what if---
04-10-2008, 10:47 AM
#1
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Thread Starter
what if---
For those who like to work with numbers and theories:
what if -- you were asked to design an aircraft which would perform much like the good old Piper Cub--
carry two people on at a cruise of 80 mph- same power as original
BUT-- you were given a inventory of material to work with that is ALL 50% lighter than anything available for the original.
Same strength n power but 1/2 the weight.
What would your airplane look like?
what if -- you were asked to design an aircraft which would perform much like the good old Piper Cub--
carry two people on at a cruise of 80 mph- same power as original
BUT-- you were given a inventory of material to work with that is ALL 50% lighter than anything available for the original.
Same strength n power but 1/2 the weight.
What would your airplane look like?
04-10-2008, 01:00 PM
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RE: what if---
It couldn't look just like the cub,reason if it is %50 lighter it would have to be made somewhat different. I think such a thing could be done using the material we can use today. As in carbon fiber and other goodies like that. Most likely we do have these planes around now,in the from of ultalights,etc. Some of them are quite neat to. This is an interesting question is it not?
04-10-2008, 01:07 PM
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RE: what if---
The original cub had a dry weight of 680 Lbs, fairly light weight cut that in half you would have a real nice LSA type of plane.
So it would look like a 350 Lb Cub, perhaps a bit longer tail moment...
Or if you prefer side by side seating a Tri-Pacer...
So it would look like a 350 Lb Cub, perhaps a bit longer tail moment...
Or if you prefer side by side seating a Tri-Pacer...
04-10-2008, 01:43 PM
#7
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RE: what if---
I've read thousands of Dick's posts and if there is one underlining theme it is the significance of aircraft weight on performance. So often you read of accounts of someones efforts in stuffing twice a big a motor into an already overweigh bloated design and wondering why it don't fly well. While more motor may make an airplane fly faster or climb faster, being able to operate at a wider range of flight speeds with a lighter weight usually makes for a better flying model.
If you cut the weight of the structure of the Cub by half, the total flying weight is reduced by a third. It would take a third less wing area, and thus the drag would be reduced by maybe 10-15%. So less power would be required to maintain speed. Excellent examples of doing more with less would be Van's Aircraft RV-9 with a O-235 (30 mpg at 150 mph), and his new RV-12 which weighs about 80 lbs less than a quite simular Rans S-19. 80 lbs means a lot in an airplane limited to 1320 lbs, and represents an increase in useful load of 16%.
If you cut the weight of the structure of the Cub by half, the total flying weight is reduced by a third. It would take a third less wing area, and thus the drag would be reduced by maybe 10-15%. So less power would be required to maintain speed. Excellent examples of doing more with less would be Van's Aircraft RV-9 with a O-235 (30 mpg at 150 mph), and his new RV-12 which weighs about 80 lbs less than a quite simular Rans S-19. 80 lbs means a lot in an airplane limited to 1320 lbs, and represents an increase in useful load of 16%.
04-10-2008, 01:58 PM
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RE: what if---
ORIGINAL: HighPlains
I've read thousands of Dick's posts and if there is one underlining theme it is the significance of aircraft weight on performance. So often you read of accounts of someones efforts in stuffing twice a big a motor into an already overweigh bloated design and wondering why it don't fly well. While more motor may make an airplane fly faster or climb faster, being able to operate at a wider range of flight speeds with a lighter weight usually makes for a better flying model.
If you cut the weight of the structure of the Cub by half, the total flying weight is reduced by a third. It would take a third less wing area, and thus the drag would be reduced by maybe 10-15%. So less power would be required to maintain speed. Excellent examples of doing more with less would be Van's Aircraft RV-9 with a O-235 (30 mpg at 150 mph), and his new RV-12 which weighs about 80 lbs less than a quite simular Rans S-19. 80 lbs means a lot in an airplane limited to 1320 lbs, and represents an increase in useful load of 16%.
I've read thousands of Dick's posts and if there is one underlining theme it is the significance of aircraft weight on performance. So often you read of accounts of someones efforts in stuffing twice a big a motor into an already overweigh bloated design and wondering why it don't fly well. While more motor may make an airplane fly faster or climb faster, being able to operate at a wider range of flight speeds with a lighter weight usually makes for a better flying model.
If you cut the weight of the structure of the Cub by half, the total flying weight is reduced by a third. It would take a third less wing area, and thus the drag would be reduced by maybe 10-15%. So less power would be required to maintain speed. Excellent examples of doing more with less would be Van's Aircraft RV-9 with a O-235 (30 mpg at 150 mph), and his new RV-12 which weighs about 80 lbs less than a quite simular Rans S-19. 80 lbs means a lot in an airplane limited to 1320 lbs, and represents an increase in useful load of 16%.
And a way not to do it would be the Legend 850 lbs with 100hp.
