Page 4 of 5 FirstFirst 1 2 3 4 5 LastLast
Results 46 to 60 of 65

Thread: Penrose Gremlin

  1. #46
    Registered User
    Join Date
    Oct 2012
    Location
    Denver, CO
    Posts
    198
    Likes (Given)
    150
    Likes (Received)
    42

    Re: Penrose Gremlin

    Quote Originally Posted by Sockmonkey View Post
    And of course my own vision of a tandem seaplane.
    A short drive shaft would move the prop aft of the wing to prevent interference and shield the prop from spray.
    Forget about the ultralight affordaplane replacement, Let's build your seaplane. It looks great!

  2. #47
    Registered User
    Join Date
    Sep 2014
    Location
    Canada
    Posts
    1,052
    Likes (Given)
    7
    Likes (Received)
    288

    Re: Penrose Gremlin

    Your sketch reminds us of the 1938-vintage Dornier 212 experimental four-seater. The engine was mounted amidship and drove the propeller through a long drive shaft. The drive shaft could tilt to raise the propeller above the waterline. During its sole flight, the prototype suffered problems with its drive shaft and stability. Photographs hint that Dornier tried to balance the 212 like a conventional airplane, but it was short-coupled and even a massive horizontal tail did not provide enough stability.

    Your idea to incorporate a lifting rear wing would allow mounting the propeller far enough aft to eliminate the pesky drive shaft. I would be inclined to mount the propeller above the trailing edge .... to reduce spray ingestion.

  3. #48
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    Quote Originally Posted by Riggerrob View Post
    Your sketch reminds us of the 1938-vintage Dornier 212 experimental four-seater. The engine was mounted amidship and drove the propeller through a long drive shaft. The drive shaft could tilt to raise the propeller above the waterline. During its sole flight, the prototype suffered problems with its drive shaft and stability. Photographs hint that Dornier tried to balance the 212 like a conventional airplane, but it was short-coupled and even a massive horizontal tail did not provide enough stability.

    Your idea to incorporate a lifting rear wing would allow mounting the propeller far enough aft to eliminate the pesky drive shaft. I would be inclined to mount the propeller above the trailing edge .... to reduce spray ingestion.
    Yep, the prop is above the trailing edge of the rear wing. The wings are in pou configuration, it's just hard to tell from the angle. The bottoms of the rudders also serve as the outriggers.

  4. #49
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    Here's a less fugly version of the delta-tailed sea-era inspired design.
    Elevons on the rear wing with the fore wing being a solid unit that can be tilted for takeoff and trim adjustment for varying passenger/cargo loads.
    Note that the rear wing is not reflexed.

  5. #50
    Registered User cluttonfred's Avatar
    Join Date
    Feb 2010
    Location
    World traveler
    Posts
    6,211
    Likes (Given)
    1925
    Likes (Received)
    2153

    Re: Penrose Gremlin

    Getting back to the original Penrose Gremlin concept, I have in mind something more like an enclosed, sleeker version of the Sunny Boxwing without the joined tips. For a single-seater with a light paramotor engine I think you could put the pusher prop aft of the rear wing trailing edge to allow a larger diameter, though turbulent flow makes for a noisy prop.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	penrose gremlin color.gif 
Views:	4 
Size:	13.3 KB 
ID:	78567  
    *******
    Matthew Long, Editor
    cluttonfred.info
    A site for builders, owners and fans of Eric Clutton's FRED and other safe, simple, affordable homebuilt aircraft

    « Voici ce que j'ai fait...vous pouvez en faire autant! »
    "This is what I have done...you can do the same!"
    --Henri Mignet (1893-1965)

  6. #51
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    Did the gremlin use the same fore-aft wing interaction for pitch stability that the pou did?

  7. #52
    Registered User cluttonfred's Avatar
    Join Date
    Feb 2010
    Location
    World traveler
    Posts
    6,211
    Likes (Given)
    1925
    Likes (Received)
    2153

    Re: Penrose Gremlin

    I don't have any weights or dimensions for the Penrose Gremlin, just the two letters to the editor and one 3-view from Harald Penrose. I do have details on the Delanne 20-T however:

    DELANNE 20-T
    Data from l'Aérophile December 1941

    General characteristics
    Crew: Two
    Length: 6.78 m (22 ft 3 in)
    Wingspan: 7.86 m (25 ft 9 in) forward wing, rear wing 5.66 m (18.6 ft)
    Height: 2.40 m (7 ft 10 in)
    Wing area: 14 m2 (150 sq ft) total, both wings
    Empty weight: 730 kg (1,609 lb) [9]
    Gross weight: 1,031 kg (2,273 lb) [9]
    Powerplant: 1 × Régnier 6 B-01 6-cylinder air cooled inverted inline, 130 kW (180 hp) (at 2,200 rpm[1])
    Propellers: 2-bladed Ratier 1380, 2.10 m (6 ft 11 in) diameter , variable pitch
    Performance
    Maximum speed: 262 km/h (163 mph; 141 kn)
    Minimum control speed: 70 km/h (43 mph; 38 kn)

    Going with single-seat microlight gross weight of 300 kg but reducing the wing loading by 50% and increasing the power loading by 33% for a microlight (proportionally more wing area and less power compared to 20-T), I get these rough numbers: 300 kg/661 lb gross, 39 hp, 8.15 m2/88 sq ft wing area, 5.2 m/17' length, 6.0 m/19' 8" front wing span, 4.3 m/14' 1" rear wing span.

