At what point does model rocketry have to morph into HPR?

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I know your statement is ment as sarcasm, but some may miss that fact and get bent out of shape....

It is just possible that I am bent out of shape. There was a reason I unsubscribed from the thread. I am weak and powerless before my compulsions. Carry on.
 
Here's a math problem: What is the carrying capacity...

While I was reading this I was sure the sentence was going to end with something regarding swallows.

As an LPR enthusiast with no dog in this fight, it seems to me that... well who cares what I think. I like balsa and paper.
 
While I was reading this I was sure the sentence was going to end with something regarding swallows.

As an LPR enthusiast with no dog in this fight, it seems to me that... well who cares what I think. I like balsa and paper.
Basswood is better......
 
Look I only saw differential equations applied much in Control Systems at mechanical engineering curriculum for undergrad. We used more calc 1,2, 3 on all those problems than diff in my experience overall. It was here is a course on diff eq and even the prof is screwing up problems then we hardly ever apply something over 1st order. It's nonsense to REQUIRE diff eq for a L2. Yes that flyer will benefit immensely from knowing how to solve it for very limited complex scenarios. This hobby needs to grow members not shrink it. They can design a supersonic rocket nozzle with algebra and tables. There are many benefits to understanding physics and knowing how to algebra. Make sure units are right. First day of engineering class the professors literally yell and beat the whiteboard with expos that units are priority. Flyers can balance chemical equations with algebra. The vast majority of engineering theory problems for students were algebra based. Although sometimes you had to find the algebra from calculus first. With the Internet these flyers will have access to calculators and software to solve certain problems. There are people that drive cars three to six inches off the tail of your bumper because they have more important stuff to do like yak on phone rather than think gee this car has a lot of kinetic energy and will take a few car lengths to stop if the car infront stops for whatever reason rapidly. We don't need differential equations on a L2 exam. Maybe they would want a basic algebra problem if they even want math problems.
 
Will the current L2's be grandfathered in after the required math proposal change? After I got out of school, I swore off math all together. I'd hate to sell all of my shinny blue motor cases.
 
They don't have to change the L2 exam is how I feel about it. There are plenty of hobbyists with GED and highschool diplomas that responsibly fly and build safe rockets and have earned L3.
 
To answer the OP - essentially you won't be able to reach that point. It is way bigger than you can achieve.

Gerald
 
I have some 4 inch LOC tube. I am resolved. If I get my L2 cert, I will use this tube to build something of not-space-aged materials and launch it on a K or L.

I have a Mad Cow Frenzy that is completely cardboard and it has flown on J motors just fine. I don't believe I have ever flown it on a K yet.
 
I was wondering...

At what point is it nearly impossible to hold a rocket together made of paper, plastic, and wood? J? K? L?

To go all the way back to the original post, I don’t think it’s about impulse, but about speed. As mentioned above, you can build a cardboard and light ply rocket for an ‘M’, but somewhere between Mach 1 and 2, the paper and balsa will give out.

That, or a good rain storm. At Bong, I regularly see people bring back rockets that have been out for recovery for more than a year. Fiberglass weathers pretty well.
 
To go all the way back to the original post, I don’t think it’s about impulse, but about speed. As mentioned above, you can build a cardboard and light ply rocket for an ‘M’, but somewhere between Mach 1 and 2, the paper and balsa will give out.
A balsa fin "may" flutter before Mach 1 depending on span and thickness. I have a scale missile with short fin span and 3/32" thickness that flutters at M2.2 and a Sandhawk with long span that flutters at M0.8 using G10 fiberglass material on FinSim and those aren't even minimum diameter kits but are running I class motors. So a J motor on paper broke a Sandhawk kit by math theory and on paper I trimmed the fin span to accept a K motor for L2. The fin span, thickness, and material along with epoxy are the limiting factors at any Mach for flutter to occur in theory. This will depend from rocket to rocket and needs to be examined closely.
 
Mike from Binder Design swears that his rockets made from 4" LOC tubing and built with standard wood glue will eat K motors for breakfast. That said, he uses some really high quality plywood for the fins.
 
They are LARGE diameter and slower likely subsonic Mach on a K. Quality thick plywood is also a good thing. I bet if you had a 41mm OD cardboard tube and 38-1200 Loki clawing for M2.5 it would shred itself especially if paired with 1:16" Balsa fins. It might flutter before it shreds.
 
Mike from Binder Design swears that his rockets made from 4" LOC tubing and built with standard wood glue will eat K motors for breakfast. That said, he uses some really high quality plywood for the fins.

