Aggressive Opposition: 98mm Minimum Diameter

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mannyskid

mannyskid

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If you are reading this, you may have read my last 98mm minimum diameter thread here:
https://www.rocketryforum.com/showthread.php?52141-98mm-minimum-diameter-rocket-N3301-at-Kloudburst

I built that rocket for an engineering project at school. It was an all fiberglass 98mm minimum diameter rocket that flew on a CTI N3301 White. Unfortunately, the rocket shredded just before burn-out. There are many theories as to what happened, but we cannot know for sure because no parts were recovered. In this build thread, I will outline then steps to correct the problems with the first vehicle.

Attached are screen captures from the simulation files and a picture of the fins. According to Open rocket, it starts out with a stability margin of 2.62 calibers and never dibs below 1.5. The is supported by the RasAero plots, saying it will not go unstable until around Mach 7. The fins on the first vehicle were considerably smaller and could have caused the rocket to be dynamically unstable around max Q. According to Open Rocket, the first rocket dipped to around 1.1 calibers of stability, so that may have been an issue. The fins on the new rocket are of the same shape, just larger.

I do not believe that fin strength was an issue on the first rocket because it continued to fly in a stable path after the shred, leading me to believe that the fins were on. Just to be sure, I will be vacuum bagging the lay-ups this time with the help of David Reese and Vic Barlow.

There has been discussion that filament wound nose cones may not be right for this kind of rocket. One kind of nose cone that I have looked at is the shockwave nose cone, but I have not heard much about them and was wondering if anyone here has any experience with those kind of nose cones.

I have a lot more information to share about the design of this rocket, but I have to go to work so I will type something up later tonight.

Manny

P.S If you have any questions to ask of information you would like share, please do not hesitate I would love to hear any comments.

fins.jpg

CP.jpg

RA.jpg

stability.jpg
 
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Remember that the larger the fins, the greater the forces on the fin root, so you need to make big, BIG, strong fillets in order to make tip-to-tip effective. If you use chopped CF in epoxy, you must take care not to pull them lengthwise or else you'll ruin the fiber orientation, making their addition fairly pointless. That will make shaping them nicely difficult, but as this is an extreme performance rocket you really ought to put the effort in and sand them smooth to give a good bonding surface for the tip-to-tip.

What resin are you going to use this time? Even though evidence suggests they were okay, I really wouldn't trust West systems as a tip-to-tip resin on an extreme performance flight. Take no chances.
 
mannyskid said:
One kind of nose cone that I have looked at is the shockwave nose cone, but I have not heard much about them and was wondering if anyone here has any experience with those kind of nose cones.
Click to expand...
My experience is limited to the 38mm and 54mm cones, where the few examples I've seen were slightly asymmetric/out-of-round near the tip. That said, they were quite robust. The vendor states that the cones use "proprietary hybrid Kevlar® impregnated resin for the tip and shoulder to improve strength and decrease brittleness." I had one fall from 2000 feet after a mach 2+ shred and survive intact.

I think you can special-order a Shockwave cone with more glass layers and potentially different resin for more heat resistance. Whether this would be better than a FWFG cone I couldn't say.
 
The 4 inch shockwave nose cone was perhaps the coolest looking and longest nose cone I have ever seen. The nose cone feels tough as well, I dont really know how tough it is, but I am certain it can take a lot of abuse.
 
There is actually a video of a shockwave nose cone lawn darted into the ground from a mile high and survived the impact. Looks like you can expect great performance from a shockwave nose cone.
 
SinfulDarkLord said:
Looks like you can expect great performance from a shockwave nose cone.
Click to expand...
Of course, we don't really know what the effects of heating and aeroloads will be. Mechanical durability at room temperature doesn't count for much here.
 
CarVac said:
Remember that the larger the fins, the greater the forces on the fin root, so you need to make big, BIG, strong fillets in order to make tip-to-tip effective.

What resin are you going to use this time? Even though evidence suggests they were okay, I really wouldn't trust West systems as a tip-to-tip resin on an extreme performance flight. Take no chances.
Click to expand...

