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"Cox Pee Wee .020 with 3D printed horseshoe backplate"

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My Southridge CNC Hyper Viper build

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My Southridge CNC Hyper Viper build

Post  RknRusty on Sat Mar 16, 2019 11:49 pm

Okay, I can't believe I'm the first one posting a build thread on the Southridge CNC Hyper Viper.

Mine is a quick kit, as you may know, since y'all bought it for me. I took it as a get well present and it worked... I'm pretty damn well! The first thing I needed to do was address the grooves scribed by the CNC tool. I used 60 grit paper and carefully went over the whole fuselage. That and become reacquainted with my shop, which has been mostly inactive for 2 years now. Wow, time passes fast when you're not having fun. It's a lot of work removing the grooves and making sure not to re-shape anything by accident. I still keep finding some, but I think some of it must be pressure indentations. I lightly spritzed it today from 3 feet away with Windex to see if some of it would swell out. The jury's still out on that. I've rounded the 4 corners of the wing slightly, as well as the flat edges of the wingtips and put more of a radius on the top of the rear fuselage, following up with 220 and 320 paper. This picture still shows some of the scribing that has now been smoothed out. I've also removed 4 grams of wood from inside the fuselage. It's all about 3/16" thick, and I took some more wood out where I thought it was structurally safe.


Next are the hardwood motor mounts. I took the option of running them full length and, for the sake of reducing stress risers, rounded the ends to match the existing radius of the CNCd shelves they sit upon.


Here it is with a Tee Dee perched on the crutch. You can see I have removed some thickness from the inside top of the cowl. It had ridges that could have abraded the bladder, plus it makes more room for it to expand with a full load of fuel too. I also made a breather hole for the venturi. The Norvel may not need it, but this will aid in future engine swapping. I think there is enough room for enough fuel. There certainly is enough for the more efficient Big Mig or AME. The Tee Dee might be close if I want 6-1/2 minutes for a Stunt run. It will be flying PAMPA at 1/2A day in September.


As for cooling and exhaust evacuation... I'm still imagining ways to handle that. The muffler for the Norvel wont fit without butchery that I'm not likely to do. Some sort of deflector and side vents are likely.


Plenty of room for cooling intake, but not the prettiest thing. I'll probably add another vent on the bottom, because the rule of thumb for heat removal is twice as much exit as intake. Texaco heads are no longer available. I do have a scruffy red one on the old Paul G. Mouse Racer Black Widow. Cooling the Norvel is more critical than the Tee Dee.


The inside of the nose will be coated with fiberglass and epoxy finishing resin. Where I've thinned the wood in the fuse could be covered with resin and carbon veil, but I didn't really take that much wood out, and it should still be plenty strong. I've never seen a plane break there. The wing will be covered with doctor paper, and I've stocked up on enough dope for a similar scheme as the Cox model.

So, thar she blows.
Rusty

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Re: My Southridge CNC Hyper Viper build

Post  NEW222 Yesterday at 2:40 am

That's a very nice model coming along very well. Keep up teh good work!
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Re: My Southridge CNC Hyper Viper build

Post  Kim Yesterday at 6:47 am

Bravo !!!!!!!!!!!!
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Re: My Southridge CNC Hyper Viper build

Post  getback Yesterday at 8:18 am

Good to see you in the shop Rusty !! The plane looks Great maiking me think more about getting myself one St.Pats Beers
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Re: My Southridge CNC Hyper Viper build

Post  roddie Yesterday at 11:30 am

Hey Rus! Great to see you getting busy building again man! That's a cool-looking kit. You mentioned concerns with engine-cooling.. so I thought I'd throw this out there. I have some grill material that may interest you.




It's light-gage steel.. and you'd need to cut it to shape. Being steel.. a panel made from it would be structural.. if epoxied into place. A piece cut to fit a rectangular-opening in the bottom of the cowl, would vent heat.. as well as provide fuel-oil drainage. I was originally thinking that you could attach it directly across the bottom of the engine-beams.. but you mentioned the beams being contoured into the surrounding cowl.

Being perforated; this grill-material would anchor solidly, using an epoxy glue.  

Here's a couple of photos showing some weight comparisons.




The perforations cut easily with tin-shears. As you can see by the 2nd photo; 2/3rds of the panel-weight was in the "solid" angle-pieces which I cut off.

