Staging/Mach 1+/Cert Level "loopholes"/other questions

Got a break in the action with my job so I'm back home with extra time for myself and can pester folks with a few queries. :-)
I'm about to put the finishing construction on a 2 stage minimum diameter rocket. There's a personal project I'm pursuing and multi-staging should give the best results for it. The sims say this thing is going to be a screamer, easily exceeding Mach 1. From cautionings I've seen here, and talking to local club members, the epoxy and plywood fins I normally use will likely fail/shred at those speeds. Any suggestions on beefing things up? Along the same lines I'm curious if a standard nosecone can be expected to also handle the stresses and friction. The one I have for it at the moment is a LOC plastic oglive cone. If friction will heat epoxy above it's operating temp it seems reasonable to expect plastic to soften/weaken as well. Also the thing with the largest motors it could hold it'll pack enough power to slip into the "J" range. Being only Level 1 (for the moment) this is breaking the rules by my interpretation of them. However I recall a posting where someone said that it applies to a single motor, not multiples. If that's actually the case I wouldn't be breaking the rules with 2 motors. Clarification? The only other question deals with the staging electronics, which is activated by the G forces of launch. I may be using it in another rocket that'll be slow accelarating for it's recovery deployment. Obviously if it doesn't arm because there's not enough G's things would get a tad "interesting". So while I wait for the company to get back with me about this specific question I thought I'd ask what's the general rule of thumb for such things, if anyone might know.
Chuck
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Unreinforced plywood fins are usually fine through mach, providing that they don't have excessive span or sweep to cause flutter.
Lots of our kits are put though mach with no glassing.

Frictional heating will not be a factor for the one or two seconds above mach. I've personally not seen any frictional heating issues until the rocket exceeds mach 3.
Mike Fisher Binder Design http://binderdesign.com
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I've got some fin hints for ya, Chuck. Flutter will get you at those speeds, drag is less to worry about. To dampen or eliminate flutter, make your fins out of multiple materials and a tapered cross-section. Also, fin shape should be like a LOC lil' Nuke or a clipped delta, like a fighter jet. The fin shoud be thicker at the root, thinner at the leading and trailing edges as well as the tip. I use G10 and plywood to form my high performance fins. .050 thick G10 with 1/16 plywood laminates on both sides about 1/2 inch smaller than the G10. Then taper sand the plywood to acheive the described shape. Use the plywood laminates as sanding guides to acheive the same results on all 3 fins. Also, sharpen the G10 leading edge and tip with a 5 to 1 ratio, and the trailing edge 2 to 1. Then blunt the edge just enough so it's not razor sharp, a safety hazard. Finally, slather on some epoxy and micro balloons and wipe with a plastic spreader to fill any imperfections. Sand smooth and you should have a thin, stout, smooth, vibration resistant fin suitable for mach+.
steve

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Gonna lump the two replies together and give a collective thank you as well as answer:

As I've not attempted doing fiberglass yet it's good to know I haven't, yet, pushed my building experience envelope.
>Frictional heating will not be a factor for the one or two seconds above mach. I've personally not seen any frictional heating issues until the rocket exceeds mach 3.
Mike Fisher Binder Design http://binderdesign.com
Also a good FYI to have and again nice to know I've not left the envelope yet. This one won't get near Mach 3, the sims saying Mach1.8 max. Not yet up for more esoteric materials with my first serious homemade ;-)
default wrote:

Nice to have some numbers, such as the taper ratios for the leading/trailing edges, for what I've been doing intuitively. The fins are triangular as in the Lil' Nuke so that point is already covered. Not having started to shape them yet I may table those for use on another project and go with the G10-ply laminant you suggested.
Thanks again to all that answered, on list and off!!
Chuck
--------------080301080004000405020009 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <title></title> </head> <body text="#000000" bgcolor="#ffffff"> <div class="moz-text-plain" wrap="true" graphical-quote="true" style="font-family: -moz-fixed; font-size: 13px;" lang="x-western"> <pre wrap=""> Gonna lump the two replies together and give a collective thank you as well as answer: </pre> <pre wrap="">&gt;Unreinforced plywood fins are usually fine through mach, providing that they don't have excessive span or sweep to cause flutter.
&gt;Lots of our kits are put though mach with no glassing.
As I've not attempted doing fiberglass yet it's good to know I haven't, yet, pushed my building experience envelope. </pre> <!---->&gt;Frictional heating will not be a factor for the one or two seconds above mach. I've personally not seen any frictional heating issues until the rocket exceeds mach 3.<br> <pre wrap=""> Mike Fisher Binder Design <a class="moz-txt-link-freetext" href="http://binderdesign.com ">http://binderdesign.com </a>
</pre> </div> &nbsp; Also a good FYI to have and again nice to know I've not left the envelope yet. This one won't get near Mach 3, the sims saying Mach1.8 max. Not yet up for more esoteric materials with my first serious homemade ;-)<br> <br> default wrote:<br>
<pre wrap="">I've got some fin hints for ya, Chuck. Flutter will get you at those speeds, drag is less to worry about. To dampen or eliminate flutter, make your fins out of multiple materials and a tapered cross-section. Also, fin shape should be like a LOC lil' Nuke or a clipped delta, like a fighter jet. The fin shoud be thicker at the root, thinner at the leading and trailing edges as well as the tip. I use G10 and plywood to form my high performance fins. .050 thick G10 with 1/16 plywood laminates on both sides about 1/2 inch smaller than the G10. Then taper sand the plywood to acheive the described shape. Use the plywood laminates as sanding guides to acheive the same results on all 3 fins. Also, sharpen the G10 leading edge and tip with a 5 to 1 ratio, and the trailing edge 2 to 1. Then blunt the edge just enough so it's not razor sharp, a safety hazard. Finally, slather on some epoxy and micro balloons and wipe with a plastic spreader to fill any imperfections. Sand smooth and you should have a thin, stout, smooth, vibration resistant fin suitable for mach+.
steve</pre> </blockquote> &nbsp; Nice to have some numbers, such as the taper ratios for the leading/trailing edges, for what I've been doing intuitively. The fins are triangular as in the Lil' Nuke so that point is already covered. Not having started to shape them yet I may table those for use on another project and go with the G10-ply laminant you suggested.<br> <br> Thanks again to all that answered, on list and off!!<br> <br> Chuck<br> </body> </html>
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Mounting them through the wall, even a little reduces flutter due to stiffness and damping.

Long root and tip clipped delta fins made of BALSA with tissue covering will handle that!!
Dont be a "pussy". Go Mach 3! :)
Jerry
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Jerry Irvine wrote:

Since it's a minimum diameter bird through the wall isn't exactly an option. But one local rocketeer had suggested once to strip the outer coating from the body tube, as well as drilling small holes, so the epoxy can get a better grip. Sounds like a good time to try it.

I think I'll save the balsa fin idea for when I rebuild the mid power prototype that caved in under the stresses...quite the learning experience that! Sounds interesting though! LOL! Just cause THIS one can't hit Mach 3 doesn't mean the NEXT won't ;-) Heck, I'll need Mach 6 just to get close to accomplishing this little project I've set before myself.....
Chuck Humming the "Impossible Dream"
--------------070602040904090800030403 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <title></title> </head> <body text="#000000" bgcolor="#ffffff"> Jerry Irvine wrote: <blockquote type="cite" cite=" snipped-for-privacy@corp.supernews.com"> <pre wrap=""><!----> Mounting them through the wall, even a little reduces flutter due to stiffness and damping.</pre> </blockquote> &nbsp; Since it's a minimum diameter bird through the wall isn't exactly an option. But one local rocketeer had suggested once to strip the outer coating from the body tube, as well as drilling small holes, so the epoxy can get a better grip. Sounds like a good time to try it.<br> <blockquote type="cite" cite=" snipped-for-privacy@corp.supernews.com"><!----> <pre wrap="">Long root and tip clipped delta fins made of BALSA with tissue covering will handle that!!
Dont be a "pussy". Go Mach 3! :)
Jerry</pre> </blockquote> &nbsp; I think I'll save the balsa fin idea for when I rebuild the mid power prototype that caved in under the stresses...quite the learning experience that!&nbsp; Sounds interesting though!<br> &nbsp; LOL! Just cause THIS one can't hit Mach 3 doesn't mean the NEXT won't ;-) Heck, I'll need Mach 6 just to get close to accomplishing this little project I've set before myself.....<br> <br> Chuck<br> Humming the "Impossible Dream"<br> </body> </html>
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Yes it is.
Through the tube to the depth of the ID is amazingly better.

