First time build of HPR question and answer

Next spring I would like to do my L1 and possibly L2 certs based on a 4" Blue Tube 2.0 airframe with 54mm MMT depending on variant rocket will be between 60 an 80 inches tall. Eventually I would like to fly this rocket on the 54mm 6XL Cesaroni L motors. My real questions are:

Does Blue Tube need to be glassed for L motors and above (i may eventually build something for L3 cert or just a new motor section with 75mm MMT)?

Is 54mm Blue Tube to much overkill for the MMT or should I use somethng else

Is 1/4" Aircraft Ply strong enough for TTW fins without glassing or carbon skinning?

Would it be necessary or just a good idea to foam the fin can?

Is 1/4" Aircraft ply strong enough for Centering Rings since I have access to a local steel company I used to work for and can have an 1/8 aluminum thrust plate cut to fit over the bottom of the airframe?

A Baffle is planned as part of the motor section coupler to the drogue/mainbays as the L1 cert will be no electronics, and the drogue bay and main bay are to be interchangeable using plastic rivets so I can use the main bay for the L1 flight, then adding the AvBay Coupler do a L2 with dual deploy. The question here is with basically two couplers in the upper section (Av Bay and motor section to Drogue bay) any special precautions needed to make sure airframe is ok?

I am not a performance junkie, so altitude/speed optimization are not important to me, but cost is (3 small children, limits my funds). While G10 is better than ply for performance, my concern with it would be making sure I get a good bond. Quality of build is my big thing along with finish quality. My open rocket sim shows the bird will weigh around 12.5 lbs in its full stack L2 or J motor and above configuration.

Disclaimer: I know many people out there say use a kit for cert flights, but I take a lot of pride in getting something I designed and build to fly right the first time.

Sounds like a good plan. 1/4" ply is more than enough, depending on actual fin design.

I wouldn't glass or foam it. Also in rockets this size baffles are very rare. Just use a good nomex blanket.

Do the fincan right and lock the rings to the fin tabs and you won't need a thrust plate.

Scratch is always a better idea than kit.

rharshberger said:

Does Blue Tube need to be glassed for L motors and above (i may eventually build something for L3 cert or just a new motor section with 75mm MMT)?

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Nope, not needed.

rharshberger said:

Is 54mm Blue Tube to much overkill for the MMT or should I use somethng else

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Any tube is fine for the MMT, including phenolic.

rharshberger said:

Is 1/4" Aircraft Ply strong enough for TTW fins without glassing or carbon skinning?

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Yes.

rharshberger said:

Would it be necessary or just a good idea to foam the fin can?

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Not necessary.

rharshberger said:

Is 1/4" Aircraft ply strong enough for Centering Rings since I have access to a local steel company I used to work for and can have an 1/8 aluminum thrust plate cut to fit over the bottom of the airframe?

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Yes, but not enough to put rail buttons into. Use separate blocks from the inside to screw into.

rharshberger said:

A Baffle is planned as part of the motor section coupler to the drogue/mainbays as the L1 cert will be no electronics, and the drogue bay and main bay are to be interchangeable using plastic rivets so I can use the main bay for the L1 flight, then adding the AvBay Coupler do a L2 with dual deploy. The question here is with basically two couplers in the upper section (Av Bay and motor section to Drogue bay) any special precautions needed to make sure airframe is ok?

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I'm not a fan of baffles. I agree with DizWolf; just use a Nomex parachute protector.

rharshberger said:

I am not a performance junkie, so altitude/speed optimization are not important to me, but cost is (3 small children, limits my funds). While G10 is better than ply for performance, my concern with it would be making sure I get a good bond. Quality of build is my big thing along with finish quality. My open rocket sim shows the bird will weigh around 12.5 lbs in its full stack L2 or J motor and above configuration.

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G10 isn't "better", it just has a different set of trade-offs. Plywood is a superior composite material for most purposes.

rharshberger said:

Disclaimer: I know many people out there say use a kit for cert flights, but I take a lot of pride in getting something I designed and build to fly right the first time.

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There is no reason to use a kit if you're up for scratch building.

Thanks for the replies David and John. John love the effort you have put into your website, it is a great resource for all of us no matter what power level we fly.

rharshberger said:

Does Blue Tube need to be glassed for L motors and above (i may eventually build something for L3 cert or just a new motor section with 75mm MMT)?

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I've seen quite a few blue tube shreds on M's. I'd say fine to L, glass for M's.

DizWolf said:

Scratch is always a better idea than kit.

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Not always. If everyone shared that view, there might not even be a hobby. Estes (a kit company) was the birth of the rocketry hobby. In fact, a large amount of scratch builds are versions of their original designs. A large majority of rocketeers who would not go out of their way to scratch build got their start with Estes or Centauri kits as kids.

I should have been clearer, I'm not anti-kit. I have many and enjoy them. For a cert, I do believe you learn more and gain more experiance by scratching/building out of parts, if you take the time to research methods.

