So, maybe I'll try a three-stager

dixontj93060 said:

+1. Very nice!

In fact, I have a rocket in process that I might use this technique on in the next couple weeks.

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I think if I were trying this again that I would attempt to de-gas the epoxy. I'm going to try that for an upcoming construction step just to see if it works.

Jim

WOW!! what an awesome build and thread!
i read a few pages ago on cost estimates. imo, those estimates were way low.
this is priceless!

For those interested, Jim wrote a couple of awesome articles for Rocketry Planet on his methods. RP is no more, but I have the files. You can find them here (if site asks for username and password both would be guest). Frankly, these should be required reading for those interested in using composites for rocketry!

https://www.rocketryfiles.com/?p=home&d=Technicalarticles/Jim Jarvis Carbon-Tutorial/

markkoelsch said:

For those interested, Jim wrote a couple of awesome articles for Rocketry Planet on his methods. RP is no more, but I have the files. You can find them here (if site asks for username and password both would be guest). Frankly, these should be required reading for those interested in using composites for rocketry!

https://www.rocketryfiles.com/?p=home&d=Technicalarticles/Jim Jarvis Carbon-Tutorial/

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Wow, I had no idea these tube were made using old school uncompressed layup techniques. REALLY phenomenal work on the finish there, Jim. Shows some incredible skill.

raptor22 said:

Wow, I had no idea these tube were made using old school uncompressed layup techniques. REALLY phenomenal work on the finish there, Jim. Shows some incredible skill.

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Thank you.

I have tried compression in the past. I once produced a tube and gave it to another flier. He added some fins (somehow) and named it the raisin rocket.

So, what I do is hang a little weight on the end of the cloth, which I think does a lot of good compared to no compression whatsoever. The tubes don't feel mushy and have lower epoxy content. I have learned that there is a limit to this, though, because when you relieve the tension, things move.

Jim

I thought the tension method was pretty clever and the results really speak for themselves.

"The raisin" . I have tried to wrap and vac bag tubes as well, and they always come out with a distinct lack of smoothness. Have you tried slipping the whole mandrel into large diameter heat shrink tubing? That produces good pressure while keeping that really nice smooth finish.

raptor22 said:

I thought the tension method was pretty clever and the results really speak for themselves.

"The raisin" . I have tried to wrap and vac bag tubes as well, and they always come out with a distinct lack of smoothness. Have you tried slipping the whole mandrel into large diameter heat shrink tubing? That produces good pressure while keeping that really nice smooth finish.

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I'm pretty sure that wouldn't work for a multi-wrap tube with more than a few wraps. But, I've been planning for some time to try that the next time I make a 54mm tube. Might try 3 wraps?

Jim

When I roll 3" tubes that are minimum diameter, I have in the past used PML coupler tubing as the mandrel. Most of my 4" tubes were rolled slightly oversized, and I typically use the PML air frame tubing for that. Well, the missing 2nd stage that I'm replacing was actually the first 4" minimum diameter tube that I've made. Following my 3" experience, I used a 4" PML coupler tube as the mandrel. Imagine my surprise when I found out that 4" PML coupler tubes have a smaller OD than a 98mm motor.

For the current tube, I used a Wildman fiberglass coupler as the mandrel. It's big enough for the motor, but the nose cone doesn't fit very well in the slightly larger tube (remember, as the 2nd stage of the 3-stager, I didn't fly the nose cone, so I still have it and I need to make it fit). So, tonight's entertainment is to try to get the tube and nose cone to match up. I don't want to sand down the air frame under the cone because that could lead to delamination at high speed. I also don't want to try and build up the base of a Von Karman nose cone. So, the plan is to use a router to turn down the diameter of the top inch or so of the air frame, and then fill the gap with epoxy to form a gentle transition from the air frame to the nose cone. It could work.

The first pic shows the problem - the ledge is pretty significant. The next three pics show the router setup. The trick is to try to control the dust, because routing carbon fiber indoors could easily turn out badly.

The routed tube turned out pretty well. Woohoo! Next, I'll wrap the top of the tube in a cylinder of mylar and then try to fill the gap with epoxy. If that works, then I'll just sand down the epoxy to fit the cone. Piece of cake.

Jim

Nice work as usual Jim

I haven't had much time to work on the project over the last few days, but I did manage to get the epoxy poured (to make the air frame match up to the nose cone. After routing off the top of the air frame, I covered the inside and outside of the air frame with mylar and then filled the gap with epoxy (laminating Aeropoxy with some high density filler, colloidal silica and graphite). I tried to de-gas the epoxy, but that didn't work very well. It's possible I was just flashing off the volatiles. I'll try that again another day. Now, I just need to sand it down to fit the nose cone.