Great points, I would stress the two above. On my last 98mm rocket I used large fillets and made the fins as small as I could while still maintaining 1.5 calibers of stability with a 98mm 6GXL. The first flight burned off the tip-to-tip which used boat epoxy, however the big fillets kept the fins on the tube. I rebuilt/bagged the fincan (which sucked) using cotronics laminating resin and post cured it along with some ceramic paint. The second flight was much better, even though it was relatively slow at Mach 2.4 (compared to an N5800 flight) the rocket was in great condition ready to fly again.
 
Some thoughts for the night:

I am about to begin construction on this rocket and I want to address all of these failure theories on the first rocket. There is only one thing that I KNOW I did wrong for sure. The fact that I did not have a vent hole. Pressure separation is most likely what happened. I had a long chat with Tim Lehr the past few days about this. Tim flew a carbon Concept 98 at AIRfest in 2004 on an N2000, Justin is currently looking for the video. He told me that his rocket only had one small vent hole and that in the video, it was clearly seen that the nose cone came off and all of the tubes were intact, the fins had not come off, and none of the charges had fired. Frankly, I was a little embarrassed that this was most likely the cause but I think that I am coming to terms with it. Him along with others have told me that if I built it the same way with a vent hole that I should succeed, but there will be a few changes.

One failure that comes to mind is the famous Mon-Gus N10000 shred from a few years ago (pictures by David Reese):
Gus N10k.jpggus flight.jpg

I cannot seem to remember if this was a drag of pressure separation issue. Gus or David can elaborate on this.

The Nose cone - I bought a 98mm filament wound nose cone on Saturday. One issue that came up is that there is an issue with the tip that rests on top, so I am having a machinist make me one with a step (this would have happened with attempt #1, but the machinist did not have enough time). I am thinking about having the tip glued in place as well with proline 4500 glue to keep it in place. Also, I will be strengthening the inside with a central tube much like Mike Passaratti did. I am also trying to find some sort of high heat coating that I can apply without melting the fiberglass.

The coupler could have been a big issue. I had the coupler sticking out of the airframe then slipping the nose over this. I realized that the inside of the nose cone is not perfectly flat, so if the nose came up even a 1/4" it could have had enough wiggle to snap it.

I am interested in the talk about West systems not being good enough for these kinds of flights (and really glad to see some real life results, thanks James!) The fastest that I have ever flown was Mach 2.2, for that flight, I had three layers of carbon, west systems, not bagged, and Proline 4500 on the TE and LE. Not a scratch on the finish of that flight (I redid that flight a few months later, the shock cord snapped but the fin can was in perfect condition still). If it were up to me, I would make sample swatches of different laminating epoxies and put them up to heat and strength tests. Alas, I do not have time to run experiments like that. I like the Cotronics epoxy that James talked about for his Incredulous rebuild, the only problem is the cost. $100 for a pint that will realistically only do on lay-up. I do not mean to sound cheap but I cannot afford that. There are a lot of things that have to go into a project like this and I only have so much money between my job and selling some of my old rocket stuff. Unless someone can give me a better solution, I will be doing a vacuum bagged lay up with West Systems.

I have one more decision to make about this flight, the motor. Of course, the logical thing to do is fly the N3301 again, but I am seriously thinking about doing the N5800. I think that it can be done with this rocket but I am a little afraid to try it and this may be my last shot at a project like this for a while so I want it to work. My brain and heart are telling my N3301, but the testosterone flowing through my endocrine system is telling me N5800. Please tell me not to do the N5800.

Manny
 
mannyskid said:
Some thoughts for the night:

I am about to begin construction on this rocket and I want to address all of these failure theories on the first rocket. There is only one thing that I KNOW I did wrong for sure. The fact that I did not have a vent hole. Pressure separation is most likely what happened. I had a long chat with Tim Lehr the past few days about this. Tim flew a carbon Concept 98 at AIRfest in 2004 on an N2000, Justin is currently looking for the video. He told me that his rocket only had one small vent hole and that in the video, it was clearly seen that the nose cone came off and all of the tubes were intact, the fins had not come off, and none of the charges had fired. Frankly, I was a little embarrassed that this was most likely the cause but I think that I am coming to terms with it. Him along with others have told me that if I built it the same way with a vent hole that I should succeed, but there will be a few changes.

One failure that comes to mind is the famous Mon-Gus N10000 shred from a few years ago (pictures by David Reese):
View attachment 130166View attachment 130165

I cannot seem to remember if this was a drag of pressure separation issue. Gus or David can elaborate on this.

