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philr

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Dec 26, 2020
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99
I also love the concept and think it could find a ready audience, but my initial reaction was that the fuselage and boom are a bit too complex. I think that coming to a point at the bottom of the point-down triangular boom and then going back out again for the rest of the triangle makes the structure very busy.

I would use the triangular boom from engine to tail but base down, point up (except in the last bay at the tail the two base tubes come together at the tail post). You could move the horizontal stabilizer to the bottom of the boom if desired and even have a triangular fuel tank. Now the top of the triangular truss forms the attach points for the wings just like triangular cabane struts and all the "frames" that form the sides and back of the fuselage can be simple rectangles or trapezoids with X-bracing or corner bracing. The seat back, for example, would be a single rectangle or trapezoid all the way up to the bottom tubes of the truss.

Another approach would be to eliminate the triangular truss boom from the forward fuselage, and instead bring everything to a point like triangular cabane struts, then built out the existing triangle behind the pilot's head to form the boom for the tail. This reduces the parts count considerably but does't really work with your engine location. It would work with a paramotor engine as a tractor on the nose of the pod or a pusher behind the pod. Taken to its logical conclusion you end up with something all triangle like Ed Fisher's Flitplane.

View attachment 112039
1624051033850.png
I removed a few pieces of tubing that now that you mentioned it seemed redundant. I really dont want to build a parasol as I want to be able to attach doors and close it in and it is higher to allow for better forward view under the engine. Structure behind seat for float mounts or tricycle gear maybe. I would build it in 2 pieces boom upside down flat on the table and cage with the floor flat on the table then suspend the boom over head and bend in the cabines cut fit and weld. Current weight for fuse tubing is 32 lbs wing aluminum is 28 lbs.
 

cluttonfred

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Yes, that does seem simpler, glad that my comments were helfpful. It's an appealing design and looks like great fun! I don't have the skills to do a stress analysis but you'll definitely want to do that to optimize the structure and minimize the number of tubes and junctions. Good luck, I hope you build it!
 

challenger_II

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Fisher County, Tx. USA
For the short span of the lower longeron, 7/8" may be overkill (and heavy, in the area you are wanting to keep light). You may wish to explore what other folks have used, in an "ultralight" aircraft steel tube structure. Quite a few examples out there, for reference. From looking at your drawing, I would guess the span of the lower longeron, from tail post to where the frame expands at the cabin area, to be about 6ft, give or take. For the anticipated flight loads of a bird with a max speed of 80mph, I would believe 5/8" x .049 wall to be adequate, if the diagonal bracing is tailored to properly direct the stresses.
Your mileage may vary.

Yes I hope to have an engineer look at this and advise. Since this is open source I dont have a budget for paying an engineer ..looking for a volunteer.
Current idea is to use 7/8" tube for the single longeron.
 

Victor Bravo

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I vote against the 2 small tubes as main spars.

One of the things that happens all the time is that someone doesn't truly understand just how hard it is to make a compliant 103 ultralight out of any traditional non-exotic material. You wind up having to use materials in their best possible shapes, and making the fullest use of whatever property they have. There are exceptions (notably the Kolb Firefly), but for the most part if you want to use metal for the wing spar in a true 103 UL, you're going to want all the mass of the spar caps as far apart as humanly possible (meaning within the thickness of the !(#*$ fabric) from the upper and lower surfaces of the airfoil.

This means extruded T-bars or angles or channels with the heavier parts of the extrusion as the caps.

My guess is that a shear web between the spar caps will increase the overall bending strength of the spar two or three times. The real engineers here can validate or de-bunk that guess.
 

pylon500

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Location
Taree Airport Australia
I vote against the 2 small tubes as main spars.

One of the things that happens all the time is that someone doesn't truly understand just how hard it is to make a compliant 103 ultralight out of any traditional non-exotic material. You wind up having to use materials in their best possible shapes, and making the fullest use of whatever property they have. There are exceptions (notably the Kolb Firefly), but for the most part if you want to use metal for the wing spar in a true 103 UL, you're going to want all the mass of the spar caps as far apart as humanly possible (meaning within the thickness of the !(#*$ fabric) from the upper and lower surfaces of the airfoil.

This means extruded T-bars or angles or channels with the heavier parts of the extrusion as the caps.

