaz and BoKu like this.
  8. Sep 7, 2019 #148

    gtae07

    gtae07

    gtae07

    Well-Known Member

    Joined:
    Dec 13, 2012
    Messages:
    1,822
    Likes Received:
    1,089
    Location:
    Georgia
    Agreed.

    Here I'd disagree, at least if the fold is done right. If I'm putting my airplane in a hangar, I have to shut down and get out anyways; I don't taxi in under power and I definitely don't taxi out. If the wing/wingtip fold procedure can be accomplished quickly, by one person, without dollies or cradles or other GSE (i.e. the wings stay attached to the aircraft and either support themselves or attach to pins a la E-2 wing fold), and with a maximum of one tool that stays with the aircraft, then I'd argue it's not a problem--and could even be a good thing. The Onex wing fold (the technical merits of which have been discussed here before) would be a good model at least from an ease and speed perspective.

    Folding, even if it's not full trailerable folding, gives you benefits like maybe being able to share a T-hangar and fitting more easily in larger hangars.




    I am still mulling over the idea of a Goat with a pair of underwing electric "power pods" built from large R/C motors and battery packs. I won't get anywhere other than maybe a bit of math until my RV is done but that seems like a nice evening "floater" on a budget.
     
  9. Sep 7, 2019 #149

    SMORGAN

    SMORGAN

    SMORGAN

    Member

    Joined:
    Dec 10, 2016
    Messages:
    10
    Likes Received:
    1
    Location:
    Sydney Australia
    As someone who flew gliders then hang gliders in the 70s and 80s and recently soled in gliders again after 45 years I would love to see plans for something with a better performance than the Goat and a lot cheaper than the Archaeopteryx available.

    The design by UltraIajt on HBA , I think it was called "footlaunchable ultralight glider" seemed to satisfy these requirements. I cant find it on HBA anymore, it seems it was never completed.

    Ron Klingberg is in the process of building version 2 of his flying wing and documenting the process on Youtube, if successful it may meet the need for a "plans based sailplane" as this thread is titled.
    https://www.youtube.com/channel/UCXhs5u7kC5pYoqNUQU9SdWw


    And gtae07 re your post 148 have you seen the video of a millennium with RC motors:

     
  10. Sep 8, 2019 #150

    John.Roo

    John.Roo

    John.Roo

    Well-Known Member

    Joined:
    Oct 8, 2013
    Messages:
    227
    Likes Received:
    164
    Location:
    Letohrad / Czech Republic
    Hello!
    As I posted in my "e-soaring thread" - last weekend was very interesting meeting in Denmark.
    We flown there with electric Phoenix, students from Akaflieg Berlin brougth project B13E and also one Discuss with FES did a nice airshow. Also electric glider winch has been presented succesfully.

    With fully charged battery I did 10 flights with co-pilots mostly between 80-100 kg weight and in total it was over 2 hours of flight time.

    Report in TV news :)
    https://www.dr.dk/tv/se/tv-avisen-m...MC2UL8l0l69XtYLyAHXuUPQNF_guqxWF7Q5-c#!/22:21
    (time from 22:21)

    Nice photos from Luise Bruen are here:
    https://www.facebook.com/Electric-Aviation-Day-110746436948426/
    It was really great day with a lot of flying :)

    I hope we will soon start with glider "e-tow" tests to show how universal electric airplanes can be :)
    We already installed in flight adjustable + feathering prop and seems that endurance will reach 2,5 hours.
    Actually we are working on 17 m (55,77 feet) wing extensions and tricycle (front wheel) undercarriage version. Both modification I would like to test fly after winter.
    Here are actually available options:
    Phoenix all versions colour.jpg
    Without wing extensions (for parking in hangar) is wingspan 10,3 m (33,8 feet).

    Here you can see how long it takes to change wing span :)
    (same system is used on electric version)

    KIT version is possible, but it will take time to make good KIT builder manual.
    However "KIT builder assistance program" is available already :)

    Have a nice day!
    Martin
    20190902_133637.jpg
     
  11. Sep 8, 2019 #151

    mm4440

    mm4440

    mm4440

    Well-Known Member

    Joined:
    Jan 14, 2012
    Messages:
    180
    Likes Received:
    38
    Location:
    LA area, CA
    Thanks for posting this John, I have been pushing the idea of homebuilt tow planes, possibly with auto based engines as a way to reduce the cost and increase the availability of tow planes. Electric would be even better. Self launching is an expensive alternative. An efficient, economical tow plane can launch many less expensive unpowered sailplanes. It would be interesting if Martin would test towing performance at both spans. If LSA type airframes rather than a motor glider would have adequate performance it would mean many more potential tow planes.
     
  12. Sep 8, 2019 #152

    John.Roo

    John.Roo

    John.Roo

    Well-Known Member

    Joined:
    Oct 8, 2013
    Messages:
    227
    Likes Received:
    164
    Location:
    Letohrad / Czech Republic
    Well... I have no experience with auto (car) engines... Rotax use cheaper MOGAS fuel (in compare with AVGAS prices), service system and warranty is available worldwide, availability of spare parts is perfect. I understand that you you want to save costs, But for aerotowing you need reliable engine.
    Electric propulsion if far not tested like combustion engines so I have still respect - don´t forget that in case of aerotowing you have another pilot (pilots) behind you. Sometimes non-experienced students.

    Aerotow tests with both (10,6 and 15 meters) wing extensions?
    That is possible. However I bet on longer wings :)
    With "similar" performance is aerotowing easy and very pleasant. You can use thermals during aerotow "together".
    I beleive that towing with motorglider with experienced glider pilot inside (with LSA or UL tow pilot license of course) can save significant amount of fuel = reduce costs even more.

