grouch
Well-Known Member
Ok so here is my first build thread. I have been wanting to build a Viper for the longest time. Back in the mid 90's I made the mistake looking at a LOC brochure and knew that I would build one of these kits sooner or later. Little did I know it would be much later! After I recently built my Onyx and successfully flew it to level 1, I decided it was time to work on a Viper. Originally I was looking at a Viper 3 because I like 3 fins and I figured three motors would keep the launch cost down a little lower than four but I soon realized the Viper 4 is much more versatile as I could fly it on two or four motors. I could also fly it on two small E's and two big G's or four small E's or four big G's, you get the idea. So with that in mind I set out to build my version of the ultimate Viper 4 that could handle anything I throw at it.
What will make it the ultimate Viper 4? I don't really know but I'll figure it out as I go along. Let's start with the centering rings. The new version of the kit no longer contains centering rings. Apparently the old rings were a pain in the ass because there is so little meat on the rings after the four 24mm holes are cut. The new kits use a coupler that you glue the motor tubes into and fill the voids between the tubes with tissue and epoxy. I knew that would work just fine but I still wanted the centering rings because I wanted to vacuum bag them with kevlar to help hold them together. After a short call to Barry at LOC, I soon had the rings in hand. Time to get the kevlar going.
Here is how this works. I sanded and trimmed up the centering rings. They were very light and delicate some might even say fragile. Then I cut some .014 mylar disk and measured out some epoxy.
Then I waxed the mylar disk to act as a mold release and provide a shiny finish on the kevlar then brushed on a very thin layer of epoxy onto the mylar. I applied the kevlar and rolled it out to smooth out the epoxy.
Next I made the centering ring sammiches. The left one is ready to go, the right one still needs it's top.
Next I folded the wax paper over the sammiches and placed them on a couple layers of paper towels to prepare them for the bag.
Then I placed a couple more layers of paper towels on top and then placed the layup in the bag. The paper towels act as a breather, allowing the vacuum to pull the air evenly around the layup. I use a small strip of breather cloth folded in half over the layup to ensure the bag doesn't get sucked up into the vacuum hose. After I was happy with the placement inside the bag, a small amount of vacuum was pulled to see how things were working out. I used about 6" here.
After I was happy with the way it looked all nice and smooth, I brought the vacuum up to 15" of mercury. All the time making sure no wrinkles were introduced. I could have stopped at around 7-8" because that is more that any clamp will ever give you but I wanted to give more. Ultimate remember?
Lastly, I placed the layup on a piece of flat plywood with another one on top and weighed it down while it cured. The plywood or weight isn't really needed for the bagging process but they do ensure that layup comes out twist free.
After 24 hours in the bag, it was time to open it up and peel back the mylars. For those of you who never tried vacuum bagging, let me tell you there is no sweeter sound than mylars being peeled off. It's like Christmas morning, unwrapping your favorite present. If you did your job right, you are left with a awesome finish and a very strong part. The whole process is very easy, just make sure you apply a smooth even coat of epoxy and the finish will come out pinhole free every time. As you can see, bagging doesn't have to be an expensive ordeal. I use a $30 hand pump (but it's a good one). My whole set up with pump, bag and clamps, vacuum connector, hose and the other little tid bits set me back about $60 and it will do everything a $300 pump will do. You just have to check on it every so often to make sure your bag isn't leaking. If it is, just give it a couple more pumps. For the record, it still had 15" over 24 hours later. Anyway, here is my centering rings before trimming.
What will make it the ultimate Viper 4? I don't really know but I'll figure it out as I go along. Let's start with the centering rings. The new version of the kit no longer contains centering rings. Apparently the old rings were a pain in the ass because there is so little meat on the rings after the four 24mm holes are cut. The new kits use a coupler that you glue the motor tubes into and fill the voids between the tubes with tissue and epoxy. I knew that would work just fine but I still wanted the centering rings because I wanted to vacuum bag them with kevlar to help hold them together. After a short call to Barry at LOC, I soon had the rings in hand. Time to get the kevlar going.
Here is how this works. I sanded and trimmed up the centering rings. They were very light and delicate some might even say fragile. Then I cut some .014 mylar disk and measured out some epoxy.
Then I waxed the mylar disk to act as a mold release and provide a shiny finish on the kevlar then brushed on a very thin layer of epoxy onto the mylar. I applied the kevlar and rolled it out to smooth out the epoxy.
Next I made the centering ring sammiches. The left one is ready to go, the right one still needs it's top.
Next I folded the wax paper over the sammiches and placed them on a couple layers of paper towels to prepare them for the bag.
Then I placed a couple more layers of paper towels on top and then placed the layup in the bag. The paper towels act as a breather, allowing the vacuum to pull the air evenly around the layup. I use a small strip of breather cloth folded in half over the layup to ensure the bag doesn't get sucked up into the vacuum hose. After I was happy with the placement inside the bag, a small amount of vacuum was pulled to see how things were working out. I used about 6" here.
After I was happy with the way it looked all nice and smooth, I brought the vacuum up to 15" of mercury. All the time making sure no wrinkles were introduced. I could have stopped at around 7-8" because that is more that any clamp will ever give you but I wanted to give more. Ultimate remember?
Lastly, I placed the layup on a piece of flat plywood with another one on top and weighed it down while it cured. The plywood or weight isn't really needed for the bagging process but they do ensure that layup comes out twist free.
After 24 hours in the bag, it was time to open it up and peel back the mylars. For those of you who never tried vacuum bagging, let me tell you there is no sweeter sound than mylars being peeled off. It's like Christmas morning, unwrapping your favorite present. If you did your job right, you are left with a awesome finish and a very strong part. The whole process is very easy, just make sure you apply a smooth even coat of epoxy and the finish will come out pinhole free every time. As you can see, bagging doesn't have to be an expensive ordeal. I use a $30 hand pump (but it's a good one). My whole set up with pump, bag and clamps, vacuum connector, hose and the other little tid bits set me back about $60 and it will do everything a $300 pump will do. You just have to check on it every so often to make sure your bag isn't leaking. If it is, just give it a couple more pumps. For the record, it still had 15" over 24 hours later. Anyway, here is my centering rings before trimming.
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