My guess is that a shear web between the spar caps will increase the overall bending strength of the spar two or three times. The real engineers here can validate or de-bunk that guess.
Pretty much agree what you're saying here, more importantly, just having the two spar cap tubes like that, and nothing else, give no torsional strength to the wing, and as the wing is viewed as supported by only a single strut, it will twist all over the place.
Interesting history note, my first ultralight (that was built by somebody else), was a (bad) clone of a Winton Cricket, which used heavy tubes for the caps, and only a few assorted shear webs (😱) and then relied on a cable attached to the trailing edge to stop twist.
Unfortunately it only stopped the wing twisting upwards, but not downwards, so when you applied aileron, they would work like trim tabs and twist the wing giving aileron reversal :oops:😱.
I made new wings with a simple capped web spar, moulded fibreglass ribs (wouldn't do that again), and sheeted leading edge to form a 'D' tube. Retained the single strut and never had any twist.
26_CricketClone.jpg
Looking carefully at this photo, one can see I'm holding left aileron, and the ailerons are moved respectively, but you can notice the washout on each wing is different and the cable on the left trailing edge looks a little loose.
For anyone interested, that's a Yamaha RD350 motor bike engine. Lots of noise...

008_Finished_Cricket_wing.png
TLAR asked if I have drawings?
Unfortunately no.
The wing section was derived by drawing a 48" centre line, then adding an 8" vertical line 12" back from the leading edge, which was marked as a point 1" above the centre line at the leading edge, and then just drawing a pleasing curve to join all said points up!
Turned out to be something like one of the later Gottingen wing sections, and actually flew pretty nice.
Structurally the wing is a 0.016" spar web with 1/2"x1/2"x0.063" extruded bulbed stringer angle, solid riveted as caps.
Doublers of 0.025" at the wing attach and strut attach points are fitted, then 5/16'x1.0" straps for the actual pickups.
I think the rear spar was a 0.020" folded 'C' channel, also with matching doubler and straps as above.
All sheeting is 0.016", as is the entire aileron structure.
I just remembered I detailed this build in my Stollite description here; #14
I never weighed this wing, but I think was actually lighter than the original alloy tube spars and trailing edge, polystyrene and plywood ribs with fibreglass sheeted leading edge wings, and definitely stronger.
 

philr

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Joined
Dec 26, 2020
Messages
99
Pretty much agree what you're saying here, more importantly, just having the two spar cap tubes like that, and nothing else, give no torsional strength to the wing, and as the wing is viewed as supported by only a single strut, it will twist all over the place.
Interesting history note, my first ultralight (that was built by somebody else), was a (bad) clone of a Winton Cricket, which used heavy tubes for the caps, and only a few assorted shear webs (😱) and then relied on a cable attached to the trailing edge to stop twist.
Unfortunately it only stopped the wing twisting upwards, but not downwards, so when you applied aileron, they would work like trim tabs and twist the wing giving aileron reversal :oops:😱.
I made new wings with a simple capped web spar, moulded fibreglass ribs (wouldn't do that again), and sheeted leading edge to form a 'D' tube. Retained the single strut and never had any twist.
View attachment 112099
Looking carefully at this photo, one can see I'm holding left aileron, and the ailerons are moved respectively, but you can notice the washout on each wing is different and the cable on the left trailing edge looks a little loose.
For anyone interested, that's a Yamaha RD350 motor bike engine. Lots of noise...

View attachment 112100
TLAR asked if I have drawings?
Unfortunately no.
The wing section was derived by drawing a 48" centre line, then adding an 8" vertical line 12" back from the leading edge, which was marked as a point 1" above the centre line at the leading edge, and then just drawing a pleasing curve to join all said points up!
Turned out to be something like one of the later Gottingen wing sections, and actually flew pretty nice.
Structurally the wing is a 0.016" spar web with 1/2"x1/2"x0.063" extruded bulbed stringer angle, solid riveted as caps.
Doublers of 0.025" at the wing attach and strut attach points are fitted, then 5/16'x1.0" straps for the actual pickups.
I think the rear spar was a 0.020" folded 'C' channel, also with matching doubler and straps as above.
All sheeting is 0.016", as is the entire aileron structure.
I just remembered I detailed this build in my Stollite description here; #14
I never weighed this wing, but I think was actually lighter than the original alloy tube spars and trailing edge, polystyrene and plywood ribs with fibreglass sheeted leading edge wings, and definitely stronger.
Thanks for your reply here. I started out with a wing design from an Ultravia Super Pelican and figured out the weight and it seemed it would get too heavy. That was a D tube but someone told me .016 was too thin so my calculations were for .020. So I was looking for a lighter method and hoping this would be easy for scratch building. I read the thread you wrote on the Stollite and it looks great but aluminum ribs is what I would use if we go that direction. From what I can see so far I need the wing panel to weigh under 30 lbs before covering. The chord is 55" and the wing is 14' long. I know this type of wing is within my ability to build but could most builders scratch build this with aluminum formed sheet ribs and can we do it light enough?
 

philr

Well-Known Member
Joined
Dec 26, 2020
Messages
99
I vote against the 2 small tubes as main spars.

