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HET Sniper 70mm EDF build

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HET Sniper 70mm EDF build

Old 11-04-2008, 08:29 AM
  #1  
devens
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Default HET Sniper 70mm EDF build

I have been wanting to build this plane for a while and I am excited to finally get going on it. Here is a look at the kit and the components going into it.

Specs:

HET Sniper 70mm EDF
JR 6200 2.4GHz reciever
HET 6904 70mm fan
HET 2W-20 motor
Tsunami 72A ESC
Futaba 3154 digital micro servos
Flight Power 3700mAh 4s 25c battery

The kit itself has very few parts. I was a little shocked not to find any directions for the kit. There is an excelent online manual however. The ESC also didn't come with any instructions. Again there is an online manual on the HET site.

So far the only work done was to clear coat the fuse. It was kinda dull. I also cut out the canopy. It is a little bit small. The dry fit didn't look good at all. I am going to have to do some work there.

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Old 11-04-2008, 11:04 AM
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Default RE: HET Sniper 70mm EDF build

Cool, I've been waiting for one of these to be built!
Old 11-04-2008, 06:58 PM
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CTulanko
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Default RE: HET Sniper 70mm EDF build

I am not sure which online set of instructions you were refering to, but there is a set at http://www.warbirds-rc.org/artman/pu...es/index.shtml

Best wishes and keep us posted,

Carl
Old 11-04-2008, 07:36 PM
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Bdsbob
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Default RE: HET Sniper 70mm EDF build

My Sniper came out nose heavy with a 4S1P EVO20 3300mah battery located under the canopy. I had to add 2.25 oz of weight in the tail to get it to balance. Flies great!


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Old 11-04-2008, 09:30 PM
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Default RE: HET Sniper 70mm EDF build


ORIGINAL: Bdsbob

My Sniper came out nose heavy with a 4S1P EVO20 3300mah battery located under the canopy. I had to add 2.25 oz of weight in the tail to get it to balance. Flies great!



Thats not good news for me with the 3700mAh pack! Are you using the green or the yellow packs by flight power?
Old 11-04-2008, 10:46 PM
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Default RE: HET Sniper 70mm EDF build

Ah, tuning in too. Im building the HET F16, but this one is next for sure.

I was wondering about the battery.. The EJF guys say I can power the sniper with 6S2500 evo lites and the 2W-25 for the fastest setup. I just unpacked the F16 tonight. I think if the sniper is set up the same dimensions, it is going to be nose heavy.

I think if you maybe put the esc in the windstream behind the motor, the CG would be easier. Im looking at that too. Im using Don's Pentium series. It has a switch mode BEC.

build away friend...
g
Old 11-05-2008, 09:32 AM
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Default RE: HET Sniper 70mm EDF build

The Sniper is notorious for having balancing problems. When it first came out, Mega 2T motors were the hot item and people were still flying NiMH's. I designed a 10 cell NiMH pack that had two sets of four cells, placed along the intakes inside the wing area, with a remote 2 cell in the nose so it would correctly balance and this worked well. Cheapbatterypacks.com took the design and sold these until NiMH’s faded from the scene and it was a good solution for balancing this model and allowed you to charge from under the canopy. The 2nd Gen 3S 2100mah Thunderpower Lipos were new and most fliers would hook two in parallel and saddle them as we did the NiMH's, along the inside intakes and they lived with having to take the wing off to charge because it was worth it for such a great flying model. They had to add nose weight under the canopy to get them to balance and this was found to be an acceptable solution.

As motors and Lipos improved, new changes were made to compensate. The best solution was to extend the intake duct a couple more inches by making a stiff coupler. This moved the entire motor/fan/ESC unit rearward and people were then able to place batteries under the canopy, while keeping the model balanced. I would recommend this as a balancing solution for the Sniper, although it requires you to make a very stiff fiberglass intake extension tube. Also, if your model is using the Monokote covered balsa wings, I would not recommend using the 2W25 as it can and has caused excessive stress on the very thin wing and folded them up during flight like closing a book. A new version of the Sniper was designed with a fiberglass wing and this was a better solution for the high power motors, although there were still a few incidences.

This model is very small and hard to see when flying and when coupled with an extreme motor will make it a real handful. Everyone likes their jets fast and this one, with a 2W motor will easily exceed 100mph, but with the top end motor, as well as the added weight of a battery, the Sniper will be a real rocket ship and it should only be attempted by those that can fly it safely and handle a crisis when they experience an air frame failure, as the standard wing will not tolerate it for long. Remember that it was designed when 3S Lipos were the norm. The F-16 is a much stronger model, with thicker glass layup and a thick, strong wing chord, so it was designed with expansion in mind...not so with the Sniper. Take it for what it's worth from the guy who build the first production model and has seen the good and bad of the Sniper over these many years.

