Has anyone on here messed around with adapting a Cessna style flap to a cub wing? It's something I've started working on and figured I couldn't be the first to try it. So looking for info on what others have done. I'm thinking about riveting a 180 and a 150 flap end to end, using 4 flap tracks and totaling 12 feet of flap, then a deep chord aileron (shortened Cessna 206 style) for the remainder of the span, approximately 56". I will be boxing the rear spar to the front spar to avoid twisting at the flap hangers, I haven't settled on a method yet, D&E style compression struts, a left and right Univair rib center sections riveted together to form a box structure, or something else. Just getting going, I'm sure there will me many hurdles to overcome. Let me know what you think. Here's a few pictures of a rough draft, just clamped together. Thanks. Joel
Fowler flaps on a cub wing?
- Thread starter eskimo77
- Start date
TurboBeaver
Registered User
Northern Maine
There was an orange n white cub at Hood Strip in Anc for years , it had Cessna 180 flaps n ailerons on it, would certainly be effective! Popular Mechanics in 1951 had an article on the original test pilot report on the then new 125hp PA18, pretty interesting read, the pilot praised the new cub but was pretty critical that he felt the flaps were not the correct size and not nearly as effective as they should be!
Was talking to BD Maule one time in the mid 1980s about a problem we were having with flaps on a then new M7, he told me he had done
Alot of experimenting with different flaps, and that he felt piper flaps were just to narrow for the wing and they should have been alot wider and not nessesarally longer so your on the right track!
Was talking to BD Maule one time in the mid 1980s about a problem we were having with flaps on a then new M7, he told me he had done
Alot of experimenting with different flaps, and that he felt piper flaps were just to narrow for the wing and they should have been alot wider and not nessesarally longer so your on the right track!
skywagon8a
MEMBER
SE Mass MA6
All of the following, Helio, Twin Bee, and Lake were certified, formally in production, airplanes in which their low speed performance depended on the contribution of long high aspect ratio flaps on their high aspect ratio wings. I believe that you can add the Beaver, Otter and Twin Otter to this list of airplanes with long high aspect ratio flaps and wings.
Long flaps are good in that their outboard section operates outside of the dirty prop wash air, in addition to the positive attributes of the lower induced drag of high aspect ratios.
Long flaps are good in that their outboard section operates outside of the dirty prop wash air, in addition to the positive attributes of the lower induced drag of high aspect ratios.
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Steve's Aircraft (Brian)
FRIEND
White City, Oregon
mike mcs repair
Registered User
chugiak AK
instead of worrying about boxing in front of hangers, just do every thing behind rear spar(or to front side of rear spar??) out of aluminum in flap bay, just like the cessna(.020??), and attach it to rear spar with a lip down to spar cap, just like the ribs attach.... then normal ribs in front of rear spar..... (it's kinda like a normal -18 behind tank bay...)
Thanks for all the comments and info. I think Mike's idea is the route I'm going to pursue. A false spar wrapped around the flap track to form a boxed cove. Then attach to the rear spar like the ribs do. Thanks to all of you for the input. I'll put up some more pics soon.
http://www.supercub.com/outlaw1.html Pretty Cool, bigger without a lot of linkages.
Small update
Did a little more on attaching flap track to the rear spar. Using flap cove sheet metal similar to the way Cessna did it, but will attach to the spar caps like the piper ribs. Cove material will run full span of the flaps. I'll have to make my own tail ribs to fill the spaces between the 4 flap tracks. Slow progress but fun trying to make it fit. Any advice is appreciated. Thanks, Joel.
Did a little more on attaching flap track to the rear spar. Using flap cove sheet metal similar to the way Cessna did it, but will attach to the spar caps like the piper ribs. Cove material will run full span of the flaps. I'll have to make my own tail ribs to fill the spaces between the 4 flap tracks. Slow progress but fun trying to make it fit. Any advice is appreciated. Thanks, Joel.Attachments
TurboBeaver
Registered User
Northern Maine
That "Outlaw" Cub at 750 lbs is certainly looking pretty impressive, is the airfoil a cub wing
Or some other flavor? This could get crazy in Valdez if he brings that up and lights it off?