Jim

JimJarvis50 said:

I'm pretty sure that wouldn't work for a multi-wrap tube with more than a few wraps. But, I've been planning for some time to try that the next time I make a 54mm tube. Might try 3 wraps?

Jim

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Why not? I'm curious why you think it would be less suitable for large multi wrap tubes.

As the vacuum compressed the tube layup you would have to somehow twist the tube to get a tighter wrap or end up with a bunch of wrinkles.

Zebedee said:

As the vacuum compressed the tube layup you would have to somehow twist the tube to get a tighter wrap or end up with a bunch of wrinkles.

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That makes sense. I have never wrapped that many layers over a positive mold before.

One possible solution might be to do the layup in stages, heat shrinking a couple wraps at a time and moving to the next layer when the epoxy has gone green.

raptor22 said:

One possible solution might be to do the layup in stages, heat shrinking a couple wraps at a time and moving to the next layer when the epoxy has gone green.

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That's the approach I took with the first thing I ever compressed. I added three layers of 6 oz glass over PML phenolic tubing one layer at a time. For compression, I used long pieces of elastic, and I used Bounty as the breather. It's been a while and I have forgotten a few key details I think, but whatever I did worked quite well and I still fly that rocket regularly.

Jim

The nose cone transition worked out pretty well. I think it will work. Before/after pics attached.

Next on the agenda is the interstage coupler. We need to go from a 6" air frame to the 4" stabilization spool (or a 4" motor if we don't use the stabilization section for some reason). The plan, showing how the motor would fit, is attached. Stu carved a nice 6" coupler with an integral support ring along with the various phenolic rings. The metal coupler is treated with Random Flying Object's special sauce so that the epoxy will stick to the aluminum (forever he says). I rolled the inner carbon tube, which mates up with an air frame sleeve that fits over the end of the motor tube (with the same tubing forming the bottom of the stabilization spool as well). When the time comes, the sloped transition will be made from Aeropoxy Light.

Jim

Jim,

In my experience of rolling carbon tubes. I have found your issue is the use of a foam roller. Since you cant really apply pressure to the fabric with a foam roller, your practically not compressing the layers flat and not creating any tension on it when you roll it. This is why you end up with that mushy feel. This happened to me as well when I used a foam roller once.

Since you already found a method via using weights to apply tension, there is no need to switch rollers.

With this method you have going, I'm certain you can even use shrink tape. Im not certain about vac bagging.

This is a 38mm carbon tube with 7 wraps of 5oz. Twill carbon. I heat shrink taped wrapped this one and it turned out great.

SinfulDarkLord said:

Jim,

In my experience of rolling carbon tubes. I have found your issue is the use of a foam roller. Since you cant really apply pressure to the fabric with a foam roller, your practically not compressing the layers flat and not creating any tension on it when you roll it. This is why you end up with that mushy feel. This happened to me as well when I used a foam roller once.

Since you already found a method via using weights to apply tension, there is no need to switch rollers.

With this method you have going, I'm certain you can even use shrink tape. Im not certain about vac bagging.

This is a 38mm carbon tube with 7 wraps of 5oz. Twill carbon. I heat shrink taped wrapped this one and it turned out great.

View attachment 289339

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Nobody likes my foam rollers. They have advantages and disadvantages.

One thing about compression is that in order to get it, epoxy has to be removed. Your tube, if 24" long, would have contained about 92 grams of carbon. If compression reduced the percentage of epoxy from 50% to 40%, then 30 grams of epoxy would have been removed and would have dripped onto your floor. Did that happen when you rolled the tube? Maybe try to quantify the benefit you actually get on your next tube if you have not already done it. I know that by adding some weight, I can reduce the percentage of epoxy by about 5%, or a reduction of about 10% in the amount of epoxy added. Not huge, but I think it helps.

Jim

JimJarvis50 said:

Nobody likes my foam rollers. They have advantages and disadvantages.

One thing about compression is that in order to get it, epoxy has to be removed. Your tube, if 24" long, would have contained about 92 grams of carbon. If compression reduced the percentage of epoxy from 50% to 40%, then 30 grams of epoxy would have been removed and would have dripped onto your floor. Did that happen when you rolled the tube? Maybe try to quantify the benefit you actually get on your next tube if you have not already done it. I know that by adding some weight, I can reduce the percentage of epoxy by about 5%, or a reduction of about 10% in the amount of epoxy added. Not huge, but I think it helps.