And Dick as you pointed out is right, weight is one of the most limiting factors on how a plane flys.
Lighter is better, or more "air" in the airplane!
Edit to add:
If I recall the 65 hp engine weighd in at about 170 lbs in the 680 lb airframe. If you took that off of the all up dry weight that would leave you with a total of 510 lbs for the rest of the airframe. If it were possibe to cut that in half that would mean an all up weight of 425 lbs dry, I wonder what that would do as far as the power requirements and wing area. If you were to maintain the parameters of 80 knot cruise and 37 knot stall as being to design goals, to keep it well within the LSA limits.
04-10-2008, 06:36 PM
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RE: what if---
And I can just see you sitting in the cockpit of a 24 foot lil' Satan....
Interesting thought. The question is just how much of a difference WOULD there be? The material may well be lighter but what about modern vs classic covering and how much dope is needed? What about the engine? Use the original at the original weight or something modern that makes the same power with less weight?
People are still the same weight and with two on board that's a very significant portion of the AUW.
So off the top of my head we sure are not looking at a HUGE loss of weight. In fact the actual framing gains may only account for perhaps a 15 to 20% reduction overall in the gross loaded weight. At that point it would provide a nice shortening of the takeoff and a little better climb rate (which was somewhat glacial with two on board on a hot day). Or it could also provide for a little more useable cargo weight if flown at the same AUW.
Interesting thought. The question is just how much of a difference WOULD there be? The material may well be lighter but what about modern vs classic covering and how much dope is needed? What about the engine? Use the original at the original weight or something modern that makes the same power with less weight?
People are still the same weight and with two on board that's a very significant portion of the AUW.
So off the top of my head we sure are not looking at a HUGE loss of weight. In fact the actual framing gains may only account for perhaps a 15 to 20% reduction overall in the gross loaded weight. At that point it would provide a nice shortening of the takeoff and a little better climb rate (which was somewhat glacial with two on board on a hot day). Or it could also provide for a little more useable cargo weight if flown at the same AUW.
04-10-2008, 06:50 PM
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RE: what if---
ORIGINAL: BMatthews
And I can just see you sitting in the cockpit of a 24 foot lil' Satan....
Interesting thought...
a little better climb rate (which was somewhat glacial with two on board on a hot day). Or it could also provide for a little more useable cargo weight if flown at the same AUW.
And I can just see you sitting in the cockpit of a 24 foot lil' Satan....
Interesting thought...
a little better climb rate (which was somewhat glacial with two on board on a hot day). Or it could also provide for a little more useable cargo weight if flown at the same AUW.
Still to be able to cut 15-20% off of the gross weight would be a major gain I would think...
A Rotax 912A gives you 80 Hp in a 122 lb package that is at least 50 lbs lighter than the original 65-80 Hp engine.
I would think that 20% would be a medium amount of weight reduction given todays alternatives. As far as covering are we talking about a covered airframe, or a stressed skin design?
04-10-2008, 07:33 PM
#12
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Thread Starter
RE: what if---
good answers -I suggested all materials - -some thought that meant structure only -I meant ALL material -engine/ covering -all of it -so 50% of original weight -
I think the plane could be good deal smaller as synergistically, the lighter plane would need far less lifting area- and OR less power for the same job
On models when we got into reduction of weight to meet class requirements - It quickly became evident that the wings could be smaller and or with much reduced airfoil thicknes as maneuvering all could happen at lower AOA- best yet - the speed could be selected - for windy or smooth air .
I think the plane could be good deal smaller as synergistically, the lighter plane would need far less lifting area- and OR less power for the same job
On models when we got into reduction of weight to meet class requirements - It quickly became evident that the wings could be smaller and or with much reduced airfoil thicknes as maneuvering all could happen at lower AOA- best yet - the speed could be selected - for windy or smooth air .
04-10-2008, 09:16 PM
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RE: what if---
Yes the airplane could then be made smaller since the plane could be smaller and still retain the same wing loading. At the same time the reduced size would have less drag and the plane would fly faster to boot.
But then we wouldn't have a Cub anymore. It would be something new and likely much like some of the more Cub like but smaller ultralights out there these days. One example being a Murphy Maverick that just happens to be made local to me.
http://www.murphyair.com/murphyair/A.../Maverick.html
Very Cub like in concept but smaller and lighter and probably flies faster.
Maverick specs-
GROSS WEIGHT 950 LB.
EMPTY WEIGHT 395-460 LB.
