Well I am up in the Fort collins/Wellington Area. If you cant find anyone please feel free to give me a shout and I would be glad to help.

Conway

Hi Ken,

I'm up in Longmont. I'd be glad to take a look.

Thanks Ken. Did you get your L2 on Saturday at Hartsel. Watched a couple of cert flights. Don't know if one was yours or not.

I sure did. I was the red Intruder with the J350 and dual deploy.

I remember it. Very nice! Wish I would have gotten a photo of it. Any chance we can hook up one evening this week or sometime this weekend for a few minutes?

Hi Ken,

Sorry I didn’t see your post sooner – don’t know how I missed it, but I did. Sometime this weekend should be very doable. Where are you located, and when would be a good time for you?

Ken

I'm about halfway between Longmont and Lafayette off of Hwy 287. Let me know if you'd like another opinion. (remember, free advice is worth what you paid for it 🙂
)

Ed

Ken, just found this. I live pretty close to you, too. In the Thornton/Northglenn area. Could you send me a pic of your rocket? Is the CG ahead of the CP by at least a body tube diameter? If you've flown it, what went wrong? The why isn't as hard to find out as you might think. Just let me know.

What happened is one of my motors cato'd (post mortem revealed a couple of the o-rings were switched) in another rocket on the 22nd at Hartsel. I was planning on flying for the first time a new bird I just finished, but didn't because I was pretty spooked after the cato. Anyway, it got me thinking about my design in ways I hadn't before. Not the design so much as the construction of it. I designed it in RockSim, so I feel pretty good about that (CG, CP, etc), but it's just how I constructed it I'd like feedback on. This is my first DD rocket and would like to feel really good how it's built before I fly it - need a little confidence picker upper...

Maybe after I get the aluminum plates done you can check it out too. I can send you a photo if you want.

Thanks
Ken.

With or without the aluminum, I can look at it. A motor CATO has nothing to do with what you did or didn't do with the design. But since you had a bad experience, it was wise to step back. I ALWAYS mark off the steps in the reload instructions (and hope no one's looking). I know that seems excessive, but that way I'm sure I have everything where it's supposed to go. I only use AT reloads--yet to try AMW and Cesaroni's. Trust me, anyone in a hurry can misplace or forget an O ring--especially the forward O ring; the nozzle rattles if you don't have aft one in). And when you're nervous, it's worse. Let's see, does the big one go in the forward end, or the aft end? (aft end--holds the nozzle in place) What about the construction bothers you in DD? You probably have the altimeter in the coupler below the upper section where your chute is packed, your batteries are secure (I use duct tape over them--really, but that's just me--I had one get knocked loose once), you've used a terminal block (though not everyone does) and made sure all the contacts are hitting the bare wire and not the insulation and that the wires haven't been bent a lot so they'll break under flight stress, you've ground tested so you know the charge will eject the chute, you've sealed the hole you stuck the wires through the bulkhead to the terminal block with either epoxy or silicone, you have the proper size hole drilled in the ebay (electronics bay) to make sure the barometric sensor will read the altitude correctly (unless you use an accelerometer like a G-Wiz LC that doesn't need a hole), and you've read the altimeter instructions and understand them, and you KNOW when you turn it on what beep sequence tells you it's happy with all the settings and continuity of the charge(s). Other than that, it's no big deal. 🙂 If you've done all this, then don't worry. I've seen the best come down without a successful ejection, and they did all the right things. Honestly, NO ONE can guarantee what will happen. Make a check list and go over it before flight. I always go away to be by myself when I prep for flight (so no one can see me marking off the reload instructions). I'm really paranoid about forgetting something. Two bad things to do: 1) be so cocky and sure of yourself that you forget something (life will get ya like that), or 2) be TOO afraid to make a mistake. Trust me, I've made many... most of them getting to Level 1. I'd rather do all the dumb stuff at that level than at a higher power. As the power goes up, so does the responsibility, and honestly it scares me. But that's probably good; it'll keep me careful. Hope this rant helps. Warren's right. I am long in the tooth. 😉

Nothing wrong Bruce with being long in the tooth. It better to have MORE info to go over then not enough. For what its worth ANY engine i build I use the intructions every time. AT, AMW, CTI any of them. Ive done it since I began and have never quit. Its a contstant reminder as you go what to do and what not to do. No shame in that at all. In fact i would consider it a smart part on any fliers list of doing things. As far as dual deploy I highly recomend doing whats Called tradistional Zipperless. I use it for every build I do that will be dual deploy. I also prefer to make my entire ebay removeable from the body as well as useable in other rockets of the same size. I deploy my appogee out the bottom by seperating the booster from the lower body half. Then at the specifed alt setting I push the nosecone of and deploy the mains. Has worked flawlessly everytime. I also belive in longer TK shock cords as well as bigger charges. Also I recomend to make yourself real familiar with your altimeter(s) and even when setting them up read the instructions like when doing the motor assembly. I also belive in multi static ports (like 3) instead of 1. But do what you feel comfortable. I have found what I do to workl real well and real easy for me. Also write yourself a preflight, tower/prelaunch, flight,recovery and postflight checksheet. That way you can go down the list as you do things. It will help alot and may just save you....................... or your rockets life.. But thats my opinions for whatever its worth. Bruce gave some all important advice I would look at his suggestions very closely as well.

I appreciate the advice. It's well taken. On the motor cato, I did (as always) read the instructions. But in this case was distracted at the crucial moment of installing the forward o-ring. Put the big one in instead of the small one. A costly mistake I will never repeat. Even with the dissapointment, especially my son's, it was a valuable and important lesson for both of us. Recover and move on.

