2 seater Cri-Cri, HummelBird or SD-1

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MicRuler

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Feb 1, 2010
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Nassau, Bahamas
I'm sure everyone here knows of such great planes as the
Cri MC-15

Hummel Bird

These specs are with 37hp 1/2 VW engine and 170# pilot.
No spins Low "G" Aerobatics
Airfoil - modified Clark-YHP (range)30-40Wing Span (ft)
18Wing Area (sq. ft.)57.2Length (ft)13' 4"Empty Weight300Gross Weight530VNE Speed (mph)145Cruise (mph)100-115Stall (mph)38Takeoff Distance (ft)300Take off over 50' obstacle (ft)1000Landing Roll (ft)800Fuel Capacity (gal)6"G" rating6.6

SD-1 Minisport

Specifications
SI unitsImperial units Wingspan 6,0 m 19.68 ft Length 4,35 m 14.27 ft Height 1,23 m 4 ft Wing area 6,0 m2 64.6 ft2 Empty weight* 110 kg 245 lbs MTOM 240 kg 533 lbs Payload* 130 kg 289 lbs Maximum pilot weight 105 kg 233 lbs Tank capacity 28 l 7.4 US gal Engine power** 20,6 kW 28 HP Fuel consumption** 6 l/h 1.32 gal/h Service loads +4/-2 g
stall speed with flaps 39

At the moment I'm a college student, I also live in the Bahamas and later on in life I'd love to own and fly an airplane preferably a Cri-Cri, SD-1 or a Hummel Bird probably with floats lol:ban:
BTW I know these are great planes and reason many persons love them is because their cheap, compact and simple engines. But I've been wondering for a while why only build models with a single seat. I own an ATV and I can tell you, I can have fun on my own but when I have company the experience is fell 20 times better. So I thought why not add another seat.

Cri-Cri out of the pot, with some modifying to the kit during construction why not add tandem seats like in the AirBike to the SD-1 or Hummel Bird.

pilots and passengers of the Airbike have comented that the seating arrangement is quite comfortable and with the seats being so close together and the rear seat occupying baggage space the Cg wont be thrown off by much, add 5-12 inches to the cockpit while extending the wingspan by 2-5 feet help the wing loading and decrease stall speed.
The original SD-1 with its 19.6 foot wingspan and 28 hp engine can handle up to a payload of 289 pounds. 2 x 130 pound passenger =260 that leaves 30 pounds of fuel or roughly 5 gallons. with an extended wingspan and a beefer engine the payload would increase by much. Baggage could be placed under the seat or if there is no passenger his seat becames the baggage rack, The landing gear may need redesigning and the cockpit's changed shape minor but the SD-1 one is made of wood and it looks easy to modify



Please forgive my Naivety no matter how old we are all still learning
 

orion

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The reason you don't simply add a second seat is that you'll pretty much have a new airplane, which you have to re-engineer, almost like a new design, especially if you don't have the original analysis. With two seats you have a wider operational CG range, which affects stability and control issues, and you have more weight, which affects all the structural components. Furthermore, with two seats you'll most likely need more power, which again can affect the stability and control characteristics and of course adds more weight and affects more structure in turn. In the end, you have a new airplane so you might as well design one from scratch.
 

lr27

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Nov 3, 2007
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130 pounds? Unless you are a sworn vegetarian and marathon runner, with knees insured by Lloyds of London, or are quite short, don't count on always weighing that little! Especially if you start building instead of running.

A mentioned, there are LOTS of two place, low wing designs out there already. Have you looked, for instance, at the KR2?
 

Dana

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The whole point of the Cri-Cri is to built a very tiny plane. The designer succeeded admirably. As soon as the requirements include a second person, the whole design changes.

-Dana

Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.
 

rbrochey

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Oct 17, 2010
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I've been doing kitplane research probably too long, but have decided on the SD-1 for a variety of reasons. I have also started a builders group that anyone interested in the SD-1 can join. The dealer you refered to is no longer handling the plane. I'm going to begin ordering sub-kits November 1. The building site is: SD1Minisport : SD-1 MiniSport Aircraft Thanks

Robert
 

rbrochey

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Will do! I talk with him fairly often and he has been great at answering all my questions... I want to do a couple minor mods and he has been very positive about it including the best engine for my altitude.
 

kennyrayandersen

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Jun 6, 2011
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Ft. Worth TX
How about an update to the thread -- did you order plans/parts for the SD-1? How's the build coming? Inquiring minds want to know!
 