Jim

Click to expand...

I'll let you know once the carbon arrives. I'll be trying something out that should work. That tube I made was 50:50, and that should be right since I mixed the same amount of resin.

JimJarvis50 said:

Nobody likes my foam rollers. They have advantages and disadvantages.

One thing about compression is that in order to get it, epoxy has to be removed. Your tube, if 24" long, would have contained about 92 grams of carbon. If compression reduced the percentage of epoxy from 50% to 40%, then 30 grams of epoxy would have been removed and would have dripped onto your floor. Did that happen when you rolled the tube? Maybe try to quantify the benefit you actually get on your next tube if you have not already done it. I know that by adding some weight, I can reduce the percentage of epoxy by about 5%, or a reduction of about 10% in the amount of epoxy added. Not huge, but I think it helps.

Jim

Click to expand...

Jim

Re dripping on the floor, I don't believe that's necessarily true. If you saturate the first wrap, then lay the second layer on top so as to absorb epoxy from the layer underneath, then rinse and repeat with subsequent wraps only adding epoxy where it's needed, you can get a very good cloth to epoxy ratio. I also can't recommend Aerotech peel ply strongly enough - that, with shrink wrap and a heat gun for compression is a ghetto layup that is strong, light, and I'm certain it gets sub 50% epoxy. You parked next to me at the last Tripoli Houston launch - if you're coming in May maybe we can run an extension cord to Random Flying Object's trailer for my heat gun and we could make a tube in the parking lot.

Barkley said:

Jim

Re dripping on the floor, I don't believe that's necessarily true. If you saturate the first wrap, then lay the second layer on top so as to absorb epoxy from the layer underneath, then rinse and repeat with subsequent wraps only adding epoxy where it's needed, you can get a very good cloth to epoxy ratio. I also can't recommend Aerotech peel ply strongly enough - that, with shrink wrap and a heat gun for compression is a ghetto layup that is strong, light, and I'm certain it gets sub 50% epoxy. You parked next to me at the last Tripoli Houston launch - if you're coming in May maybe we can run an extension cord to Random Flying Object's trailer for my heat gun and we could make a tube in the parking lot.

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I'm always happy to roll a tube, and it would be worth trying to shut down RFO's spy operation.

On two occasions, I quantified the amount of epoxy that is removed from a tip to tip carbon layup with three layers of carbon. In both cases, the epoxy content of the hand layup was around 55%, and this was reduced to around 40% with bagging. If you go through the math, the bagging is removing about half of the epoxy added during the hand layup. I think tubes are similar, except that the initial epoxy content could be a little lower. So, compression should remove a third to a half of the epoxy from the hand layup (using 6 oz 2x2 twill, which is mostly what I use).

I've seen many examples of heat shrink tape, shrink tubing, mylar with heat shrink tape, etc., where the result is a nice smooth tube. Generally, when I ask how much epoxy was removed, the answer is usually that a little epoxy came out the ends or leaked between the seams of the tape, but not really all that much. I would argue that significant compression was not really achieved. I wish I had more time to try different things, so it's good to hear the experiences of others, particularly if something works well. I would like to see some numbers though.

Jim

JimJarvis50 said:

I'm always happy to roll a tube, and it would be worth trying to shut down RFO's spy operation.

On two occasions, I quantified the amount of epoxy that is removed from a tip to tip carbon layup with three layers of carbon. In both cases, the epoxy content of the hand layup was around 55%, and this was reduced to around 40% with bagging. If you go through the math, the bagging is removing about half of the epoxy added during the hand layup. I think tubes are similar, except that the initial epoxy content could be a little lower. So, compression should remove a third to a half of the epoxy from the hand layup (using 6 oz 2x2 twill, which is mostly what I use).

I've seen many examples of heat shrink tape, shrink tubing, mylar with heat shrink tape, etc., where the result is a nice smooth tube. Generally, when I ask how much epoxy was removed, the answer is usually that a little epoxy came out the ends or leaked between the seams of the tape, but not really all that much. I would argue that significant compression was not really achieved. I wish I had more time to try different things, so it's good to hear the experiences of others, particularly if something works well. I would like to see some numbers though.

Jim

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The point of the process is that the epoxy you want removed is never applied in the first place. Compression is via the weight of the hanging cloth, the epoxy brush, a bondo spreader, then the compression from the shrink wrap. I'll do the math on my next tube, weighing the cloth before and the tube after, and I'll let you know if I'm able to get ratio numbers that would pique your interest.