I think I have it thought through pretty well. With only two concerns I'll address shortly. The Ebay uses an RRC2 configured to deploy the main at 800'. I do have three static ports. I'm using a 1/2 pvc cap to hold the charge (also made out of pvc) at the forward end of the bay. I have a terminal block to connect the charge to. The wires from the terminal block are feed through a small hole in the bulkhead to the altimeter, which is epoxied to seal the hole. I have a Missle Works low profile switch to arm/disarm the electronics mounted on the tube of the bay so I can arm/disarm while on the pad. I'm not using shunts for the charge though. I'm also not using an electronic chage for deployment of the drogue. I wanted to use motor deployment initially. The upper airframe containing the main and nose is attached to the ebay with button head screws that screw into threaded inserts that are set in a 3/4 in plywood ring inside the bay. The altimeter is mounted to two 1/8" aircraft plywood sheets that sandwich two 3/16" tubes and slides onto two 3/16" threaded rods. Wingnuts on each end of the rods hold the bulkheads and entire assembly together.

The two concerns are:

1. I was unable to find 1/4" aircraft plywood sheets (12"x24") for the fins that wasn't warped or twisted in some way, so I laminated two sheets of 1/8" sheets together. It's pretty stiff, but I'm worried that the lamination may not hold under extreme stress or upon a hard landing on a fin.

2. The rocket has a 54mm MMT so I can fly a 54mm J. I built a motor adapter out of 38mm MMT stock, a couple of 54mm -> 38mm centering rings and on the aft end added a third ring larger than 54mm to act as a thrust ring. That whole assembly is made with JB Weld. I'm wondering though, since the AT motors really only butt up to the MMT (the aft enclosure is only as large as the MMT), whether or not a need some type of metal washer (or other material) to go between the aft enclosure and the adapter to transfer some of the load outwards away from the MMT.

Maybe I'm over thinking this, but those are my two main concerns. I thought about getting some hardware to prevent the fins from de-laminating (don't know what it's called) that has a very flat head the fits through a hole with another very flat head on the opposite side. They both screw together and will hold two pieces of wood together very tightly with a very low profile, but I don't know the affect those would have on the aerodynamics of the fins.

Anyway, sorry for rambling. It's always nice to get a second opinion.

Ken.

The two concerns are:

1. I was unable to find 1/4" aircraft plywood sheets (12"x24") for the fins that wasn't warped or twisted in some way, so I laminated two sheets of 1/8" sheets together. It's pretty stiff, but I'm worried that the lamination may not hold under extreme stress or upon a hard landing on a fin.

The first question on this I would have is what types of adhesive did you use to laminate the two together? Did you sand them with a fairly coarse grade sandpaper?How about clamping them together really tight?I have seen this done many times and it works just fine If you used a good slow based expoxy like west sytems or areopoxy or a like kind that has the abillity to sink in to the pores of the wood it will bond fine. Even seen normal wood glue work great for this, I recomend to sand the pieces that will touch together with a fairly coarse grit sandpaper anywhere from 80 to 320 would work. something to make surface area for the advesive to bite as well as to penatrate. Then of course a tightly clamped and alowed to dry nice and slow.

Have you looked into G10 fins ? pretty strong and will do more then what you want them to do. plus easy to use.

2. The rocket has a 54mm MMT so I can fly a 54mm J. I built a motor adapter out of 38mm MMT stock, a couple of 54mm -> 38mm centering rings and on the aft end added a third ring larger than 54mm to act as a thrust ring. That whole assembly is made with JB Weld. I'm wondering though, since the AT motors really only butt up to the MMT (the aft enclosure is only as large as the MMT), whether or not a need some type of metal washer (or other material) to go between the aft enclosure and the adapter to transfer some of the load outwards away from the MMT.
No you should be fine here.

You allready have a thrust ring as the outermost ring for the adaptor. That will be sufficent. What way are you going to rertain the engine? Have you looked at the Areopack retainers(the best and they wrok on all motors AMW and AT and Loki and CTI.) with their adaptors? Or even the slimline retainers (only works well with AT CTI and Loki possibly but not AMW) they are great but I have to admit Im not fond of the fat that you have to do alot of this and that to get them to work with AMW. They to have the slimeline adaptors.. Just some suggestions..

Maybe I'm over thinking this, but those are my two main concerns. I thought about getting some hardware to prevent the fins from de-laminating (don't know what it's called) that has a very flat head the fits through a hole with another very flat head on the opposite side. They both screw together and will hold two pieces of wood together very tightly with a very low profile, but I don't know the affect those would have on the aerodynamics of the fins.

Anyway, sorry for rambling. It's always nice to get a second opinion.

Ken.

You shouldnt need any hardware for the fins. And its always good to think things thru and also get many opinions. There are many ways to make things work and most all of them are great.

Listen to Conway. I didn't realize your rocket was that big. Fin cans are great, too. As Conway said, if you rough up what's going to be glued, whether it's plywood or fiberglass, it will bond better for the reasons he gave--IF you clamped it well; if not, you're gonna leave air and spaces inside, and that takes away from the strength you need. I used plywood (don't remember the thickness and it wasn't two pieces glued together) on a rocket that size, and it was fine... until the booster came down without a chute from a couple thousand feet and snapped two fins off. Didn't break the fins though. That was one of my many learning experiences. And, your ebay sounds fine.