Greg Covey

Since I am not using the gear or retracts, the nose wheel opening seemed like a great place to mount a bungee hook. I cut the fixed nose gear wire with a Dremel tool and CA'ed it into place. The wire is held very solid by the plywood bracket.

whissel_blowa

I am sorry but I just dont get this, 700 watts and 55 amps equals ridiculously low voltage, which means really high internal resistance of the pack and/or the wiring.

4 cell pack = 16.8v fully charged. You are saying your voltage is at 12.72, thats a drop of 4.08 volts under load. Divide this by 55 amps and you have 74mR internal resistance in play here.
The Chinese 4000mah 4s pack I am using in my Lander Panther shows 14.3v under load at 56A, thats an internal resistance of only 44mR.


I am not trying to have a go at you Greg, but you did say to Devens: One key item is your FlightPower pack...it can deliver the power without much loss from voltage drop.

Yet the figures posted show the complete opposite. We all know Enerland makes the cells that flightpower uses, they are basically a Polyquest XP or XQ cell, rebadged by many. I believe these cells cannot perform well enough for EDF anymore, they may have been good 18 months ago but the Chinese ran past the Koreans almost a year ago now and have never looked back.

I run a wemotec minifan PRO with a HET 2W18 in my F16, it runs at 55A & 800w on 2500 4s1p 25c packs, I fly it 50% WOT and 50% fooling round, the pack comes out around 45 degrees C and I put back 2300mah usually. 15 abusive flights on one pack so far and it still holds over 3.5v per cell under a 22c load.

Just seems a bit biased when all the reviews centre around FlightPower packs when they obviously cannot stand up to the stress of the review model...

Falconjet50

Greg, I am lookinjg at the new HET F-18 90MM EDF. Have you heard anything about this? I am very interested in doing retracts, I think there will be a little more room to work with in the 90mm version. Little Screamers just put out a 90mm motor. Take a look at it , see if this will work on a 6s set up. Thanks.

Falconjet50

Also Greg is it possible to use the rudder on the F-18, is there a way to use the dual rudder?

devens

My HET sniper kit came without any exit ducting. I have tried a piece of transparancy and the fan is greater than 8.5 inches in circumfrance. What would you suggest as ducting material?

evan-RCU

I'd put a couple hard wood block fillets inffront of and behind the bulkhead to reenforce it a bit...

Greg Covey

FalconJet,

Yes, you can see the 90mm F-18 at [link=http://www.rc-warbirds.com/index.php/cPath/64_86]R/C Warbirds[/link]. It is not a twin but substitutes a 90mm fan for twin 70mm fans. Some EDF folks focus on efficiency or cost or both so the 90mm version is good for them. I can't argue with those qualities but also like the cool sound that only a twin can provide.

You're referring to the new [link=http://www.hobby-lobby.com/littlescreamers.htm]JetScreamer 1490[/link] in the Wemotec Midi Fan PRO for 5mm shafts. I haven't been a fan of outrunners in EDF but maybe this will change things.

The twin 70mm F-18 has the option for dual rudders. If I was using retracts to fly off pavement, I would install the rudder(s). Too keep things light for my grass belly landing version, I decided not to install the rudders.

devens,

You are using the right material for exit ducting. Perhaps you can simply tape two pieces together using double-sided cellophane tape or find a legal size piece at Staples or OfficeMax.

evan,

Good advice! I am slowly adding some extra epoxy to parts of the existing formers but I'll check for weak spots on the bottom.

-
Here are few photos showing both wing halves installed.

I deviated a bit from the manual's suggestion for installing the horizontal stabilizers. I glued one on at a time using 5-minute epoxy and held them in place while it set. I then CA'ed the elevators in place afterward. Unlike the self-aligning wing halves, the stabilizers and fins are manually aligned. Ben from Texas noted this earlier as being a difficult area. I wonder if he has test flown his F-18 yet?

Pepperpete

I am extremely interested to see if this can be hand launched. There is no way I would invest in a bungie system. Takes all the fun out of it for me.

