I puzzled over how to name this post for quite some time. I'll tell the tale and then you'll see why.
We had a late start on our day at the range due to Sam having a school event in the morning, so it was afternoon before we got to the launch site.
As I unloaded the car I realized that I hadn't charged my AltimeterTwo since I last flew it more than a year ago. That meant it was almost certainly "flat" inside my rocket. I cracked open the payload bay and sure enough, there was no charge at all. I fortunately had come prepared to charge USB powered devices and got the altimeter plugged in and charging while I worked on the rest of the rocket.
I began loading up the 232H123-14A motor I purchased last and pulled out my Android with OpenRocket on it to determine what delay I should use, only to discover that I hadn't gotten the motors loaded into the rocket configuration file and therefor couldn't run a simulation. I was left to guess as to expected altitude and what delay I needed to use. Based on past experience I guessed I would fly 2000'-2500' and opted to not make any adjustment to the delay grain, as they have always been just right, or on the short side for Flying Colors, and loaded the motor.
I then waited around while the altimeter was charging. I set up my cameras at the pad and test recorded a flight of another Vulcanite. With the number of rockets headed to the pads slowing to a trickle I decided it was time to get Flying Colors assembled and flown. Final assembly was quickly completed and soon Flying Colors was on its way, atop a column of black smoke and sparks. I lost sight of it for a short time, but spotted the smoke trail as it was descending and saw the recovery system deploy. Since it had headed up wind it landed reasonably close to the launch site. Samantha and I quickly reached it. Everything looked fine at first, but then Sam spotted the "zipper." Thanks to the fiberglass reinforcement I did during the build it isn't bad and should be reparable, but it could keep me from flying next month. I need a number of supplies in order to do the repair right. It has been suggested that I cut off the damaged portion, but if I do that the payload bay coupler is going to hit the recovery system mount point inside the airframe.
Of course this damage could have been avoided if I had made appropriate decisions. When I discovered I couldn't simulate the flight I should have aborted the launch. If I had simulated the flight I would have seen that I needed to adjust the delay grain by 3 seconds. Since I didn't make this adjustment Flying Colors descended some 400' before ejecting the recovery system which allowed it to build up a head of steam which resulted in the "zipper" when the recovery system did deploy. I'm lucky to have gotten off with as little damage as I did and will definitely take this lesson to heart. Don't guess, simulate. If you can't simulate, don't fly.
So, back to naming this post. With the damage that occurred to the rocket during the flight I considered several names for the post, along the lines of "Rocket vonZipper!", but decided most folks wouldn't get the reference. Also I'm not happy about the outcome of the flight, so I'm not really in the mood to joke about it.
Photo Album: 2012-11-03, AARG Launch, Hutto, TX
Video: AARG, 2011-11-03
TopLinks
|
|
 |
Showing posts with label Fiberglass. Show all posts
Showing posts with label Fiberglass. Show all posts
Saturday, November 3, 2012
Wednesday, September 1, 2010
Fin Reinforcement
I finished sanding out the fillets on the fins and decided to get going this evening on the reinforcement of the fins. I set up the airframe on my workbench and applied fiberglass to one side of one set of fins. This time I applied the epoxy before applying the fiberglass. I still had to apply epoxy to the fiberglass after I laid it on the rocket. Unfortunately I'm going to have more sanding to do as the epoxy has obviously settled into the area of the fillets. I'll also have to apply more epoxy to fill the texture of the fiberglass after the current round of epoxy has cured. I'll only be able to do one side of one fin at a time as I'll have to have the fin horizontal while the epoxy is curing. I'm going to first get the glass applied to all three sides of the rocket before I tackle this step. The thing I hate most about it is how wasteful it will be of my epoxy. I have to mix a full pump up and won't come close to using it all. I don't have any projects waiting in the wings that I can use excess epoxy on either. :-(
Photo Album: Tip to Tip Fins
Photo Album: Tip to Tip Fins
Tuesday, August 31, 2010
Busy Weekend
On Friday afternoon I installed the centering rings on my engine tube. Since I plan to install an Aero Pack Engine Retainer I had to alter the assembly instructions slightly. The instructions call for the centering rings to be mounted 1/8" from each end of the engine tube, but the motor retainer requires 3/8" for mounting. I checked the fit with the rear centering ring moved 1/4" forward and found that that puts the forward edge of the ring right at the back of the fin slots in the tube, so proceeded to assemble the engine tube in this configuration. I then prepped the bad area of fiberglass on my payload bay tube for patching by sanding out the bad area and feathering out the surrounding area.
