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Caley

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Some of you met me over in High Power part of the forum where I introduced myself, and talked about where I hope to go in the hobby.

I already built my first mid-powered model, a Stretch Blobbo, though I did have trouble matching engines to the over weight air frame. But that is done, and I am now going to build my Madcow Mini DX3 mid-powered rocket. I purchased it with an option, a fiberglass nosecone. I also think the nomex parachute protector was optional, and I have that also.

The nose cone is a super tight fit, so I am guessing I will need to sand down the part that plugs into the upper rocket body. Not sure just how tight things are supposed to fit. Is there a test you do, like maybe have it tight enough that when you pull, it makes a popping sound? Silly of me to think about such trivial things, but I am still trying to learn these bigger models. My only rocketry experience was back in 1971 with low powered ESTES rockets

The kit came with 1/4 inch diameter lugs to fit on a launch rod. I'm not sure that this is OK or this model, which has a 1 5/8 inch diameter body. But there is really little room for backing ply squares for launch lugs.

A concern of mine is that this model seems to be a high performance type, that will attain pretty high flights. Since my eyes are pretty bad now, I am wondering if I should obtain a payload bay insert, and add some kind of electronics. If so, just what can I put in a bay that is only about 4-5 inches long, and maybe 1.5 inches in diameter? I am guessing that it might be smart to purchase the Jolly Logic Chute Release since adding an altimeter, 9VDC battery and all the other stuff just won't fit in such a tiny rocket body. I was also thinking of one of those loud noise makers to attract my attention if or when I finally get close to it. I'm not sure the JL chute release provides a peak altitude readout, so I might need a second tiny altimeter to see just how high and fast this little critter goes. I'm sure all of this equipment could be transferred into another model if needed.

The kit also came with what I believe is a Kevlar shock cord that is one body length long, and a nylon shock cord that is 1.5 rocket bodies long. From all that I have seen in videos, this equates to about only half of what seems to be the norm for length, and it splits things, so something could possibly come loose. My thought is to purchase the same size Kevlar for at least three bodies length.

I will be flying off of the Lucerne Dry Lake Bed with the ROC Club. From what I have seen, this area is rock hard except after the rains, and when it gets wet, it is not a good thing to drive out on. Cars tend to get stuck in the gooey glue. But back to the reason I mention rock hard landing area. The provided parachute is 18 inches in diameter for their model weight of 9.5 ounces. I believe that since I build things like tanks, that could approach 15 ounces, especially if I add the payload bay insert and electronics.

I guess that is about all I have for the intro to what I will be building. If anyone has suggestions or something to add before I start this build, please, please mention it. I am still in a steep uphill learning curve. I know next to nothing about the newer, more complex hobby of model rocketry. Thanks Caley Ann
 

smugglervt

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Caly,

The usual way to determine if the nosecone fit is relatively simple. You should be able to hold the rocket by the nosecone without it separating, however, with a gentle shake the nosecone should come loose. I don't use launch lugs on my MPR builds but instead use the T-nuts like the ones sold at Apogee Rockets. they have held up quite well on my Estes Pro II rockets. The Jolly Logic Chute Release does not have an altimeter in it but I partner my JLCR with a Jolly Logic Altimeter 3 for data logging. The Alt 3 is pretty small and can be connected to a smart phone via Bluetooth which is pretty convenient. For recovery harness in my Pro Series II, I use 1/8 inch Kevlar braided cord from the motor mount to the top of the airframe and then nylon attached to that for at least a length of 3 or 4 times the length of the rocket. I ran a quick SIM in OpenRocket for that model (not knowing your finished weight) and it looks like an 18" chute should bring it down at around 20 fts which should be ok. You can always up the chute to a 24" one since you will be using a JL chute release and won't have to worry about it drifting off too far.
 

Caley

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Hi Jim, I appreciate your comments on my new little rocket.I think the 24 inch diameter parachute might be best for the area I will be launching on. I got to talk to a few people while visiting one of the events, and from what I gather, the stock chutes generally do not slow the decent enough to prevent some kind of damage. They usually go one size up because of the rock hard landing surface. We fly in the desert here in southern California.

I will get some of that 1/8 inch Kevlar braided cord. I really don't like the idea of splicing two different types of cord together. I'm sure the way I have done it will not come apart. Tying triple knots and then using to secure the loose ends. But I tend to like neatness in everything I do. In other words I am picky to the point where I have sometimes irritated people. I guess that is my failing.

Since I don't have a cellular phone. the JR III Altimeter probably isn't something I need to spend money on. I think the JR II probably will be adequate for me. Why no phone? for 40 years I was leashed to either a beeper or cell phone because of my various jobs. I got to the point where I hate phones.