G-LOADING (NORMAL) +5.7 -3.8
POWER RANGE 53-65 HP
WING SPAN 29' 5" (std) or 32' 5" (extended)
LENGTH 20' 8"
FUSELAGE WIDTH 37"
WING CHORD 60"
TAIL SPAN 106"
AIRFOIL 4415 (MODIFIED)
J3 Cub specs
General characteristics
Crew: one pilot
Capacity: one passenger
Length: 22 ft 5 in (6.83 m)
Wingspan: 35 ft 3 in (10.74 m)
Height: 6 ft 8 in (2.03 m)
Wing area: 178.5 ft² (16.58 m²)
Empty weight: 765 lb (345 kg)
Useful load: 455 lb (205 kg)
Max takeoff weight: 1,220 lb (550 kg)
Powerplant: 1Ă— Continental A-65-8 air-cooled flat four, 65 hp (48 kW) @ 2350 RPM
Yep, that pretty much holds water I'd say.
And I hear you about the "formula" of the designs. It was quite noticable in pattern for example that the wing area shifted as the emphasis on how the models were flown shifted. Or maybe it was just the fuselages got so darn big.....
But then we wouldn't have a Cub anymore. It would be something new and likely much like some of the more Cub like but smaller ultralights out there these days. One example being a Murphy Maverick that just happens to be made local to me.
http://www.murphyair.com/murphyair/A.../Maverick.html
Very Cub like in concept but smaller and lighter and probably flies faster.
Maverick specs-
GROSS WEIGHT 950 LB.
EMPTY WEIGHT 395-460 LB.
G-LOADING (NORMAL) +5.7 -3.8
POWER RANGE 53-65 HP
WING SPAN 29' 5" (std) or 32' 5" (extended)
LENGTH 20' 8"
FUSELAGE WIDTH 37"
WING CHORD 60"
TAIL SPAN 106"
AIRFOIL 4415 (MODIFIED)
J3 Cub specs
General characteristics
Crew: one pilot
Capacity: one passenger
Length: 22 ft 5 in (6.83 m)
Wingspan: 35 ft 3 in (10.74 m)
Height: 6 ft 8 in (2.03 m)
Wing area: 178.5 ft² (16.58 m²)
Empty weight: 765 lb (345 kg)
Useful load: 455 lb (205 kg)
Max takeoff weight: 1,220 lb (550 kg)
Powerplant: 1Ă— Continental A-65-8 air-cooled flat four, 65 hp (48 kW) @ 2350 RPM
Yep, that pretty much holds water I'd say.
And I hear you about the "formula" of the designs. It was quite noticable in pattern for example that the wing area shifted as the emphasis on how the models were flown shifted. Or maybe it was just the fuselages got so darn big.....
04-11-2008, 04:16 PM
#14
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Thread Starter
RE: what if---
ORIGINAL: BMatthews
Yes the airplane could then be made smaller since the plane could be smaller and still retain the same wing loading. At the same time the reduced size would have less drag and the plane would fly faster to boot.
But then we wouldn't have a Cub anymore. It would be something new and likely much like some of the more Cub like but smaller ultralights out there these days. One example being a Murphy Maverick that just happens to be made local to me.
http://www.murphyair.com/murphyair/A.../Maverick.html
Very Cub like in concept but smaller and lighter and probably flies faster.
Maverick specs-
GROSS WEIGHT 950 LB.
EMPTY WEIGHT 395-460 LB.
G-LOADING (NORMAL) +5.7 -3.8
POWER RANGE 53-65 HP
WING SPAN 29' 5" (std) or 32' 5" (extended)
LENGTH 20' 8"
FUSELAGE WIDTH 37"
WING CHORD 60"
TAIL SPAN 106"
AIRFOIL 4415 (MODIFIED)
J3 Cub specs
General characteristics
Crew: one pilot
Capacity: one passenger
Length: 22 ft 5 in (6.83 m)
Wingspan: 35 ft 3 in (10.74 m)
Height: 6 ft 8 in (2.03 m)
Wing area: 178.5 ft² (16.58 m²)
Empty weight: 765 lb (345 kg)
Useful load: 455 lb (205 kg)
Max takeoff weight: 1,220 lb (550 kg)
Powerplant: 1Ă— Continental A-65-8 air-cooled flat four, 65 hp (48 kW) @ 2350 RPM
Yep, that pretty much holds water I'd say.
And I hear you about the "formula" of the designs. It was quite noticable in pattern for example that the wing area shifted as the emphasis on how the models were flown shifted. Or maybe it was just the fuselages got so darn big.....
Yes the airplane could then be made smaller since the plane could be smaller and still retain the same wing loading. At the same time the reduced size would have less drag and the plane would fly faster to boot.
But then we wouldn't have a Cub anymore. It would be something new and likely much like some of the more Cub like but smaller ultralights out there these days. One example being a Murphy Maverick that just happens to be made local to me.
http://www.murphyair.com/murphyair/A.../Maverick.html
Very Cub like in concept but smaller and lighter and probably flies faster.
Maverick specs-
GROSS WEIGHT 950 LB.
