Low aspect ratio sport plane ideas

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

AhzeeDahak

Member
Joined
Apr 8, 2020
Messages
7
I have been working for a while on a design that is very close to the goals of this thread (trailerable LAR LSA) but just slightly outside the OP’s goals (7’6” width folded, 2.1 AR.)

I made the decision to go with a fuselage pod below the wing in order to make ingress/egress easier, make the landing gear simpler and stronger, and to provide better visibility for training purposes. The recent turn in the conversation made me think it might be appropriate here.

I don’t want to hijack the thread if this is too far afield. Would there be interest in my posting the three-view here?
 

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
I have been working for a while on a design that is very close to the goals of this thread (trailerable LAR LSA) but just slightly outside the OP’s goals (7’6” width folded, 2.1 AR.)

I made the decision to go with a fuselage pod below the wing in order to make ingress/egress easier, make the landing gear simpler and stronger, and to provide better visibility for training purposes. The recent turn in the conversation made me think it might be appropriate here.

I don’t want to hijack the thread if this is too far afield. Would there be interest in my posting the three-view here?
Share it here. It seems to be totally on topic. Here are my most recent drafts. One edition with central wheels and another with more know trigear.
 

Attachments

  • E6AB4507-B16E-49E8-BED1-1048EC5F8FC4.png
    E6AB4507-B16E-49E8-BED1-1048EC5F8FC4.png
    240.8 KB · Views: 22
  • AC2EB1D9-2E27-4AE7-A9F1-319D7F7D1447.png
    AC2EB1D9-2E27-4AE7-A9F1-319D7F7D1447.png
    262.3 KB · Views: 21
  • 4BA1CFA7-F62A-47F7-B080-31BD212783A6.png
    4BA1CFA7-F62A-47F7-B080-31BD212783A6.png
    235.7 KB · Views: 19
  • CE923F3A-3FC8-4903-A78C-3BFA369B626C.png
    CE923F3A-3FC8-4903-A78C-3BFA369B626C.png
    226.1 KB · Views: 19
  • 85BA669C-823E-4E5B-92E9-5FB689629B31.png
    85BA669C-823E-4E5B-92E9-5FB689629B31.png
    238 KB · Views: 19
  • 1CC8C6D2-9051-478C-BE41-7A4F71EFF894.png
    1CC8C6D2-9051-478C-BE41-7A4F71EFF894.png
    236.4 KB · Views: 18

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
By the way ... here is my first attempt to have the pod only at the upperside. I admit ... it is not a beauty.
View might be better. Looks are less.
 

Attachments

  • F97379C6-765B-4709-922C-2C6157C0B6AC.png
    F97379C6-765B-4709-922C-2C6157C0B6AC.png
    240.9 KB · Views: 13
  • 22548B69-A475-42D2-BE8C-E361B48B0260.png
    22548B69-A475-42D2-BE8C-E361B48B0260.png
    226.9 KB · Views: 11
  • 5D932F72-937B-4339-96DC-80277B372040.png
    5D932F72-937B-4339-96DC-80277B372040.png
    208.5 KB · Views: 9
  • 169CD62E-890E-4A65-91EB-D623F2D70055.png
    169CD62E-890E-4A65-91EB-D623F2D70055.png
    211.7 KB · Views: 13
  • 637839FB-9409-48D9-86E0-0C7AA84AC1C2.png
    637839FB-9409-48D9-86E0-0C7AA84AC1C2.png
    244.4 KB · Views: 14

Vigilant1

Well-Known Member
Supporting Member
Joined
Jan 24, 2011
Messages
7,892
Location
US
Opinion (general): Any hoped-for visibility at low grazing angles through glazing may prove quite disappointing, especially if it is impractical to put dark, matte material in the illuminated part of the nearby interior. Also, pilot sightlines should include the need to put instruments in a convenient spot.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
2,772
Location
Canada
Opinion (general): Any hoped-for visibility at low grazing angles through glazing may prove quite disappointing, especially if it is impractical to put dark, matte material in the illuminated part of the nearby interior. Also, pilot sightlines should include the need to put instruments in a convenient spot.