Strega1

My Feedback: (7)

Hello Gregg,

In answear to your comment, have I flown my F-18 Jet, the reply is " no ". I tested the fans ( make sure they are turning the right direction ) and found out that I had to use an additional battery to power up the the 2.4 reciever and servos. Since I didn't want to use an additinal battery, extra weight, I shot an e-mail to the guy whom I purchase the jet from. He told me I had to use an external ESC. So I bought one for 23.00 bucks. I recieved it on friday the 21st.
I need to splice the ESC to the battery and the reciever and add the vertical fins and balance it.
The reason I haven't finished it, is because of the price of kerosene, about 50.00 bucks a 5 gallon container. I guess I'm going to break down and buy it so I can work nights and finish it by this saturday.
I have just retired this April of 2008. I have the opportunity to work part-time for UPS as a package loader from 3:00 am to 7:00 am. I have an interview this afternoon at 2:30 pm. I'll keep you posted.

Ben Cubillos

Greg Covey

Ben,

Thanks for the update. I'll assume you meant BEC not ESC. I will be using a [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXSWL3&P=ML]CC BEC[/link] in my F-18 probably programmed to 5.5v since my S75 servos are not rated for 6v. This simply means that they don't have longevity specs on 6v so they only rate it for 4.8v.

Good luck on your interview!

Pete,

We'll see. My best estimation is that this bird is built for speed and may need a faster launch to get airborne. The thin wings are low drag which means low lift at low speeds. A simple bungee can be made from a corkscrew dog leash anchor and surgical tubing or cord from a home improvement store. I may also try the mini-bungee that came with my V-Pro MIG 15 instead of my bigger machined one with a foot launch that I use on the Hayoe F-18 twin foamie.

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The elevator servos installed per the manual instructions. It is up to the builder to cut slots in the fuselage side for the servo arms. Since the servos run in opposite directions, I ran both leads up front and mixed them into a spare channel on my Spektrum AR6100 receiver. The remaining control horns in the kit didn't match size so I used similar ones I had on hand. The linkages were provided in the kit. One clevis is soldered to the rod and the other is adjustable.

Strega1

My Feedback: (7)

Hello Greg,
You are right, it is a BEC. Please understand that I,m new to electric flite and I'm learning as I go along. Some times I come across as a "Maroon ", A Buggs Bunny term.
I have learned quit a bit about Lipos, BECs, Fans, motors, wire connections and flying EDJ. Ever sinse I flew the Hobby Lobby F18 jet, I was hooked. I had to have a faster and bigger one. I figure I could spend about $ 1000.00 for a great one. HET gave me that oppotunity.
Greg, UPS is willing to hire me if I pass a background check. If and when I get hired, I will probably be the oldest "giszzard" in " preloud ".
I'll talk or post later.

Ben Cubillos

rcmiket

Hey Ben, Think you might be ready Sunday? Let me know.
Mike

Strega1

My Feedback: (7)

Hello Mike,
I will do my damnest to have it ready, hopefully. Hey Mike, on a sad note. Al(Fagio) past away sometime within the last four days. I saw it on the obbis this morning.

Ben Cubillos

Greg Covey

My AMMO [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXLWY5&P=7]28-45-3600[/link] motors arrived so I tested them in the HET [link=http://www.ejf.com/index.php?main_page=product_info&cPath=82_80&products_id=230]6904[/link] 70mm EDF unit. I was prepared to swap out the 4-blade rotor with either an MPI or Wemotec 5-blade rotor but did not find it necessary as the power measurements were great for my application.

My test stand is used for 70mm and 90mm EDFs (and soon my E-Turbax 120mm from [link=http://www.jethangar.com/]JHI[/link]) as well as my VTOL project balancing. The front gear fit inside the pink foam blocks so that the plane can "hover" or balance off my back porch or table. Note that safety glasses are used when testing EDFs.

I measured 680w at 52 amps using two 25C 4s packs; the 12oz ThunderPower eXtreme V2 3300mAh pack and the 13oz FlightPower EVO25 3700mAh pack. This will provide a combined 1360 watts for a twin set-up that uses two of everything.

whissel_blowa

You really need to get some more capable batteries for these sorts of power systems, thats just over 13 volts under load, shows a lot of sag. That motor is close to the HET 2W18 in Kv and with a pack capable of holding around 14.5v you should be seeing 800-850 watts per fan. Would be nice to know RPM figures, makes it much easier to compare the motor/fan combo with other known setups like the 2W20/6904.

