Viper F5D - RC Groups
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Dec 09, 2009, 07:53 PM
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Viper F5D

Well after having a blast with my Sunracer II, I decided it was time to get something a little bigger that I can push a little faster. So up comes the Viper from Stratair. You can find more info here:

I had seen a number of videos and comments here on RCG about the Viper, but somehow had my mind set on a Jibe2 when they got in stock. I had heard that the Vipers were going to be in stock soon, so decided to wait and and get Bob's opinion on them before I pulled the trigger. I have found before that Bob at SUSA is very good judge of quality and he gave this one a big thumbs up.

I normally call Tam from Tam Jets the "Candy Man" because everything he sells appeals to my senses (Fast, Sleak and Rare), but I'm starting to think Bob is not far behind.

DECEMBER 11, 2009
Okay, the Viper showed up today and was packed very nicely as usual from SUSA. I have had problems with FedEx in the past, but they managed to do a good job with this one.

Opened the box and everything I ordered was perfectly packed and wrapped. After I got the plane out of all the wrapping I could really appreciate the quality of it. Full carbon wing with kevlar fuse and CF reinforcements in all the right places. The instructions are not in English. Not really a big deal because, let's face it if you are planning to fly this plane you should know what you are doing. I can see the ailerons are a bit different than anything I have done before, but pretty sure I can figure it out.

One thing I have always had issues with is planes with a red bottom as they tend to look 'black' in the sky and orientation becomes an issue. It becomes a really big issue at over 160mph. Given the limited number of Vipers that came in my color choice was limited to Orange/Black. Yellow was my first choice, but given the great contrast I don't think there will be any issue with visibility.

There is no time like the present, so I decided to start the build; after all how hard could it be? I have my table setup and wanted to dive into the ailerons first. First thing you will notice is the pockets are already marked out, but are still covered by the CF skin. I started with a sharp hobby knife but it was making slow progress. I decided to just cut an "X" across the skin and use some scissors and a dremel to clean it up. 5 minutes on each side and they are ready to go.

Then I had a "moment" know the ones that make you wonder what the heck. After I have the servo pocket opened up I see that there is no hole to get the servo extentions down the wing. Thankfully the inside walls were made of soft balsa so some picking away at it and I got it open. Note the wing is thin; let me take that back...VERY thin. Take your time and just slowly chip away at it.

Next I need to make a hole in the saddle area for the wires to exit and I am praying that there are no other ribs in there; thankfully there isn't. I fished the extentions down the wing and out the hole. I lot easier than I expected.

Time to stop for the night. Tomorrow will be the tough part, aileron linkages.

DECEMBER 13, 2009
Okay, back to work. I spent some time looking at the aileron linkages and a bit unhappy that I need to cut into the wing. Plus it is very different than any kind of linkage I have done. I can see that the thought is to minimize drag, but I'm not sure it is going to make enough difference to justify it. However, up for trying something different I'm going to give it a try.

Looking at the servo extentions I'm using I decided to remove the female connector and hardwire them together. This way I can suck up the wire slack inside the wing.

Next I center the servo, trim the servo arm, make sure it is going in the right direction...and make some rough measurments to see where the cuts need to be. I do a bit more fiddling to make sure I have it right, mask off the area I'm working on and start cutting. The key I found was to not glue anything in until everything fits perfectly. Then I epoxy the control arm in first. Once set, I work on the fine servo placement to get a solid link with no slop.

In this case, I wrapped the servo with tape and used silicon glue. This way if I need to get it out, I can just cut the tape and out it comes.

These hyperion servos look really nice and fit perfectly. The programming was a pain as you need to install a bunch of different software, run batch files to get the registry entries right...etc. Eventually I got it though.

It took about two hours to get one aileron perfect, I will start on the other one later tonight.

DECEMBER 14, 2009
Okay, the second aileron took about 45 minutes now that I have a the routine figured out. The one is really solid and good movement as well.