Good suggestion about painting the back side of cockpit structural members matte black to minimize contrast and glare.

As for instrument panel location ... Start by bolting instruments to the backside of a structural member (ala. Bensen gyro-copter).
Alternately, "install" all the instruments in an iPad and bolt the iPad to a swivelling mount. The swivelling mount will allow you to shift the iPad around the cockpit until you reach a happy medium.
 

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
Opinion (general): Any hoped-for visibility at low grazing angles through glazing may prove quite disappointing, especially if it is impractical to put dark, matte material in the illuminated part of the nearby interior. Also, pilot sightlines should include the need to put instruments in a convenient spot.
If you are refering that the angle between line of vision and plane of window needs to be not shallow (for example values larger than 30 degrees) i understand your point of view. The chance to glare in the glazing gets bigger at shallow angles.
About instruments: I am sure my FAR103 design will have as little instruments as possible. No need for artificial horizon and so. I once met a frenchman who flew with only the Mignet spring speed indicator under his high wing. I asked why not a altimeter? He said: its very simple. If sheeps are small dots, you are high. If sheeps are large recognisable shapes, you are low. If you landed and see the sheep have horns, you are in trouble.
Placement of instruments is best in neighborhood of normal line of sight while flying, but i have seen a lot of weird locations of instruments. As long as you can be happy yourself it is ok for me.
 

cluttonfred

Well-Known Member
Supporting Member
Joined
Feb 13, 2010
Messages
9,523
Location
World traveler
The “all undeneath” pod variant is cuter than I thought it would be. I would give it it taller landing gear, both to get the pilot’s rear end higher off the ground and to allow access to the cockpit without crawling. Otherwise, it works very well in my opinion.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
2,772
Location
Canada
"
... Placement of instruments is best in neighborhood of normal line of sight while flying, but i have seen a lot of weird locations of instruments. As long as you can be happy yourself it is ok for me.

Yes.
During my numerous sketches of a BV141 replica, I noticed that the original had a narrow strip of 7 basic instruments along the top of its windshield. This fits with the original mission of artillery spotter, hence the emphasis on downwards visibility. Most of my sketches retain the same "eyebrow" instrument panel supplemented by an iPad for a GPS moving map display. The iPad would fold out of the way - beside the throttle - similar to the drinks trays in airliners.
 

erkki67

Well-Known Member
Joined
Feb 18, 2010
Messages
2,756
Location
Romont / Fribourg / Switzerland
Share it here. It seems to be totally on topic. Here are my most recent drafts. One edition with central wheels and another with more know trigear.

for this layout, go with a 4 Wheel taildragger with the tail wheels attached to the inbd section of the 3 part construction.
For the steering on ground you have several options, even non conventional ones.
 

rotax618

Well-Known Member
Joined
Oct 31, 2005
Messages
1,594
Location
Evans Head Australia
The design seems like it will have poor yaw control, immediate control of yaw without an immediate roll response is necessary for takeoff when only the nosewheel is in contact with the ground - the ”winglets” will probably be ok when you are clear of the ground but Nostradamus can see a problem.
 

AhzeeDahak

Member
Joined
Apr 8, 2020
Messages
7
Here is the podded LSA I've been working on. Side doors and side stick for easy access. Rear seat elevated 6" above the front for forward visibility for both pilots. Solo from the front. Gear sized for 10fps decent rate. Sized for 80-120HP motors.
 

