Copying a Kit

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Who_Cares

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I was wondering if anyone could give me any advice on this. I've been flying a LOC/Precision IV for a bit now and I love the rocket. However, I think I'm ready to move on to my level 2 certification, but I also don't want to spend $300 on a kit. Right now I am planning on copying the LOC IV kit. By that I mean buying a Public Missiles fiberglass air frame with precut slots, Public Missiles custom fins (the same shape as the LOC IV's), and a couple of centering rings and a motor mount tube. This would allow me to reuse the nose cone, parachute, shock cord, and the instructions from my LOC IV kit without any additional modification.

Like I said, I would like to get my level two certification. I haven't modeled this in OpenRocket yet, but the aerodynamics and CP should be the same right? All I need to worry about is the center of gravity being changed and the added weight so I might need a bigger parachute? If I want this thing to go at least mach 1 how thick should the fins be if I don't want to do tip to tip fiberglass?
 

Wallace

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Standard boilerplate stuff. 1/8" G10 or canvas phenolic from Mike at MAC Performance will be fine. With quality epoxy and good sized fillets you could surface mount 'em and break mach without a problem. The only thing working in your favor is the fact that you can use parts you already have. I have a few rockets myself that share nose cones, av bays and electronics. I have 4 different 54mm cases but only one set of closures. 5 different rockets with Aerotech retainers but only own one retaining ring. I have a lot more rockets than I do parachutes . I dont fly 'em at the same time so until I lose or break it I don't need more. costwise kits are the best deal going. Price the parts individualy and see.
 

rcktnut

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Standard boilerplate stuff. 1/8" G10 or canvas phenolic from Mike at MAC PCopying a Kiterformance will be fine. With quality epoxy and good sized fillets you could surface mount 'em and break mach without a problem. The only thing working in your favor is the fact that you can use parts you already have. I have a few rockets myself that share nose cones, av bays and electronics. I have 4 different 54mm cases but only one set of closures. 5 different rockets with Aerotech retainers but only own one retaining ring. I have a lot more rockets than I do parachutes . I dont fly 'em at the same time so until I lose or break it I don't need more. costwise kits are the best deal going. Price the parts individualy and see.
+1 Better off, cheaper buying a new kit.
 

DaveW6DPS

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The nose cone and such should be fine. You may need a larger parachute, depending how much additional weight there is.

Instead of ordering an airframe the same length, you might consider a longer tube, to help move the CG forward.

As for going Mach, there is a lot more to fin design than thickness. Backswept fins like those on the LOC IV are not great for transonic flight. I would suggest more research there. If you are ordering custom fins it may not cost more for fins that will handle Mach speeds easily. I do sometime use thicker fins and flat edges to increase drag enough to stay below transonic speeds.

I also like to group rockets so that nose cones, e-bays, etc., can be used on more than one rocket. It also means I have spares if something stop working.
 

Who_Cares

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Again, I'm just trying to keep costs down as much as possible. If I do choose to go for a kit instead has anyone ever had any experience with a Madcow Twitch?
 

Wallace

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You might wanna make sure they actually have one in stock first. Otherwise I have several Madcow rockets. They make nice stuff.
 

DaveW6DPS

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Again, I'm just trying to keep costs down as much as possible. If I do choose to go for a kit instead has anyone ever had any experience with a Madcow Twitch?
I have quite a bit of experience with Mad Cow, but not the Twitch specifically. It seems pretty small for level 2 motors, so definitely include a tracker!

The Mad Cow 4 inch DX3 is close to the same price, and I have seen several level 2 flights on it. It flies very well on J and many K motors.
 

MikeyDSlagle

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Put a J420 in your LOC IV and let er rip, easy L2. Build your Mach-machine after.
Both LOC and Binder offer kits that can get you L2 easily and can likely handle Mach+ just as easily, and several for less than the price of a PML glass tube. I don't know what fin shape is best for Mach+ flights so no advice there. But shop around and fall in love with another kit.
If you want a glass LOC IV, go for it. Don't sweat "costs". I did that with my L1 and it just have me a headache lol. Build what you want. Fly it how you want...as long as it is done safely.
Amwprox sells LOC kits and offers fiberglassing; for a 4" kit it's 30 bucks.
 

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I have the Twitch, but not the DD version. It flies great on I motors but fins are kind of thin.
 