    LSA (UL) airframes are OK for aerotowing.
    More and more aeroclubs in EU are towing with light planes.
    We did a lot of tests incl. tests with tenzometric systems in tow cable.
    But still are many PPL pilots "sure" that tow plane must be heavy and with at least 150+ hp :)
    And in some special situation they are of course right.

    Electric aerotowing is interestign challenge.
    Beside of good motor and controller cooling will be necessary to watch battery temperature.
    Energy costs are really low, but please don´t forget that costs / flying hour are not only costs for fuel.
    You need to count "overhaul" or exchange of batteries etc. (on case of combustion engines is overhaul or engine etc.)
    Lifetime of batteries (most expensive part) depend a lot also on operating temperature.
    Also is necesary ground infrastructure on arifield allowing to re-charge at least with 15-20 kW of power.
    And during re-charging is necessary to watch temp. of batteries again.
    And I could continue... :)

    Phoenix aerotow.jpg
    Phoenix heavy aerotow.jpg
    20190809_143417.jpg
     
  13. Sep 8, 2019 #153

    gtae07

    gtae07

    gtae07

    Well-Known Member

    Joined:
    Dec 13, 2012
    Messages:
    1,822
    Likes Received:
    1,089
    Location:
    Georgia
    Unfortunately this isn't currently legal unless you can convince the FAA otherwise. Standard E-AB operating limitations explicitly prohibit using the aircraft to tow gliders, I assume because that's considered a commercial activity.

     
  14. Sep 8, 2019 #154

    Hot Wings

    Hot Wings

    Hot Wings

    Well-Known Member HBA Supporter

    Joined:
    Nov 14, 2009
    Messages:
    6,448
    Likes Received:
    2,360
    Location:
    Rocky Mountains
    An auto based tow plane makes sense - if - a tow plane makes sense.
    A tow plane still means a minimum of 2 persons, with the same free time allotment, to get a glider in the air.
    << >>
    Current self-launching options are expensive. The expense is also a high personal up front cost. Compared to the cost of a new factory winch or tow plane it's not all that expensive. That personal expense has to be compared to the value and convenience of solo operation. There are, or at least can be, self launch options that cost far less than the 6 figure cost of the state of the art.
    << >>
    A more efficient tow plane is desirable and can launch cheaper unpowered sailplanes, but the root problem still remains - coordinated manpower, or the lack thereof.
     
    gtae07 likes this.
  15. Sep 8, 2019 #155

    BBerson

    BBerson

    BBerson

    Well-Known Member HBA Supporter

    Joined:
    Dec 16, 2007
    Messages:
    12,201
    Likes Received:
    2,401
    Location:
    Port Townsend WA
    I owned and operated a tow plane. And the Grob was bought for a two seat motorglider tour business that was explored for years and didn't work for me.
    I think one solution is the very smallest possible motorglider. How that is defined is by the particular niche flight purpose.
     
    Last edited: Sep 8, 2019
  16. Sep 8, 2019 #156

    mm4440

    mm4440

    mm4440

    Well-Known Member

    Joined:
    Jan 14, 2012
    Messages:
    180
    Likes Received:
    38
    Location:
    LA area, CA
    Hi, I believe the towing exclusion is in a sample Op Limits and is commonly included. I do not think it is a regulation. One needs to find a cooperative DAR. In the EAA-FAA discussions on the update of E-AB regs the FAA has been positive on the subject of experimentals towing, non-commercial.
    All options need to be explored if soaring is to survive in the USA.
     
    BJC likes this.
  17. Sep 8, 2019 #157

    Victor Bravo

    Victor Bravo

    Victor Bravo

    Well-Known Member

    Joined:
    Jul 30, 2014
    Messages:
    6,227
    Likes Received:
    5,037
    Location:
    KWHP, Los Angeles CA, USA
    Folding wings that swing rearward the same way as a sailplane trailer works is the answer. Several motorgliders have already used this. Your cost to do this type of flying is 15 minutes before and after flying. Your gain is that three of them can fit in one hangar, and you have good soaring performance. About five pounds of extra weight for the folding mechanism.
     
  18. Sep 8, 2019 #158

    Topaz

    Topaz

    Topaz

    Super Moderator Staff Member

    Joined:
    Jul 30, 2005
    Messages:
    13,873
    Likes Received:
    5,482
    Location:
    Orange County, California
    You know, if you read FAR 91.319 in detail, it says that experimental aircraft are prohibited from carrying people or property for compensation or hire. That doesn't include towing, does it?

    Also, subsections (e), (f), and (g) provide some interesting direct exceptions that allow towing for experimentals that are operated as LSA's.

    Worth exploring.
     
  19. Sep 8, 2019 #159

    mm4440

    mm4440

    mm4440

    Well-Known Member

    Joined:
    Jan 14, 2012
    Messages:
    180
    Likes Received:
    38
    Location:
    LA area, CA
    Hi VB, not sure about the trailer reference. The wing panels of a sailplane are the longest parts to be fitted in the trailer so a sailplane with wing folding at the rear spar which is typical of light planes with folding wings (some fold at main spar) would make the trailer inconveniently longer. It would make one person rigging and storage easier. One of the features of the VSA is it would fit on a small boat trailer of about 16'. The weight of the folding parts would be more than you think but likely worth it. Check the Stemme outboard wing fold mechanism.
     
  20. Sep 8, 2019 #160

    Victor Bravo

    Victor Bravo

    Victor Bravo

    Well-Known Member

    Joined:
    Jul 30, 2014
    Messages:
    6,227
    Likes Received:
    5,037
    Location:
    KWHP, Los Angeles CA, USA
    I did not mean in a trailer, I mean alongside the fuselage leading edge down
     

Share This Page



arrow_white