Kraft/paper tubes for Level 1 cert?

[umcoo]

Hi all,

I'm currently scratch-building my first venture into 29mm motors. I had some spare BT-80 so based it around that. I was initially thinking of using it for MPR and getting experience of F and G impulse. I was curious if it could also be used as a Level 1 cert model and use a lower thrust H motor?

My query is, with using Apogee BT-80 with TTW fins, would this stand up to the lower end of H impulse class? I've seen mixed responses, some saying it will be fine, and others saying it's asking for trouble.

Looking for folks with any experience of this.
Thanks all

 

[dhbarr]

Should be fine. I did my L1 on an Estes Mammoth, H97J. What it won't do is stand up very well to early / late deployments.

 

[thzero]

I can't say I've done it, but I do have a BT80 based rocket for F/G dual deployment that I do plan to run at some point on a small H, like an H128W (its only 29mm tube). That one sends it to a simulated 2.437' on a 29.2 ounce rocket (thats with dual deploy running an altimeter and gps trackers). H97 for me goes to 2700 simulated. H70 is 3200

BT80 I've found is great for F/G with single deploy, JLCR deploy and even electronic deployment (flying at non-HPR fields). That being said, I'd probably really recommend like LOC 2.6"+ tubing for a Level 1.

My query is, with using Apogee BT-80 with TTW fins, would this stand up to the lower end of H impulse class? I've seen mixed responses, some saying it will be fine, and others saying it's asking for trouble.

 

[Handeman]

A lot of people have done L1 cert flights on Estes Pro Series rockets. They hold up fine.

Since they are designed for E, F, & G motors, the issue is how high they fly on H motors and if you can get it back popping the main at apogee.

My thought has always been, if you want to Cert L1, it's probably because you want to fly L1 size motors. If that's the case, I highly recommend a 38mm MMT in a 3 - 5 lbs. rocket (4 - 8 lbs if you fly on a smaller field or have a low COA) then you can fly all the H & I motors after your cert without having to build another rocket right away. YMMV

 

[thzero]

Yeah Estes Pro Series have bit heavier tubing than stand BT-80. I have the stuff from both Estes and Apogee.

handeman has good suggestions. Unless you are like me where your l1 then L2 rockets became trophies

 

[techrat]

BT-80 tubing by itself might hold up a few times. Have you got any couplers? Or could you fabricate an inner tube and glue it to the outer tube? No wait, better idea: Quasi-glass. There's a technique to fortify the tube using Nylon ladies stockings and Minwax polycrillic. It's like fiberglassing the rocket, but lighter. I'm thinking about trying this on a Der Big Rad Max, but it couldn't hurt on your L1-BT-80 project. If I were you, I'd spend a little time looking at techniques to fortify the BT-80 tube. Estes tube is kind of thin, but you can beef it up a bit with some work. Personally, for an L1 project, LOC Precision makes some really substantial 2.6" tube that will really take abuse. If you've never built one of their kits, spend $40 and try one out. Their Park Flier Sandhawk is $40, the Scout is $40, and the kits are top notch quality.

 

[umcoo]

Thank you, all. I'll perhaps just keep this scratch build for F and G motors, then look to stronger tubes for L1. I'm in no rush.

It sounds like it could probably survive an H motor, but would be a shame to unnecessarily destroy it if I'm unsure.

 

[Handeman]

Thank you, all. I'll perhaps just keep this scratch build for F and G motors, then look to stronger tubes for L1. I'm in no rush.

It sounds like it could probably survive an H motor, but would be a shame to unnecessarily destroy it if I'm unsure.

I like the way you are thinking on this. A larger, stronger, L1 rocket is probably the best bet.

Then again, if it does shread, it's only a rocket. You can always build another and the way I look at it, if you can't handle destroying, or losing a rocket, keep it on the ground.

Good luck with your flights...

 

[SolarYellow]

BMS has heavy-wall 2.6-inch tube.

T80-34	2.600x2.558x.021x34in long	$9.00	BUY
T80H-34	2.640x2.558x.041x34in long (white Heavy wall)	$10.00

Cost is about the same as LOC, and it sounds like the description is effectively the same, too:

• 2.56" (63mm) Airframe Tubing: White Tube 2.56″ ID x 2.63″ ODx30″ in length. Same ID as BT-80 but with thicker walls resulting in a slightly wider OD. Excellent durability and still light weight!

 

[Handeman]

Why not buy 3" or 4" or 5.5" tubing for a L1 rocket? It doesn't have to be small diameter. If you are sticking to small diameter because they cost less, you might want to reconsider building a L1 rocket. Not only does the cost of the motors go up, but the cost of the rockets do too.

The thing about L1 certs, if you are used to F & G motors, you tend to think about the rocket flying on that level of power. L1 motors are 2x to 4x as powerful as the largest G and can easily lift 8 lbs., 4" rockets to acceptable altitudes. How high do you want to go. Part of what you will learn when flying L1 motors is how much more powerful that range of motors are.

As a general observation, I have seen that L1 will pretty much fly to 2x - 4x the altitude of MPR. L2 will easily fly 2x - 8x the altitude of L1. You have to compensate for the higher power with heavier, larger diameter rockets if you want to stay under the east coast COAs.

I will admit I'm used to east coast venues with lower waiver and lots of trees, creeks, swamps, corn fields, and unfriendly landowners.

I highly recommend doing sims on the rocket, with the L1 range of motors, to determine what range of altitudes you will be flying to and how those altitudes will work at your normal launch site. You might find a heavier and wider diameter rocket works much better for your launch site with L1 motors than you expected.

 

[jmasterj]

Tube fins are fun, easy to build, and draggy enough to stay low even at smaller diameters. I have a tube fin rocket made from BMS T80H that flies great and not terribly high on Hs of all sizes.

 

[Jacktango22]

This is the perfect thread for me. Recently retired and deep into the hobby again about a year. Have been doing designs on Open Rocket and then building in my basement shop. I have drill press, band saw etc. so I am able to do quite a bit.

I want to do a level one next summer and what I have in my “inventory” for this so far is a 3 inch .05 inch heavy duty kraft tube that is 34 inches long and weighs about 7 ounces. Also have a nose cone and a tube coupler.

Not sure what I will do next at all except play with design variables on Open Rocket and see what happens.

This is so much fun … I get to be a kid again.

 

[bjphoenix]

I think 4" diameter is good for level 1, it stays reasonably low so you can see it, it can use motor ejection. If you have a large field and want to use dual deploy then you can go smaller, and lots of people do. I've heard of people stuffing some pretty big motors in the Estes Big Daddy for instance. The first LOC kit I built was a Vulcanite- 2.25" diameter tubing and it came with a 38mm motor mount. Put an H or an I in that one and it would go pretty high.

 

[Hobie1dog]

Thank you, all. I'll perhaps just keep this scratch build for F and G motors, then look to stronger tubes for L1. I'm in no rush.

It sounds like it could probably survive an H motor, but would be a shame to unnecessarily destroy it if I'm unsure.

Good plan, go with a stronger airframe