The Nose cone - I bought a 98mm filament wound nose cone on Saturday. One issue that came up is that there is an issue with the tip that rests on top, so I am having a machinist make me one with a step (this would have happened with attempt #1, but the machinist did not have enough time). I am thinking about having the tip glued in place as well with proline 4500 glue to keep it in place. Also, I will be strengthening the inside with a central tube much like Mike Passaratti did. I am also trying to find some sort of high heat coating that I can apply without melting the fiberglass.

The coupler could have been a big issue. I had the coupler sticking out of the airframe then slipping the nose over this. I realized that the inside of the nose cone is not perfectly flat, so if the nose came up even a 1/4" it could have had enough wiggle to snap it.

I am interested in the talk about West systems not being good enough for these kinds of flights (and really glad to see some real life results, thanks James!) The fastest that I have ever flown was Mach 2.2, for that flight, I had three layers of carbon, west systems, not bagged, and Proline 4500 on the TE and LE. Not a scratch on the finish of that flight (I redid that flight a few months later, the shock cord snapped but the fin can was in perfect condition still). If it were up to me, I would make sample swatches of different laminating epoxies and put them up to heat and strength tests. Alas, I do not have time to run experiments like that. I like the Cotronics epoxy that James talked about for his Incredulous rebuild, the only problem is the cost. $100 for a pint that will realistically only do on lay-up. I do not mean to sound cheap but I cannot afford that. There are a lot of things that have to go into a project like this and I only have so much money between my job and selling some of my old rocket stuff. Unless someone can give me a better solution, I will be doing a vacuum bagged lay up with West Systems.

I have one more decision to make about this flight, the motor. Of course, the logical thing to do is fly the N3301 again, but I am seriously thinking about doing the N5800. I think that it can be done with this rocket but I am a little afraid to try it and this may be my last shot at a project like this for a while so I want it to work. My brain and heart are telling my N3301, but the testosterone flowing through my endocrine system is telling me N5800. Please tell me not to do the N5800.

Manny
Click to expand...

I will tell you not to do the N5800 with West epoxy. No way, no how. I suggest N2540 G3.

Failure is not an option, right? Do it the right way at whatever cost, or don't do it. If it's not done by LDRS, then don't fly it at LDRS. Don't get launch fever and shred another big investment.
 
CarVac said:
I will tell you not to do the N5800 with West epoxy. No way, no how. I suggest N2540 G3.

Failure is not an option, right? Do it the right way at whatever cost, or don't do it. If it's not done by LDRS, then don't fly it at LDRS. Don't get launch fever and shred another big investment.
Click to expand...

Agreed with CarVac
 
To elaborate:

You have limited income, so save up until you can actually afford the right materials and then fly it with 100% confidence in success. Slow down a little so you can spend money at a sustainable rate for your income.

You complain about the cost of a hundred-dollar pint of epoxy, when you are trying to fly a motor that costs one-thousand-one-hundred-fifty dollars in a case that costs six-hundred-thirty dollars. Something is not right there. Make up a budget for the project, acquire the money somehow (legally), and then you won't have to complain about how much the epoxy costs: you will have the money set aside for it.

Is someone else funding the motor? Don't disappoint them by wasting their investment in a rocket that failed due to cost and time saving measures.
 
I'm going to agree with Carlo as well, you can't spare any expense on materials, or you will be preparing for a re-kit mid flight.

I recommend against using tip-tip, or composite fins at all, unless your layup can cover the leading edges and stop that sort of shred. Phenolic leading edges, aluminum/titanium/steel leading edges, or otherwise would be a far wiser choice than laying more composite over.

Tip-tip is used for two basic reasons:
1) Strengthen attachment to the tube to prevent the fin from shearing or peeling off
2) Increase rigidity of the fin to reduce the chances of flutter induced breakage.

The right structural epoxy, and the right fin geometry can negate both issues fairly quickly, but so long as you're using OTS tubing you will run into issues with strength between CF layers.

Any sort of project like this requires far outside the box thinking. I know that for Project 60K we encountered a few parts that we would definitely not use again, all OTS.
 
