L1/L2 Scratch Build

[AstroAbaqus]

Dear all I would like to present to you all the results of my efforts in the last months once finished I will rename it "Set".

This is intended to be a flexible design that will allow me to gain all the skills required for Level 1 and Level 2 certification and despite I know there is always the risk of overbuilding, this has been a very important learning process and in fact, if I will redo this probably I will do things a bit differently and probably better. So in the end despite I do not expect excellent performances it will help me in this voyage.

I am sorry that I do not start this early one since it would be for sure better for my learning process. It is based on two 102 mm LOC tubing, PNC Apogee components ogive (the same of the Zephir I love it), a 54 x 600 mm LOC MMT. I also have used 2 LOC couplers and 1 Stiffy for the e-bay and of course a switch band.
Fins, centring rings and plates for baffle and e-bay are based on 6 mm birch plywood, all designed by me on cad and lasercat in a shop close to my university for a reasonable price.



As a construction material, I went on 2 components industrial epoxy, Gurit Ampro, micro-glass fibre to increase the strength of the fillets and in particular to avoid dry bonds (max 8% in weight to be added I used 5%). In addition, I used fused silica for the external fillet and glass fibre to practice with a composite layup. Here below you can see my initial work on the internal fillet and the glass fabric applied the day after to give more rigidity to the fin assembly. I also designed and used a fin jig, which due to the double slots on the centring ring was not very important, but allowed me to take confidence with the process, and is ready for future birds.



I realised the baffle from scratch and the initial idea was to guarantee a zipperless design. To improve the strength I applied two layers of 6 0z glass fibre, one per side. Finally, I installed the U-bolt and applied epoxy on the hardware.



After this step, I cut the fin slot on the first 4 inch LOC tube and slide in the entire motor assembly. I had to carefully remove a few external layers of the paper to guarantee a perfect fit. After this dry fit was done, I proceeded in applying epoxy internally to bond the centring rings to the airframe. This step was very successful but also is my first mistake. I forgot to install the support for the rail button and now I have to find a way to do this safely. Also the motor retainer has been installed using JB weld.



At this point, I started to sand the glossy layer of both airframes and started to do the external fillet, which came out nice, but probably will need some more sanding. I used the fumed silica from West System and Gurit Ampro epoxy resin, I mixed until the mixture had a peanut butter consistency.

 

[AstroAbaqus]

The more recent step has been the glassing of the upper section, which was a challenge because I had never did this before and also the lack of a wide workspace required a creative solution. However, the outcome has been nice and solid. After several reading I decided to completely remove the external paper, and I regret I did not performed the same operation on the lower body BEFORE installing everything. As I said, lot of learning.



Already dried, just to avoid the frosty weather of my cellar.



Finally, my last work was on the electronic bay, which is pretty standard but will need other work, like installation of the switch, canisters etc. As hardware probably I went a bit beefy, since they are all 6 mm U bolt and quick links. Probably a 5mm would be more than enough.



I know is not a proper build thread, but I really wanted to share this since was a really nice experience so far, and I have used so much the search button of this forum xD every time I had a question. New update will come in the next few weeks.

 

[MadRocketer]

This is intended to be a flexible design

It does have some sweet curves!

 

[Donnager]

This is intended to be a flexible design

It definitely looks flexible.

 

[AstroAbaqus]

Dear all I have now two crucial questions before I can carry on with this build.
Question 1

As I mention due to a mistake durign the assembly I forgot to apply the rail buttons and now I have no access to the inside of the lower section. One of the two buttons I will propably put just at the base where the retainer is located, there is plenty of space for a piece of plywood and I will use JB Weld since this will be a roasty area. Howver the second one I need to get creative since the baffle close my way to the top of the forward centring ring. What do you suggest to solve this issue? I found some solutions, but they were in a post for LPR so I am not sure they are applicable to HPR as well.

Question 2

As you can see in the picture above I decied to use a baffle, on which I have the U bolt. Now I was wondering, do I fix with epoxy the airframe section which will house the drogue? Or I link with plastic rivets the section to the ebay? In this latter solution I would have a zipperless design. But do I really need this? I have10 meter of shock cord I am not going to make things more complicated?

Thank you all in advance!

 

[Titan II]

#1 Well nuts

 

[teepot]

Might use rail guides instead of buttons.

 

[thzero]

Well sounds like you haven't attached the airframe with the baffle to the lower section, so why not just install a rail button as close to the top of the motor mount as you can get? Might not be perfect.

