BD-5 microjet attempt - Page 2 - RC Groups
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Aug 22, 2004, 01:50 PM
Alfredo Rubio's Avatar
WOW!!!!!! a pager fan!!!! I hope too the plane will flies very son Yhoshua built the prop version in Freeflight No-Cal, some tricky to trim, but finelly flew very fine, good luck.

Evenu Shalom Aleheim.

Alfredo Rubio
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Aug 22, 2004, 03:10 PM
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waow... does it work?
Aug 22, 2004, 04:17 PM
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RNAF's Avatar
I really like it! It doesn't matter if it won't fly or if it's a powered glide, I like it!
Respect 2 u

Aug 22, 2004, 06:15 PM
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Dave, I surlly hope it will fly. Pete, I was looking for that motor ever since it was first posted, but they just don't import it over here. I woull'd defiantly give it a try if I had one. I added a more clear picture for the fun placment. I've tried to make everything as streemline as possible. Aerogel, I just happend to have the fun from another project. It's far from being optimize but some how it turnd out that it loads the 4.5 ohms Didel motor to it max efficiency ( not power ! ). The blades are flat and aren't even twisted. After it will fly I'll try to make a more efficient prop.
Duct Fun Data: 3v 0.21A 2.15 gr' thrust
3.5v 0.25A 2.55 gr' thrust
4v 0.28A 3 gr' thrust
so assuming a working voltage of 3 to 3.6 volts there is deffiantly a need for two funs, or maybe an M20 fun, and the plane should weight no more then 12 grams. Also, one 60mah batt. can still be used to power both.

Alfredo, you're funny Hava nagila...
Aug 22, 2004, 08:38 PM
My member is not
Zlatko's Avatar
Nice work nachman,
Great detail and precision.
With your ducted fan unit, try adding a bit of tube after the fan, same diameter as the main shroud and about the same lenght. That should give you perhaps another 20% thrust ( like duct D here ). What material did you use for the fan and duct?
BTW, I love BD-5s as well. For people interested this is a good site , they have a plan for a Super BD-5 .
Last edited by Zlatko; Aug 22, 2004 at 08:42 PM.
Aug 22, 2004, 10:08 PM
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Pete P.'s Avatar
That thing kicks butt ;-) Is beautiful!!!! All it need sit more power to zip along!!
Aug 23, 2004, 04:56 AM
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bmutlugil's Avatar
Hi Nachman,

Very good and inspiring, I am sure everyone seeing this thread will have the desire to build a BD-5.. The machining is impressive as always..

Best regards,

Aug 23, 2004, 05:05 AM
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RNAF's Avatar
I wonder how a BD-10 would do?
Nachman I have confidence in you! Good luck with your to-come-flights!!!
Keep us updated!

Kind regards,
Aug 23, 2004, 05:11 AM
Registered User
RNAF's Avatar
Oh, I just figured something, what about your airfoil? Don't you want an under-cambered one for more effective lift? Your current airfoil looks like the standard Clark-Y which gives less lift for smaller models?

Aug 23, 2004, 08:45 AM
Registered User
Is there a modeler that doesnt admire the lines ??????
You've just inspired me to finnish my speed400 version-its been hanging unfinnished for 2 yrs .
Aug 23, 2004, 09:19 AM
devilscries's Avatar
thats dead sexy
Aug 23, 2004, 01:31 PM
Alfredo Rubio's Avatar
Thanks Nachman you posted in the tech datta you got a max of 3 grams in thrust, do you can tell me the BD-5 total weight?

Ruaj Aleheim

Alfredo Rubio
Aug 23, 2004, 07:31 PM
Registered User
I've made another Duct-fun with a counter rotating prop this time. So now it has about 4 to 6 grams total thrust for a 14.5grams plane. I'll check how it flys over the weekend with throtle only and then it will be time to re-do the airframe with lighter balsa and add some actuators ( probably 2 x 28 ohms 4mm motors).
Zlatko, I'll check what you sugested and add it if it helps. Another 20% is a lot.
Dave, the airfoil is the same as the one on the original rubber power plans, and I have no idea what it is, but seems to be working well on this plane. It doesn't need to glide fast to stay in the air.
Aug 23, 2004, 08:32 PM
Alfredo Rubio's Avatar
The guys who knows about edf planes said the thrust mus to be the 50% of the total weight, and I noticed you put the motors in pusher configuration, if you let me to say, maybe is better in tractor configuration, because the stators (the fixed blades) working cleaning the flow, I mean in a stight flow and not turbulence, this is wath makes a fan eficient, I have a FF BD-5 plan too and the wing profile is flat bottom, I did a search in google about the BD-5 and a custom plane has 2 jets in fuse sides as the Learjet!!!

where do you get this tiny fans?


Alfredo Rubio
Aug 23, 2004, 08:49 PM
My member is not
Zlatko's Avatar
One fan was very nice and looked good, but now you are just showing off . If you can make one that nice than you are good, if you make 2 then you are better, if you make more we WILL buy them ) ... PLEASEEEEE!!
Alfredo is correct but that will change the balance, but then again you did put 2 fans on it . A quick way to test my sugestion is to make the duct from paper and tape. I am currious to see by how much the thrust is improved.
I didn't even see the "counter rotating props" bit, I was too buissy looking at them. NICE!
Last edited by Zlatko; Aug 23, 2004 at 08:53 PM.

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