Okay,

So I realize that if I will not use the right materials that I should not do it at all. I am not saying that the Cotronics epoxy is out of the question, I simply mean that one pint may only do one lay-up, so I may end up spending three hundred dollars on glue. In two weeks of working I may make $300-400, but business is slow and I have not been working as much so I am not making nearly as much. Yes, I am flying some expensive stuff. The casing was funded for (by my dad's company) but I am paying for the motor. I am getting the discount since I am buying it this weekend and it will be $800, but it is still going to take a chunk out of my cash. Other things that still have to be paid for include electronics, recovery gear, and carbon cloth. Cotronics is not out as an option, but is lower on the list of options due to cost.

You guys are telling me how I should not do it if I am not using the right materials but you do not suggest any alternatives. One kind of epoxy that I have heard of and is in my price range is aeropoxy. The only person I have heard of using aeropoxy is Dave Triano of Shadowaero. In his video, he talks about a 98 minimum diameter flight that he did on a Frank Kosdon N motor to just over Mach 3 using aeropoxy and the rocket was still good to use. If you guys have used this kind of epoxy on any extreme flight, please share your experience and persuade me to use that product.

CarVac, what kind of epoxy are you using for the Bare Necessities nose cone?

If there are any other epoxies that one might suggest, let me know so that I can consider all options.
 
Manny , you are on the right track . I flew a 3 inch rocket on a M 1315 at LDRS in 2002 and the same thing happened to me as you . I had a single 1/8 inch vent hole that ( guessing here ) was blocked by my main parachute. needless to say it blew the cone off and flew exactly like yours , minus the front half of the rocket dead straight . Here's a couple pictures of a small rocket we built and flew to 40 miles . It has a solid steel tip that I turned on a early Curtis cone , using all high temp epoxy . The tip actually overlapped the cone by .150 to keep the cone from delaminating. The body tubes where 4.5 inch fiberglass tubes reinforced with couplers . Flew on a LOKI 6 inch full P / baby Q to a 4.5 inch full N / baby O .


Eric


https://www.youtube.com/watch?v=KZWk5W0Vzc4

ic1.jpg

ic2.jpg

untitled.png
 
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mannyskid said:
Some thoughts for the night:

I am about to begin construction on this rocket and I want to address all of these failure theories on the first rocket. There is only one thing that I KNOW I did wrong for sure. The fact that I did not have a vent hole. Pressure separation is most likely what happened. I had a long chat with Tim Lehr the past few days about this. Tim flew a carbon Concept 98 at AIRfest in 2004 on an N2000, Justin is currently looking for the video. He told me that his rocket only had one small vent hole and that in the video, it was clearly seen that the nose cone came off and all of the tubes were intact, the fins had not come off, and none of the charges had fired. Frankly, I was a little embarrassed that this was most likely the cause but I think that I am coming to terms with it. Him along with others have told me that if I built it the same way with a vent hole that I should succeed, but there will be a few changes.

One failure that comes to mind is the famous Mon-Gus N10000 shred from a few years ago (pictures by David Reese):
View attachment 130166View attachment 130165

I cannot seem to remember if this was a drag of pressure separation issue. Gus or David can elaborate on this.

The Nose cone - I bought a 98mm filament wound nose cone on Saturday. One issue that came up is that there is an issue with the tip that rests on top, so I am having a machinist make me one with a step (this would have happened with attempt #1, but the machinist did not have enough time). I am thinking about having the tip glued in place as well with proline 4500 glue to keep it in place. Also, I will be strengthening the inside with a central tube much like Mike Passaratti did. I am also trying to find some sort of high heat coating that I can apply without melting the fiberglass.

The coupler could have been a big issue. I had the coupler sticking out of the airframe then slipping the nose over this. I realized that the inside of the nose cone is not perfectly flat, so if the nose came up even a 1/4" it could have had enough wiggle to snap it.

I am interested in the talk about West systems not being good enough for these kinds of flights (and really glad to see some real life results, thanks James!) The fastest that I have ever flown was Mach 2.2, for that flight, I had three layers of carbon, west systems, not bagged, and Proline 4500 on the TE and LE. Not a scratch on the finish of that flight (I redid that flight a few months later, the shock cord snapped but the fin can was in perfect condition still). If it were up to me, I would make sample swatches of different laminating epoxies and put them up to heat and strength tests. Alas, I do not have time to run experiments like that. I like the Cotronics epoxy that James talked about for his Incredulous rebuild, the only problem is the cost. $100 for a pint that will realistically only do on lay-up. I do not mean to sound cheap but I cannot afford that. There are a lot of things that have to go into a project like this and I only have so much money between my job and selling some of my old rocket stuff. Unless someone can give me a better solution, I will be doing a vacuum bagged lay up with West Systems.