Who_Cares

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Put a J420 in your LOC IV and let er rip, easy L2. Build your Mach-machine after.
Both LOC and Binder offer kits that can get you L2 easily and can likely handle Mach+ just as easily, and several for less than the price of a PML glass tube. I don't know what fin shape is best for Mach+ flights so no advice there. But shop around and fall in love with another kit.
If you want a glass LOC IV, go for it. Don't sweat "costs". I did that with my L1 and it just have me a headache lol. Build what you want. Fly it how you want...as long as it is done safely.
Amwprox sells LOC kits and offers fiberglassing; for a 4" kit it's 30 bucks.
Oh whoops I forgot to mention I did attempt a level 2 cert with my LOC IV with an Aerotech J270W. The fins shredded towards the end of the burn. No the fins did not become dislodged (the base of all three fins were still attached to the body), the plywood was literally shredded off because they were 1/8th plywood.
 

Cl(VII)

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Cheapest way. Strip paint off fin can off your LOC IV, do a t2t fiberglass job on it, fly. You would be in about $25 with Zpoxy and hobby shop/auto parts fiberglass cloth.
 

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Cheapest way. Strip paint off fin can off your LOC IV, do a t2t fiberglass job on it, fly. You would be in about $25 with Zpoxy and hobby shop/auto parts fiberglass cloth.
cheapest way to get there? buy more LOC tubing and toss thicker fins on. :)
I did talk with some of the guys at my Tripoli launch and they didn't think there would be any way for me to recover the airframe and motor mount. I would be skeptical about the strength of the fins if I sanded the airframe and shredded parts of fin down and placed new fins over the top, even with tip to tip. Although it is an intriguing idea, I would have to be convinced it is safe.
 

Cl(VII)

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I did talk with some of the guys at my Tripoli launch and they didn't think there would be any way for me to recover the airframe and motor mount. I would be skeptical about the strength of the fins if I sanded the airframe and shredded parts of fin down and placed new fins over the top, even with tip to tip. Although it is an intriguing idea, I would have to be convinced it is safe.
Good attitude. If you aren't sure it is safe don't fly it.
 

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I've taken more than one rocket and peeled away the body tube to expose the motor tube and centering rings. I'd do that, add thicker fins, maybe glass them to the motor tube then slide the fin can up a new LOC 4" tube. You be out about $30 bucks.
 

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Good attitude. If you aren't sure it is safe don't fly it.
I think I may try it at some point in time. Maybe by sanding off the paint for the entire airframe and wrapping the whole airframe in fiberglass to cover the pre-cut fin slots, then adding new fins on top of the fiberglass and using tip to tip.

I've taken more than one rocket and peeled away the body tube to expose the motor tube and centering rings. I'd do that, add thicker fins, maybe glass them to the motor tube then slide the fin can up a new LOC 4" tube. You be out about $30 bucks.
Otherwise, this also another interesting idea, only thing that sucks is that I would have to make my own slots for the fins.
 

MikeyDSlagle

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Email LOC. Tell em you need some 1/4" fins and a coupler, maybe a stiffy too, along with all the bits needed to make a new fin can...only 54mm this time, they'll slot the tube for ya. Mechanically attach the fin can so it can be removed if need be (not necessary but why not). Bevel the fins. Build it solid, don't need a tank.
I've flown my Binder DesignTyrannosaur on a CTI K600, RRC3 reported 1400+ ft/s, not sure if that was accurate though.
Just be sure your fin can is well built.
 

tomsteve

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if you have some power tools, fins are pretty easy to make and plywood can be purchased at a local hobby shop or a place like hobby lobby or michaels. ive made quite a few sets( and upgraded balsa to ply on LP rockets) with my scrollsaw and disc sander.
could probably cut them with a hand saw even.
 

3stoogesrocketry

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If you want to save the rocket , take a belt sander or random orbital sander or dremel and remove all the old epoxy and plywood that protrudes from the surface . You will then need to rotate your new fin slots 60 degrees from the old ones . Cut new fins out of 1/4 inch 7 ply , can be sourced at most hobby craft stores , and install them with good epoxy . Then you can lay some automotive fiberglass , 5 dollars , to seal the airframe where your old fins protruded and reinforce your fins . Add another J270 and your good to go . I did this on a Binder Design Excel Plus that sheared a fin off and cracked another .
 

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if you have some power tools, fins are pretty easy to make and plywood can be purchased at a local hobby shop or a place like hobby lobby or michaels. ive made quite a few sets( and upgraded balsa to ply on LP rockets) with my scrollsaw and disc sander.
could probably cut them with a hand saw even.
I was thinking just ordering custom fins from always ready rocketry. They wouldn't be more than $15. Or if I wanted to I could get custom fiberglass fins from Public Missiles which is also cheap.
 

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If you want to save the rocket , take a belt sander or random orbital sander or dremel and remove all the old epoxy and plywood that protrudes from the surface . You will then need to rotate your new fin slots 60 degrees from the old ones . Cut new fins out of 1/4 inch 7 ply , can be sourced at most hobby craft stores , and install them with good epoxy . Then you can lay some automotive fiberglass , 5 dollars , to seal the airframe where your old fins protruded and reinforce your fins . Add another J270 and your good to go . I did this on a Binder Design Excel Plus that sheared a fin off and cracked another .
A solid idea, and I could combine the reinforcement of the airframe with tip to tip reinforcement.
 

