Building a Heavy Lift aircraft
10-08-2013, 01:40 PM
#3
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10-08-2013, 01:56 PM
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10-11-2013, 09:40 AM
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Assuming you're looking at something like the SAE heavy lift competition there area a couple that stand out. The Selig 1223 was designed for exactly this sort of thing. It's a very high lift airfoil that is very draggy. But covering ground in these competitions isn't an issue. Lifting lots of weight, doing a set pattern and landing safely is what it's all about. So something draggy like the 1223 is fine.
There is also an Eppler airfoil with the same sort of shape that has done well from what I've read. I don't recall the number for the profile.
For any other sort of use I would not consider these to be good choices since they are so focused on this one style. In effect they are cleaner versions of a wing with the flaps permanently in the down position. Not the best option for normal flying around.
Note that in both situations that these airfoils rely on absolute accuracy of shape to deliver the promised performance. This means you're looking at accurately cut foam cores and sheeting or fiberglass and epoxy vacuum bagging to achieve the tight tolerance values needed.
What is tight enough? You're looking at the shape being accurate to within .005 to .008 inch all across the wing. You MIGHT get most of the performance if it's within .010 to .015 in some spots but that's a crap shoot gamble.
Needless to say the need for accuracy means that conventional open frame construction with film covering is right out of the question. And the thin curled trailing edge means that conventional balsa and sheeting is pretty much a non starter as well.
If you're wanting this for some other reason than one of the heavy lift competitions perhaps expand on your request so we can point you towards a better option.
There is also an Eppler airfoil with the same sort of shape that has done well from what I've read. I don't recall the number for the profile.
For any other sort of use I would not consider these to be good choices since they are so focused on this one style. In effect they are cleaner versions of a wing with the flaps permanently in the down position. Not the best option for normal flying around.
Note that in both situations that these airfoils rely on absolute accuracy of shape to deliver the promised performance. This means you're looking at accurately cut foam cores and sheeting or fiberglass and epoxy vacuum bagging to achieve the tight tolerance values needed.
What is tight enough? You're looking at the shape being accurate to within .005 to .008 inch all across the wing. You MIGHT get most of the performance if it's within .010 to .015 in some spots but that's a crap shoot gamble.
Needless to say the need for accuracy means that conventional open frame construction with film covering is right out of the question. And the thin curled trailing edge means that conventional balsa and sheeting is pretty much a non starter as well.
If you're wanting this for some other reason than one of the heavy lift competitions perhaps expand on your request so we can point you towards a better option.
Last edited by BMatthews; 10-11-2013 at 09:43 AM.
10-13-2013, 12:18 PM
#8
To answer the rest of your question, on configuration, go for a conventional tractor with trike landing gear, high wing or shoulder wing.
H-stab about 20% of wing area, 2.5 to 3 chords back. V-stab 30-40% of H-stab area.
Ballraced wheels are a great help
The two in the photos did well in a similar comp in the UK. The twin boom one lost a wheel on the final flight when fully loaded and failed to take off, but the silver one in the photo won the comp by lifting a payload of 7300g, with a takeoff weight of 10200 grams (16.12 lb and 22.53 lb) using an Irvine 40 engine and 11x6 Graupner prop.
Both used the Selig S1223
Last edited by alasdair; 10-13-2013 at 12:25 PM.
10-15-2013, 04:56 PM
#9
Been involved with the SAE Aerodesign since 2005 as the pilot for the University of Windsor. First year out the team took first in the advanced division with a flying wing since then the only airfoil I have seen that works is the S1223. Unlike what has been previously mentioned all the winning teams used open framework design with some sort of iron on film covering. The bare minimum of structure to do the job open bays all over the place.
14 ft span for 2012 finished 2'nd open class and the 2005 flying wing that took everything
Dennis
14 ft span for 2012 finished 2'nd open class and the 2005 flying wing that took everything
Dennis
10-15-2013, 08:04 PM
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Well... I could see the 1223 being somewhat OK with an open frame and film IF the trailing edge was fairly wide and accurately cut from wood to ensure the accuracy of the strong flap like cusp integral to the section's promised performance.
Or did these built up winners use something more conventional?
Or did these built up winners use something more conventional?
10-16-2013, 07:32 AM
#11
Trailing edges were hand cut from either solid stock or built up stock and range from 3 1/2 inches to as little as 1 1/2 inches. The first video is the 14 foot span university projects flight engine was a Jett .65 https://www.youtube.com/watch?v=g8xC-pE6RoA
This video is my own creation S1223 airfoil no ailerons to keep the integrity of the airfoil but spoilerons instead on the top of the wing near the tips. 1000 square inches less than 7 lbs wet OS .61 from a grass field lifting over 20 lbs. Open bay conventional construction is visible in the video. I also used a Gurney Flap on the trailing edge. Mine is the second plane yellow and blue for the win. https://www.youtube.com/watch?v=vBgWUceKmR0
As to drag and speed one of the Universities designs was powered with two Jett .32 on pipes flew very fast
http://www.youtube.com/watch?v=cx7w57MDQ5U
This video is my own creation S1223 airfoil no ailerons to keep the integrity of the airfoil but spoilerons instead on the top of the wing near the tips. 1000 square inches less than 7 lbs wet OS .61 from a grass field lifting over 20 lbs. Open bay conventional construction is visible in the video. I also used a Gurney Flap on the trailing edge. Mine is the second plane yellow and blue for the win. https://www.youtube.com/watch?v=vBgWUceKmR0
As to drag and speed one of the Universities designs was powered with two Jett .32 on pipes flew very fast
http://www.youtube.com/watch?v=cx7w57MDQ5U
10-20-2013, 05:22 PM
#12
Nice thread, but isn't it funny how often one of these gets going with lots of responses and meantime the original poster has disappeared? It actually happens a lot. Not that there's anything wrong with that.
10-21-2013, 04:19 AM
#13
Dennis
10-22-2013, 08:14 PM
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As the CD for the 2013 AIAA DBF, it is very interesting to see different aircraft designed for the same mission requirements. Some you look at and wonder if the advisor ever read the requirements to the students. Others are very, very sophisticated. The interesting thing is that all models have to be flow before the competition (complete with in the air photos/video). Come the day of completion and a lot of the models never make it into the air. Some one forgot to tell the kids about the most important design rule "density altitude". Gets the planes every time. What you designed to fly at sea level just doesn't work at 3,000 ft on a 100 degree day with a relative humidity of 5%.