I have one more decision to make about this flight, the motor. Of course, the logical thing to do is fly the N3301 again, but I am seriously thinking about doing the N5800. I think that it can be done with this rocket but I am a little afraid to try it and this may be my last shot at a project like this for a while so I want it to work. My brain and heart are telling my N3301, but the testosterone flowing through my endocrine system is telling me N5800. Please tell me not to do the N5800.

Manny
Click to expand...

Don't do the N5800, do the O3400. It will push you higher, and probably be less stressful on the airframe than the N5800.
 
Manny,

The pint size of cotronics will be more than enough for your project. If you’re not going that route, I would at least use Aeropoxy over West Systems since it has a higher Tg. Proline 4100 may also be another cheaper option, it claims a room temp Tg of 245F and even higher with a post cure although good documentation is a bit scant. With that said my guess is that an N5800 using the latter three epoxies will still end up making your rocket look like this, if you're lucky.
 
mannyskid said:
Okay,

One kind of epoxy that I have heard of and is in my price range is aeropoxy. The only person I have heard of using aeropoxy is Dave Triano of Shadowaero. In his video, he talks about a 98 minimum diameter flight that he did on a Frank Kosdon N motor to just over Mach 3 using aeropoxy and the rocket was still good to use. If you guys have used this kind of epoxy on any extreme flight, please share your experience and persuade me to use that product.
Click to expand...

I second this question about Aeropoxy. I remember reading somewhere about a strength comparison between Aeropoxy and other commonly used epoxy systems and I beleive the result was that Aeropoxy was much stronger. This being said, I don't know if it has the same heat shielding properties as the Cotronics stuff.

Phil
 
bobkrech said:
The Cotronics 600 F laminating epoxy resin is the real deal, and is the easiest high temperature epoxy resin to obtain.

Duralco™ 4460 for layups.
Click to expand...

A couple of questions for you -

Any idea what the shelf life is on this? I don't see any MSDS pdfs on their site.

The data sheet says it can be used up to 600F with a cure in moderate temperatures. Is this room temperature or some elevated temperature?

[Edit] Looks like 4 hours at 250F cure. https://www.matweb.com/search/datasheettext.aspx?matguid=16b6640c5780400798e5e8da5b580e56
 
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These 98mm minimum diameter rockets reminds me of the olden days when Honda built these incredible engines for their racing bikes. . .And then attempted to wrap a stable/ride-able motorcycle around them.

Often enough it didn’t work, Honda had more than one HRT bike nicknamed the “Flexi Flyer”. Sometimes Honda even put engines* into their street bikes that were way beyond the frames ability to handle the torque and horse power. Along with the swing-arm and the wheels and tires and brakes and chain and forks and shocks; Sound familiar?

*I am specifically referring to the CBX 1000 but there were others.

Good luck with your current attempt.
 
Manny:

We are using PTM&W 5712 300-F capable epoxy for Bare Necessities.

We bought a 600 dollar 5-gallon bucket of it, and have used it on many other projects too. The advantage of this resin is that it cures hard at room temperature, which is as I understand better than Cotronics 600f epoxy which doesn't harden except at high temperature, requiring tooling to withstand that. We can instead demold the part and then post cure it for full properties, allowing us to use inexpensive plastic molds.

However, we think it still needs thermal protection in order to withstand the flight so we designed our upcoming nosecone to have a thick layer of microballoons in 200-F capable Aeropoxy laminating epoxy.
 
CarVac said:
Manny:

We are using PTM&W 5712 300-F capable epoxy for Bare Necessities.

We bought a 600 dollar 5-gallon bucket of it, and have used it on many other projects too. The advantage of this resin is that it cures hard at room temperature, which is as I understand better than Cotronics 600f epoxy which doesn't harden except at high temperature, requiring tooling to withstand that. We can instead demold the part and then post cure it for full properties, allowing us to use inexpensive plastic molds.