As 100ft takeoffs in no wind may just not cut it anymore, and the bar is going start at 50ft or better,
Otherwise:
Just stay home............ about the time he drops the flaps n ailerons down on that bad boy, he will
Certainly have the crowds full n undivided attention!
Eskimo77, keep the pictures coming that is looking great and lets hope you can qualify in the new
50ft catagory with yours!
Or some other flavor? This could get crazy in Valdez if he brings that up and lights it off?
As 100ft takeoffs in no wind may just not cut it anymore, and the bar is going start at 50ft or better,
Otherwise:
Just stay home............ about the time he drops the flaps n ailerons down on that bad boy, he will
Certainly have the crowds full n undivided attention!
Eskimo77, keep the pictures coming that is looking great and lets hope you can qualify in the new
50ft catagory with yours!
skywagon8a
MEMBER
SE Mass MA6
eskimo,
What are you doing in front of the spar to take the twisting loads when the flaps are down. That sheet metal in your pictures is only fairing materiel except that it can be used for side loads from the hinges with a right angle clip.
What are you doing in front of the spar to take the twisting loads when the flaps are down. That sheet metal in your pictures is only fairing materiel except that it can be used for side loads from the hinges with a right angle clip.
mike mcs repair
Registered User
chugiak AK
not sure thats enough strength... probably better to spar web also, with stiffener on front...
might also consider something on front side that comes over top and bottom of spar than attaches to hanger.. kinda strap like with a twist..??
once you add the ribs behind spars & attach them & the front ribs, there will be no more than normal twisting issue as asked above, the ribs keep the spar upright
probably a strap from rear portion to tie into front rib.... I like that better than the strap I mentioned above... kills 2 birds with one strap....
I keep going back and forth on weather you would want to line up on a forward rib, and i think the thought above makes it make sense to line up hanger on a forward rib....
The flap tracks will have a window cut in them to completely encompass the spar, the angle brackets are mostly for locating them on the span. The hangers will be lined up with a rib or a compression strut/rib, not sure yet. Just getting rolling on the project. The pictures aren't completely clear. I'll put a couple up tomorrow with the setup removed from the spar for clarity. This is way more interesting than working on those certificated birds. Thanks for the input. Joel
mike mcs repair
Registered User
chugiak AK
i like that!!
Here's a couple pics removed from the rear spar. Before someone tells me that plywood is not an acceptable material for flap tracks I will let everyone know that it's a template and I'm actually going to use Play-Doh for the final parts.;-) I hope this clears up some of my plans. Still wondering if I need to tie it to the front spar to minimize twisting forces.Attachments
skywagon8a
MEMBER
SE Mass MA6
The short answer is YES. Where and how is the question.
Answering this question through he eyes of a computer is difficult. You need to establish in your mind where (and how much) the load path goes when the flap is fully deflected at the maximum airspeed expected. How much force is the air going to place into the flaps when fully deflected? Where is this force going to travel into the wing structure? The force needs to be zeroed out at the end of this path. Along the way you need to determine that the parts of the structure are strong enough not to fail with the loads applied times a factor of 1.5.
The Cessna wing is one big box with the loads taken up within the ribs and the skin structure. A Cub wing does not have the skins so you need to place all of the loads into another distribution system.
The spar needs to be prevented from twisting at the points where the flap loads pass through. If you cut the window in the tracks as you describe, you will need to know that the tensile strength of the section which passes below the spar is adequate. This will take some mathematics. Then the section which is in front of the rear spar will need to be attached to something which will support that load forward without deflections.
Then you need to consider that those sections which are in the prop blast can withstand the extra buffeting without failure over time.
Do this in a safe manner. you do not want one flap to fail when in a maneuver from which you can not recover. I can think off the top of my head of two separate accidents where the failure of one flap caused the destruction of the airplane. A Twin Bonanza and a Pond Racer (P-51 look alike). One of them was fatal.