On Saturday I fiberglassed, patching my payload bay tube and adding a layer of the fiberglass sleeving to the engine tube between the centering rings. The primary motivation for adding the fiberglass to the engine tube is to account for the extra thickness of the airframe tube when mounting the fins. There is an added benefit in that the fiberglass should also strengthen the connection between the engine tube and the centering rings.
One of these days I will learn that fiberglass doesn't like making 90° bends. I cut the sleeve for the engine tube quite a bit longer than the tube in order to allow for fraying as I worked the sleeve over the centering ring and stretched it out on the engine tube. I thought I'd be able to bend the sleeve up along the centering rings. This proved harder than I anticipated. Once I had my epoxy applied I found that I couldn't keep the fiberglass in contact with the tube as it approached the centering rings. I had a length of the shrink tubing available that was the right length, but I couldn't see how I was going to keep it from contracting lengthwise while I shrunk it as the centering rings would keep me from holding it with my pliers. I decide that I had to try using the tubing anyway, as I wasn't getting what I wanted without it. When I tried to pull the shrink tubing on over the engine tube the fiberglass pulled off the engine tube and ended up a wadded mess inside the shrink tubing. I pulled the shrink tubing back off and straightened out the fiberglass. I ended up doing this twice as a second attempt yielded the same results. I finally resorted to cutting two lengths, each about 1" in length, from the shrink tubing and working them onto the engine tube. After sorting out the fiberglass yet again I put one at each end of the engine tube and shrank them in place, using my stirring stick from my epoxy to push the tubing sections towards the centering rings as I heated them. I did a better job of this apparently at the forward centering ring than at the aft one. The finished product has a fairly tightly radiused curve in the glass as it transitions up onto the centering ring with the gap under the radius filled with epoxy. At the aft end the radius isn't as tight and there are areas that are not epoxy filled.
On Sunday I installed the engine tube in the airframe and proceeded to install the fins. I had to use my Dremel with an engraving cutter to cut out the radiused fiberglass at the aft centering ring in order to get the fins to insert into the slots. The poor bonding at the aft centering ring worked in my favor in this case, making it easy to remove the obstruction.
On Monday I used Loctite Repair Putty to form fillets between the fins and the airframe. I worked on sanding out the fillets, but ran out of time. More sanding tonight.
Photo Album: Fiberglassing 103
On Saturday I fiberglassed, patching my payload bay tube and adding a layer of the fiberglass sleeving to the engine tube between the centering rings. The primary motivation for adding the fiberglass to the engine tube is to account for the extra thickness of the airframe tube when mounting the fins. There is an added benefit in that the fiberglass should also strengthen the connection between the engine tube and the centering rings.
One of these days I will learn that fiberglass doesn't like making 90° bends. I cut the sleeve for the engine tube quite a bit longer than the tube in order to allow for fraying as I worked the sleeve over the centering ring and stretched it out on the engine tube. I thought I'd be able to bend the sleeve up along the centering rings. This proved harder than I anticipated. Once I had my epoxy applied I found that I couldn't keep the fiberglass in contact with the tube as it approached the centering rings. I had a length of the shrink tubing available that was the right length, but I couldn't see how I was going to keep it from contracting lengthwise while I shrunk it as the centering rings would keep me from holding it with my pliers. I decide that I had to try using the tubing anyway, as I wasn't getting what I wanted without it. When I tried to pull the shrink tubing on over the engine tube the fiberglass pulled off the engine tube and ended up a wadded mess inside the shrink tubing. I pulled the shrink tubing back off and straightened out the fiberglass. I ended up doing this twice as a second attempt yielded the same results. I finally resorted to cutting two lengths, each about 1" in length, from the shrink tubing and working them onto the engine tube. After sorting out the fiberglass yet again I put one at each end of the engine tube and shrank them in place, using my stirring stick from my epoxy to push the tubing sections towards the centering rings as I heated them. I did a better job of this apparently at the forward centering ring than at the aft one. The finished product has a fairly tightly radiused curve in the glass as it transitions up onto the centering ring with the gap under the radius filled with epoxy. At the aft end the radius isn't as tight and there are areas that are not epoxy filled.