Greg Covey

After first sanding the leading edges so that they tapered to a smaller diameter, the ducted fans fit into the carbon ducting like a snug glove. They appear to only need some tape to secure them in place but I will likely cut some custom foam pieces for additional support.

balistc1000

Look's great, I'm real interested in this kit. Can't wait to see it fly!

AYATES

My Feedback: (2)

does anyone have any tricks for balancing a edf unit ? I have a gws a4 skyhawk with an common sence t-rex 450 motor, common sence 45 amp esc and common sence 2600 mah 14.8 v. battery. It just seems kind of loud and has a little vibration. Any help would be apreciated.
Thanks, Adam Y.

AYATES

My Feedback: (2)

does anyone have any tricks for balancing a edf unit ? I have a gws a4 skyhawk with an common sence t-rex 450 motor, common sence 45 amp esc and common sence 2600 mah 14.8 v. battery. It just seems kind of loud and has a little vibration. Any help would be apreciated.
Thanks, Adam Y.

Greg Covey

There are two stages to properly balance the EDF rotor. Since many of the EDF rotors already come dynamically balanced, the first stage is usually a sanity check but you should balance the rotor on a device like this Dubro [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD712&P=7]Tru-Spin Prop Balancer[/link]. The rotor should not favor dropping one side as you rotate it. You can either sand the heavy side or dab some clear nail polish on the lighter side.

The second step is to insure that the rotor adapter sits properly on the motor shaft. Even if the rotor is balanced, it will vibrate if the adapter is not properly seated. This can be checked by rotating the rotor when it is on the motor and look for the tip going off center. If it is off center, you can usually adjust it by forcing it in the desired direction after loosening the nut...then retest.

AYATES

My Feedback: (2)

Greg,
Thanks for the info. I'll take your advice and let you know how it goes.
Thanks, Adam

Greg Covey

Good luck, Adam.

The exhaust tubes were trimmed about 10mm to eliminate the molding marks and obtain the recommended 58mm diameter.

I extended the three motor wires by 20" on both of my FlightTech 60A ESCs. I also eliminate the On/Off switch by soldering the wires together. When plugged into the Spektrum AR6100 receiver, the red center wires will be removed because the internal BEC is not needed. I am using an external CC BEC set to 5.5v.

The Mylar (PVC) thrust exhaust tubes were made using the conical template that comes in the manual and the Mylar sheets that come with the HET kit. I used double-sided tape to create the tube and then added a strip of regular cellophane tape along the outside for added support.

Greg Covey

I decided that the simplest approach to secure the fans was to glue them in place using Zap Goo II which is similar to plumbers goop. The glue remains flexible when dry and bonds virtually everything. After first testing the motor direction for air flow, I ran a ring of glue around the outside front of the fan housing and pressed it in place.

The thrust tubes were inserted from the rear of the exhaust tubes and taped into position. The hatch cover simply pressed onto the fuselage and is held by magnets. I will add a few pieces of cellophane tape for added security.

I did a quick motor run test on each side and found no vibrations. The air flow out the rear was impressive!

devens

I use Zap Goo also. It is great for glueing servos in place! Usually you can peel whatever you glue off if you use enough force. The the glue remnents remove farily easily also. Do you think you will have trouble removing the fan if you have a motor failure? I know in my sniper there isnt much room to grab ahold of the fan shroud. I don't think I could break my fan loose if I glued it and needed to remove it for any reason.

D [8D]

Strega1

My Feedback: (7)

Hello Greg,

It's nice to be back. My computer crashed last wednesday, November and it has been hell trying to get it fixed. I haven't been working on my F18 jet. I have been down with the flue and it is no fun, especially the running nose. This week my wife has me doing home repair jobs and that is no fun either. Looking at the latest pics on rc universe and your jet, is looking great. Question, where are you placing the reciever, front or back? Doesn't look like there is enough room where the fans are. I'm placing the 5s lipo underneath the canopy. MaxAmps made the 24" cables from the fans the the Lipo upfront. I just can't picture long servo and ESC's extension wires to place the reciever up front. I had to do the same sanding to the fan housing to get them to fit. I wasn't planning on using adjesive to hold the fan units in place. the fit was tight. Maybe I should. I'll keep posting.

Ben Cubillos