Point!
Come on over to my side of the fence.
Jerry
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Been away for a few days, playing catch up.
Jerry Irvine wrote:

In the mid-powered prototype I did this and it worked quite well, actually mounting the fins to the motor mount. I just have this gut feeling to not do it on this one due to the greater stresses. If I'm wrong I guess I'll find out soon enough.

If that's an offer to join in on this personal madness of mine, you're on, and I'll take whatever assist is out there from anyone else who wishes to offer too. I will however decline joining in on any of the political/interpersonal conflicts I've seen on the list. On that I will remain adamantly remain neutral and not participate.
Chuck
--------------030603070307020601000909 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <title></title> </head> <body text="#000000" bgcolor="#ffffff"> &nbsp; Been away for a few days, playing catch up.<br> <br> Jerry Irvine wrote:<br> <blockquote type="cite" cite=" snipped-for-privacy@corp.supernews.com"> <blockquote type="cite"> <pre wrap=""> Since it's a minimum diameter bird through the wall isn't exactly an option. </pre> </blockquote> <pre wrap=""><!----> Yes it is.
Through the tube to the depth of the ID is amazingly better.</pre> </blockquote> &nbsp; In the mid-powered prototype I did this and it worked quite well, actually mounting the fins to the motor mount. I just have this gut feeling to not do it on this one due to the greater stresses. If I'm wrong I guess I'll find out soon enough.<br> <blockquote type="cite" cite=" snipped-for-privacy@corp.supernews.com"> <blockquote type="cite"> <pre wrap="">I'll need Mach 6 just to get close to accomplishing this little project I've set before myself..... </pre> </blockquote> <pre wrap=""><!----> Come on over to my side of the fence.
Jerry</pre> </blockquote> &nbsp; If that's an offer to join in on this personal madness of mine, you're on, and I'll take whatever assist is out there from anyone else who wishes to offer too. I will however decline joining in on any of the political/interpersonal conflicts I've seen on the list. On that I will remain adamantly remain neutral and not participate.<br> <br> Chuck<br> </body> </html>
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On Tue, 11 May 2004 14:53:28 -0400, Zathras of the Great Machine

It is NOT a good idea to try new construction techniques when you are shooting for M1.8! Try them on safer models first, or go with what you know. FWIIW, the current MR speed record is M1.42 with an AT F80. The rocket used 1/16" plywood swept fins that look similar to clipped Alpha fins. Please note that the fin root bending stiffness is key to keeping the fin flutter speed above the flight speed. Surface mount fins is a given. However, the root bending stiffness will be mostly determined by local body tube flexure. What you want to do is make sure that the motor fits tightly in the rocket around the fins so that the body hoop stress increases the root bending stiffness. Of course you could just glue the fins directly to the motor, but then it could not be a proper model rocket.

Possibly, but you also want the fins to be thin and small for low drag. Balsa or foam covered with fiberglass might weigh less that plywood or G10, but is it worth all the extra work?

??? Odds are if the prototype fails you will not want to rebuild it, and if it does not fail, you will never see it again. It's all about the learning from doing.

Getting Zathras and friends back on the tube?
Alan
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It is if you are using experienced consultation, you are following a safety code, and the rocket cost is under 100% of your asset value.

Speed =/ mass

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Alan Jones wrote:

The original idea of the post was to be sure I wasn't exceeding my personal skill envelope at this time with this rocket. And if so, what must be learned to make it flight worthy/safe? In general it would seem I stand a fair chance it'll do as hoped as long as I ere to the cautious. Anything new learned from these postings I'll try with smaller toys first. Also I'm not aiming for Mach 1.8, that's just the results the "dream team" motor selection will give. Ideally staying below Mach would likely be the better for this first step but the commercial motors are too powerful/high thrust. I'd prefer lower thrust and longer burns. Yes, I know, that means playing with EX motors amongst other things. All in good time and the time is not yet now.

