SEW-SLO 30" Foamboard Wing
Currently I am in a “Foamy frenzy”, averaging a new plane each week….go figure
Anyway, I wanted to try a flat plate foam flying wing….Lots of commercial shaped airfoil EPP kits are available….but I wanted to scratchbuild one….I couldn't find one that met all my requirements exactly...
Finally, I decided that I would design one myself….
1. Easy to build, and fast to build
2. Would use my common foamy components…ie BW 1300KV motor, 10A ESC, 9g Servos
3. Could fly slow….I like to fly in small parks….I have speed demons already (Draken, Starfighter V2, Firefly on Steroids)
5. Easy to launch…no bungees, no baseball throws, etc.
The result was the “SEW-SLO”…Super Easy Wing – Sloflyer
It certainly exceeded my expectations (which were to crash and burn!) and meets all my goals above….its stable, has a very gentle stall even with a rearward CG, can fly very slowly (~4oz/sqft), was built in under 3 hours, and is 100% Dollar Tree Foamboard with the paper left on($1 total for the foam)…and it takes off right out of my hand….in fact, I can stand it on its winglets on the ground at a 70 deg angle, give it full throttle, let go (see end of video) and it just takes off in a steep climb!
With a stock BW 1300, 8040HS prop and a 3S 500mah battery, I cruise around at ½ throttle for over 6 minutes….full throttle is unlimited vertical….this configuration weighs only 8.3oz…with >2sqft of wing, that’s 4oz/sqft….a real floater….with a 1100mah pack its only ~4.6oz/sqft….lots of flight time and it feels almost the same except for a little more stable in gusty winds….
Here is a video of its maiden flight and plans…the CG was an 1/8” more forward than the plans for the first flight and it was a bit nose heavy….but ½ throws still made it roll very well…
My only change in the future would be to try a little bigger winglets….in gusty winds, it does have a little side to side bounce occasionally…nothing that affects stability or manuverablitiy, but since this is my first wing, I want to see if it changes anything…
Note the 3M extreme strapping tape used as a spar on top and bottom, and as reinforcing on the nose top and bottom.....this is the only bracing...the tube motor mount is also held in by tape over its top...
The plans are not tiled since you just draw the straight lines to the dimensions given directly on the foamboard..the paper is left on the foamboard for strength....ultra simple and easy..
Last edited by Atx_Heli; Jun 03, 2011 at 11:05 AM. Reason: added ground launch to video
I did go ahead and try a high KV motor....my BW crapped out in the normal style of all "thru the tunnel" winds by fatigue cracking on one of the winding pigtails as it passes from front to back...
so I popped in a Dave North BW rewind...KV~2K....runs about 11A on 3S with a 6x4.....8A on 2s....still has plenty of vertical on 2s....gets up and goes on 3s.......very versatile platform...
I had been flying in winds gusting to 27mph Sunday and had the wind jerk the plane while I was holding it by the tail ready for launch....put some creases laterally in the wing behind the prop slot, effectively giving the wing a little airfoil bow...not broken just bowed...
so I ran a couple of skids of 5mm depron underneath down the length on either side of the prop slot....wing's dead flat again...would probably recommend doing this from the get go....no difference in flight characteristics....
So, I liked the results of this design so much, that I wanted to try to get a more durable version....although at a 3 hour, $1 construction, its almost like "why bother?"
But I wanted to see if I could retain all the flight characteristics(ie weight and stiffness) in a "bullet proof" version...that meant EPP...but it has to be stiff for speed and tearproof for the "bullet-proof" name...
I decided to use a modified form of the RCFoamFighter Henry's fiberglass tape +3M90 spray adhesive technique..using a lighter weave tape that you can get at HomeDepot....ie sheetrock joint tape....and add a KFm2 panel for additional strength/stiffness....
The bulletproofing of my SEW-SLO design worked out very well....
I did gain 1.7oz of weight, although I think at least .5 oz was paint...I tried (in vain) to get the 6mm black EPP solid white on the top...sprayed and sprayed to no avail..won't do that again!
I also used 2-56 pushrods to eliminate any flex at all at speed and the elevons are 6mm Depron also...and the added KFm2 panels...all contributed to the small extra weight...
but...no flex in flight noticed at 60+mph and it is as smooth as silk on the controls....and I think will be tear and crash proof under most circumstances...
so I went from 4oz/sqt to 4.7oz/sqft , but I don't notice it a bit...