Thanks for running the RocSim. I tried to use the trial version, and just couldn't get any practical information from it. I was told it provides very limited function in its trial version. So I am having to rely on others for that type of help, or just use luck with the motors and equipment choosing. Caley Ann
 

Caley

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Jim, It just crossed my brain that when I mentioned launch lugs, you came back with t-nuts. I think there is a problem with me and proper descriptions of parts. When I mentioned launch lugs, I meant the little 1/4 inch round cardboard tubes you use to slip over the launch rail. I'm not sure how your t-nuts can attach to either a launch rod or rail. Maybe you can explain what you were saying. Thanks Caley Ann
 

tHoagland

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I recently finished building one of these myself. I ended up putting an Eggfinder Quantum (and 2S LiPo battery) in the AV bay and setting it up for dual deployment. This is tight AV bay but everything fit.

As Jim suggested above, I used 1010 rail buttons instead of launch lugs. Mid and High power rockets often use a square Aluminum extruded rod that has a "T" shape on the side. The rail buttons match that shape and slide in the "T". This has the advantage of having a sturdier/longer launch rail (1" square) without having a giant launch lug on the side of your rocket. (https://www.madcowrocketry.com/1010-rail-button-pack/) . Ones on the post above, use T-Nuts which make them easy to install.


Good Luck with the build.
 

Caley

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Are most rails basically the same size to accept these little rail buttons? I still don't know what ROC uses out beyond the first row of launch pads, which use various sized launch rods. Hopefully things are fairly standard.
 

dhbarr

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Are most rails basically the same size to accept these little rail buttons? I still don't know what ROC uses out beyond the first row of launch pads, which use various sized launch rods. Hopefully things are fairly standard.
Almost every club has 1010 rail, esp. in mid-to-high power.
 

Caley

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Thanks Guys! I will have to place another order to Apogee on Monday for the buttons, shock cord and something I forgot in my first order, RocketEpoxy, and of course, I might as well invest in those two Jolly Roger units, as well as a noise maker. Apogee looks like the carry one that attaches to the eyelet bolt ring, but I would prefer it to reside somewhere else, as the JR Chute Release probably needs to remain somewhere with lots of room.
In order to install those buttons, I will have to only put on the forward engine holder tube ring on with glue, while the other just is fitted to keep things straight. I'll install the fins next, and lastly install the rear engine holder ring. I saw that in a video. Because the area inside the tube is so small, this is the only way I install some ply backing. I don't trust things, like having one of the buttons come loose because it is only attached to cardboard. From what I see, I can only use 1/16 to 3/32 ply as backers. I have a good stock of that from my free flight model airplane hobby. The trick will be getting things in place with such a small diameter tube, but I think it can be done.
 

rharshberger

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Thanks Guys! I will have to place another order to Apogee on Monday for the buttons, shock cord and something I forgot in my first order, RocketEpoxy, and of course, I might as well invest in those two Jolly Roger units, as well as a noise maker. Apogee looks like the carry one that attaches to the eyelet bolt ring, but I would prefer it to reside somewhere else, as the JR Chute Release probably needs to remain somewhere with lots of room.
In order to install those buttons, I will have to only put on the forward engine holder tube ring on with glue, while the other just is fitted to keep things straight. I'll install the fins next, and lastly install the rear engine holder ring. I saw that in a video. Because the area inside the tube is so small, this is the only way I install some ply backing. I don't trust things, like having one of the buttons come loose because it is only attached to cardboard. From what I see, I can only use 1/16 to 3/32 ply as backers. I have a good stock of that from my free flight model airplane hobby. The trick will be getting things in place with such a small diameter tube, but I think it can be done.
Many of us are moving away from launch lugs all together and switching to rail buttons since rails are much stiffer. The most common railbutton is for the 80/20 Inc. 1010 rail, for larger rockets ( over 25lbs or so) 1515 rails and buttons. There are also mini and micro buttons for 20mm mini rail and 15mm micro rail. All sizes of rail buttons are available from Randy at www.Rail-buttons.com
 

Caley

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Rich, Thank you for the link. I will be building my models rail buttons. This hobby is very complex, so I need to digest all the ins and outs before I actually start this build. Right now I need quite a few items to start. Caley Ann
 

rharshberger

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Rich, Thank you for the link. I will be building my models rail buttons. This hobby is very complex, so I need to digest all the ins and outs before I actually start this build. Right now I need quite a few items to start. Caley Ann
Your welcome, just be aware that not all clubs have the 15mm and 20mm rails, most all of them have 1010 (1"), and many of them have 1515 (1.5"). Probably every club currently flying still maintains a collection of 1/8", 3/16", and 1/4" launch rods at the minimum and some high power clubs can have 3/8" and 1/2" rails. Check with the clubs you plan on flying with to see what GSE (Ground Support Equipment) they have or you can provide your own. I have a 15mm rail that I take with me to our club launches and I have donated one to the club as well.
 

