I have two words for you my friend (not counting this lengthy sentence). Big 'chute.
Build thread: Blackfish
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Ya, big 'chute + JLCR. Or at least, bigger chute than usual for me. I usually opt for smaller parachutes on models that I think are likely to be pretty much landing-proof. Not this one!
OK, caught up now.
The one thing I might have done differently would be to harden the ends with a thin or thinned epoxy rather than CA. But if you think what you've got is overkill, and I don't disagree, then epoxy would be even overer kill.
LIPS!
I briefly thought of a JLCR, but then thought you wouldn't want the weight, and might not have enough altitude to support two deployment events. So I was just thinking about going "a size up" from whatever you'd normally use for a rocket of this size/weight.
Yes. But I *have* been curious to experiment with thinned epoxy as an alternative to CA for hardening nose cones. Wouldn't commit it to critical part until I had worked out the process.
If I confirm that the JLCR would work OK in a BT60 (it is made to) then I would probably try to use it for E flight, which should be over 1000'. For Ds or below it's probably not appropriate.
This may not work for what you want to do, but I have used a gentle application of heat from a heat gun to warm and thin epoxy. It starts to get quite thin and flows easily which makes it easy to coat a surface and penetrate to some depth. I've done it with BSI epoxy, which seems to be safe when heated, but I've heard that some epoxies can release noxious fumes when heated (not good). Also, the finishing resins (like Z-poxy or BSI 20 minute) is quite a bit thinner than the average epoxy. (standard TRF notice: wear gloves with epoxy)
Finishing resins, warmed epoxy, and thinned epoxy are all options here. Thinning epoxy weakens it somewhat but for hard-coating balsa that shouldn't really be an issue.
Experimentation is needed to see what works best, and to refine the technique.
lakeroadster
When in doubt... build hell-for-stout!
Neat thread Neil, love the attention to detail and the documentation of events.
Will the fins be through wall?
I ask because on my Hammerhead Shark all the fins and canards are papered and they are all through the body tube wall. Some are just through the body/coupler and flush with the I.D., and at the rear they are all the way through to the motor mount. It also has a full length internal coupler tube. Where am I going with this? The strength of the attached fins is amazing. The internal coupler basically triples the wall thickness over a std body tube. So the through wall fins have a great foundation to attach to.
Dare I say "Hell For Stout ?"
Will the fins be through wall?
I ask because on my Hammerhead Shark all the fins and canards are papered and they are all through the body tube wall. Some are just through the body/coupler and flush with the I.D., and at the rear they are all the way through to the motor mount. It also has a full length internal coupler tube. Where am I going with this? The strength of the attached fins is amazing. The internal coupler basically triples the wall thickness over a std body tube. So the through wall fins have a great foundation to attach to.
Dare I say "Hell For Stout ?"
Howzit Neal! Just FYI a JLCR can be set to activate from as low as 100' alt.(IIRC).
The lowest I would go is 200' cuz you need as much as 50' for the chute to fully deploy.
Wouldn't be concerned too much about the weight: 0.6 oz. and it's forward of the CG.
Combine it with a big chute and you have the best of both worlds: Minimal wind drift and a soft landing.
Cheers.
The lowest I would go is 200' cuz you need as much as 50' for the chute to fully deploy.
Wouldn't be concerned too much about the weight: 0.6 oz. and it's forward of the CG.
Combine it with a big chute and you have the best of both worlds: Minimal wind drift and a soft landing.
Cheers.
Yes. However, they'll be plain old TTW, no additional reinforcement in the BT around the fin slots. That should be good enough here.
Good heavens, are you trying to pierce armor with that thing?
Yes, I can imagine that with a coupler the TTW fins should be extremely strong. Pockets on the MMT or internal fillets can also add strength, but it's overkill for this rocket or any LPR really.
Yeah, I haven't used it yet so I don't have a feel for it. Dunno if I'd be inclined to use it on a low-ish flight (say, 500'-600'), although maybe there's really no good reason not to.
But on flights upwards of 1000' it seems like it should greatly improve my chances of getting it back.
I know it officially fits BT60 but not clear if it's really a good idea. At minimum, I want it for my 2" rockets so I can use some bigger motors with them, but it'll really be nice if it works well in a BT60 (not coincidentally this and my next two builds are all BT60).
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Crazy idea, but what the heck?! We want to protect those pointy tail cones.
