Cardboard/Plywood Parts to a 100k

[boatgeek]

Agreed the motor thrust is nicely conservative. It is worth noting the booster section on my rocket with a motor mount is only 5 pounds. I could easily double wall this entire rocket and keep the mass low. Paper has some real advantages It is worth noting that a lot of the composite rockets are over-engineered.

The biggest issue I see on the sim is the sustainer velocity. It is over Mach 3. I always paint my plywood with West Systems epoxy to seal them, but I suspect that is an issue.

Could you run the sim with a K350 as the last stage? It's a lot slower burn so it might be lower drag in the places where it counts. On the other hand, you lose a lot of impulse so it might not be worth it.

Alternatively, you could do a minimum diameter final stage with a Loki L840 or L480 for roughly the same impulse.

 

[AlexBruccoleri]

K350 gets 81.5k and L840 gets 99.2k. I cannot find the L480 but maybe I am just not seeing it.

 

[AlexBruccoleri]

Could you run the sim with a K350 as the last stage? It's a lot slower burn so it might be lower drag in the places where it counts. On the other hand, you lose a lot of impulse so it might not be worth it.

Alternatively, you could do a minimum diameter final stage with a Loki L840 or L480 for roughly the same impulse.

Also I forgot to reply to the second question. Minimum diameter might be possible but relying on the top surface of the paper seems nearly impossible to me. A through-the-wall joint, is a lot stronger especially when mounted into a centering ring.

 

[jqavins]

Attached

Captain, I'm detecting a strange atmospheric anomaly.


The speed and mach number don't track because the speed of sound changes with altitude; I totally get that. And the discontinuity in the mach number during the descent is surprising to me, but could be due to some quirk in the standard atmosphere model, on which subject I'm no expert. What's anomalous is that there's no corresponding discontinuity at the same altitude on the way up. One would expect that, if there's a discontinuity in the speed of sound at some special altitude, it would show up in both directions. Or it shouldn't be there in either direction. On way or the other, they should match, shouldn't they?

Also I forgot to reply to the second question. Minimum diameter might be possible but relying on the top surface of the paper seems nearly impossible to me. A through-the-wall joint, is a lot stronger especially when mounted into a centering ring.

One can do a compromise between surface mount and TTW by making a fin tab that's only as deep as the wall's thickness. I've seen some kits with a series of short slots and a corresponding series of shallow tabs, like dental molding. Of course, TTW with the tab root on and MMT and the tab also locked into a CR is a whole bunch stronger, but the dental molding tabs should give a worthwhile improvement.

Another possibility is to use solid wood "fillets". Place strips of wood square stock, triangular stock, or cove molding^* (preferably with one edge sanded to fit the body tube, but that's not altogether necessary) and let them serve as fillets. (If the face against the tube isn't sanded to fit, epoxy can fill in the gaps, provided they are small.

* Here is a source for basswood cove molding. (Can you tell I've thought about this before? Never done it, though.)

 

[AlexBruccoleri]

I do not know. I am not sure how rocksim is written. I use the sims and back of the envelope calcs as a guide. I match flight data to get better cd estimates after I fly. The SIM is telling me that this challenge is possible without some crazy set of air started motors. A LOC style rocket to even 80k would still be a fun project.

 

[AlexBruccoleri]

Captain, I'm detecting a strange atmospheric anomaly.

View attachment 552500
The speed and mach number don't track because the speed of sound changes with altitude; I totally get that. And the discontinuity in the mach number during the descent is surprising to me, but could be due to some quirk in the standard atmosphere model, on which subject I'm no expert. What's anomalous is that there's no corresponding discontinuity at the same altitude on the way up. One would expect that, if there's a discontinuity in the speed of sound at some special altitude, it would show up in both directions. Or it shouldn't be there in either direction. On way or the other, they should match, shouldn't they?


One can do a compromise between surface mount and TTW by making a fin tab that's only as deep as the wall's thickness. I've seen some kits with a series of short slots and a corresponding series of shallow tabs, like dental molding. Of course, TTW with the tab root on and MMT and the tab also locked into a CR is a whole bunch stronger, but the dental molding tabs should give a worthwhile improvement.