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newimaging

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Jun 29, 2011
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Los Angeles, CA
Interesting idea, I always loved the Cri-Cri. I am trying to get our EAA Chapter a bit more active, so I build a new website, and started a "Design Group Forum Topic"
I`ve been running into Burt`s Boomerang at several airshows, and thought a great first brainstormer to a project would be a mix of the Boomerang and a Cri-Cri. I know it sounds kinda crazy, but will sure get some conversation going, which is what its all about. If anyone is interested, I`d love to have you join the discussion

"Mini Boomer" Design
 
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topspeed100

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130 pounds? Unless you are a sworn vegetarian and marathon runner, with knees insured by Lloyds of London, or are quite short, don't count on always weighing that little!?
Right I am 240 lbs and and two my calibre dudes with rug sacks are 500 lbs. The airbike seating can only work in an airbike type o plane. However having said that I did try in several sketches to imply the White Lightning seating where the backseater is facing rear..that enables the best CG positioning and aerodynamical shape for the fuse.
 

Aircar

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Newimaging et al --your 'Miniboomer' link doesn't work for me --maybe it has expired but from the context I gather it might be a twinned CRI CRI as in two fuselages (four engines) and a new centre section joining the two hulls -- seems that twin bodies are back in the Zeitgeist what with Burt Rutan's BiPod the pipistrel G4 Brown CarPlane etc .

This would seem to be a feasible concept to me -- doubling the fin area is especially good since the moment of inertia of the two bodies in yaw goes up markedly but you can use the self same components pretty much and in fact add extra wing area in the centre section plus you lower the span loading greatly --you probably would want to use only one mainwheel on each hull rather than duplicate the spring gear or maybenot .

The bonded aluminum skin construction is as for the schreder sailplanes that I worked on and later also built an ultralight with 0.016 2024 bonded skins on hot wired in place styrofoam ribs --worked well .

I knew Morry Hummel quite well (lived around the block from him in Bryan Ohio )and admired the Hummel bird (converted from Windwagon using new fuselage skins and HP glider canopy etc plus Morry's 1/2 VW ) -- doing a Siamese twin version as a two seater would be a bit more difficult as losing one motor out of two is worse than one out of four in assymetrics and total thrust but as Morry used to say "friends don't let friends fly two strokes"
 

Aircar

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A second thought --can anyone photoshop a twinned CRI CRI perhaps ? --how about using one horizontal tail to join the fins (OV 10 Bronco style ) . Would it now be a CRI CRI CRI CRI ?

I will post a few of my mad twinned concepts on this thread and see what the reaction is -- the previous comments 'debunking' the idea of shoehorning a second pilot into something as tightly constrained as either a CRI CRI or hummel bird are quite true but the thought of "Twin Mustang" treatment is worth some consideration perhaps -- the Fouga Gemenaux is another duplicated design that comes to mind --the use of pre existing detail components and starting from existing hardware needs consideration. (even re mounting engines on the centreline eliminates the engine out case --push pull is possible also ..........
 

Aircar

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Excellent link Newimaging --and 'open source' concept (the Ligeti Stratos was similarly offered as open source but it has inherent problems --it went in inverted killing the designer . I was involved inadvertently from the very start after showing Charles the Lippisch design with the configuration and discussing the 'bullroarer' descent of the easy Riser biplane shown on a video at a meeting of the ultralight group ....... alas )

The assymetric layout is much more complex than duplicate bodies and identical outer wings etc as for CRI CRI -- re locating the engines and props of the CRI CRI to the centre section makes sense (and the airflow effect around the canopy with one engine out is unneccesary ) --the Swedes designed an assymetrical aircraft in 1943 --very much like the well known Blohm und Voss recon design --their's was called Tungt Jaktflygplan (sounds like 'fighterplane' -drawing shows six cannon )-- it had push pull engines driving contrarotating pairs of props at each end .

Better to go with doubled up standard components where possible -- three CRI CRI pods if you want three seats I guess Or back to back seating in one pod .... or....
 

Aircar

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Maybe readers could look at "multi body designs" and "twin Cozy" for other thoughts on older threads --the idea of reducing structure weight in a two seater by having separate pods spread along a wing was proposed by Cmdr Nick Goodhart as a way to get a workable TWO man powered aircraft by reducing structural weight, increasing span greatly and also giving yaw by differential thrust (the Toucan and Hertforshire two seat/ one fuselage MPAs hoped to get a better power to weight ratio than singles --something like the present GFC favouring multiseat aircraft in terms of economy as seat miles per gallon.
 
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