Get two or three Chop Sticks. Dowels would also work. Hey, maybe even PENCILS, with the rubber erasers at the bottom. Glue them on the back next to the fins so they stick out the back maybe three or four inches past the motor. Round the aft tips for safety purposes. I'll leave it to you to come up with a paint scheme (call them Remoras or "Fishlets" or something.) Maybe attach them in such a way so that if they break (or more likely WHEN they break-- I think the term is "frangible", and no that is NOT Klingon or Swahili!) they are easily replaceable. These should be the first thing to hit the ground (in fact, if you launch on grass or plowed earth, you might even literally "stick" the landing.)
Is there room between your motor mount and the body tube for "holes" into which you could stick um, sticks, that could be easily replaced if they break?
Get two or three Chop Sticks. Dowels would also work. Hey, maybe even PENCILS, with the rubber erasers at the bottom. Glue them on the back next to the fins so they stick out the back maybe three or four inches past the motor. Round the aft tips for safety purposes. I'll leave it to you to come up with a paint scheme (call them Remoras or "Fishlets" or something.) Maybe attach them in such a way so that if they break (or more likely WHEN they break-- I think the term is "frangible", and no that is NOT Klingon or Swahili!) they are easily replaceable. These should be the first thing to hit the ground (in fact, if you launch on grass or plowed earth, you might even literally "stick" the landing.)
Is there room between your motor mount and the body tube for "holes" into which you could stick um, sticks, that could be easily replaced if they break?
Not really.
It's an interesting idea to try to design in (on another rocket) some sacrificial landing impact absorbers, but there'd be no practical way to do it on this rocket at this point without messing things up. And while I fret over the pods, I feel like with sufficient care in construction than can be made to survive a normal landing.
Now, if the rocket finds the road, then all bets are off.
I guess the saying is true: Great minds think alike!
Heh.
Did that on my Starship Excalibur to protect the points of the trailing fin edges.
Sorry for the crappy picture, the model was not easily accessible and I shot the pic from halfway across the room.
Bonus: makes a pretty good display stand too.
Nytrunner
Pop lugs, not drugs
Neil has only recently come to the position that it's acceptable to have more than one active build thread at a time
And only just barely!
Even more than that, though, I *always* like to do a bunch before starting the build thread so I'll have a decent queue of material to post at the beginning. For those who build faster it wouldn't be as much of an issue.
If you know you're launching (well, landing) on a soft field, you could use a small 'chute to deliberately come in hot and be sure to stick it.
lakeroadster
When in doubt... build hell-for-stout!
Good heavens, are you trying to pierce armor with that thing?
The nosecone is rather unconventional... heavy loads are better handled by a good strong back.
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A few things to consider before heating epoxies:
- Heating the epoxy speeds up the curing process, a lot. So you better be quick and have a long-curing epoxy to begin with. The level of curing acceleration can catch one off-guard, especially when a 30-minute epoxy gels inside a syringe in about 5 minutes (ask me know I found that out).
- Different epoxies react differently to varying levels of heat. Some start forming air bubbles, others do the opposite and release the bubbles (e.g.: Rocketpoxy) at one level of heat, but start forming new ones if you over-heat them.
- Some strength is lost when curing too fast (not as many molecular bonds are given time to form), though I wouldn't worry about it in this application.
West Systems (WS) 105/206 (or 105/205) is a great choice for when low-viscosity epoxy is desired.
WS is wonderfully easy to work with, does not stink, and cures reliably and predictably. But slowly.
WS has almost water-like viscosity, can be applied by brush. It soaks nicely into porous materials (paper and balsa wood) for super-strong bonds.
The only downside is that it cures into a super hard surface that may be tricky to sand.
Definitely harder than CA.
I use WEST System epoxies and it is fairly common to use a heat gun on a low setting to thin the epoxy so it penetrates deeper and let the air bubbles rise to the surface.
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MAIN FIN ASSEMBLY, PART 2
There needs to be a way to attach the rings (cue Marvin voice) to the fins. The angled (salami cut?) rings make it even trickier. I am helped, though, by the fact that the rings are small and should not be absorbing any significant impact.
Each ring will be slit at the "inside" (closest to the airframe) and slid over the fin. Small pieces of 1/16" balsa are affixed to each side of the fin to give the ring edges something to glue to.