I like G10 for fins if you have a way to cut the materials..3/32nd sheet is not that expensive and saves so much time in finishing . Mine has been cut with a Harbor Freight cheapie rotary tool and their small diamond cutting wheels.

You may even want to do a 75mm in this..not to pop a 6xl iMax (9976ns) but there are some interesting 1g and 2g loads from AT and CTI in the 75mm. Also if you want to do 2700ns plus in 54mm as the 'go for it' flight there is only two choices in loads. I am going to be flying a Vindicator soon with a L1000W soon..and that will almost top it out..have acquired a 75mm 4 inch fiberglass rocket used ..but the Vindicator is so cool and when I built it had no idea after flying I J K in it I would be looking at 3-5k ns for it but now those motors will have to go to the new rocket.

Agree with the others too about kits, I like kits but realistically the fiberglass kits don't come with retainers, shock cord bridals, av buy hardware , harness or chutes . There is also no real downside to 75mm substitution except one more retainer adapter to buy or borrow. Both Aeropacks are expensive, both are Through the Wall fin capable, both have room to do the briday mounted to the shock cord . The 75mm almost filling up the tube from the rear looks totally bad *ss !

Kenny

Mike is it still possible to get the Thor or are those gone forever, having only just gotten back into the hobby after a 15 year hiatus, I have seen several and really like the design, I also like the Tyrannosaur and may be acquiring one of those next summer ( I could just build it without the smallest fins and that would look an awful lot like the Thor . Im also a fan of the Devestator (both versions). I try and support the vendors and kit companies as much as I am financially able to cuz with out them we would all be flying LPR/MPR.



Rich.

Ken,
I may yet build it from the beginning with a 75mm MMT for the Aerotech 75/5120 case, even though I will probably only fly it once on an M for L3 cert, I will probably fly it mostly with 38s and 54s depending on finish weight.

So from what I've seen so far, up to L no problems with my design ideas so far. M class carbon/glass the fins and tube or just the fins?

rharshberger said:

Mike is it still possible to get the Thor or are those gone forever, having only just gotten back into the hobby after a 15 year hiatus,

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BSD high power rocketry owns the rights to the Thor.

rharshberger said:

Does Blue Tube need to be glassed for L motors and above (i may eventually build something for L3 cert or just a new motor section with 75mm MMT)?

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I've flown an all bluetube rocket multiple times on a L2200G (which is the largest L motor you can buy). It was heavy as all get out (~51lbs in a 6" airframe) which made it go quite a bit slower, but it flew just fine. I would have been comfortable flying it 3-4 more times before I'd want to repair anything. Just watch out for water, I know the new bluetube is more moisture resistant, but that was our biggest issue when the rocket landed in a puddle.

If you start getting into larger M's or N's or are going high mach numbers I might start worrying a bit.

Thanks for the info Mike, like I said earlier hoping to acquire a Tyrannosuar from you next spring or summer.

rharshberger said:

Thanks for the info Mike, like I said earlier hoping to acquire a Tyrannosuar from you next spring or summer.

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No problem. I got to see the Tyrannosaur next to a Thor at a recent launch. The Tyrannosaur is a much nicer looking rocket IMO.

rharshberger said:

Ken,
I may yet build it from the beginning with a 75mm MMT for the Aerotech 75/5120 case, even though I will probably only fly it once on an M for L3 cert, I will probably fly it mostly with 38s and 54s depending on finish weight.

So from what I've seen so far, up to L no problems with my design ideas so far. M class carbon/glass the fins and tube or just the fins?

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I think you are thinking this through before committing to a design or money..very good.

Your designs are good and your methodology is very sound..you can build an L3 capable rocket but wont be able to use it for your L3 flight based on the current requirements ..which are a pre approval for L3 project ..and I dont think you can petition for that without being L2 already.

Think 1 to 3 grain motors for 75mm motors and that goal will dictate the other pieces..the tasty motors on my bucket list are : k1499 and the L910 .

If you go with FG fins and are through the wall with full tabs wildman style ..they should stay on to mach 1.5 without tip to tip. If you go blue tube you may want to do a single wrap of fiberglass to help smooth out the spiral .

If I was doing today would center on a 2.6 or 3 inch thin walled fg with 54mm (almost min diameter) and do a 4 inch fg with those gorgeous fw metal tipped nose cone and 75mm for L3 .

Kenny

Binder Design said:

No problem. I got to see the Tyrannosaur next to a Thor at a recent launch. The Tyrannosaur is a much nicer looking rocket IMO.

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Im kinda with you on that.

Just finished reading one of the pdfs on Wildman style injectable fillets and fin tabs, looks easy enough.

At the moment I am looking towards two different birds because of the L3 cert pre-approval requirement.

TTW is pretty much the way I build everything these days as long as its not MinD.

Those von Karman style metal tipped NCs do look way cool.

Thanks for your thoughts Kenny.

Ken brings up a good point:

CTI 75mm 2 grain K'&L's are substantially less money than 54mm K's & L's , 35-45.00 for same or better performance.