Carl
Old 11-07-2008, 10:09 AM
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Default RE: HET Sniper 70mm EDF build


ORIGINAL: CTulanko

Also, if your model is using the Monokote covered balsa wings, I would not recommend using the 2W25 as it can and has caused excessive stress on the very thin wing and folded them up during flight like closing a book. A new version of the Sniper was designed with a fiberglass wing and this was a better solution for the high power motors, although there were still a few incidences.
Carl

Sounds like you have a lot of experience with this model. My model is new and it has balsa sheeted wings with monokote covering. Do you think I have an older model? I have read where guys were glassing their wings. I am afraid of the added weight that would bring.

Thanks for the intake extension tip. I will take advantage!

I woulds like to note as part of my build that the posterboard that comes with the kit acording the the online manual was missing. The ESC was out of any packaging and in a plastic bag. I assumed this was to preprogram the ESC. The strange thing was that all of the connector were on the ESC but the opposite connectors for the motor and battery were not included. The connector are like motor connectors not deans pins and out of all the connectors I have in my box none fit.
Old 11-07-2008, 05:06 PM
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Default RE: HET Sniper 70mm EDF build

I have spoken with a manufactures rep in regard to the wings. He stated that yes there used to be an issue with the wings. They went to the fiberglass wings but have since gone back to a foam sheeted balsa. The rep assured me that I have nothing to worry about with the wing integrety. Apparently the exhaust tube was supposed to be clear plastic and included with the decals. It is missing also. The rep is sending out the exit tube and the connectors. I think a section of exit tubing might work as a spacer to move the motor/fan back.
Old 11-08-2008, 07:57 AM
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Default RE: HET Sniper 70mm EDF build

Devens,

I am using the EVO20 4S1P 3300's. I found out only after building the Sniper that I had to add 2.25oz of weight in the tail to get it to balance. The suggestion to move the fan back is a good one and I will be doing this soon.

Duralite Batteries has a good clearance sale on Flightpower going on right now.

Here is my setup-

Sniper
2w20
CC 80 ESC
AIL-Hitec Thin wing MG servos
ELEV -Hitec MG
Eflite EC3 connectors
separate 800mah 2 cell lipo receiver battery
CC BEC as voltage regulator for receiver battery
Spektrum AR500
Bungee dolly system

-
Bob
Old 11-08-2008, 02:23 PM
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Default RE: HET Sniper 70mm EDF build

Do not use part of the exhaust tube material he is sending as it is too thin and only good for exhaust, as the thrust will keep it expanded. You will need something stiff, like homemade layered firberglass that won't collapse under the vaccum in the intake.
Old 11-26-2008, 10:30 AM
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Default RE: HET Sniper 70mm EDF build

Made some progess on the Sniper. When I assembled the fan/ motor the fan was not centered in the shroud and acctually rubs the side. I have dissasembled and tried to adjust within the tolerance of the motor mounting holes with no luck. I guess I am going to have to shim the motor. I also started hinging the flight surfaces. I always pin my CA hinges with t-pins then cut them off with a dremel tool. I noticed that the stock hinges where stuck in their slots like there was a small amount of glue already on the hinges. when the hinge was removed the outer layer (white wicking layer) was torn off leaving a clear plastic tab. I am substituting for some different CA hinges.
Old 11-26-2008, 06:32 PM
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Default RE: HET Sniper 70mm EDF build

Wrap thin masking tape around the motor body around the area that just sits inside the housing, create an interference fit, this will help greatly in lining the motor up. It takes a lot of time to build a 6904 well, and you need to make it perfect if you want to leave it in the plane permanently! Oonce you have the motor centered you need to fit the collet and then run the motor up slowly and observe the collet rotation, keep positioning it until it is rotating without any/too much runout. Then drop the rotor on and tighten the bolt up, spin it up slowly and feel the housing for vibration, if it starts to vibrate as the RPM comes up stop, reposition rotor and collet and try again. Keep doing this until you find the sweet spot where there is either no vibration, or only a tiny harmonic about 1/4 throttle which will come and go within a couple of clicks of the throttle stick. All 6904's are like this and the 30 mins you spend getting it right will be worth it.

Rub marks on the housing are deposited blade, scrape them off carefully with an exacto knife, you can remove all the deposit this way and maintain the level and smoothness of the housing.

I always put the ESC behind the fan but out of the duct, I cut a rectangular hole in the duct and then place the ESC over the hole so that the heatsink side is in the hole. Then tape the ESC in place with plenty of masking tape, keeps it cool, keeps your weight towards the back, keeps the airflow unobstructed and reduces the chance of ESC joint fatigue from being buffeted in the exhaust.
Old 11-26-2008, 10:19 PM
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Default RE: HET Sniper 70mm EDF build

Thanks, great information!
Old 11-29-2008, 05:08 AM
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Default RE: HET Sniper 70mm EDF build

believe ctlanko about the wing!! i've experianced it 1st hand and i glassed the centersection 8" out top and bottom,it folded at the glasses end,cost me big time,imo glassing is'nt enough,you ned to add a spar the total length of the wing. now this is only if you use bigger 4s and motor setups,its not a matter of if but when its folding if left stock
Old 11-29-2008, 11:02 AM
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Default RE: HET Sniper 70mm EDF build


ORIGINAL: BASHER

believe ctlanko about the wing!! i've experianced it 1st hand and i glassed the centersection 8" out top and bottom,it folded at the glasses end,cost me big time,imo glassing is'nt enough,you ned to add a spar the total length of the wing. now this is only if you use bigger 4s and motor setups, its not a matter of if but when its folding if left stock

In talking with a gentelmen at Electric Jet Factory I posed that concern. He said that the wings were back to a balsa sheeted foam with denser stronger foam. Apparently an older version had weaker foam, then a second version was built up balsa I beleive. I think I will add a carbon fiber spar just for insurance. This is my first EDF by I am a proficient pilot so I am sure I will push the envelope.

