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Old Nov 17, 2001, 10:14 PM
GBR2 is offline
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Snohomish, WA
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Viper Twin Kit Evaluation

My Viper Twin arrived today and I'd like to give my impressions of the kit. The box the kit arrived in is quite strong and everything within arrived with no damage. All the heavy components are packaged in sealed plastic bags that are stapled into a "sealed" area of the box. Being a foam kit, the actual fuselage is made up of only 5 pieces of foam. All of the carbon fiber spar channels are molded in as are the two servo mounting holes with molded servo lead channels. That is a nice touch as you don't have to cut into the foam itself. With in the canopy area, there is a nice molded area for the battery pack and a large open area to place your radio gear. Due to the space available, a receiver with either a top or end block could easily be used here without the worry of over stretching wires. There are even molded in recesses where the canopy velcro pads will install. The molding continues with spaces for each motor. My only concern here is if the foam will compress to much or actually tear once the motors are mounted with the supplied zip ties. I would personally elect to apply some thin fiberglass to this area to strengthen it up. Having done all of this built in molding, I was a bit surprised to see that there was no antenna channel molded into the structure. I would have thought this would have been easy to do.

The best/worst part about the molded wing has to do with the interlocking structure. Where the two wings attach to the middle piece, the molded interlocking system is GREAT. Everything fits tight and would make alignment quite easy. The "worst" part is the lack of this same interlocking of the wingtip to the wings. There are molded in bumps at the end of the wing and matching holes in the wingtips but the holes aren't deep enough and this is nothing more than a built in alignment tool. It works but doesn't add any strength to this part of the structure. In all likelihood gluing on the wingtips would probably be fine. My Zagi wingtips are held on with Velcro and I've never had one come off or been ripped off, so if they were glued on I wouldn't have any problem with them. I suspect the same with the Viper Twin although I know people seem to be concerned about them for some reason. Maybe if I'd ever crashed my Zagi I might think differently but for now I see no reason not to glue them in place.

The wood elevons look like they are laser cut. The wood is quite nice and had no warp in either piece. The nice touch here is that the control horn mounting holes are already there. I always hate doing it myself, this way the placement is exact. As I said, nice touch.

The Lexan canopy is really nice. Has a thick heavy feel to it. You will definitely be doing yourself a service if you get a pair of curved Lexan cutting hobby scissors.

The carbon spars are nice. Quite stiff and should do their job if properly installed. The nice touch here is the aluminum spar jointer. Lots of strength here and the surface of the rod is already scored so when it fits into the spar there will be lots of good gripping area for the epoxy. Other nice touches include two 6" servo extension wires. They look like they will fit my JR connectors with no problem, I'm unsure how they would work with Futaba connectors but probably do work. Only those people with the old style Airtronics servo connectors would be out of luck here. Another nice feature is that a Dean Ultra style connector is already attached to the battery, both wires of the ESC and to one end of the motor wire harness.

Please note that these are NOT Deans Ultra Connectors but some copy of them. Don't know if they are gold plated in the say way as genuine Deans but they fit the Ultra connectors OK. For the female connectors I would recommend putting some powdered graphite into the holes and then blowing it out. Makes connecting and disconnecting MUCH easier.

The Castle Creations Pixie 20 is a class component. Castle Creations makes great speed controls and the inclusion of it in the kit is a welcome one rather than having some no name ESC thrown in or not included at all. I've used Castle Creation ESC's in several large electric power sailplanes and they are a joy to use.

The Speed 400's are Promax 400's from MPI and they look nice but a Speed 400 is a Speed 400. I was a bit surprised to see that the capacitor from motor terminals to case are external to the motor rather than being internal as I've seen on just about every other Speed 400 that I have seen. No problem with it but I was just surprised. The external caps also tend to hide the + terminal marking. Just look carefully and you should find it buried beneath the cap somewhere.

The last nice touch to talk about is the pushrods that are already prebent with a Z bend on one end. There is also included kwik links but I prefer Sullivan's, so I will replace those. All in all the kit is quite complete and JetSet has paid attention to a lot of small details that make putting a kit together a more enjoyable experience. OK, one more nice touch. The instructions appear to be fairly well written with lots of pictures, color ones at that. I haven't read every word yet but what I did read seemed to be straightforward and complete in its description, always a plus.

So what didn't I like. I didn't like the way the motors were packed in with all the other hardware. That hardware includes small screws which could easily lodge themselves within the motor through the openings towards the rear of the motor. I would advise anyone to make sure they have all their hardware plus do as good a visual inspection as possible BEFORE applying any power. It would be nice if the motors were within their own plastic bag within the larger bag so there would be no worry about this possibility.

I also purchased the stiffer props and adaptors but there was no directions to describe mounting procedures or how the props should go on. I'm sure I can figure it out but a small sheet would have been nice.

I don't like the tip mounting/alignment interface. Would have liked to have seen the same sort of finger interlock as used at the wing/main body junction. However, as I said previously, I'm not so sure that they will be a problem, I just would like to see greater strength there.

I'm not sure about the foam. I haven't build an FMA kit that is also suppose to be made of Arcel, so I don't really know what I'm suppose to be seeing. I do know that the foam can be dented. I pressed it in with my finger in the battery compartment area. A similar piece of EPP foam bounces back to shape. If this is the same sort of stuff they make car bumpers out of, isn't it suppose to bounce back to shape?? As I said, I've never dealt with Arcel foam so I don't really know but I do know if you ding it, the dent is probably there to stay. That having been said, the foam does appear to have more strength than Styrofoam, so it is something different. If you are going to paint the plane be prepared to put in a lot of work preparing the surface, plus I can only imagine that putting one of those cool designs, such as are displayed on the box, would take longer to do than assembling the plane!

In addition there are any number of places on the wing and center section that look like the injection ports. Along the leading edge there are a number of them (bottom of wing). In these places the airfoil in not level with the rest of the surface. It is as if a large flat bottom drill was pressed into the foam leaving round circles where the front edge is almost flat with the wing surface but the back edge is about 1/8" deep. The instructions don't say if you are to fill these in or what. On my center section one of these injection sites look like it came out above the surface and someone sliced it off, leaving a rather large shallow depression in the wing surface (bottom, leading edge area). I don't have a digital camera, otherwise I'd take some pictures of it.

I'm not sure if I want to attempt painting or try covering with Econocote like MikeB33 did. I'll have to weigh all the components both before and after assembly before I decide. Personally, I wouldn't mind paying more to have all the painting done, especially the flag motif as shown on the box and ads but I'm sure that would skyrocket prices quite a bit. So I'll just have to decide when the time comes how to finish it.

Only other thing I wonder about is the servos. I know JetSet recommends HS-55's but they seem awful light weight for a plane that is suppose to move out at 50mph or so. I got some MX-50 HP's that have 23 oz. of torque vs. the 13 of the HS-55's and I still wonder if that is enough. The HS-81's are 32oz of torque. I'm sure they have flown the Viper with the 55's but they still seem pretty light weight. This is just MY OPINION.

Overall, the kit is pretty complete, they did a nice packaging job, for the most part the components are good quality and well done. There might be some kinks or "bugs" that will be spotted as people build the kits but all in all they did a nice job. Now I just have to build and fly it.
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Last edited by GBR2; Nov 17, 2001 at 10:24 PM.
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Old Nov 20, 2001, 09:43 AM
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Good information here. Thanx for the post.

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Old Nov 20, 2001, 03:37 PM
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Where did you get the MX-50 HP servos? I'm not familiar with those.
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