Another possibility is to use solid wood "fillets". Place strips of wood square stock, triangular stock, or cove molding^* (preferably with one edge sanded to fit the body tube, but that's not altogether necessary) and let them serve as fillets. (If the face against the tube isn't sanded to fit, epoxy can fill in the gaps, provided they are small.

* Here is a source for basswood cove molding. (Can you tell I've thought about this before? Never done it, though.)

I had similar thoughts on tabs and interesting call on the molding. For what it is worth, the upper stage of this rocket is pretty simple to test. A Laser Loc kit gets you started. Try building one : )

 

[waltr]

I had similar thoughts on tabs and interesting call on the molding. For what it is worth, the upper stage of this rocket is pretty simple to test. A Laser Loc kit gets you started. Try building one : )

Yep, the LaserLOC has interlocking fin tabs that are the BT thickness.
Then tip to tip glass on the fins.
I just built the 54mm one (LaserLoOC 223). Did come out very nice and was not hard to do the glassing.

 

[AlexBruccoleri]

Yep, the LaserLOC has interlocking fin tabs that are the BT thickness.
Then tip to tip glass on the fins.
I just built the 254mm one (LaserLoOC 223). Did come out very nice and was not hard to do the glassing.

While I am currently opposed to tip to tip glassing, I might be convinced otherwise. Do you think that process is apartment safe? pics?

Oh and nice work! Looking forward to seeing pics of the flights.

 

[waltr]

Epoxy should be apartment safe. It smells a little but nothing like polyester resin or even most spray paints.

 

[jderimig]

While I am currently opposed to tip to tip glassing, I might be convinced otherwise. Do you think that process is apartment safe? pics?

Oh and nice work! Looking forward to seeing pics of the flights.

Tip2tip glassing is totally unnecessary.

(Plus you would be diluting your plywood and paper purity for no real benefit.)

 

[AlexBruccoleri]

Tip2tip glassing is totally unnecessary.

(Plus you would be diluting your plywood and paper purity for no real benefit.)

I agree 200%.

 

[MClark]

On LaserLOCs in the day the thing to do was drill several rows if tiny holes along where the fins attached and soak with CyA. The entire inside of the tube is also soaked.
Must use the thinnest CyA available.
Have see. LL 2.1 (the minimum diameter 54) no fiberglass on K250 several times

M

 

[jqavins]

Epoxy should be apartment safe. It smells a little but nothing like polyester resin or even most spray paints.

Work either very carefully or, better, over a large plastic sheet. A little epoxy at a time for assembly? Sure, do that at the dining room table over newspaper. A glassing operation? Big plastic sheet. (If you do it at all.)

 

[AlexBruccoleri]

On LaserLOCs in the day the thing to do was drill several rows if tiny holes along where the fins attached and soak with CyA. The entire inside of the tube is also soaked.
Must use the thinnest CyA available.
Have see. LL 2.1 (the minimum diameter 54) no fiberglass on K250 several times

M

Thanks for sharing that. Old school rocketeers did some pretty awesome flights with LaserLOC's. Maybe I should be more open minded to minimum diameter.

 

[AlexBruccoleri]

Work either very carefully or, better, over a large plastic sheet. A little epoxy at a time for assembly? Sure, do that at the dining room table over newspaper. A glassing operation? Big plastic sheet. (If you do it at all.)

In internet fantasy land, apartment builds seem great. In the real world not so much. My wife was not thrilled when I bevelled fins for a LOC 7.5 Goblin. I put plastic sheets down and still dust got everywhere. This is not a real contest, and do what is fun and safe. The general premise is to push the altitude boundaries with LOC-style rockets.

To respond directly, BSI and West Systems epoxy is no problem in an apartment. Other types could be an issue. One nice thing about LOC-style rockets is the glue is often stronger than the materials so fussing too much to find ultra strong epoxies is not that helpful. It is more about the correct use of the adhesives and knowing where the stress points are.

 

[boatgeek]

In internet fantasy land, apartment builds seem great. In the real world not so much. My wife was not thrilled when I bevelled fins for a LOC 7.5 Goblin. I put plastic sheets down and still dust got everywhere. This is not a real contest, and do what is fun and safe. The general premise is to push the altitude boundaries with LOC-style rockets.