Caley

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Rich, I will write to ROC to find out just what kind of launch rods and rails they have. Caley Ann
 

Swissyhawk

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I haven't seen any mention of motor retention. You'll need to get some kind of motor retention. I've used the Estes ones with H motors. They look kind of clunky but they hold up and they are cheap. I like the Aeropac retainers but they are kind of pricey relative to a Mini Dx3. Aerotech makes a nice 29 mm Aluminum retainer that is in the middle as far as price.

https://www.apogeerockets.com/Building_Supplies/Motor_Retainers_Hooks/Screw-on_Retainers_29mm?zenid=je5i14icebt839int2103e4tt3

http://www.buyrocketmotors.com/aerotech-29mm-anodized-aluminum-motor-retainer/


If you are worried about space for backing nuts for the rail buttons, you can always use rail guides. They glue onto the outside of the tube with nothing sticking into the body tube. They work well. Here's just one example. There are others out there.

https://www.apogeerockets.com/Building-Supplies/Launch-Lugs-Rail-Buttons/Rail-Buttons/Conformal-Rail-Guides-for-38mm-Tube

There's usually no single right way, but instead there are lot's of good ways. When I first started out, each time I built a rocket I would try doing 1 or 2 things differently; maybe a different epoxy or different way of mounting the harness. Heck, just with rail buttons, you can use t-nuts, weld nuts, well nuts, pem nuts, and some don't even use nuts at all. Lot's of choices out there.
 

dhbarr

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Estes 29mm plastic retainer would stick out a bit on this model, can be trimmed down.
 

Caley

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Gregg, Thank you. I like that conformal rail guide. It looks like a good choice for such s mall body.. I made the mistake of purchasing the ESTES motor retainers. I will need to order something that actually fits, a they are too big a diameter. The aluminum looks pretty good if they come in the correct diameter.
 

smugglervt

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I've seen where folks have ground off the ribs on the Estes retainers caps which makes them more suitable for small diameter rockets.
 

Caley

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It's not the body diameter. It is the motor tube which is about 1/16 of an inch smaller than the retainer.
 

noffie79

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I have the same rocket. I didn't put a retainer on mine. I wrap masking tape around the motor until I get a nice snug fit into the motor mount tube.
 

Caley

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noffie, I kind of like the idea of a retainer. I need to upgrade this model so that when I build my Torrent, I have some experience with all those parts
 

rharshberger

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If the retainer is larger than the motor tube its a pretty easy fix, epoxy a wrap or two of cardstock around the motor tube until the retainer slides on easily but not too loose, then epoxy on normally.

My usual method is to slather a thick layer of JB weld onto the motor tube and retainer (piece that mounts to motor tube only) then put the retainer on the motor tube, then take a heavily waxed or motor casing wrapped with scotch tape (type used for gift wrapping) and use it to center the threaded ring on the motor tube (wipe out excess epoxy that squeezed out before inserting motor). Let motor sit in tube until epoxy reaches the stage where its starting to set then remove the motor carefully to prevent the ring from moving.
 

Faroutspacenut

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Hi Caley, I'm in the process of building the "big brother" to yours -- the 2.6" version. I'll also be planning to launch it out at Lucerne, so maybe I'll see you on the lakebed! I had the same question about the supplied kevlar/nylon combo for recovery. Decided to replace it with one single long piece of kevlar I had on hand. I hadn't thought about a larger chute, but since you mention it (and I'm building heavy) I might look into going a size up myself. Good luck with the build!
 

Maxitout

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Hi Caley!
I fly with ROC, and there will be plenty of rods and rails to choose from. Mostly, people seem to be using more rails than rods, but they are available. I'll be out there in April, but any of the members will be more than happy to help out. It's a good group. See you there!

Phil L.
 

Caley

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Rob and Phil, I would love to fly in April, but my body is not cooperating. Had a bad case of dehydration, or I think it was. Hopefully I am still alive to make it in May. The delay gives me a chance to join ROC online.
 

Caley

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I finally has a little success getting an order to Apogee in. Between my local IP taking the system down for maintenance three days straight, and the fact that our gale force winds might also be causing havoc, I have been extremely sick for the past week. Nut I finally got the conformal rail guides, a motor retainer, and Rocket Epoxy. At least if I survive whatever is keeping me down, I might actually start building. Caley Ann
 

crazyed

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Some of you met me over in High Power part of the forum where I introduced myself, and talked about where I hope to go in the hobby.