On Sunday I installed the engine tube in the airframe and proceeded to install the fins. I had to use my Dremel with an engraving cutter to cut out the radiused fiberglass at the aft centering ring in order to get the fins to insert into the slots. The poor bonding at the aft centering ring worked in my favor in this case, making it easy to remove the obstruction.
On Monday I used Loctite Repair Putty to form fillets between the fins and the airframe. I worked on sanding out the fillets, but ran out of time. More sanding tonight.
Photo Album: Fiberglassing 103
Tuesday, August 24, 2010
Sanding out the "bulge".
I sanded out the bulge in the fiberglass on the payload bay. Almost as soon as I touched it with the sand paper it disintegrated, leaving a nasty void in the fiberglass with epoxy underneath. Now I have to figure out how to fix it.
Photo Album: 2010-08-24, Patching the Payload Bay
Photo Album: 2010-08-24, Patching the Payload Bay
Sunday, August 22, 2010
Fiberglassing 102
So today was the day to strip the shrink wrap from the practice tube and see what I had. I'm not completely happy with the results. As you can see in the photos there are areas the appear to correspond with where I started heating the shrink wrap that are not bonded to the underlying tube. The areas are also rough when compared to areas further away, as if there is significantly less epoxy in them. My first impression was that I may have held my heat gun on these areas too long and somehow caused this.
With this information in hand I proceeded to glass the real airframe and payload bay tubes. I decided that the easiest way to do them would be to mount them up adjacent to each other on a single PVC pipe, with a small gap between them. I then slid the fiberglass on them and secured it. When applying the epoxy I again found myself working excess fiberglass down the length of the tubes. Apparently the epoxy is acting as a lubricant and allowing the glass to slide along the tube and I suspect even more importantly along the weave.
I made what I feel was a mistake when I started putting the shrink wrap tubing on. Without thinking about it I started sliding the tube on from the end that I had worked the excess fiberglass down to. As I was pulling the tubing up I started seeing the fiberglass come off of the airframe tube as I was obviously pulling slack up the with the shrink tubing. I stopped and pulled the shrink tubing back off and then pulled it on from the opposite end.
I made sure my heat gun was on its low temperature setting to ensure I didn't overheat the fiberglass, due to my impressions from the practice tube. I shrank the tubing without any apparent complications until I got down to the payload tube. There I had a bulge that I could not get out.
I hung the tube up and let it cure. I then grabbed the practice tube and sanded it with 80 grit paper to prep it for a layer of epoxy per Soller Composite's recommended process. With the tube prepped I applied the epoxy and hung it up to cure.
Next I took the coupler tube and used the fiberglass sleeve to line it. This proved to be somewhat tricky, as the sleeve's natural tendency is to contract, not expand (think Chinese finger trap). This proved to be a real problem after I applied the epoxy. I ended up working the fiberglass until the epoxy got very tacky in order to get it adhered to the inside of the tube. Any force that pulled toward the ends of the tube would cause the sleeve to contract and pull away from the tubing. The ends absolutely refused to bond, particularly the end where I'd started applying the sleeve and had come hard around the end of the tube. It finally got to the point where the epoxy was so tacky that attempting to manipulate the fiberglass any further was doing as much harm as good due to it attempting to adhere to my glove.
