LOC Precision King Viper III - 2022 Build

[DMehalko]

Time for some more fun on the bench! After tinkering with some smaller clusters and airstarts, I find myself enjoying the multiple motor rockets, so time to amp that up a bit! Aside from being the most expensive per newton way to fly, I think they are pretty neat .

So with that, the KV3 is next on my build table. Not a ton of information on these and only a build thread or two here on the forums, but seems this is a 'shred prone' rocket. Specifically around the motor tube to airframe transition and possible fin attachment. However I feel confident doing a bit of glass and carbon work should make this a stout fun build to bring to the bigger launches (hopefully not famous last words).

Like all LOC kits, nice quality parts and a bunch of them for that matter in this bird. Should be fun!

 

[Theory]

NICE and will be following

have always liked this kit

 

[H_Rocket]

I can tell you this…

Even glassed with a truckload of reinforcement 3 X K550 is outside the performance envelopes!

 

[n3tjm]

I would love to have a KV3 but I would never be able to afford to fly one

 

[DMehalko]

NICE and will be following

have always liked this kit

Get one!!

I can tell you this…

Even glassed with a truckload of reinforcement 3 X K550 is outside the performance envelopes!

What happened and what was reinforced? This is the combo i was looking towards!

I would love to have a KV3 but I would never be able to afford to fly one

Ya this wont be a regular flyer, 3 K motors will be about $450-$500 per flight with todays prices lol

 

[StreuB1]

I could have sworn that Eric Cayemberg has flown his KV3 on K550's.....

 

[justforfun]

I flew mine back in the later 80s.

Used, Scott Dixon (Vulcan), I think they were called Hellfire (low smoke), 3- L750 motors.

Worked just fine. Nothing was fiber glassed.

I looked, can't find a photo. Flew at LDRS @ Colorado Springs, can't remember the dates.

Roy

 

[StreuB1]

L750 hellfires were amazing as were Energon L1100's.

 

[H_Rocket]

What happened and what was reinforced? This is the combo i was looking towards!

Both times with 54mm 4g (1750) K550-ish EX motors

• BT an MMT were glassed,
• Tip to tip on the fins
• 1/2" threaded rod up the center of the MMTs (also served as a retainer and lower recovery hardpoint.
• Chopped glass & epoxy poured into the channels between the MMTs
• The MMT assembly recessed into the lower BT and the bottom filled with chopped glass & epoxy

First try - came off the pad beautifully and came apart at about 2,000' - too far out to really see the failure in progress. it appeared to fail at the MMT/BT interface

-rebuild-

Second try (no I don't learn easily) - Had several observers and the failure occurred at about the same time. As it approached the failure point, it was coning very badly. We suspect the CG shifted so much that it started gyrating wildly (akin to coning) and basically applied too much stress on that joint. The joint survived, the material directly above it did not.

-built a new one with no reinforcements-

Flys great on mid I to baby J (Three CTI I180 Skids).

 

[DeeRoc29]

Love the KV3! Always a crowd pleaser. Flies good on trios of J275's and J135's. The plan is 3xK185's for LDRS40. Mine isn't reinforced at all. I wouldn't even consider K550's or hotter motors.

 

[Rocketjunkie]

Used, Scott Dixon (Vulcan), I think they were called Hellfire (low smoke), 3- L750 motors.

Worked just fine. Nothing was fiber glassed.

Wasn't that the Mother Lode? (7.5" with 54mm inside 3" motor tubes.) The King Viper was 5.5" with 54 mm motor tubes. I saw the Mother Lode go over 10,000' on 3 L750s at LDRS VIII. They were low smoke at the time, changed to smoky sam by LDRS XI. Switching propellant cost about 800 N-s There were a few Hellfire ones made during the transition.

 

[ECayemberg]

I did the (3) K550s in the mother lode. (3) 55-4G sparkies is the biggest I’ve done in the KV3 so far. Mine doesn’t have an ounce of glass on it.

Good news: the current fin planform is significantly less flutter prone and therefore less shred prone. Trailing edge taper and a much smaller tip chord gives you a superior fin design while still providing plenty of fin area.

Looking forward to your build!!!