Barkley said:

The point of the process is that the epoxy you want removed is never applied in the first place. Compression is via the weight of the hanging cloth, the epoxy brush, a bondo spreader, then the compression from the shrink wrap. I'll do the math on my next tube, weighing the cloth before and the tube after, and I'll let you know if I'm able to get ratio numbers that would pique your interest.

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Perhaps you have a tube you could weigh now? All you need is to know what carbon you used and how many wraps. Alex could do that too.

Jim

JimJarvis50 said:

Perhaps you have a tube you could weigh now? All you need is to know what carbon you used and how many wraps. Alex could do that too.

Jim

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Sadly this isn't an option, but I should be making another tube soon.

Barkley said:

Sadly this isn't an option, but I should be making another tube soon.

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Same here, I'll let you know when I make another when the carbon arrives. I doubt I have any other tube that has less resin content.

I've made more progress on the staging coupler (to go from 6" to 4"). One of the things that makes this a little tricky is that the coupler has to be designed to accept the stabilization spool, if we use it, or the sustainer motor if we don't. Note that there is a support ring inside the coupler for either the stabilization spool or the motor, but the ring has a cut-out area for wiring if the motor is used as well as space below the ring for the nozzle. So far, I've gotten everything glued together. Random Flying Object's aluminum treatment seems to have worked very well, and I don't think the coupler will ever come apart.

The center tube in the coupler has a "key" to prevent the parts from rotating during flight. In this case, I cut the female part of the key in the tube to fit an existing male key on the stabilization spool. It fits just fine (I'm very pleased with myself over that one). With the key cut in the transition coupler, I have poured the male part of the key in a tube that will cover the base of the motor (i.e., the part of the motor case that extends below the sustainer air frame). This would be used if the stabilization spool is not used during the flight.

The next step will be to form the sloped transition at the top of the coupler.

Jim

JimJarvis50 said:

I've made more progress on the staging coupler (to go from 6" to 4"). One of the things that makes this a little tricky is that the coupler has to be designed to accept the stabilization spool, if we use it, or the sustainer motor if we don't. Note that there is a support ring inside the coupler for either the stabilization spool or the motor, but the ring has a cut-out area for wiring if the motor is used as well as space below the ring for the nozzle. So far, I've gotten everything glued together. Random Flying Object's aluminum treatment seems to have worked very well, and I don't think the coupler will ever come apart.

The center tube in the coupler has a "key" to prevent the parts from rotating during flight. In this case, I cut the female part of the key in the tube to fit an existing male key on the stabilization spool. It fits just fine (I'm very pleased with myself over that one). With the key cut in the transition coupler, I have poured the male part of the key in a tube that will cover the base of the motor (i.e., the part of the motor case that extends below the sustainer air frame). This would be used if the stabilization spool is not used during the flight.

The next step will be to form the sloped transition at the top of the coupler.

Jim

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Glad I could help, let me know if you guys need any other metal parts treated. FYI, it works with titanium and stainless also. For mounting electronics I use treated aluminum or stainless standoffs, mount them to the PCB, put a bit of epoxy on the other end of each standoff, place the assembly on the sled and there you go, perfectly aligned PCB mounts.

I've made some progress on the transition to the interstage coupler. I had a sanding jig I made several years ago. I really hadn't expected to reuse it, but here's an opportunity. The transition is sort of in mid-build at the moment, but I think it will work out fine.

Jim

What is the stabilization spool, and how does it work?

CoyoteNumber2 said:

What is the stabilization spool, and how does it work?

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It's a spool piece that includes active stabilization electronics and canard fins. The development of it over the last year plus is here:

https://www.rocketryforum.com/showthread.php?122042-I-could-use-just-a-little-guidance

On my three-stage flight last September, I used it to try to bring the second/third stage vertical before the second stage motor lit. Didn't work quite as planned. I will likely try it again on a two-stage flight this year, installed between the stages.

Jim

I was reading this over and thought of a building technique from fiberglass boats. They faced all the same issues you do, plus EPA clamping down on the VOCs coming off polyester resin. There are a couple of different patented approaches, but they all basically add resin after the vacuum is pulled on the cloth. As I understand it, they lay out all of the layers of the cloth, pull down a vacuum, then open up valves between the part under vacuum and a reservoir of resin. The tricky part is knowing how far the resin will flow before it starts setting up to make sure that you wet out all the fabric completely. A description of the one of the patented versions is here: https://www.boats.com/how-to/scrimp-system/

I have no idea if this would work for thin-walled carbon tubes, but it might be worth experimenting with if you have some extra carbon fiber cloth hanging about. Or you could just send that extra cloth to me.