I had experimented with this fiberglass tape and 3M90 on trial pieces of foam, and it adds about 12-14g/sqft per layer....so you can use that for calculations in the future...
here is a video of it flying....can't really call it a SEW-SLO (Super Easy Wing-Slowflyer) any more since it took all day to build instead of 3 hours of the original..ie not SUPER easy....but it is a great combination of slow and fast, is still a small park capable flyer, and should last for a long time
Thank you very much for posting this wing design. I really think I can build this one! I have several Dollar Tree 3mm foam boards that I can use.
The only part I don't understand is how the motor gets mounted. In your pictures the battery covers this up. Going by the shaded part in your plan, it appears to be a GWS stick mount perhaps glued to the wing. Is this correct?
I happen to have some of those wooden mounts and the HK red aluminum stick mounts for brushless motors that I can use. I just can't tell what you did with yours.
I am not very good at isometric drawing, but here is a shot...
the mount is a plastic 8mm stick mount....see picture below...radial insert is not used for Blue Wonder/2730/2712 style motors...their 8mm bearing tube just pushes in...just push in and tighten...the radial insert has 16mm and 19mm holes which will fit a jillion motors in the 22-28mm diameter class...
here is a US source...or you can get them from HobbyKing in HK...
the wing is notched out for it so that it fits flush with the bottom on the wing...since its 10mm high and the foamboard is ~5mm with paper on, that leaves it sticking up 5mm above the wing....a flush bottom doubler covers it on the bottom....two side doublers on top will have their tops flush with the top of the mount....allowing strapping tape over the top...no glue...makes it very easy to reclaim for the next model...and has a little give in crashes...
hope this helps...
19" Mini SEW-SLO
I am enjoying this wing a lot!
so I decided to see if it translated into a mini version..
the target was an HK1811-2000 10g motor....on a 3S and a 5030HD prop, this motor can pull 8oz and approach 40mph
I wanted to keep the wing loading in the 4-5oz/sqft range to "keep it in the park" so to speak, AND fit on a single 1/2 sheet of 6mm Depron....
the result is shown below....19" wingspan, 13" overal front to back..
6A esc and 2, 9g servos complete the electronics...
only reinforcing are a couple of doublers, a bamboo skewer, and some 3M Extreme packing tape....its been nose-in crashed several times,without effect..until I ran into a power line tower this afternoon and ripped the wing...a few drops of CA and it was back in the air!
AUW is 4.3oz with a 3s 500mah Lipo.....for a 5 oz/sqft wing loading and 2:1 power to weight ratio for unlimited vertical
using a 250mah pack would give 4.3 oz/sqft....
the construction is still Super Easy, so it still belongs in the SEW-SLO family...
here is a video of its maiden flight and plans...again, just measure and cut, no need for templates or tiled plans...
note that the plans include a set of wingtip KF/drag panels....I am going to try to see if I can remove the winglets and just use these....
I picked this trick up from the Assassin wing design in which the solid EPP wing panel is cut to present a flat face near the wingtip to eliminate the need for winglets (which are needed only at low speeds anyway)....it is similar to using drag flaps or wedges...since this wing is a flat plate, I reason that just adding doublers near the wingtip will provide the drag....making them similar to KF panels, however short they be, might also give some delay in tip stall as well....might even reduce the overall drag, while still providing enough frontal drag to provide yaw stability.....we'll see this week....I will try top and bottom, and then just top, if that works....
Update: the KF/drag panels do work at slow speed….no yaw….however, removing the winglets makes the wing prone to snapping during loops, at the top….at full power, its no problem, but at lower power levels, you get a snap to upright most of the time…
So here are the results of my experiments:
1. Baseline: no KF/drag panels and Winglets that extend to back of elevons
-flys great fast and slow…rolls fast…easy inverted
2. No Winglets, top and bottom panels
-flys good fast and slow…no yaw bounce…
however, snaps in loops easily if there isn’t a lot of speed at the top of the loop…same inverted…rolls a lot slower
3. No Winglets, top panel only
-gets some yaw/roll issues at low speed…same snap issues in loops
4. No Winglets, no panels
-fast flight the same….rolls faster…still has the same snap at the top of loops…roll/yaw wobbles at slower speeds..
5. Short Winglets: I tired some that stopped at the beginning of the elevons….the tip stall/snap issue in loops reappeared…its very important that the winglets extend to the back of the elevons
I much prefer flying the wing with winglets…
So, the panels do work (use top and bottom), but this wing/elevon shape on a flat plate does need winglets, primarily to eliminate the tip stalls in loops….I might try some stall fences in the future to see if I can eliminate that in the winglet free versions…
Gliding the "bullet-proof" version
I love climbing up as far as I dare with this wing, cutting power, adding some up trim to slow it, and just watch it glide for minutes!
mounted a keychain camera on its nose and took this video this morning...
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