Each piece is cut at an angle to it'll be (mostly) hidden inside the ring.
Then the pieces are glued inside that handy outline printed onto the fin templates used for papering the fins:
Before the glue is set I check and adjust alignment by sighting down the edge:
Note the edges of the balsa pieces that will glue to the ring are beveled slightly.
Getting there!
There needs to be a way to attach the rings (cue Marvin voice) to the fins. The angled (salami cut?) rings make it even trickier. I am helped, though, by the fact that the rings are small and should not be absorbing any significant impact.
Each ring will be slit at the "inside" (closest to the airframe) and slid over the fin. Small pieces of 1/16" balsa are affixed to each side of the fin to give the ring edges something to glue to.
Each piece is cut at an angle to it'll be (mostly) hidden inside the ring.
Then the pieces are glued inside that handy outline printed onto the fin templates used for papering the fins:
Before the glue is set I check and adjust alignment by sighting down the edge:
Note the edges of the balsa pieces that will glue to the ring are beveled slightly.
Getting there!
That beveling is a nice touch. As always, I love the attention to detail.
Thanks, I hope it actually works...
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If I can chime in on the warm flow of epoxy, I do this all the time with Aeropoxy. I use the wand from my SMD/soldering workstation as the heat source which has the advantage of adjustable temp range of 100~500 ℃ (Of course I keep it under 200 °F for the epoxy). For applications like strengthening wood, you can thin Aeropoxy with denatured alcohol. And yes, the alcohol will reduce the epoxy's strength but it will still be strong enough for the application.
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Oh, one of my favorite things. One part that serves TWO purposes.
So these little pieces on each side serve to
1. Attachment/guidance point for the rings (sort of like the balsa strips on the Plasma Dart) and
2. Provide a broader stronger attachment surface for the pod.
Love it!
Would that be called a gusset?
I leave it to others to answer, since I have no idea.
Before I decided to use the slot and tab assembly, those pieces *were* going to reinforce the fin/pod joint and then would probably have been genuine gussets. Now, though, I don't think they're really doing any of that, just providing a grab point for the rings.
Any gusset experts out there?
Fore and aft fins, also 3/32" basswood papered with white glue and copy paper (for consistency):
I might very well go to glue-papered basswood in the future when I need strength and can handle the weight. Quite nice to work with.
New business idea: I do nothing but paper fins for people. I swear I could do it all day long. Soooooo satisfying. Don't ask me why.
(I miss the dancing marshmallow man)
I might very well go to glue-papered basswood in the future when I need strength and can handle the weight. Quite nice to work with.
New business idea: I do nothing but paper fins for people. I swear I could do it all day long. Soooooo satisfying. Don't ask me why.
(I miss the dancing marshmallow man)- Joined
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Other than strength, any advantages to papering basswood over balsa?Fore and aft fins, also 3/32" basswood papered with white glue and copy paper (for consistency):
View attachment 408320
I might very well go to glue-papered basswood in the future when I need strength and can handle the weight. Quite nice to work with.
New business idea: I do nothing but paper fins for people. I swear I could do it all day long. Soooooo satisfying. Don't ask me why.
I think it was in Sport Rocketry magazine a former Estes model builder was saying that he used basswood rather than balsa for all the non flying demo models because it was easier to finish.
A side effect of strength: easy to handle. I'm not likely to put fingernail marks in it accidentally, and I can sand quite vigorously without having to worry so much about oversanding. Especially helpful when sanding off excess paper.
I'm not giving up balsa, but I might try to work basswood into the rotation more often.
When you need better strength but are more weight sensitive, remember that laying up your own balsa plywood is basically the same process as glued papering.
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with the exception that papering also in most cases takes care of the filling of the grain. I agree, though, laminated balsa is the bomb for providing strong balsa, especially when you have compound curves, points, or other, what do you call them, "fiddly bits". I use 1/16" balsa 3 ply for my rotor stops on my helis and air brake rockets, they have to be strong in both horizontal and axial planes for their intended use. This technique would be good for rockets that have pods at the ends of fins, you can cut the center piece span a couple of mm short, outer pieces normal, makes a natural "groove" for the pod to settle into. I use the groove as a slot to hold the pull band extensions in place during launch.
https://www.rocketryforum.com/threa...uilt-thread-air-brake-recovery-rocket.145077/
see post 2