I starting on the elevator and concerned about the wire having a bit too much play in it to allow for solid control. To get around this the tray that I built for the elevator servo will have a block to glue the outer control tube to so there is a solid connection on both ends. The tray was easy enough to build with some scrap material sitting around. The tricky part was getting it all in the fuse and hooked up. Since there are no adjustable clevises everything has to be dry fit then glued into place.

The elevator control horn had to really be cut pretty much to the point where the hole is right on the elevator surface. In fact I had to redrill the hole since it was much larger than the supplied wire.

The general process that I went through was to snake the plastic sleeve down through the back until it came up into the battery area. I then cut off about 3" of the plastic because it is the same length as the wire and I need the wire to stick out. Then I fed the wire down the sleeve until it came out into the battery area. I then fed both the sleeve and the wire through the pre-drilled block on the end of my servo tray, used my Z-Bend pliers and put the control arm on. I put a couple drops of CA to secure the sleeve to the wood block and this end was done.

Now I slid the entire unit back into the fuse close to the final position while pulling on the sleeve from the tail to keep it as solid and straight as possible. Now you should have about 6" of extra sleeve / wire and now it was time to figure out how to get a control horn in there. I decided to offset the horn a bit to give it more clearance. Once I was happy with the placement, I used epoxy and let it setup. The hole in the horn was basically right next to the control surface. I next removed all of the excess/exposed sleeve from the wire.

Now that servo was centered, I placed the elevator surface on the tail and marked the bend location on the wire. I made the L-bend and cut off the excess. Now I removed the tail section, slid the wire into the hole as I placed the elevator on the tail. Screwed it all in and checked the fit. Some last minute radio trim adjustments go it perfectly centered. Now I just secured the end of the L-bend with some shrink tubing and CA.

I now went back and tested the movement with the radio. Once happy I glued the servo tray to the fuse.

Next came the charge/safety plug and the RX placement. I just drilled an appropriate size hole for the small charge plug and got it installed with very little drama. Next I drilled a couple of holes for the AR6250 antenas near the rear of the wing saddle. Got all of the wires cleaned up and tucked behind the servo tray. I used a couple of short 6" entensions for the ailerons so I won't have to pull the RX in/out each time. The I used some packing tape to hold everything down and keep them out of the way.

Test fit the battery and CG is right on; which I'm very glad about since there is very little room to move it if it was off. Everything is plugged in and tested and seems to work great.

Final weight was 1lbs, 7oz for the airframe and an additional 10oz for the battery. A total of 2 lbs, 1oz flying weight, or 935 grams.

Last item is to get the control surface min/max setup as well as some spoiler/elevator mixing in.

The final setup on this one was:
APC 4.1x4.1
CC 10amp BEC
Hyperion 4S-2600-35C Lipo
Spektrum AR6250
SUSA's Charging/Safety Plug

Excellent Service & Shipping from Bob at SUSA.
Excellent finish on the plane; flawless.
The firewall was predrilled for my motor
The aileron servo bays were very nice
Super streamlined everything. Made for speed.
Full carbon wing & tail section

Would have like to have the servo bay rib so it would need to be manually cleaned up.
The control linkages were not ideal. I like adjustable hardware and straight connections rather than L-Bends.
Tight fuse makes for slow and careful planning
To be determined how my 2.4 radio will work with so much carbon, but should be okay
Not a big deal, but the instructions were not in English. The reality is all they needed to translate is the CG and control range specs.
Last edited by sbritton; Dec 16, 2009 at 12:23 PM.
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Dec 15, 2009, 10:15 PM
You down with EPP?
johnnyrocco123's Avatar
Wow! I watched that video of the viper on 6S with the mega 16-25-2.

That is the fastest I have ever seen a hotliner move.
Feb 13, 2010, 08:32 AM
Registered User
miche's Avatar
Hi, Nice built. Did you balance @ 55mm?

Originally Posted by sbritton

Test fit the battery and CG is right on; which I'm very glad about since there is very little room to move it if it was off. Everything is plugged in and tested and seems to work great.
Jan 09, 2012, 02:38 AM
Registered User
LVSloper's Avatar
tag; What is the CG for the Viper?
Last edited by LVSloper; Jan 09, 2012 at 07:52 PM. Reason: CG?

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