Attachments

  • Witchmoth 3-View.pdf
    1.5 MB · Views: 63

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
The design seems like it will have poor yaw control, immediate control of yaw without an immediate roll response is necessary for takeoff when only the nosewheel is in contact with the ground - the ”winglets” will probably be ok when you are clear of the ground but Nostradamus can see a problem.
I guess soon you will post "I TOLD YOU" :D
 

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
Here is the podded LSA I've been working on. Side doors and side stick for easy access. Rear seat elevated 6" above the front for forward visibility for both pilots. Solo from the front. Gear sized for 10fps decent rate. Sized for 80-120HP motors.
Looks like you have been working on this idea for some time. Impressive. Looks like ideal for reconnaissance (spelling??).
I just wonder about one thing. Placing the prop totally under the huge wing, without any prop flow over the wing, will that not give a bad influence? Remember, i am not a engineer. Just a thinker.
 

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
I just did a rough calculation. I calculated the frontal area of the different wings to compare the difference. At first i had to say that thick airfoils really sucked. Gaining nearly 50% in frontal area. But than i made a rough estimate of the added fuselage needed to house the pilot. And now the numbers are getting closer to each other. The winner would have been a Horten airfoil with a root chord thickness of 22 and all the other ribs at 14%. The next in line are the Marske airfoil wings with 12.7% thickness. There is little difference between the upperpod and the semi-pod (edition with tiny upperpod and some underpod). The Horten airfoil which changed from 20% to 12% thickness is the next in line.
The ones who had the worst frontal area are the overal 19% thick wing and the thin wing with the underpod.
Here are the numbers:
2022-05-30 comparing frontal areas.PNG
But now ... what would be a good choice to make. You might think differently but my brains would say: "take the thin wing with the semi-pod". Why? Because it gives the possibility too to have shorter landing gear legs. And the glazing of the leading edge is not so large.

Again ... i repeat ... the areas of the added pods are ESTIMATES. Don't shoot me if i did it wrong.
 

U+fly

Active Member
Joined
Nov 25, 2021
Messages
38
By the way ... here is my first attempt to have the pod only at the upperside. I admit ... it is not a beauty.
View might be better. Looks are less.
Well, if you do use the "Cri-Cri" canopy, it could look very slick (all transparent) and the yaw stability may be OK, with your winglet/rudder at about the same distance back as the "Cri-Cri" (and you have 2)
 

Attachments

  • CriCri_0.jpg
    CriCri_0.jpg
    122.9 KB · Views: 10
  • cricri_eclate_1600x1158.jpg
    cricri_eclate_1600x1158.jpg
    153.4 KB · Views: 9

cluttonfred

Well-Known Member
Supporting Member
Joined
Feb 13, 2010
Messages
9,523
Location
World traveler
Quick thought...with the "all underneath" pod, why not go with a single rudder with most of its area below the wing and simple trailing edge elevons? You could end the pod in a rudder post or use a couple of struts to support an all-moving surface like the Mignet HM.160. Control runs get simpler with a pushrod or two cables straight back to the rudder and cables or pushrods to the elevons. It would be easy enough to have have a few removable pins that allow the rudder to fold 90° and the elevons to disconnect and still allow the wings to fold.
 

nestofdragons

Well-Known Member
Joined
Jun 8, 2016
Messages
717
Location
Near Antwerp, Belgium
I am also wondering how much parasite drag will influence the numbers in my Excell. I guess that the upper and lower pods with the thin wing (M35A airfoil) will no longer be that good. Semi-pod might still be good. I guess it will have less parasite drag.

How bad is my thinking here? 🤔 🤔 🤔 🙈🙈🙈
 

challenger_II

Well-Known Member
Joined
Jul 15, 2009
Messages
1,084
Location
Fisher County, Tx. USA
On another note:
All of the design concepts that have been depicted in this thread, the pilot has been placed rather far back. With LAR planforms, be they circular, delta, or rhomboid, it has been my experience that the major mass needs to be kept ahead of 25% Mean Aerodynamic Chord to get the bird to fly right. Any slight aft CG, and the bird is hugely unstable and wants to dutch roll badly.
 
Top