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Apr 01, 2007, 11:51 PM
Ming's Avatar
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Discussion

Windrider F35 foamy jet


Dear All

I am planning to make a F35 electric foamy jet as following 3D drawing, any suggestion on
EPP or EPS foam material?
32 inch wingspan or smaller?
use 64mm or 70mm EDF?
Aileron or just taileron?
What kind of color sticker decal to use?
Clear or just foam canopy?
Need landing gear?

Ming Lou
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Apr 02, 2007, 12:17 AM
3d and EDF, some scale
MustangAce17's Avatar
Ming,I would like it EPS foam, Wemo Microfan size or 50mm,32 inch ws is good and clear canopy(would be great to try a VTOL version if cheap enough). Looking great and put me on the list for sure
Apr 02, 2007, 12:45 AM
Registered User
Ed Waldrep's Avatar
I'll say 68 to 70mm edf, that way the very common wemotec Minifan 480 can be used. It's a great fan that can absorb a lot of power, comes with a metal adapter that's held on by grub screws (not glue like the GWS), and there's a lot of models out there that use that size fan: many of the RBC kits, and there's probably thousands of HET F-18 arfs that have been sold over the years. The models may crash eventually but usually the power system survives.

That being said, a larger 90mm size would be nice so that it can absorb the weight of retracts. Retracts are more available in the 90mm/6 lb range, smaller than that and there choice of air retracts is very limited and expensive. Maybe retracts wont be a must but having the option of fit them without heavy modification is a nice feature.
Apr 02, 2007, 03:11 PM
Registered User
ARCHER7153's Avatar
It should be able to ROG. Eps with 70 edf clear canopy
Apr 03, 2007, 06:19 AM
Ming's Avatar
Thread OP
OK..
Hereis the specifications:
EPS foam material
32 inch wingspan
46 inch lenght
70mm EDF with BL motor
3S 2100mAh Lithium Polymer battery
25A ESC and two Futaba #3107 servos
Total take off weight less than 2.25 lbs.
Taileron control

Ming Lou
Apr 03, 2007, 08:39 AM
3d and EDF, some scale
MustangAce17's Avatar
sounds great Ming
Apr 03, 2007, 06:23 PM
Registered User
ARCHER7153's Avatar
Great
Apr 03, 2007, 08:59 PM
1.21 gigawatts
EDDIEGIGOWATTS's Avatar
ming i hope you are going to market this f35 like the airbus 380
i want one
Apr 03, 2007, 09:08 PM
EDF rules... :)
AirX's Avatar
The picture you posted did not show much of the inlets and duct, how are they defined in area at the inlet and area at the outlet?
Bad duct will not make it much fun and if you do it right it will sell easily because the performance will be there.

Eric B.
Apr 05, 2007, 06:31 AM
Ming's Avatar
Thread OP
Eric

Yes, I have some problem on the duct design.
If the fan diameter is 100%, can I make the inlet 88% and outlet 85% or even smaller?
Because the real F35 inlet is quit small.

Ming Lou
Apr 05, 2007, 09:31 AM
Registered User
Ed Waldrep's Avatar
FSA (Fan Swept Area) is the area of the opening where the air goes through the fan. In other words, find the area of the entire face of the fan, the subract the area of the motor/spinner/hub, the result is the FSA.

Here's an example
WeMoTec Mini fan 480
Fan Shroud ID 2.715"
Motor tube OD 1.27"
Max Area 5.79 sq. in.
Motor tube area 1.27 sq. in.

Fan swept area 4.52 sq. in[U].
Tailcone diam. 100% 2.4"
Tailcone diam. 95% 2.28"
Tailcone diam. 90% 2.16"

The inlets may look quite small but if you measure and calculate the area you may find plenty of area. 100% of the FSA is the goal, a bit under you'll be ok, a bit larger is OK. You can go way above that and possibly improve static thrust, but too large and the scale looks begin to suffer (look at the huge nacelles on the GWS Me 262 and you'll see what I mean, they're way oversized) and there's increased drag at higher speeds because too much air is going in.