 

[Hobie1dog]

Wow $500 for flight ? This is a rich man sport I'm in trouble, or in the wrong place

 

[crossfire]

Wow $500 for flight ? This is a rich man sport I'm in trouble, or in the wrong place

That's nothing. How about a 8k RC helicopter. Each crash will cost you at least $600 in parts.

 

[Hobie1dog]

That's nothing. How about a 8k RC helicopter. Each crash will cost you at least $600 in parts.

The harder you play, the more you pay.

 

[Rocketjunkie]

Wow $500 for flight ? This is a rich man sport I'm in trouble, or in the wrong place

The rocket in my avatar is on 2 Aerotech M0775DM at $550 each just for the reloads. Even C6-5 motors are close to $4 each.

 

[Rcktmike]

I have the sister Classic Kit OOP Ultimate max 7/38 mm mount ,My next fly hopefully is J853r and 2/ I211w not the same price as yours to fly though

 

[DMehalko]

Eeesh, so maybe I should dial back my thrust wants on this one lol. Good conversations and inputs above, DeeRock your build looks great!

Got going on this one, stripping the glassline for better epoxy penetration, plus will wrap the tubes in a light 2oz cloth after all said and done, mostly for finishing reasons here but also to add a little strength. Going to double up on bulkheads for more surface area to bond the motor pipe assembly into the booster airframe also

Finally, just looking at adding a small bit of 'flair' on the motor-to-airframe transition, but figure this could also add a small bit of support too, pictured is a cardboard template but will make these out of 1/8" ply laminated in carbon fiber, again mostly for aesthetics

 

[rfjustin]

Do you need those fins beveled?

 

[Rcktmike]

yes i did both siides that is an old kit only .125 thick, but a pain being six of them

 

[H_Rocket]

KV-III on 3 x K550 (ex)


New KV-III on 3 x CTI I180SK

 

[green dragon]

yes i did both siides that is an old kit only .125 thick, but a pain being six of them

Should be thicker than .125 on the Ultimate Max... the 4" version used .125 ply - my 5.5 has 3/16" .

Sadly lost on first flight at Geneseo when one of the 3x Kosdon I500 kicked in late cousing a 45 degree boost and loss across the river

 

[DMehalko]

Do you need those fins beveled?

Im old fashioned using a hand plane lol, but i might take you up on services in the future!!

KV-III on 3 x K550 (ex)


New KV-III on 3 x CTI I180SK

Beautiful birds!

Should be thicker than .125 on the Ultimate Max... the 4" version used .125 ply - my 5.5 has 3/16" .

Sadly lost on first flight at Geneseo when one of the 3x Kosdon I500 kicked in late cousing a 45 degree boost and loss across the river

Ugh sorry to hear, we have a local (Conway Stevens) who builds amazing starters, definitely going to use his products for getting these 3 puppies lit as soon as poosible

 

[DMehalko]

ANYWAYS, back on this project! Delays with some other small builds and some LPR fun (i still love lpr ).

That said, im going to try and crack this thing out for Airfest, which is in about 2.5 weeks! Time to get to work . Next on my list was to double up the aft bulkhead as I dont want this thing to fold there, will add a bit more surface area bonding and rigidity, along with giving me more 'meat' to pin this into the airframe (more on this later). So I picked up an extra centering ring and hacked it up a bit. Next up was getting the root fins beveled to fit as tight as possible into the motor pipes.

Didnt feel like making a fin jig for this, so going with the simplistic bubble level method which works here

 

[StreuB1]

Don't be shy with epoxy and filler!!! Build it like an anchor. Looking forward to seeing it at Airfest.

 

[DMehalko]

Don't be shy with epoxy and filler!!! Build it like an anchor. Looking forward to seeing it at Airfest.

Ya planning on doing some carbon tip to tip also, need this thing to survive! haha

Finished up the fin tacking, next up will be fillets and fiberglassing the airframe, not before a quick dry fit though

 

[DMehalko]

Got to work on the fillets, i was curious how big i would have to make them to allow for the carbon to lay nice, but a quick dry cloth test with some scrap proved it will be just fine. Just need some fresh peel ply and will get to work tip to tipping these fins

 

[DMehalko]

Putting the fin can/motor assembly aside to get the upper booster section and payload glassed, again using soller sleeves here of course

 

[DMehalko]

Getting going on the fins

 

[DMehalko]

Round 1, done, 2 more to go today