Just say the word, and I'll stuff the flat-panel in a bubble-mailer.. and send it your way.  Smile
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Re: My Southridge CNC Hyper Viper build

Post  RknRusty Yesterday at 12:12 pm

Thanks, Roddie, I'll let you know. I'm still in the head scratching mode now. I'll try to get some useful work done on it today.
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Re: My Southridge CNC Hyper Viper build

Post  Ken Cook Yesterday at 8:33 pm

If your running bladder, cooling is a non -issue for the most part. The engine runs cooler due to having a constant fuel supply. I never had a Rev-Lite Norvel overheat in fact it's just the opposite. They rarely get hot enough. When the model lands, the engine is barely warm to the touch.  The TD gets much hotter, seeing that much cylinder sticking out of the model, I highly doubt cooling will be  a issue. What would concern me though is keeping the model flying at speeds conducive to stunt. Your not going to achieve that using bladder easily. The other problem I see is that when using a tank, the engine leans throughout the flight. A bladder goes richer therefore when you need the most power in the overheads in this could be a issue unless your carrying a large enough bladder. Cramming a lot of fuel into a small bladder tube can create false pressure offering a rich run then going over lean.
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Re: My Southridge CNC Hyper Viper build

Post  944_Jim Yesterday at 9:23 pm

Roddie, where did you score the grill? Is it a PC fan vent?

TIA!
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Re: My Southridge CNC Hyper Viper build

Post  RknRusty Yesterday at 10:24 pm

Here's today's build installment:

I didn't like the way the nose of the TD was rubbing the starter spring, so I removed it. Without it, I was able to mount the engine with a degree or so of outboard thrust offset. Ity took some more sanding the holes, but it still looks neat.


And this will be the very first time I have ever EVER bored perfect holes in the beams. I got the tabs exactly where I wanted them and put a tiny drop of thin CA in each screw hole. Double checked and trimmed the cowl holes to fit perfectly, and with the engine glued in place, I bored the pilot holes. I'm not going to unglue the engine, just gonna screw it down. Only thing is I didn't add aluminum bearers... I forgot about those, but it'll work. If I decide it needs them, I'll put them in. I already have several sets drilled and ready. I don't care for the screws, so a trip to Lowes may be in my near future. I cannot locate a source for 2-56 threaded inserts, or I would have used them


Okay, a good weekend. Next weekend I will be occupied with birthday related stuff, so no shop time for the old man. But it looks like good WX on Tuesday and Thursday. And Daylight Savings time is forecast for the foreseeable future too. Yaaaazoo!!
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Ken Cook wrote:If your running bladder, cooling is a non -issue for the most part. The engine runs cooler due to having a constant fuel supply. I never had a Rev-Lite Norvel overheat in fact it's just the opposite. They rarely get hot enough... What would concern me though is keeping the model flying at speeds conducive to stunt. Your not going to achieve that using bladder easily... A bladder goes richer therefore when you need the most power in the overheads in this could be a issue... Cramming a lot of fuel into a small bladder tube can create false pressure offering a rich run then going over lean.

Ken, thanks for kicking me right in the... brain cells. I knew that. I always tell people how bladder fed engines are self protecting and cannot overheat. DUH! Huh...

In my experience my planes only change to a rich run 3 laps before the shutoff. The cowl has a very roomy diameter so it won't be squeezing the sides of the bladder. I haven't measured its length yet(should have) but I think I can fit 3-1/2 inches of fuel in it. This 4 minute flight is on 2-1/2 inches of fuel and I think another 1/2 - 1 inch will work on the new 1/2A Pattern rules where we only have to fly one lap between stunts. We'll be following the 2019 Brodak rules.

Please understand I'm not arguing. If it won'r run well, then I'll relegate it to sport flying and enter one of my BFS, because I've put as much as 5 inches of fuel in those bad boys with good steady runs. Oh, and another fuel economy fix is that I could change to the Big Mig, because it'll fly another minute on the same volume of fuel as the Tee Dee will. You're possibly right about being too fast too. But I have 6 months till our 1/2A day contest. In any case I'm sure the little Bugger will be fun to fly. I started turning circles in the house. And I got tired and dizzy, Lol.
Rusty

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Re: My Southridge CNC Hyper Viper build

Post  getback Today at 8:33 am

That's pretty cool gluing the engine in to drill the pilot holes , i started using the auto-matic punch but it has to bee adjusted because of being aggressive . Also drill one hole to bolt engine down , and set for the others for reedies works good for me . I didn't know the Texaco Hd adpt. was no longer available / did you miss dy light saving time day ?? St.Pats Beers
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