Using like a tee nut you should be able to get it in with a bit of epoxy using a stick, ruler, etc. and some tape rolled up (or use double sided tape). Test and see how far you can get it, then drill a hole there, get some epoxy on the flange of the nut, stick nut in hole, screw.

Something like this
https://www.apogeerockets.com/Building_Supplies/Rail_Buttons/1in_1010_Rail_Button_Standard

Dear all I have now two crucial questions before I can carry on with this build.
Question 1

As I mention due to a mistake durign the assembly I forgot to apply the rail buttons and now I have no access to the inside of the lower section. One of the two buttons I will propably put just at the base where the retainer is located, there is plenty of space for a piece of plywood and I will use JB Weld since this will be a roasty area. Howver the second one I need to get creative since the baffle close my way to the top of the forward centring ring. What do you suggest to solve this issue? I found some solutions, but they were in a post for LPR so I am not sure they are applicable to HPR as well.

 

[Sooner Boomer]

As I mention due to a mistake durign the assembly I forgot to apply the rail buttons and now I have no access to the inside of the lower section.

I've got a couple of high power rockets I built using buttons, and glued the nuts/bolts together inside the body tube. Now I'm told that buttons can wear out. If/when that day comes, I will sand off a small area where the new buttons will go, drill an appropriately sized set of holes, apply at least two coats of thin CA to toughen the cardboard/phenolic airframe, then use pointed "sheet metal" screws (included w/the buttons).

 

[AstroAbaqus]

Might use rail guides instead of buttons.

I was thinking to that, but I am not sure just epoxy bond is sufficient since I would like to fly this on lvl 2 motors, but that’s definitely a possibility.

Well sounds like you haven't attached the airframe with the baffle to the lower section, so why not just install a rail button as close to the top of the motor mount as you can get? Might not be perfect.

Using like a tee nut you should be able to get it in with a bit of epoxy using a stick, ruler, etc. and some tape rolled up (or use double sided tape). Test and see how far you can get it, then drill a hole there, get some epoxy on the flange of the nut, stick nut in hole, screw.

Something like this
https://www.apogeerockets.com/Building_Supplies/Rail_Buttons/1in_1010_Rail_Button_Standard

the problem is exactly that, I epoxied the baffle so I have no access to the forward center ring.

as suggested I may do a larger hole for housing a well nut, or I can use very dense epoxy to fix it and bother only when it will wear down.

 

[jmasterj]

Especially since the recovery won't be able to snag on it, a well nut seems like a good choice.

 

[David Schwantz]

If you do not have access to the forward CR, just make a GOOD measurement from the Lip of the body tube to the top of the CR. Add 1/2 the thickness and drill a hole and attach.
Fly away rail guides can be used, no buttons needed.
Launch tower, again, no buttons needed.

 

[thzero]

the problem is exactly that, I epoxied the baffle so I have no access to the forward center ring.

as suggested I may do a larger hole for housing a well nut, or I can use very dense epoxy to fix it and bother only when it will wear down.

Ah, was hard to tell. But yeah a well nut would work quite well, especially as someone pointed out there isn't anything to get caught up on the bolt's protrusion

 

[AstroAbaqus]

Ah, was hard to tell. But yeah a well nut would work quite well, especially as someone pointed out there isn't anything to get caught up on the bolt's protrusion

Then well nut will be thank you all for the suggestion, by looking from apogee components looks like an m4 well nut is ok.

Any suggestion on leaving it a zipperless design?

Again many thanks!

 

[thzero]

I'd say leave it "zipper less". I build most of my stuff that ways these days. Means I can shorten or lengthen parachute bay, etc.

I use either tnuts (ground down to be flush with coupler) or print 3d rings to hold threaded inserts. Bit overkill and adds weight.
Easier to remove than those rivets for me

With fiberglass tubes if be more inclined to just thread the holes. Considering the thickness of the LOC tubing, could probably do same with it after applying CA to the hole to be threaded.

 

[AstroAbaqus]

After nearly a months I had chance to continue to work on my LVL 1 and LVL 2 rocket. I completed the avionics bay and gave a second coat of epoxy with peel-ply over two of the tube sections, which came simply amazing. I also installed hardware and I am waiting for small drill bits to connect the ejection canisters and terminal blocks. I added for now a key switch with the obligatory flight tag.