One of the things that happens all the time is that someone doesn't truly understand just how hard it is to make a compliant 103 ultralight out of any traditional non-exotic material. You wind up having to use materials in their best possible shapes, and making the fullest use of whatever property they have. There are exceptions (notably the Kolb Firefly), but for the most part if you want to use metal for the wing spar in a true 103 UL, you're going to want all the mass of the spar caps as far apart as humanly possible (meaning within the thickness of the !(#*$ fabric) from the upper and lower surfaces of the airfoil.

This means extruded T-bars or angles or channels with the heavier parts of the extrusion as the caps.

My guess is that a shear web between the spar caps will increase the overall bending strength of the spar two or three times. The real engineers here can validate or de-bunk that guess.
See my response to Pylon500 above. I want to design so that it will be strong light and easy to build...seems we may need to forget easy to build and go back to a aluminum D tube. Looking at easily found extrusions for spar caps what do you think makes sense. Pylon 500 said .016 for spar web and most parts. My reason for posting Hero here is the wealth of knowledge and I am sure to design a better plane if I get feedback here.
 

challenger_II

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Jul 15, 2009
Messages
496
Location
Fisher County, Tx. USA
If you do a weight comparison between a .020" formed-sheet rib, and a 1/2" (I do realize you have previously stipulated a 3/8" tube) rib, you will find the built-up tube rib to be lighter. It is, also, infinitely easier to form and build than a formed-sheet rib.
Some would suggest using .016" sheet for the ribs, but the flanges would have to be re-enforced, to prevent your rivets from pulling through.
For sheeting, .016" is rather delicate, and will be easily damaged when in use on the completed aircraft.
One might use a sheet "cuff" on the leading edge, and false ribs to maintain the leading edge profile in the wing section.


Just food for thought.
 

philr

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Joined
Dec 26, 2020
Messages
99
Pretty much agree what you're saying here, more importantly, just having the two spar cap tubes like that, and nothing else, give no torsional strength to the wing, and as the wing is viewed as supported by only a single strut, it will twist all over the place.
Interesting history note, my first ultralight (that was built by somebody else), was a (bad) clone of a Winton Cricket, which used heavy tubes for the caps, and only a few assorted shear webs (😱) and then relied on a cable attached to the trailing edge to stop twist.
Unfortunately it only stopped the wing twisting upwards, but not downwards, so when you applied aileron, they would work like trim tabs and twist the wing giving aileron reversal :oops:😱.
I made new wings with a simple capped web spar, moulded fibreglass ribs (wouldn't do that again), and sheeted leading edge to form a 'D' tube. Retained the single strut and never had any twist.
View attachment 112099
Looking carefully at this photo, one can see I'm holding left aileron, and the ailerons are moved respectively, but you can notice the washout on each wing is different and the cable on the left trailing edge looks a little loose.
For anyone interested, that's a Yamaha RD350 motor bike engine. Lots of noise...

View attachment 112100
TLAR asked if I have drawings?
Unfortunately no.
The wing section was derived by drawing a 48" centre line, then adding an 8" vertical line 12" back from the leading edge, which was marked as a point 1" above the centre line at the leading edge, and then just drawing a pleasing curve to join all said points up!
Turned out to be something like one of the later Gottingen wing sections, and actually flew pretty nice.
Structurally the wing is a 0.016" spar web with 1/2"x1/2"x0.063" extruded bulbed stringer angle, solid riveted as caps.
Doublers of 0.025" at the wing attach and strut attach points are fitted, then 5/16'x1.0" straps for the actual pickups.
I think the rear spar was a 0.020" folded 'C' channel, also with matching doubler and straps as above.
All sheeting is 0.016", as is the entire aileron structure.
I just remembered I detailed this build in my Stollite description here; #14
I never weighed this wing, but I think was actually lighter than the original alloy tube spars and trailing edge, polystyrene and plywood ribs with fibreglass sheeted leading edge wings, and definitely stronger.
I did a comparison like you suggested and you were right. I can make it lighter I am at 24 lbs for the main parts (no doublers, strut attachment fitting or fuse attach calculated yet). I first figured it out using mostly .016 but then checked .020 and this 24 lbs is .020 main spar web and rear C channel spar and ribs.
The ribs are 21" apart with a false rib between the drag box covers 2 rib bays top and bottom with .016. My thought is that with a few templates and a router and a flanging tool for the lightening holes I think I wouldn't have more time into it than built up wood ribs. What do you think?
RIBLETT 30_615 MODEL ONLY.jpg
 