Who_Cares

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Email LOC. Tell em you need some 1/4" fins and a coupler, maybe a stiffy too, along with all the bits needed to make a new fin can...only 54mm this time, they'll slot the tube for ya. Mechanically attach the fin can so it can be removed if need be (not necessary but why not). Bevel the fins. Build it solid, don't need a tank.
I've flown my Binder DesignTyrannosaur on a CTI K600, RRC3 reported 1400+ ft/s, not sure if that was accurate though.
Just be sure your fin can is well built.
How would you attach a non permanent fin can?
 

JohnCoker

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Plywood fins can be made easily by hand. Hobby shops carry high-ply plywood sheets in various thicknesses and sizes as small as 12" square.

Tubes can be purchased from a variety of places. Consider phenolic for a rocket that will be flown a lot because it is more durable than cardboard and can be worked with hand tools.

I put together a comparison of airframe materials which might be helpful:
jcrocket.com/body-tubes.shtml
 

captbk

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What ever airframe you decide on make sure it's compatible with your LOC nose cone. Just sayin.
 

beeblebrox

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AMWPROX has LOC 5.56" V2's and the stretch version on sale... $110 for stretch version, 38mm mount perfect for L2... waiting on my order now! cant beat that with a whip!
 

MikeyDSlagle

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How would you attach a non permanent fin can?
Glue the coupler into the fin can leaving at least a caliber sticking out. Inside the coupler put wood blocks to accept threaded inserts or T nuts, epoxy them if you'd like. You can use removable rivets (without the wood blocks) or self tapping screws, I just prefer machines screws with the inserts.
I slide the airframe onto the coupler, drill the holes, then remove the airframe so I can work inside the coupler.
Seriuosly, consider stepping up to 54. 38mm is good for getting your L2 but not for an honest to God L2 rocket. While there is a plethora of J motors, L2 goes beyond J, and how many Ks or Ls are in 38mm? The answer is 2 Ks and 0 Ls. But to each his own.
 
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Who_Cares

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I have decided to attempt to repair my LOC IV by cutting off and sanding down the remaining bits of fin and paint on the fin can. Then I'll surface mount some new plywood or fiberglass fins and do tip to tip. Before I attach the new fins I might just go ahead and sand the paint off of the entire airframe and wrap it with a couple layers of fiberglass for a bit of strength, but mainly for longevity.
 

beeblebrox

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Glue the coupler into the fin can leaving at least a caliber sticking out. Inside the coupler put wood blocks to accept threaded inserts or T nuts, epoxy them if you'd like. You can use removable rivets (without the wood blocks) or self tapping screws, I just prefer machines screws with the inserts.
I slide the airframe onto the coupler, drill the holes, then remove the airframe so I can work inside the coupler.
Seriuosly, consider stepping up to 54. 38mm is good for getting your L2 but not for an honest to God L2 rocket. While there is a plethora of J motors, L2 goes beyond J, and how many Ks or Ls are in 38mm? The answer is 2 Ks and 0 Ls. But to each his own.
I believe in the kiss rule, 38mm is my choice for L2, kit ordered....
pk58.jpg
Will be a great rocket for H & I motors too... Just get certified, then go for broke! I see many people fail going too complex for a cert flight, keep altitude low, just make it work...
 

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I believe in the kiss rule, 38mm is my choice for L2, kit ordered....View attachment 379290 Will be a great rocket for H & I motors too... Just get certified, then go for broke! I see many people fail going too complex for a cert flight, keep altitude low, just make it work...
I completely agree. I just want to get level 2 certified than enjoy myself at level 2 with a 54 or 75mm motor rocket.
 

DaveW6DPS

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Oh whoops I forgot to mention I did attempt a level 2 cert with my LOC IV with an Aerotech J270W. The fins shredded towards the end of the burn...
I guess no one else is going to point this out, but I hate seeing things like this. Entering grumpy old man mode...

The LOC IV is designed for F through H motors. Putting a J motor in it with potentially four times the total impulse it was designed for, without extensive mods, is just not a good idea. It doesn't seem you learned anything from this experience. I hope whomever went through your level 2 checklist learned something--that they did a poor job "assisting" you to have a failure.

Stay with level 1 for a while, and work on learning how to do things right. Many of these mishaps happen to people who push the envelop before they are ready. When you do think about level 2, look at legitimate level 2 rockets instead of just "Put a J420 in your LOC IV and let er rip".
loc iv.JPG
.
 
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