To respond directly, BSI and West Systems epoxy is no problem in an apartment. Other types could be an issue. One nice thing about LOC-style rockets is the glue is often stronger than the materials so fussing too much to find ultra strong epoxies is not that helpful. It is more about the correct use of the adhesives and knowing where the stress points are.

It would be more apartment-friendly to bevel fins with a low angle block plane with sanding as a touchup. One disadvantage of the boat type epoxies is that they go soft at a lower temperature. If you’re looking at high-ish Mach flights, that may not work for you.

 

[jderimig]

In internet fantasy land, apartment builds seem great. In the real world not so much. My wife was not thrilled when I bevelled fins for a LOC 7.5 Goblin.

Just need to innovate. Look at the sanding screen blocks that hook to a vacuum cleaner that drywall mudders use.

 

[jqavins]

With a little ingenuity you can probably hook a vacuum cleaner nozzle to sand paper (not screen) holder of some sort. I used to go t a barber who had hooked vacuum cleaners hoses to all of the clippers in the shop. Which did a great job of keeping hair bot off the floor and out of the customers' shirts. Some tape, zip ties, and imagination can go a long way.

 

[StreuB1]

Go to a local park and do your work there. It is very common around my place to see people at a few parks doing "home crafts" at the park. Painting a window, craft painting, etc.

Not sure where you live so weather right now might be an issue, but its an option. It also gets you outside and enjoying the weather......when its nice.

 

[AlexBruccoleri]

“It has begun” Will update more when I get a chance. In short, full M in a 5.5” cardboard rocket with full recovery. Photo credit: @mtnmanak

View attachment 1u3a0223.jpeg

 

[thzero]

“It has begun” Will update more when I get a chance. In short, full M in a 5.5” cardboard rocket with full recovery. Photo credit: @mtnmanak

View attachment 614549

To a 100k?

 

[boatgeek]

“It has begun” Will update more when I get a chance. In short, full M in a 5.5” cardboard rocket with full recovery. Photo credit: @mtnmanak

View attachment 614549

Is that a single stage? I'm very curious to see how you get there. 100K and not minimum diameter sounds very difficult. Not that it's not possible, I just want to see more.

 

[OzHybrid]

To a 100k?

Read the full thread. It's a theoretical exercise being built in a flat......

 

[AlexBruccoleri]

Read the full thread. It's a theoretical exercise being built in a flat......

It’s not as theoretical as i intended anymore…but it only just began.

 

[OzHybrid]

It’s not as theoretical as i intended anymore…but it only just began.

Start a new thread. 20k M cardboard tube build.

 

[AlexBruccoleri]

A few general comments. A project like this is often a journey and is supposed to be fun. I expect to need lots of tests flights leading up to the higher altitude flight. Much of that can be achieved without going to Black Rock or FAR. For example the full airframe on an N2000 and dummy weights in the upper stages to test the coupler strength is possible.

Contrary to what it may seem, I am not opposed to fiberglass or other advanced composites. In fact I am moving more and more towards fiberglass due to its robustness in handling and recovering from trees.

To start this project I finished up two fairly basic LOC Precision kits. Both mostly built on my kitchen table with hand tools and a sheet of plywood to protect the table. The first was a LaserLoc 313 built stock and the second a custom LOC Magnum with a 98 mm mount. The LaserLoc was damaged in a tree recovery on a test flight. I replaced part of the airframe and it’s not as a strong as the original. I did the first “stress” test flight on the airframe with a K550. It was not super high performance but it was exciting and recovered without damage. I flew the Magnum on an M750 which was a gentle and majestic flight, also recovered without damage though I need to inspect it more. Part of it got stuck in a tree and it could be dinged from recovery.

A fun next step that avoids too many custom parts could be a Magnum as a booster and staging to a LaserLoc.

I am likely going to need to move away from HPR for awhile. When I got back into the hobby, it was supposed to be a family activity and my wife was into it. It has gotten more difficult with toddler kids, but I may be able to participate in a few launches a year. That being said I wanted to start this project and fly the projects I finished. If I continue I can try larger motors in the rockets I built. A full K or baby L in the LaserLoc will be exciting.