Perhaps not for this HP prototype. But if it performs well enough nothing says a bit of tweeking isn't in order afterwards.

does not fail, you will never see it again. It's all about the learning from doing.

The failure in the prototype was in a homemade transition piece, the altimeter I have needs a larger diameter tube than the motor/rocket. I thought I'd made the tolerances close enough but found to the contrary when the G load and slip stream snapped the thing in two like a breadstick. Also the prototype was an independant, if linked, project.....the biggest bang without going Level 1. An attempt to entice the average person into the hobby with something impressive. It's only been tabled whilst I build the HP bird, not cancelled.

Hey! If Trekkies can do it, so can B5 fans!!! ;-)
Chuck
--------------090604050906010403000006 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1"> <title></title> </head> <body text="#000000" bgcolor="#ffffff"> Alan Jones wrote:<br> <blockquote type="cite" cite=" snipped-for-privacy@4ax.com"> <pre wrap="">On Tue, 11 May 2004 14:53:28 -0400, Zathras of the Great Machine <a class="moz-txt-link-rfc2396E" href="mailto: snipped-for-privacy@raex.com">&lt; snipped-for-privacy@raex.com&gt;</a> wrote: </pre> <pre wrap="">It is NOT a good idea to try new construction techniques when you are shooting for M1.8! Try them on safer models first, or go with what you know. FWIIW, the current MR speed record is M1.42 with an AT F80. The rocket used 1/16" plywood swept fins that look similar to clipped Alpha fins. Please note that the fin root bending stiffness is key to keeping the fin flutter speed above the flight speed. Surface mount fins is a given. However, the root bending stiffness will be mostly determined by local body tube flexure. What you want to do is make sure that the motor fits tightly in the rocket around the fins so that the body hoop stress increases the root bending stiffness. Of course you could just glue the fins directly to the motor, but then it could not be a proper model rocket.</pre> </blockquote> &nbsp; The original idea of the post was to be sure I wasn't exceeding my personal skill envelope at this time with this rocket. And if so, what must be learned to make it flight worthy/safe? In general it would seem I stand a fair chance it'll do as hoped as long as I ere to the cautious. Anything new learned from these postings I'll try with smaller toys first. Also I'm not aiming for Mach 1.8, that's just the results the "dream team" motor selection will give. Ideally staying below Mach would likely be the better for this first step but the commercial motors are too powerful/high thrust. I'd prefer lower thrust and longer burns. Yes, I know, that means playing with EX motors amongst other things. All in good time and the time is not yet now.<br> <blockquote type="cite" cite=" snipped-for-privacy@4ax.com"> <blockquote type="cite"> <blockquote type="cite"> <pre wrap="">Long root and tip clipped delta fins made of BALSA with tissue covering will handle that!! </pre> </blockquote> </blockquote> <pre wrap=""><!----> Possibly, but you also want the fins to be thin and small for low drag. Balsa or foam covered with fiberglass might weigh less that plywood or G10, but is it worth all the extra work? </pre> </blockquote> &nbsp; Perhaps not for this HP prototype. But if it performs well enough nothing says a bit of tweeking isn't in order afterwards.<br> <blockquote type="cite" cite=" snipped-for-privacy@4ax.com"> <pre wrap=""><!---->??? Odds are if the prototype fails you will not want to rebuild it, and if it does not fail, you will never see it again. It's all about the learning from doing.</pre> </blockquote> &nbsp; The failure in the prototype was in a homemade transition piece, the altimeter I have needs a larger diameter tube than the motor/rocket. I thought I'd made the tolerances close enough but found to the contrary when the G load and slip stream snapped the thing in two like a breadstick. Also the prototype was an independant, if linked, project.....the biggest bang without going Level 1. An attempt to entice the average person into the hobby with something impressive. It's only been tabled whilst I build the HP bird, not cancelled.<br> <blockquote type="cite" cite=" snipped-for-privacy@4ax.com"> <blockquote type="cite"> <pre wrap="">Chuck Humming the "Impossible Dream" </pre> </blockquote> <pre wrap=""><!----> Getting Zathras and friends back on the tube?
Alan</pre> </blockquote> &nbsp; Hey! If Trekkies can do it, so can B5 fans!!! ;-)<br> <br> Chuck<br> </body> </html>
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