However, we think it still needs thermal protection in order to withstand the flight so we designed our upcoming nosecone to have a thick layer of microballoons in 200-F capable Aeropoxy laminating epoxy.
Click to expand...


There is also Cotronics Duralco 4461 laminating resin which is 500F degree stable and cures at room temperature. Post cure for 4 hours at 250F.
 
mannyskid said:
I had a long chat with Tim Lehr the past few days about this. Tim flew a carbon Concept 98 at AIRfest in 2004 on an N2000, Justin is currently looking for the video. He told me that his rocket only had one small vent hole and that in the video, it was clearly seen that the nose cone came off and all of the tubes were intact, the fins had not come off, and none of the charges had fired.

One failure that comes to mind is the famous Mon-Gus N10000 shred from a few years ago (pictures by David Reese):I cannot seem to remember if this was a drag of pressure separation issue. Gus or David can elaborate on this.Manny
Click to expand...


Manny,

I can only speculate, but I think you *may* have dumped a fin right at the end of your burn on your N-3301 attempt. This may explain the circular curve in the smoke trail. If the NC failed, the smoke trail would likely have remained straight(ish). On you flight video, a spectator can be heard asking “why’d it turn?” A fin coming off may explain the “turn.” Again, only speculation on my part, it is simply my .02 seeing some shreds in my days.

Here is the video from Tim’s Carbon Concept 98 that met its maker at Airfest in 2004:
https://s68.photobucket.com/user/rfjustin/media/KLOUDBUSTERS/Concept98ATN-2000_zps8d488740.mp4.html

Also Gus’s N-10,000 flight from 2010:
https://s68.photobucket.com/user/rfjustin/media/Tripoli%20Indiana/GusN10000_zpsd03076b2.mp4.html



Justin
 
degreaser said:
A couple of questions for you -

Any idea what the shelf life is on this? I don't see any MSDS pdfs on their site.

The data sheet says it can be used up to 600F with a cure in moderate temperatures. Is this room temperature or some elevated temperature?

[Edit] Looks like 4 hours at 250F cure. https://www.matweb.com/search/datasheettext.aspx?matguid=16b6640c5780400798e5e8da5b580e56
Click to expand...
MSDS wouldn't have the shelf life of the product. I'd call or e-mail Cotronics for the info, but I'm guessing it's pretty good, probably at least 2 years. BTW - The link to the datasheet with the cure temperature/time was in my post.

This epoxy is a laminating epoxy. It has a low viscosity so it will penetrate and wetout the entire layup. I personally would make an molding jig to assist in the layup and curing. I know this is more work that some of the more enthusiastic younder members care to do, but it will result in a better oucome. If you machine an internal plug from ultrahigh molecular weight polyethylene, polypropyolene, or reprocessed PTFE, you can spray the plug with mold release and place your FG or CF cloth over the plug. Then if you make a cavity mold that when mated with the covered plug allows you to pour in the resin, you will obtain a "finished" FG or CF NC that can be placed in your oven for heat treating. If you use the polyethylene or polypropolyene you can heat cure in 2 steps, at 180 F for several hours to cure the resin, and then remove, demold, and cure for 2 hours at 250 F or higher, or do it in one step with the reprocessed PTFE.

Alternative mold making materials may be purchased from https://www.smooth-on.com/ a spectacular souce for porfessional grade plastic molding materials. In this case you could turn a wooden or plastic NC plug and make a casting mold from silicon, polyurethane or other plastic. You would then make an internal plug, spray on release and proceed as above.

In any case, you will obtain a profession grade high temperarure composite layup.

You can also maike a ceramic (silica or alumina) NC from the Cotronics castable ceramics. I've used them as liners inside steel nosecones to protect electronics from very high temperatures, but never for external application, but either would be RF transparent, and extremely temperature resistant and strong at temperature.

Bob
 
Burner said:
There is also Cotronics Duralco 4461 laminating resin which is 500F degree stable and cures at room temperature. Post cure for 4 hours at 250F.
Click to expand...
That will also work as well, and will also wet well as it has a low viscosity. It gives up a little in long term temperature stability, but aerodynamic heating is not long term, so 4460 and 4461 may well have the same short time behavior. You can always cure it at 350 F or 450 F which will improve the short term high temperature properties.