Late in the day I was able to use the coupler tube as a gauge and determined that I could strip the shrink tubing from the airframe and payload bay tubes. I was really eager to do this in order to see my results and investigate the bulge on the payload bay. As you can see in the photos the bulge is an area that is not bonded to the underlying tube. My conclusion at this point is that when I smoothed the fiberglass back out after pulling the shrink tubing on from the wrong end that I missed a spot. I thought I had it all, but the evidence speaks for itself.
The main airframe tube looks great. I applied scotch tape over the pre-cut fin slots in order to prevent them getting filled with epoxy. It looks like I left a scrap of tape on the tube, though I really don't remember it. I don't see this as a real problem.
I don't think I'll be able to repair the bulge on the payload bay tube. I do have a solution though. The practice tube has plenty of good sections, so if the original payload bay is unsalvageable I'll cut a new one from the practice tube.
With this information in hand I proceeded to glass the real airframe and payload bay tubes. I decided that the easiest way to do them would be to mount them up adjacent to each other on a single PVC pipe, with a small gap between them. I then slid the fiberglass on them and secured it. When applying the epoxy I again found myself working excess fiberglass down the length of the tubes. Apparently the epoxy is acting as a lubricant and allowing the glass to slide along the tube and I suspect even more importantly along the weave.
I made what I feel was a mistake when I started putting the shrink wrap tubing on. Without thinking about it I started sliding the tube on from the end that I had worked the excess fiberglass down to. As I was pulling the tubing up I started seeing the fiberglass come off of the airframe tube as I was obviously pulling slack up the with the shrink tubing. I stopped and pulled the shrink tubing back off and then pulled it on from the opposite end.
I made sure my heat gun was on its low temperature setting to ensure I didn't overheat the fiberglass, due to my impressions from the practice tube. I shrank the tubing without any apparent complications until I got down to the payload tube. There I had a bulge that I could not get out.
I hung the tube up and let it cure. I then grabbed the practice tube and sanded it with 80 grit paper to prep it for a layer of epoxy per Soller Composite's recommended process. With the tube prepped I applied the epoxy and hung it up to cure.
Next I took the coupler tube and used the fiberglass sleeve to line it. This proved to be somewhat tricky, as the sleeve's natural tendency is to contract, not expand (think Chinese finger trap). This proved to be a real problem after I applied the epoxy. I ended up working the fiberglass until the epoxy got very tacky in order to get it adhered to the inside of the tube. Any force that pulled toward the ends of the tube would cause the sleeve to contract and pull away from the tubing. The ends absolutely refused to bond, particularly the end where I'd started applying the sleeve and had come hard around the end of the tube. It finally got to the point where the epoxy was so tacky that attempting to manipulate the fiberglass any further was doing as much harm as good due to it attempting to adhere to my glove.
Late in the day I was able to use the coupler tube as a gauge and determined that I could strip the shrink tubing from the airframe and payload bay tubes. I was really eager to do this in order to see my results and investigate the bulge on the payload bay. As you can see in the photos the bulge is an area that is not bonded to the underlying tube. My conclusion at this point is that when I smoothed the fiberglass back out after pulling the shrink tubing on from the wrong end that I missed a spot. I thought I had it all, but the evidence speaks for itself.
The main airframe tube looks great. I applied scotch tape over the pre-cut fin slots in order to prevent them getting filled with epoxy. It looks like I left a scrap of tape on the tube, though I really don't remember it. I don't see this as a real problem.
I don't think I'll be able to repair the bulge on the payload bay tube. I do have a solution though. The practice tube has plenty of good sections, so if the original payload bay is unsalvageable I'll cut a new one from the practice tube.
Photo Album: Fiberglassing 102
Saturday, August 21, 2010
Fiberglassing 101
Today, for the first time in some 30 years, I did fiberglassing. The last time was working with my Dad to do some body work on a rusted out fender and then he handled the epoxy mixing. Today was the first time I would do the entire process on my own.
For this reason I purchased the practice tube I previously spoke about and today it was time to glass it.