Where are you located? Your handle implies Alaska or the Canadian far North.
Dave Calkins
Registered User
Anchorage, Alaska
..as I recall.....aviat doubled up the ribs at each flap hanger...
mike mcs repair
Registered User
chugiak AK
kill 2 birds at once, just rivet it to the center rib(s)(make a sure rib and hanger are adjacent to each other
Skywagon, I'm in Kenai Alaska. My thoughts on tying the spars together inline with the hangers has me thinking a couple different options. OPTION 1. Line hanger up with a compression strut that attaches to the spar caps on both spars instead of the web. OPTION 2. A single piece hanger and rib cut out of approx. 3/16" aluminum plate, essentially a machined univair rib 3/16" thick with angle riveted to the top and bottom flanges for lateral stiffening. HEAVY, but strong. My main concern is when washing out the wings will this setup allow enough twist in the wing without too much stress? OPTION 3. Rivet two univair center section ribs (one left and one right) together to make a boxed rib, essentially a hollow version of option 2. OPTION 4. Install tubing compression struts one from the top of the rear spar to the top of the front spar, and one bottom to bottom. These would be attached as the hand sketched drawing illustrates. Would allow wing wash without much binding, but would allow racking fore and aft between the spars, but the ribs would counter the racking but will they take that load? The other pics show the tail ribs that I've been messing with. Thanks for the interest and comments. JoelAttachments
mike mcs repair
Registered User
chugiak AK
You are over engineering this...
step back, go look how other wings have been made since the 40's?? the normal ribs do the job you are worried about and the ribs might of been no where near the hanger.... your tail ribs and otter sheet will spread the load fine.... but for good measure attach it to a Univair rib if you want...
actually the normal bad areas are the butt rib/attach tabs breaking at rear spar top if you have cub like tank area... and the gas tank lid, the rear screw holes crack out from the twisting
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Thanks Mike, I probably am overthinking it, just don't want to figure out that I rushed it and screwed the pooch. I did some fitting and found that I don't need to make my own tail ribs, I can just trim a standard rib and it fits perfect. I think that I'm going to go with Dakota ribs for the standard rib placement and use a left and a right univair rib riveted on either side of the flap track with the rib flanges riveted together just to be overly cautious. Thanks for helping me hash through this guys. Joel
Attachments
mike mcs repair
Registered User
chugiak AK
http://dakotacub.com/index.php?option=com_gescart&Itemid=30&category=1
might verify their rear rib brace location is same as you think on original piper ribs......
might verify their rear rib brace location is same as you think on original piper ribs......
Steve's Aircraft (Brian)
FRIEND
White City, Oregon
New Dakota ribs that I just installed...
For your reference...
Brian
Sent from my iPhone using Tapatalk
For your reference...
Brian
Sent from my iPhone using Tapatalk
Thanks guys. I have some Dakota ribs I've looked at on my bosses pa-12 project and I will just have to move that diagonal brace toward the spar by one rivet which will require slight trimming on the bracket attached to the spar face, should be pretty painless. I will feel a little bad carving up brand new ribs, but I'll get over it. Thanks for the pictures Brian. Thanks for the interest everyone. Joel
mike mcs repair
Registered User
chugiak AK
FYI a pa-12 rib is like 1/4" SHORTER. Behind rear spar. And so are the flap and aileron hangers. Tan pa 18
A small update on the project. Got the materials for my flaps, and have been riveting a bit. It is essentially a 182 and 150 flap end to end resulting in a 141" flap. It has 4 hangers and 2 actuator points. I'm working on getting the Cessna flap track slots mapped out on CAD so I can use a CNC router to cut out the flap track/rib combo pieces. The flaps will extend to 40 degrees, but that is probably going to be overkill, but it's nice to have the option even if it's rarely used. In the pictures there is a piper aileron layed on top of the flap for size comparison.Attachments
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