Bob
 
This thread has been pretty dead lately so I thought I would revive it and give you guys some construction updates.

The rocket has fins now. I used four Mongoose 98 fin guides to align them and they are pretty dead perfect. I also made the fillets with Proline 4500 glue, the same epoxy as used for filleting on the first rocket. This time the fillets are bigger, they are 3/4" diameter versus 1/2" diameter on the first rocket, not monster but large. I may end up making the fillets a little bigger to reduce the corner for better adhesion of the carbon fiber fabric. Today I bought 6 yards of carbon from Jeff Davenport (JDcluster) that he got from US composites (5.7 Oz. 2X2 twill). Some time in the next couple weeks I will be heading to Vic Barlow's house to vacuum bag the carbon with the help of him and David Reese.

I bought a black filament wound nose cone to use for this project. One possible failure point on the original project was the coupler to the nose cone since it was a slip joint and not glued in. This time the coupler will be epoxied in, the coupler that I have has a VERY good fit and has absolutely no wiggle. I will also be getting an aluminum nose cone tip machined with a shoulder in it. I wanted to do this for the last rocket but the machinist did not have enough time in his schedule. I will also have a slightly different approach to the altimeter bay that I will describe in the next post.

fillet.jpg

full stack.jpg
 
Basically, the altimeter bay is a 2.6" diameter fiberglass tube that will be bolted to the forward closure. On the last rocket, the altimeter bay was not tied to the airframe in any way so it was possible for it to spin with the forward closure. This time, I glued a wooden ring (pressboard so that I can drill into the side) and will glue a short section of coupler to this ring and have 6 small machine screws through the airframe into inserts in the wood. This will disallow the altimeter bay from spinning. I used the new rocketpoxy from John Olevich to glue the ring to the tube. I like this epoxy, it is easy to work with and it really stay where you put it. I still don't know exactly how I am going to do the sled, but I have a few ideas. For deployment, I plan on using redundant Archetype Cable cutters to deploy the main. On Saturday at Bong, Judy Lubin test flew one in her Formula 75. I watched how she put it together and the flight worked very well. I like the system for its simplicity.

There are still many uncertainties on the deployment and a lot of testing that needs to be done, so I better get moving because I have 6 weeks until I leave for Black Rock!

bay 1.JPG

coup ring.JPG

hidden bulkhead.JPG

rpoxy.JPG
 
mannyskid said:
Basically, the altimeter bay is a 2.6" diameter fiberglass tube that will be bolted to the forward closure. On the last rocket, the altimeter bay was not tied to the airframe in any way so it was possible for it to spin with the forward closure. This time, I glued a wooden ring (pressboard so that I can drill into the side) and will glue a short section of coupler to this ring and have 6 small machine screws through the airframe into inserts in the wood. This will disallow the altimeter bay from spinning. I used the new rocketpoxy from John Olevich to glue the ring to the tube. I like this epoxy, it is easy to work with and it really stay where you put it. I still don't know exactly how I am going to do the sled, but I have a few ideas. For deployment, I plan on using redundant Archetype Cable cutters to deploy the main. On Saturday at Bong, Judy Lubin test flew one in her Formula 75. I watched how she put it together and the flight worked very well. I like the system for its simplicity.

There are still many uncertainties on the deployment and a lot of testing that needs to be done, so I better get moving because I have 6 weeks until I leave for Black Rock!
Click to expand...

What type of parachute are you using? How are you going to bundle it? How are you gonna keep it from buffeting and ripping the cable tie?
 
A couple things I've noticed that I figured I'd chime in about:

  1. Scuff up your FG parts.
  2. Your nose cone tip idea could even be improved a little more....see if you can get one made that has an external sleeve that engages the OD of the cone 0.25" to 0.5". This will prevent aero heating of the fiberglass termination at the tip
  3. Terminate your carbon layup behind your bevel, not at the edge of the fin. Use your "ablative" coating on top of the bare G10 bevel and over the edge of the CF.

I'm working on a 76mm MD booster for 1.5 through 3 grain motors. I'm ignoring items 2 and 3 on my own list as the speeds won't be nearly what yours will be. But please take some 80 grit to those fins!
 

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