I'm using the West Systems epoxy and fiberglass sleeve sold by Soller Composites with the 207 hardner.
I started by borrowing a trick from Vern Knowles and using foam to make centering rings to mount my tube on a PVC pipe. I then slid the fiberglass sleeve down the tube and used masking tape to secure the first end to the PVC pipe. I then worked the fiberglass back along the tube to make it as snug and even a fit as I could. I used the masking tape to cinch down the sleeve on the second end of the PVC and then borrowed again from Vern. I masked off all but a narrow band of the sleeve and then applied the same 3M Super 77 adhesive he used to prevent fraying. I gave that a bit of time to set up then cut the sleeve off and finished securing the second end to the PVC pipe with more masking tape.
I then mixed up the epoxy using the pumps I'd purchased to ensure the proper ratio of resin and hardner. To apply the epoxy I opted to just pour it onto the fiberglass and then use my gloved hand to spread the it along the tube. The only issue I had was when I was working at the end of the tube the fiberglass wouln't adhere despite having plenty of epoxy. Apparently I still had some slack in the sleeve that I'd not been able to work out during prep. I was not overly concerned about this as I intended to use heat shrink tubing to squeeze out excess epoxy and this would also have the affect of compressing the fiberglass against the tube while the epoxy cured, ensuring there would be no long term issue.
I did find that I'd mixed up more epoxy than I really needed and like my fellow local rocketeers I was trying to find something to do with the excess. Unfortunately I didn't come up with anything. It wasn't a whole lot and I'm not sure that using only 2 pumps of resin and hardner would have made enough epoxy.
The heat shrink tubing went on without any difficulty and performed as advertised. The tube is now hung (as recommended by Jon Soller) in the garage while it cures. Tomorrow I intend to strip the shrink tubing from it and dismount it from the PVC so I can glass the real airframe, payload bay, and coupler tubes. Fortunately the heat shrink tubes that were missing from my order showed up in the mail today.
Photo Album: Fiberglassing 101
For this reason I purchased the practice tube I previously spoke about and today it was time to glass it.
I'm using the West Systems epoxy and fiberglass sleeve sold by Soller Composites with the 207 hardner.
I started by borrowing a trick from Vern Knowles and using foam to make centering rings to mount my tube on a PVC pipe. I then slid the fiberglass sleeve down the tube and used masking tape to secure the first end to the PVC pipe. I then worked the fiberglass back along the tube to make it as snug and even a fit as I could. I used the masking tape to cinch down the sleeve on the second end of the PVC and then borrowed again from Vern. I masked off all but a narrow band of the sleeve and then applied the same 3M Super 77 adhesive he used to prevent fraying. I gave that a bit of time to set up then cut the sleeve off and finished securing the second end to the PVC pipe with more masking tape.
I then mixed up the epoxy using the pumps I'd purchased to ensure the proper ratio of resin and hardner. To apply the epoxy I opted to just pour it onto the fiberglass and then use my gloved hand to spread the it along the tube. The only issue I had was when I was working at the end of the tube the fiberglass wouln't adhere despite having plenty of epoxy. Apparently I still had some slack in the sleeve that I'd not been able to work out during prep. I was not overly concerned about this as I intended to use heat shrink tubing to squeeze out excess epoxy and this would also have the affect of compressing the fiberglass against the tube while the epoxy cured, ensuring there would be no long term issue.
I did find that I'd mixed up more epoxy than I really needed and like my fellow local rocketeers I was trying to find something to do with the excess. Unfortunately I didn't come up with anything. It wasn't a whole lot and I'm not sure that using only 2 pumps of resin and hardner would have made enough epoxy.
The heat shrink tubing went on without any difficulty and performed as advertised. The tube is now hung (as recommended by Jon Soller) in the garage while it cures. Tomorrow I intend to strip the shrink tubing from it and dismount it from the PVC so I can glass the real airframe, payload bay, and coupler tubes. Fortunately the heat shrink tubes that were missing from my order showed up in the mail today.
Subscribe to:
Posts (Atom)