EPP Foam Combat Plane 28"



Here's a build of the popular Leadfeather Yak 55, scaled from 32" to a 28" wingpan and made with heavier 1.9# EPP foam.  This plane is optimized for streamer combat, with really good speed, agility and durability.  The total cost of foam and parts can come in under $70.  See the parts list below.   

The build guide at racores.com is a good reference to use.  The guide is written for the lighter 32" Yaks, but the build steps are very similar.  The "wedge shaped tail stiffeners" and "small foam quarter circles" referenced in the racores.com build guide are not used and not needed with the heavier 28" version of the Yak.

The plans for the original 32" Yak can be found on rcgroups, and there is a build guide posted.  I modified the layout to scale it down to a 28" wingspan, "EPPYak55-28_multiPage.pdf", and it can be printed on standard 8.5"x11" letter-sized sheets.  When printing, set "Page Scaling" to "None".  I've also posted a "full" version, "EPPYak55-28_full.pdf".

To cut out the foam I printed the paper sheets, taped sheets together as needed, attached sheets to the foam with double-sided tape, and then cut through with an exacto knife.  I used a metal ruler for the straight lines and free-handed the curves, following the printed lines on the sheets.  I used UHU Por for gluing the foam pieces together.

See here for a gallery of pics.
See below for videos.

Notes:

A
7.0mm x 1.2mm carbon strip is mounted in the wing, and a 5.0mm x 0.6mm carbon strip is mounted in the elevator.  The easiest way I've found is to slice through foam, insert the strip, and then glue with thin CA and accelerator.  Pieces of 5.0mm x 0.6mm carbon strip can be mounted to the leading edges of the wing for reinforcement, attached with epoxy and blenderm tape.  Short pieces can also be mounted between the wing and the fuse, as shown in this picture.

I used blenderm tape for hinging the control surfaces.  Hinges can also be done with UHU Por and Welders glue, as described in the racores.com build guide.  For decoration, most any kind of paint can be used, or even magic markers.  I painted with Testors All Purpose Spray Enamel (in the small can).  One thing to be careful of is not to apply too much paint, as it will add weight to the airframe.

A strip of blenderm tape along the bottom of the fuse helps to protect it.  Putting double-stick tape on the leading edges of the wing can make it easier to catch streamers.  Quick field repairs can be made with blenderm or packing tape.  Tears in the foam can be repaired permanently and cleanly with UHU glue (giving it a few hours to set if the two sides can't be air dried for 5-10 minutes before pressing together).  Using CA to repair EPP results in "hard spots" in the foam.

A nice plywood firewall for mounting the motor is available from RA CoresLarge Plywood Firewall.  (Various other accessories are also available there).  Gluing the plywood firewall to the foam with epoxy works well.  The screws that come with the servos can be used to attach the motor to the firewall.  Be sure that the grub screws on the cylinder of the motor mount are not too loose, or the motor may come out in flight; but also beware of tightening them too much or the motor may bind up.  Installing them firmly with some blue threadlock is a good way to do it.


Pushrods can be made using carbon-fiber rods and music wire:

Carbon Fiber .070 40" Rod
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKAE5
http://www.rcfoam.com/product_info.php?products_id=736

Music Wire: .032 Diameter x 12" Long: 4 pc K&S 5501  $0.99
http://www.horizonhobby.com/Products/Default.aspx?ProdID=K%2BS5501
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWU97

One thing that can help is to make the heat shrink a bit "short" on each end so the CA can get in between the music wire and the carbon rod.  Music wire with a .040" diameter will also work.  Using Dubro Mini E/Z Connectors on the servo control horns makes it easier to adjust the lengths.



Parts list:

9mm 1.9# White EPP Foam, 1 Sheet, Size 18"x36"  $8.25
http://www.rcfoam.com/product_info.php?products_id=1599

Carbon Strip 7.0mm x 1.2mm x 1000mm 20-112 $3.90
http://www.rcfoam.com/cart.php?target=product&product_id=708

Carbon Strip 5.0mm x 0.6mm x 1000mm 20-109 $2.30
http://www.rcfoam.com/cart.php?target=product&product_id=705

Carbon Fiber .070 40" Rod  $1.40
http://www.rcfoam.com/product_info.php?products_id=736
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXKAE5

Hinge Tape, 1 Roll (Blenderm 1"x 5 yards) 40-002  $2.99
http://www.rcfoam.com/product_info.php?cPath=199&products_id=490

Dubro Micro2 Control Horn (2) #919  $1.26  (qty 2)
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXJGT5

Music Wire: .032 Diameter x 12" Long: 4 pc K&S 5501  $0.99
http://www.horizonhobby.com/Products/Default.aspx?ProdID=K%2BS5501
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXWU97

Dubro Mini E/Z Connectors (2) #845  $2.89  (qty 2)
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAHE6

FC 28-12 Brushless Outrunner 1534kv 16A 39g FC2812  $6.10
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5423

(Alternate source for motor):  EMAX CF2812 Brushless Outrunner Motor  $7.45
http://www.valuehobby.com/power-systems/brushless-motors/out-runner-brushless-motor/emax-cf2812-outrunner.html

GWS EP Propeller 8x4 (6pcs/set) GWS-DD-8040  $3.54
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=10046

3mm Prop Saver w/ Adapter & 3 bands 3MPRPSVR  $1.49
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=3738

(alternate) Prop Saver (3mm Shaft) EMX-AC-0548  $1.05
http://www.valuehobby.com/prop-saver-3mm-shaft.html

HXT900 9g / 1.6kg / .12sec Micro Servo  $2.69  (qty 3)
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=662

Hobbyking SS Series 18-20A ESC (card programmable) HK-SS20A-HW  $7.38
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6548

(alternate ESC) Hobbyking SS Series 18-20A ESC (USA Warehouse) HK-SS20A  $7.02
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17793

Hobby King Battery Monitor 3S HKing-3S  $3.99
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7223

OrangeRx Spektrum DSM2 Compatible 6Ch 2.4Ghz Receiver ORNG6  $5.99
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11965


Battery options:

Turnigy 1000mAh 3S 30C Lipo Pack (USA Warehouse)  $8.99
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=21124

Turnigy 1000mAh 3S 30C Lipo Pack T1000.3S.30  $8.91
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9491

GENS ACE LIPO 1000mAh 25C 11.1V Battery
http://www.hobbypartz.com/98p-25c-1000-3s1p.html

If using the Turnigy batteries you'll probably want to attach a male XT60 connector to the ESC.



Video of streamer combat with foam planes at the QMFC Holden field, September 9, 2010.  Good collision at 1:50.





Video of streamer combat at the QMFC Holden field, November 8, 2009.  Using BP Hobbies Fun Foam planes, which are cheap and fly well, but are brittle and tend to need lots of repairs between flights.  Video edited and posted by Tom D.





Here's a video of indoor combat taken with a FlyCamOne2 mounted above cockpit area of my Leadfeather Yak. First part is a bit of flying with rear-facing camera, then front-facing during streamer combat, with a couple of crashes. Edited using VirtualDub.





For the archives, here's a previous version of the EPP Foam Combat Plane.



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ET Heli