    I could see reducing the aspect ratio to get the span even smaller, say 5.0 m/16' 5" span for the front wing, and also getting the overall length down to about 4 m without the long inline engine and rear fairing of the 20-T. That's down around Baby Great Lakes size, smaller than a Smith Miniplane! At that size it would be easy to build each wing in one piece from tip to tip and you could hangar the plane in an inexpensive prefab garage, shed, or Quonset hut as small as 5.5 m x 5.5 m/18' x 18' square.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	1024px-Delanne_20-T-2_photo_L'Aerophile_December_1941.jpg 
Views:	2 
Size:	50.2 KB 
ID:	78570   Click image for larger version. 

Name:	Delanne_20-T-2_3-view_L'Aerophile_December_1941.jpg 
Views:	3 
Size:	48.0 KB 
ID:	78571  
    *******
    Matthew Long, Editor
    cluttonfred.info
    A site for builders, owners and fans of Eric Clutton's FRED and other safe, simple, affordable homebuilt aircraft

    « Voici ce que j'ai fait...vous pouvez en faire autant! »
    "This is what I have done...you can do the same!"
    --Henri Mignet (1893-1965)

  8. #53
    Registered User cluttonfred's Avatar
    Join Date
    Feb 2010
    Location
    World traveler
    Posts
    6,211
    Likes (Given)
    1925
    Likes (Received)
    2153

    Re: Penrose Gremlin

    Quote Originally Posted by Sockmonkey View Post
    Did the gremlin use the same fore-aft wing interaction for pitch stability that the pou did?
    Delanne's designs did not use a Mignet-style variable-incidence front wing to control pitch but I have seen conflicting reports on whether the pitch and roll control was divided between the two wings or not. Penrose seems to have envisioned straightforward elevators on the rear wing and ailerons on the front wing, which I believe was how the Westland P.12 was set up. That's where I would start, though it would be interesting to play around with elevons on the rear wing and simple flaps on the front wing.
    *******
    Matthew Long, Editor
    cluttonfred.info
    A site for builders, owners and fans of Eric Clutton's FRED and other safe, simple, affordable homebuilt aircraft

    « Voici ce que j'ai fait...vous pouvez en faire autant! »
    "This is what I have done...you can do the same!"
    --Henri Mignet (1893-1965)

  9. #54
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    I should clarify.
    Even without the variable incidence front wing, the downwash from it might increase the lift of the rear wing. If so, deflecting both fore wing ailerons down would have the same effect and eliminate the need for elevators on the aft wing, thus reducing the parts count and number of control runs.
    If you were willing to settle for two-axis control, fore wing elevons means you could use fixed rudders and not need any runs through the aft fuselage.

    Also, if the fore and aft wings do interact, then both will contribute to roll authority even with control surfaces only on the front wing.

  10. #55
    Registered User cluttonfred's Avatar
    Join Date
    Feb 2010
    Location
    World traveler
    Posts
    6,211
    Likes (Given)
    1925
    Likes (Received)
    2153

    Re: Penrose Gremlin

    I would really like to steer this thread clear of the two-axis vs. three-axis Mignet formula debate. Delanne did espouse a version of the tandem wing "slot effect" discussed by Mignet and even a sort of "tunnel effect" due to the addition of the endplate rudders (see image below from Koen's Nest of Dragons site).

    Click image for larger version. 

Name:	delannecontrol.jpg 
Views:	1 
Size:	23.5 KB 
ID:	78572

    That said, all the Delanne designs had three-axis controls as far as I know. I believe that elevons on the front wing only would be a bad idea as you'd lose two axes of control at once at the stall. Like I said, I'd probably start with ailerons in front and elevators at the rear but I'd be interested in the possibility of rear elevons as a possible simplification.
    *******
    Matthew Long, Editor
    cluttonfred.info
    A site for builders, owners and fans of Eric Clutton's FRED and other safe, simple, affordable homebuilt aircraft

    « Voici ce que j'ai fait...vous pouvez en faire autant! »
    "This is what I have done...you can do the same!"
    --Henri Mignet (1893-1965)

  11. #56
    Registered User
    Join Date
    Sep 2014
    Location
    Canada
    Posts
    1,052
    Likes (Given)
    7
    Likes (Received)
    288

    Re: Penrose Gremlin

    Dear Sockmonkey,

    Pretty sketch. If you can pivot that main wing to stow fore-and-aft (ala. CV-22 Osprey VTOL) you could dock in a regular marina slip.
    If the aft delta wing is less than 8 feet wide, you could trailer it home or store it in an ISO shipping container.

  12. #57
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    Quote Originally Posted by cluttonfred View Post
    I would really like to steer this thread clear of the two-axis vs. three-axis Mignet formula debate. Delanne did espouse a version of the tandem wing "slot effect" discussed by Mignet and even a sort of "tunnel effect" due to the addition of the endplate rudders (see image below from Koen's Nest of Dragons site).