Standing in my living room is really intimidating, especially knowing how much time it took to take it from a screen to reality. But it will fly and also Cesaroni hardware arrived. I will use an i350 for its first flight and an i540 for a second one. The plan is then to prepare it for a level 2, probably after a few more flights with the i540, which is at the moment the most powerful lvl1 motor I can use.

I am working a bit also on a homemade GPS module that can send data back to a receiving station with a maximum distance of 2 km, which if DD works should help me in not losing it, in future I will need a more powerful RX/TX radios.

 

[dhbarr]

I've got a couple of high power rockets I built using buttons, and glued the nuts/bolts together inside the body tube. Now I'm told that buttons can wear out. If/when that day comes, I will sand off a small area where the new buttons will go, drill an appropriately sized set of holes, apply at least two coats of thin CA to toughen the cardboard/phenolic airframe, then use pointed "sheet metal" screws (included w/the buttons).

I use machine screws and just daub the hole with epoxy before I drop it in. Ends up with a little dome over the end of the hardware on the interior and a tiny fillet around the base of the rail button.

 

[Handeman]

Any suggestion on leaving it a zipperless design?

I built my L2 cert rocket as a zipperless design. I've never built another DD rocket with a zipperless design. It's just not needed for DD. I've never used a motor back-up with DD so my apogee charges have always been at apogee. Never needed zipperless for that. Having the lower tube connecting to the av-bay was just a pain during prep.
If you do use a zipperless design, make sure you have a really good ball bearing swivel on the fincan. It will spin fast. +100 RPM. Don't trust the non-ball bearing swivels unless you want a totally twisted shock cord.

 

[AstroAbaqus]

Well it as been a while and I had to complete few steps. The first was the fiber glassing of the lower section. I had the "brilliant idea" of doing it after have installed the fins so I had to do the tip to tip layers first and then fibreglassing the rest of the tube. Surprisingly after the use of peel ply it came out very nice, but in future fiberglass sleeves or in any case 2 coupler to avoid issues at the edges, and for finishing probably is better Mylar rather than peel ply (less rough).

My first ever tip to tip... I have learn SO MUCH. Luckily I had some experience with the upper section and I bought a HUGE amount of resin with slow harder so I had all the time to work. In some areas I had drops, too much resin, I solved by sanding and then applying a bit of resin plus peel ply. Next time peel ply will go immediately.



After this I applied fiberglass on the rest of the tube and I sanded it down with a 180, gave a dusted and removed any grease or other things with IPA.



Final result after peel ply and further, very light sanding with 180 and 240. Oh I forgot, I also learn the obvious xD you cannot fiberglass the leading edge if the are straight 90 degree. So I used epoxy with glass micro fibres to seal it all along the edges and I removed the excess with some sanding.



Then I decided to realise and 3D print a tailcone section. I honestly did for domestic reasons but also because I believed that having the MMT in case hitting on an hard landing, would be an issue. So I created this tail-cone, which with a filling of 90% essentially is solid. I can easily screw the retainer and I practiced a bit before fixing it. In extreme case I have a pair of rubbered pliers which works very well



Also for the first time I used a sandable filler like Bondo, which was amazingly good, but produces a tremendous amount of smell during curing and dust when sanding. Unfortunately I do not have any picture of this step. Today instead I started to paint it... and I already know that it will be a challenge. The primer when so well, the bottle was really high pressure and the nozzle was so good a joy using it. For the nosecone I applied first a plastic bonding promoter to make the paint to stick better to the plastic. Then I applied the chrome paint. This went less well since the can was REALLY hard to operate and took me a bit to learn on how to spray with that. So I will have to sand some areas and repaint. Before I forgot this is the rocket without av-bay, since for lvl 1 cert I will fly with motor ejection. The total weight is 2776 grams ( without motor ) and with an i470 it should go at 650 meters with a lift off velocity of around 20.4 m/s.

 

[AstroAbaqus]

Here we are, my bird is painted, in the single deploy configuration for my Lvl 1 certification. The ebay and the other piece of airframe still to be painted and made ready for DD. The paint job is far from perfect imperfection due to being always busy but I wanted to get tho a kind of end. However, this entire project was basically a learning process, I know a ton more than 1 year ago when I started to draw it on CAD.

With a nice 48 inch parachute shock cord and so and 54-38 adapter it weights 2776 grams. It will fly with an I470 WT. Looking forward to see her in the sky. More picture will come!