I am working on the build slowly. Mostly metally with planning. I have got the electronics soldered up and I am working on the fan assembly. I plan to post some pics soon. I am building a test stand and playing with the motor assembly. Thanks to whissel blowa I am hopfully going to have something that works. It is amazing the lack of instruction provided with stuff in this industry!

Well it is 48 and no wind today so the build will be on hold a few more hours. Off to the field! [8D]
Old 12-02-2008, 08:55 AM
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Default RE: HET Sniper 70mm EDF build

here is a pic of the hinges supplied with the kit compared to a couple of CA hinges from other manufactures. The hinges on the bottom came with the HET kit. I will be substituting hinges.
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Old 12-02-2008, 09:11 AM
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Default RE: HET Sniper 70mm EDF build

I had a real hard time centering the motor and fan in the shroud! It was so far off center I had to enlarge the motor mount holes and not use the centering ring. Once the fan was centered I tested it for balance and it ran with very little vibration. I could say no vibration! Mounted the ESC in the duct because of limited access behind the fan. The first pic is of the fan off center and rubbing the shroud. The second pic is of the motor off center in the mount to center the fan.
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Old 12-02-2008, 09:30 AM
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Default RE: HET Sniper 70mm EDF build

Here is a pic of the fan assembled and another of the fan installed in the fuselage.
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Old 12-02-2008, 10:33 AM
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Default RE: HET Sniper 70mm EDF build

Funny thin I'm having the same issues (See EFlite - F16 Thread http://www.rcuniverse.com/forum/m_78...mpage_9/tm.htm ) I Was thinking of gradually scraping away some plastic with an Exacto or a Reamer, but now that I see the pic a Dremmel will work as well... I was just concerned with taking too much off and getting too close to the center rung, and weakening the plastic....
Old 12-02-2008, 11:47 AM
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Default RE: HET Sniper 70mm EDF build

I looked at your post in the f16 thread and I don't think we have the same issue. The ovaled openings are motor cooling openings not mounting holes. Your motor looks small from what I can see. The dremel was for grinding on the fuse to get the fan in the fuselage.
Old 12-02-2008, 12:00 PM
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Default RE: HET Sniper 70mm EDF build

I jumped to the wings to start there assembly. I appears they have added a wood spare in the wing. There was supposed to be tunnels for the aileron wires but non were found. I will have to make some. You can see the spare in the pic if you look close.
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Old 12-03-2008, 09:06 AM
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Default RE: HET Sniper 70mm EDF build

Well last night I took an iron to the covering. I must say the covering is very good on the kit (what there is of it). I had some minor wringles on the bottom of one wing and the edges to go over is all. I also cut out some of the decals and applied a few of them. I mounted the elevator on the horizontal stab. I did not use the CA hinges that came with the kit. I enlarged the slits and drilled a hole in the center of the hinge slot. I will use t-pins to pin the hinges and cut the access pin away with a dremel. I'll show pictures of the pinning process. I dry fit the stab on the fuse. It does not fit square with the fuse notch. I had to twist the stab in the yaw axis to get it to be square. The build instructions on the HET website shows and highlights how the stab fit squarely on the fuse. (not on my kit!)

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Old 12-05-2008, 10:23 AM
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Default RE: HET Sniper 70mm EDF build

I am working on the battery compartment and the cock pit now. I am in the planning and design stage. I was thinking that I would line the battery compartment with white beaded foam. I would cut pieces to fit in the nose cone, below, and beside the battery. One concern I have is the fact that there is no airflow around the batteries. I am have second thoughts about encapsulating hot batteries in foam. Another option is to build a lite ply tray and strap them in with velcro.

For the cockpit I am working on the method to secure the canopy. The canopy is the access to the batteries so screws would be inconvienient. I have some earth magnets so I am thinking earth magnets with some type of latch. I have lost canopies from electrics before and it is a bummer. Trying to find a canopy in a corn field is like looking for a needle in a hay stack.
Old 12-08-2008, 09:10 PM
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Default RE: HET Sniper 70mm EDF build

By all means add a spar. I was going to use a carbon arrow shaft for mine. This would be quick and easy. Here is a link to mine http://www.rcgroups.com/forums/showthread.php?t=876488

Do a search on Sniper wing failure on RCGoups. I came up with alot. Its a very thin wing. It is very nice and flies well but it needs a spar

Jeff

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