    That said, all the Delanne designs had three-axis controls as far as I know. I believe that elevons on the front wing only would be a bad idea as you'd lose two axes of control at once at the stall. Like I said, I'd probably start with ailerons in front and elevators at the rear but I'd be interested in the possibility of rear elevons as a possible simplification.
    Yeah, I've gone over the material on his site. Love that place.
    With tandems the front wing is supposed to immediately drop a little and un-stall, so it's probably not a deal-breaker. You would have to keep fighting to stall it in order to lose control.
    If the rear wing is the short one you might lose a little roll authority with just elevons, but probably not enough to be troublesome. The slot effect likely compensates as the good low-speed control was mentioned. The short lever arm means the rear wing with elevons would have to be just as beefy as the main wing though.
    The longer strut-braced front wing would be easy to make foldable.
    I can see a potential positive with using elevators on the rear wing in that you could get away with having the wings be closer together than can get away with on a flea.
    The slot between them is a fixed size so you can shrink it down to the limit, and pushing down on the tail rather than pulling up with the fore wing means you can pull out of a sharp dive.
    Quote Originally Posted by Riggerrob View Post
    Dear Sockmonkey,

    Pretty sketch. If you can pivot that main wing to stow fore-and-aft (ala. CV-22 Osprey VTOL) you could dock in a regular marina slip.
    If the aft delta wing is less than 8 feet wide, you could trailer it home or store it in an ISO shipping container.
    Thank you. It's a 3-D sketchup model actually. Yep, the wing pivots. The delta on a small one-man version would just be eight feet.

  13. Likes spaschke liked this post
  14. #58
    Registered User cluttonfred's Avatar
    Join Date
    Feb 2010
    Location
    World traveler
    Posts
    6,211
    Likes (Given)
    1925
    Likes (Received)
    2153

    Re: Penrose Gremlin

    Here's a question....

    Except for the early gull-wing types, Delanne's own designs all seemed to use varying sweep between the forward and rear wings so that the wing roots were closer together than the wing tips. I don't mean artists' impressions, I mean drawings or models or full-size aircraft by Delanne himself such as this image from a 1950 Air Trails article.

    Click image for larger version. 

Name:	delanne mag pic trimmed.jpg 
Views:	21 
Size:	67.0 KB 
ID:	78625

    Any thoughts on why? I ask because I prefer the simplicity of unswept, constant-chord wings, but I am wondering if there is a downside that I am missing in this configuration.
    *******
    Matthew Long, Editor
    cluttonfred.info
    A site for builders, owners and fans of Eric Clutton's FRED and other safe, simple, affordable homebuilt aircraft

    « Voici ce que j'ai fait...vous pouvez en faire autant! »
    "This is what I have done...you can do the same!"
    --Henri Mignet (1893-1965)

  15. #59
    Registered User
    Join Date
    Apr 2014
    Location
    Flint, Mi, USA
    Posts
    1,483
    Likes (Given)
    390
    Likes (Received)
    391

    Re: Penrose Gremlin

    Quote Originally Posted by cluttonfred View Post
    Here's a question....

    Except for the early gull-wing types, Delanne's own designs all seemed to use varying sweep between the forward and rear wings so that the wing roots were closer together than the wing tips. I don't mean artists' impressions, I mean drawings or models or full-size aircraft by Delanne himself such as this image from a 1950 Air Trails article.

    Click image for larger version. 

Name:	delanne mag pic trimmed.jpg 
Views:	21 
Size:	67.0 KB 
ID:	78625

    Any thoughts on why? I ask because I prefer the simplicity of unswept, constant-chord wings, but I am wondering if there is a downside that I am missing in this configuration.
    Was wondering about those things too. Sweeping them puts the tip rudders further back, lets the fuselage be shorter and lighter, and clusters all the heavier hardpoints where the wings attach into one place, which also saves weight. I think it also gives you a tad more wiggle room on where the CG is.
    For downsides, a swept wing tends to have more twisting force applied to the root unless it's really low aspect yes?
    That's going to apply to any swept wing regardless unless it's a flying wing type craft.
    I'm not sure how the sweep affects the interaction between the fore and aft wings. If they're more than a couple chord lengths apart vertically and horizontally, probably not enough to worry about. If they're close enough together for the dpwnwash from the front wing to increase the lift of the rear wing, (which happens even without a moving fore wing) then I don't think it would screw anything up, but I don't know for sure.

  16. #60
    Registered User Tiger Tim's Avatar
    Join Date
    Apr 2013
    Location
    Thunder Bay
    Posts
    2,589
    Likes (Given)
    1381
    Likes (Received)
    1451

    Re: Penrose Gremlin

    Quote Originally Posted by cluttonfred View Post
    Click image for larger version. 

Name:	delanne mag pic trimmed.jpg 
Views:	21 
Size:	67.0 KB 
ID:	78625
    I love that half of the models on that table look to be profile balsa chuck gliders, and that big model at the back is really something.

  17. Likes Sockmonkey liked this post

Posting Permissions

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