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philr

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Joined
Dec 26, 2020
Messages
99
If you anyone is interested in this air foil Riblett 30-615 here is a spread sheet I made.Spreadsheet
I bought Harry Ribletts book GA Airfoils from EAA a few years ago. Very interesting and ground breaking I think, If you look at all the homebuilt designs using his airfoils there are some real performers. I saw one thread on here that did a comparison (I think it was a Peit) with the original airfoil and a Riblett airfoil. They obviously didn't read his book well. You cannot simply compare changing only the airfoil. Most aircraft if using a Riblett airfoil but still using a slab horizontal stabilizer will not stall the main wing but rather stall the tail. Harry advocates using a long tail length (chord x 3 currently my design is only 2 x chord would like it longer but pounds ad up) and a high aspect ratio horizontal stab with a symmetrical 6% thick airfoil . Also since the airfoils behave very well at high angles of attack having CG at 35% is very possible these changes net a higher cruise due to less trim drag and lower stall as the horizontal stab is lifting weight at stall. Since none of those changes were made to compare the airfoil mentioned above I don't think it was a fair evaluation.
 
Last edited:

pylon500

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Joined
Dec 26, 2003
Messages
395
Location
Taree Airport Australia
If you look at my finished, uncovered wing in #30, you will see my spar was set further back than your rib in #35.
Having the D tube being about quarter chord (12"of a 48"chord), as well as being close to the maximum thickness point, gave me a fairly light yet reasonably strong single strut wing made mainly of 0.016".
I forgot to mention in the earlier post that I used 2024-T3, as opposed to the 6061-T6 regularly found in ultralights.
My shear-web maintained stiffness through having only a 13" rib spacing (this being a twelve foot wing panel), the fibreglass rib being sufficient. Although if I were making that wing again I would use 0.016" alloy ribs, possibly with another 0.016" 1/2x1/2 angle nestled at the rib spar flanges for two or three ribs around the strut area, and maybe the root rib.
looking at your Riblett section, and your proposed web location, and if you intend to use 6061-T6, I would use 0.020" for the web and leading edge as you have a smaller dimension D tube trying to resist a greater torsional load.
As for ribs themselves, I'm probably biased being an Aircraft Sheet Metal worker, so I would form sheet ribs over wooden form blocks. I would also file relief grooves in the blocks and use fluting pliers to aid the curve, not chop out a bunch of bent over tabs that will crack and break off!
rib_blocks.png

These are a bunch of (tapered) rib blocks for another project...
formed_ribs.png
And some ribs being formed on said blocks.
As for fuselage moments, back in my youth I built control line (U control) stunt models, and best design practices usually said between 2 and 2 1/2 times the average chord between centre of pressure of the wing and centre of pressure (the elevator hinge line) of the tail. 2 1/2 times if using coupled flaps, and the flaps geared to only half the angle of deflection of the elevator. If you made them equal, the flap just turned into an airbrake.
03_Alvin.2.jpg
Shades of Nobler 🤔 (this is a VERY old photograph, I'm about 15 in 1973).
Practically, just remember that the longer the moment arm, the smaller the tail can be...
 

challenger_II

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Jul 15, 2009
Messages
496
Location
Fisher County, Tx. USA
Phil, to give you a reference point, my Hipps Reliant wings, wood, 4ft chord and 14ft span per panel, covered, weigh in at 37# per panel. The Hipps airfoil is not as thick a section as the Riblett.
 

philr

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Dec 26, 2020
Messages
99
Phil, to give you a reference point, my Hipps Reliant wings, wood, 4ft chord and 14ft span per panel, covered, weigh in at 37# per panel. The Hipps airfoil is not as thick a section as the Riblett.
Is the Hipps Reliant an aluminum wing?
 

challenger_II

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Jul 15, 2009
Messages
496
Location
Fisher County, Tx. USA
Wood wing, fabric cover. My apologies, for not having stated that. Is why I gave it as a reference, as, when you compare wood weight per cubic inch to aluminum weight per cubic inch, you can get an idea of how much metal will be required to build a comparable wood wing equivalent.
 
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