He also will supply you with a full length coupler if you want to try a 4" M flight. If I ever do a L3 Cert, this is the way I'd go. No glass, all class.
 
Surprised no one has even mentioned it yet. LOC sells a few kits that are designed for L motors with no modifications and all their kits are cardboard & plywood.
 
They are LARGE diameter and slower likely subsonic Mach on a K. Quality thick plywood is also a good thing. I bet if you had a 41mm OD cardboard tube and 38-1200 Loki clawing for M2.5 it would shred itself especially if paired with 1:16" Balsa fins. It might flutter before it shreds.

Wait did you just use M2.5 and 1/16" balsa fins in the same sentence? :confused:
 
Wait did you just use M2.5 and 1/16" balsa fins in the same sentence? :confused:
Bullsh*t exaggeration to prove how cardboard and balsa would fail in such scenario for a minimum diameter.
If it worked then all these kit companies would ship HPR as Estes does for Mach 2.5 operations. But they don't.
 
For those who don't know, balsa can be as dense as spruce. But that's not the density end we generally find available. A thick walled cardboard tube made with the right "paper" and polyurethane or phenolic glue could take a bit of heating and a bit of punishment. Make the fins a wedge shape and a half inch thick at the trailing edge, and then saturate with phenolic resin and cure (if you can get the resin and know how to cure it). Make the nosecone out of phenolic saturated white oak. I'm thinking it could scale up to a decent size min diameter. It might be necessary to sheathe the leading edges with a bit of metal but that's been done before.

Of course, that probably isn't exactly what the OP had in mind!

Gerald
 
I have a Mad Cow Frenzy that is completely cardboard and it has flown on J motors just fine. I don't believe I have ever flown it on a K yet.

Mine flew great on a AT K270. Not so great on the CTI K600.
 
[video=youtube;M_FCQ550770]https://www.youtube.com/watch?v=M_FCQ550770[/video]
Let the flutter do the talking.
 
Un-reinforced 1/8" aircraft ply fins wont survive a K550 in a 8lb rocket, it rained parts for a couple of minutes, but MAN WAS IT COOL! (It was someone else rocket of course):cool2:
 
While I was reading this I was sure the sentence was going to end with something regarding swallows.

As an LPR enthusiast with no dog in this fight, it seems to me that... well who cares what I think. I like balsa and paper.

European or African balsa?
 
Un-reinforced 1/8" aircraft ply fins wont survive a K550 in a 8lb rocket, it rained parts for a couple of minutes, but MAN WAS IT COOL! (It was someone else rocket of course):cool2:

Yeah I finally saw an ad for that rocket, mentioning 1/8" fins. I thought, yep, that explained it. Made for good video, anyway.
 
European or African balsa?
Whelp. Balsa Eurospec is not listed darn it. But these other European trees have higher density than other trees.
https://www.google.com/amp/s/www.engineeringtoolbox.com/amp/wood-density-d_40.html

So I'm assuming balsa follows that trend. It's colder and maybe more sappy? Idk. Maybe quality control will be better with engineering specifications on the material being exported from a distribution center compared to a 3rd world nation. But something environmentally affected those trees in Europe to have higher density. I don't think German bias is good answer.
 
For those who don't know, balsa can be as dense as spruce. But that's not the density end we generally find available. A thick walled cardboard tube made with the right "paper" and polyurethane or phenolic glue could take a bit of heating and a bit of punishment. Make the fins a wedge shape and a half inch thick at the trailing edge, and then saturate with phenolic resin and cure (if you can get the resin and know how to cure it). Make the nosecone out of phenolic saturated white oak. I'm thinking it could scale up to a decent size min diameter. It might be necessary to sheathe the leading edges with a bit of metal but that's been done before.

Of course, that probably isn't exactly what the OP had in mind!

Gerald

Just how do you cure phenolic resin? I'm thinking source some 29mm balsa nosecones from Balsa Machine and phenolicise them for a non-plastic minimum diameter build. Why must you tease me?
 
European or African balsa?

Whelp. Balsa Eurospec is not listed darn it. But these other European trees have higher density than other trees.
https://www.google.com/amp/s/www.engineeringtoolbox.com/amp/wood-density-d_40.html

So I'm assuming balsa follows that trend. It's colder and maybe more sappy? Idk. Maybe quality control will be better with engineering specifications on the material being exported from a distribution center compared to a 3rd world nation. But something environmentally affected those trees in Europe to have higher density. I don't think German bias is good answer.

Who are you who are so wise in the ways of science?
 
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