Well xman's project just got a lot more interesting, assuming the usual equilateral triangular cluster, the X has no choice but to swap rockets--maybe for economy a separate fin can that keeps all else the same, or gulp, cluster H's. That would be about as ballsy a L1 cert as I can imagine, esp when new to HPR. Would not recommend it, esp on sat.
JS

He could do 3 H128's.

That's still within the limits of L1.

Still, it is definitely a challenge, and would make for an interesting cert attempt.

Maybe Xman can post some construction info. 80+ # of thrust for an up til now E flyer seems strong, but if everything is epoxied and the fins aren't balsa or bass, it has a chance.
J

Oh - absolutely agreed, which is why I stated it would be an interesting and challenging attempt, but doable.

If either of you have RockSim I can email you the design. Here are the basics though:

Length: 65"
Diameter: 4"
Span diameter: 14"
Mass: 53.5 oz (no motors), 66.3 0z. (with motors)
CG: 31.9" (as measured from the top)
CP: 50.5" (margin 4.6)
Airframe: PM Kraft Phenolic
Fins: 1/8" Birch aircraft plywood (through the body). Area between the first and second rings will be filled with foam to stablize the fins.
Plastic nose code (PM)
1/4" plywood clustering rings

I used epoxy on all gluable parts. The only thng not shown on the design are the rail buttons, but these shouldn't have a large affect on the CG/CP positions.

According to the NAR website, I might be able to cert on weight alone (their req. is 53 oz - don't know if that includes engines or not)

kp.

Correction on the CG/CP values. In the previous post the engines weren't loaded. With the engines loaded the values are:

CG: 39.7
CP: 50.4

kp

You can't cert on weight alone. Strangely enough, there are designs that you must be certed to fly, but that you cannot cert on. This appears to be one of them (unless you wanted to go with an H128X3 cluster). Do you have another 29mm rocket that you could cert on an H128 before the launch of the cluster? If so, that would be the way to go.

Thanks. I do have another I can cert on. It's a LOC Precision kit - "Graduator". The recommended motor is a G40-10. It's 13 oz, 39.5" and 2.63 in diameter. Don't know if that will work or not with an H motor. Should go really high if it will!

That'll work, though it will go HIGH (4000 feet) on an H128

I'd trust it before the 3 motor cluster though, and it's not like it'll drift out of the launch site 🙂

I checked the regs and as usual CJL is right about requiring that one motor be H or I--but clusters are allowed on NAR L1, L2 certs, not L3. Three wimpy H's if we could come up with the cases seems what Xman needs. Now heres an L1 cert flight to remember--clustered g80's in a booster, and an H something for sustenance. 8)
J

You guys are crackin me up. All I wanted to do is launch a big rocket and already I'm thinking about certification. I'll go for the three wimpy H's if you help me prep the vehicle being this is my first. Certainly wouldn't want to kato on the first attempt, but it would be a flight to remember, fer sure. Tell ya what, lets hook up on Friday or Saturday (the 5th or 6th) and you can can give the thumbs or or down on an H cluster launch. The default is the LOC kit with an H rather than a G.

kp

I've got one H128 case, and Joe (cowan) has another. We need a third. I'll be down there saturday early morning, and I'll help after I get my big flight up. It would be nice if it worked though - would definitely be a fun flight 🙂

Here is my 2 cents, If you want to fly 3 H's I have a case you can use. Also Joe, Dave Way, and I use Fuddrucker Igniters. I have a pile of them, they are super dependable. I have never had one fail to fire. Stop by and you can have some. Also you will need a clip whip no matter your motor combo. I use a Thrustline super nice. cjl, e-mail me @ tim4glr@aol.com I have some things you were looking for. I will also have a pile of K motors for sale at the launch. Tim with Giant Leap 8)

I can't remember what I was looking for (other than some of the 18mm D's), but email sent. Also, agreed that fuddruckers are nice - I was going to reccomend quickburst, but either will work great for those. As for clip whip? Not necessary. The only use for one is a BP cluster without long enough igniter leads. The HPR clusters work fine (and in many cases better) with twisted leads, as there are fewer connections and fewer wires, resulting in less chance of a short or a bad connection.

This is shaping up into a nice cooperative effort--gonna be a great cert flight. Now here is where we get into the serial ve parallel issue, as we want this to go off flawlessly. I used to believe parallel was the way to go, but have read too many cluster experts argue for serial wiring. With serial of course, the only way to get continuity is with three good igniters. But there are other reasons: the best IIRC is that all three igniters see the same amperage simultaneously. If its well above the threshold for ignition all three should go more or less at the same time. With parallel there is a greater chance of one getting a head start, and with the rockets motion pulling the other(s) out. So the argument goes, not taking sides, just an issue to consider.
J