EMPTY WEIGHT 395-460 LB.
G-LOADING (NORMAL) +5.7 -3.8
POWER RANGE 53-65 HP
WING SPAN 29' 5" (std) or 32' 5" (extended)
LENGTH 20' 8"
FUSELAGE WIDTH 37"
WING CHORD 60"
TAIL SPAN 106"
AIRFOIL 4415 (MODIFIED)
J3 Cub specs
General characteristics
Crew: one pilot
Capacity: one passenger
Length: 22 ft 5 in (6.83 m)
Wingspan: 35 ft 3 in (10.74 m)
Height: 6 ft 8 in (2.03 m)
Wing area: 178.5 ft² (16.58 m²)
Empty weight: 765 lb (345 kg)
Useful load: 455 lb (205 kg)
Max takeoff weight: 1,220 lb (550 kg)
Powerplant: 1Ă— Continental A-65-8 air-cooled flat four, 65 hp (48 kW) @ 2350 RPM
Yep, that pretty much holds water I'd say.
And I hear you about the "formula" of the designs. It was quite noticable in pattern for example that the wing area shifted as the emphasis on how the models were flown shifted. Or maybe it was just the fuselages got so darn big.....
04-11-2008, 05:24 PM
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RE: what if---
Half the weight Cub, would look just like the original. But then two fat fellers and more gas could be carried.
MTY
P.S. OK, lets make it easier to board to exit. (You know for us older fat fellers!)
P.P.S. I guess that if you made it easier to enter and exit it would be a CHAMP.[8D]
MTY
P.S. OK, lets make it easier to board to exit. (You know for us older fat fellers!)
P.P.S. I guess that if you made it easier to enter and exit it would be a CHAMP.[8D]
04-11-2008, 08:45 PM
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RE: what if---
ORIGINAL: dick Hanson
oh yeh - -FWIW I designed a large Tipo - (guys called it the Hippo Tipo -in83-) and it was soundly rejected -too slow - but I had designed it to fly and maneuver at slower speeds
oh yeh - -FWIW I designed a large Tipo - (guys called it the Hippo Tipo -in83-) and it was soundly rejected -too slow - but I had designed it to fly and maneuver at slower speeds
I'd say you got caught up in the whole "it's not about the flying. It's about what the judges want and expect to see.". And that's the problem with any event where opinions rather than stopwatches or measurements are used. It takes time to bring a new appearance to the forum that the judges will get used to and accept.
I remember seeing your Hippo Tipo in the magazines back then. I thought it would have been you that named it that. And here it was your... *ahem*.... "friends" that named it for you....
This discussion reminds me of reading about why adapting the 30's racing planes for military duty just didn't work out. At first it seems like a great idea. The racers were far faster than the military planes. So great, let's just add some guns and call it a day......
But wait, the racers land pretty darn fast. Faster than our pilots are used to. And adding guns and ammo just made them heavier and land even faster. OK, we'll add some wing area, That'll slow them down to where they can land slow enough.... But wait, you just made the airplane heavier twice over with guns and ammo and increased size. Now there isn't enough fuel and range to fly the missions. OK, we'll add some extra fuel tanks... But wait, we forget the pilot armor and the weight of the self sealing gas tanks. OK, we'll make it a little bigger to handle the weight of those things and the extra gas we need to carry.... Oh, oh, the engine isn't big enough to fly the plane at the speed we requested. I guess we'll need to put in the bigger engine. And we'll need more gas to maintain the range now too. Oh, and while you're at it could you add racks for a couple of 500 lb bombs and make sure the plane can still take off? THERE'S A GOOD FELLOW!
OK! LEt's see what we've got now! ! ! ! Hmmmmmm........ It seem's like our Roscoe Turner flown Laird Meteor just turned into a P47 Thunderbolt..... WHERE DID WE GO WRONG! ! ! ! !
Actually no where. The two planes are designed to do what they need to do. It's just that the right answers for the two quetions are different.
04-12-2008, 02:36 PM
#17
Senior Member
RE: what if---
One of our U-2 test pilots made a complaint about the program management.. every time Lockheed came up with a performance improvement, the management upped the payload, and the improvement went away. 
04-12-2008, 05:30 PM
#18
Senior Member
RE: what if---
ORIGINAL: Tall Paul
One of our U-2 test pilots made a complaint about the program management.. every time Lockheed came up with a performance improvement, the management upped the payload, and the improvement went away.
One of our U-2 test pilots made a complaint about the program management.. every time Lockheed came up with a performance improvement, the management upped the payload, and the improvement went away.
That pilot didn't understand what was important.
Payload was important. The pilots' enjoyment wasn't.
And typical of pilots, the improvement hadn't gone away. It'd been utilized to improve mission capability and mission performance. If the U-2 was carrying more cameras, it was still carrying more cameras, for example.