For exhaust aim for about 85 to 90 percent of the FSA.

Another thing to consider is the fan location. For most fighter type edfs, with the battery in the nose under a hatch, the fan needs to be placed with it's face toward the trailing edge of the wing. A fan access hatch on the bottom of the airplane usually looks better than one on the top.

Also, the battery mounting area up front should be made as long as possible to allow room for different sizes, lengths, and weights of batteries to be used. Some users will want to upgrade the power and making a small opening for only one size of battery that can't be moved makes upgrading difficult, a heavier battery would cause problems with balance.

Another factor is inlet ducting....it should be kept far apart until mid wing, then it should come together to meet at the fan. The reasoning is this will allow room between the ducting for a battery to slide farther back to achieve proper balance. A stock size battery may not need to go back that far, but with a power upgrade a heavier battery may be needed. However, you still need to make room for retracts on the outside, so there must be some room between the outside of the fuselage and the ducting, so back from the inlets in the front the ducting can head toward the center of the airplane but not at a really sharp angle, then once you get past the rearmost end of a battery the ducting can make another turn toward the center of the airplane and join in front of the fan. Avoiding sharp turns is important, make gradual turns if possible. With molded foam this is easily achievable.

The inlet ducting should be of a fairly constant area between inlet and fan. The area will actually increase because you're going from 100% FSA at the inlet to the full diameter of the fan at the back which is more than 100% FSA, that is unless you place a round fairing that matches the diameter of the fan in front of the fan, then fairing would end at the spinner (with some fans the spinner would be left off and the fairing would almost touch the hub so there's a smooth transition but it depends on the fan). Look at pictures of the Harrier VTOL inlets to see what I mean. If the inside of the fuselage is left open with no inner inlet walls, that creates drag and limits top speed.

On further thought, a 90mm sized airplane is better able to carry the weight of retracts and larger batteries, and can run with larger tires thus making takeoff from longer grass feasible. Power could be anywhere from 350 watts for a light floater to over 1000, depending on the motor and fan. Also, there aren't many 90mm size foam airplanes out there, and there's already a few different 70mm fan F-35s out there on the market (Scorpio, RBC, Oakdale (well that's a 90 but it's reall on the small side). A length of about 46 to 50 inches would be nice.
Last edited by Ed Waldrep; Apr 05, 2007 at 09:50 AM.
Apr 06, 2007, 08:41 PM
EDF rules... :)
AirX's Avatar
Hi Ming,

Eds on it. I like the 90mm size too if it makes a difference as like ED said there are a lot of 70mm versions out there already.

Eric B.
Apr 19, 2007, 12:29 PM
Ming's Avatar
Thread OP
Dear Fellow

Still far away to mass production, like to share some of drawing here:

Ming Lou
Apr 20, 2007, 11:11 PM
1.21 gigawatts
EDDIEGIGOWATTS's Avatar
looks great MING,, keep up the good work
Apr 23, 2007, 09:02 AM
Registered User
Quote:
Originally Posted by Ming
Eric

Yes, I have some problem on the duct design.
If the fan diameter is 100%, can I make the inlet 88% and outlet 85% or even smaller?
Because the real F35 inlet is quit small.

Ming Lou
My basic knowledge of bernulli .. would tell me that inlet and outlet are effecting the airflow resistance ... and the outlet will play a role between trust and speed ... so bigoutlet means not only less resistance, but also more trust and less speed.

So ... for a "slow" park bird ... I would go for outlet bigger then inlet.

I additional ... I personally buy only EPP airplanes now ... sure gears are more expensive then frame ... but rebuild and fix a birds at every bad landing it is not my dream ... after have beat hard my EleBee and Su-29 with no fix needed ... I'm not for spend hobby time on fixing

e_lm_70

PS: I personally like birds in a 120cm 140cm wing span ... so ... maybe a bigger EPP with dual duct ... it will be my idea next bird


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