I already built my first mid-powered model, a Stretch Blobbo, though I did have trouble matching engines to the over weight air frame. But that is done, and I am now going to build my Madcow Mini DX3 mid-powered rocket. I purchased it with an option, a fiberglass nosecone. I also think the nomex parachute protector was optional, and I have that also.

The nose cone is a super tight fit, so I am guessing I will need to sand down the part that plugs into the upper rocket body. Not sure just how tight things are supposed to fit. Is there a test you do, like maybe have it tight enough that when you pull, it makes a popping sound? Silly of me to think about such trivial things, but I am still trying to learn these bigger models. My only rocketry experience was back in 1971 with low powered ESTES rockets

The kit came with 1/4 inch diameter lugs to fit on a launch rod. I'm not sure that this is OK or this model, which has a 1 5/8 inch diameter body. But there is really little room for backing ply squares for launch lugs.

A concern of mine is that this model seems to be a high performance type, that will attain pretty high flights. Since my eyes are pretty bad now, I am wondering if I should obtain a payload bay insert, and add some kind of electronics. If so, just what can I put in a bay that is only about 4-5 inches long, and maybe 1.5 inches in diameter? I am guessing that it might be smart to purchase the Jolly Logic Chute Release since adding an altimeter, 9VDC battery and all the other stuff just won't fit in such a tiny rocket body. I was also thinking of one of those loud noise makers to attract my attention if or when I finally get close to it. I'm not sure the JL chute release provides a peak altitude readout, so I might need a second tiny altimeter to see just how high and fast this little critter goes. I'm sure all of this equipment could be transferred into another model if needed.

The kit also came with what I believe is a Kevlar shock cord that is one body length long, and a nylon shock cord that is 1.5 rocket bodies long. From all that I have seen in videos, this equates to about only half of what seems to be the norm for length, and it splits things, so something could possibly come loose. My thought is to purchase the same size Kevlar for at least three bodies length.

I will be flying off of the Lucerne Dry Lake Bed with the ROC Club. From what I have seen, this area is rock hard except after the rains, and when it gets wet, it is not a good thing to drive out on. Cars tend to get stuck in the gooey glue. But back to the reason I mention rock hard landing area. The provided parachute is 18 inches in diameter for their model weight of 9.5 ounces. I believe that since I build things like tanks, that could approach 15 ounces, especially if I add the payload bay insert and electronics.

I guess that is about all I have for the intro to what I will be building. If anyone has suggestions or something to add before I start this build, please, please mention it. I am still in a steep uphill learning curve. I know next to nothing about the newer, more complex hobby of model rocketry. Thanks Caley Ann
My finerglass minidx3 had just enouph room for all dual deploy parts. A missile works #2 and missile works sled with barrery holder. The nose cone section holds most of the drogue laundry. Used rail buttons. It is a high performance flyer even on a, G64. Also used aeropak retainer. No problems . Awesome bird...my Friend Brett bought me this for Christmas 2 yrs back and it is one tuff bird. . He has,flown his on big H motors with great results. I recommend motor retainer and dual deploy. :)
.
 

Caley

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Crazyed, Thanks for the good word on this model. I tried to start the build, but I need to figure out a fix for it already. The motor tube centering rings are loose. I think that very thin strips of masking tape can fill the gap. Then I can tack things in place with CA, then epoxy things

I purchased an AeroPac retainer ring for this rocket. I also purchased conformal rail guides
 

Caley

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I have started the build. So far I have done the motor tube with centering rings, and attached the Kevlar shock cord to that assembly. I had to ad one wrap of masking tape to the centering rings in order to have them fit properly.

I've inserted the motor tube in the lower rocket body tube. I ended up using a barbecue skewer to place epoxy far enough up past the fin slots so that I wouldn't get epoxy in those slots, then slid the motor tube partially into the lower rocket body tube and added epoxy to the lower centering ring. Then I slid the motor tube the rest of the way in, and tested the fins in the slots to make sure nothing interfered with them. I added a small fillet around the inside of the motor tube where it meets the lower body tube.

I have put one fin on, and expect to get the other two mounted today.

I then will put fillets on the fins, and then finally add the motor retention rings, and that should get me done with the lower airframe, other than painting it.

I am still awaiting the small EBAY I ordered. When that comes, I can work on the middle section of the model. Caley Ann
 

Banzai88

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If you're setting it up for dual deploy, it can be a real challenge. I ended up putting Egg Quark in mine. Works like a champ.
 

Caley

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I looked at the EggTimer Quark. It's nice, but I don't have the soldering talent to put it together. I'm waiting on another tiny dual deployment gizmo that Apogee Components sells, or if I can find something else, will purchase that. The thing has to be small to fit inside the EBAY, and it needs to be able to work off of 3.7V lipo. Caley Ann
 
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