- Giant Leap Rocketry - Honeycomb Composite Fins
- Giant Leap Rocketry - Slimline Retainer (38mm)
- Hartle Engineering - Solid Resin Nose Cones
- Roachwerks Custom Turnings - X-20 Dyna Soar Nose Cone Kit (BT-60)
- Matt's Railbuttons (railbuttons.com)
- Into the Wind - Nylon Tape
- Semroc - BT-60 Baffle
- CEN-TECH - Model 90899 Multimeter
Giant Leap Rocketry - Honeycomb Composite Fins
This is a review of Giant Leap Rocketry's 'Aerospace Composite' Honeycomb fins. These fins are offered in 1/8, ¼, ½, and 3/8 inch thicknesses and in 15 pre-defined shapes. If you want to cut your own, you can also buy the raw stock. Giant Leap describes their composite fins as follows: "Giant Leap Rocketry now offers the ultimate in fin material. This aerospace composite material is used in advanced aircraft. It is much stronger than wood, more rigid than G-10 (for equivalent thickness). Lighter than wood, 1/3 the weight of G-10." The material itself consists of "An inner layer of NOMEX(TM) honeycomb, sandwiched between either thin G-10 Fiberglass or Carbon Fiber!"
My fins are 1/8" thick in style #8. Referring to the first photo, the root edge along the fin tab is 7.375", the span (not including the fin tab) is 4.875", and the overall length is 11.625". You specify the thru-the-wall tab by identifying your body and motor tubes. Mine have tabs for a 3" tube and a 29mm motor mount.
The first thing I noticed about the fins is how light they are! I can't vouch for Giant Leap's numbers, but here are my qualitative impressions. To me they seem as light as 1/8" balsa and as rigid as 3/32" G10. I don't have equivalent fins in these materials to weigh and bend, but these are my guesses. They would even be more rigid if framed in a hardwood dowel.
You can see the honeycomb structure in the next photo. The outer layers of fiberglass are very thin, probably thinner than 1/64", and if you look back at the first photo you can clearly see the honeycomb pattern through the G10.
Giant Leap suggests that you epoxy a dowel, hardwood strip, or even a G10 strip to the edges of the fin. This will hide the rough edges and will strengthen the fins. It seems that I always have to do something different, and this is no exception. For the leading edge, I attached a 1/8"x1/8" balsa strip with PerfectGlue Type 2 (similar to thick CA). This was easy to sand to a smooth shape. For the other outer edges, I filled the exposed honeycomb with Fill-n-Finish. Since Nomex® doesn't cut neatly, there were exposed fuzzy things hanging out all over. I soaked the edges in PerfectGlue to harden them, sanded them down, and refilled them. My one worry is a bit of flexing will pop the balsa off, but only time will tell. The next photo shows the framed fin mounted to a body tube.
When mounting the fins, one problem became evident. The fin tab in the front is 1/8" longer than in the back. At first, I thought I would simply have to trim the short section of the fin overhang immediately behind the tab. However, it turned out that this depth was correct for the tubes I was going to use, so I would also have had to trim the entire tab. Another possible fix would have been to extend the frame 1/8" further down. This would have left a small gap in the root tip that would have been easily filled. Unfortunately, I figured this out after I had finished. The good news is that the gaps were easily plugged with small pieces of the balsa I used to frame the leading edge.
So, that's it for now. This review is of the stand-alone fins. I'll follow up with a review of the rocket, and will note how the fins hold up. The basic material warrants full rating of '5'. Despite the fact that I easily remedied the fin tab issue, I will have to deduct a point from my rating, moving the rating to a '4'. In my experience, this is not typical for Giant Leap's work and I hope this was an isolated incident.
This material is a bit pricy, but if you want tough, light fins, I think you will be impressed. If anyone else has used these fins, please add a comment. I'd really like to hear how easy it is to cut the raw material.
Giant Leap - Slimline Retainer (38mm)
This is a brief review of Giant Leap Rocketry's 38mm snap-ring style SLIMLINE Motor Retainer. SLIMLINE retainers are also available for 29mm, 54mm, 76, and 98mm motor tubes. There are also motor adapters, boat-tail retainers, and a newly released threaded SLIMLINE retainer system. Note: Giant Leap has improved and added to their line of retainers. This review may not reflect their current product.
The SLIMLINE retainer system includes a sleeve, a snap ring, and a spacer washer. The instructions come on a single 5" x 8" sheet and include diagrams. The sleeve is black anodized aircraft-grade aluminum (6061-T6), and the two rings are stainless steel.
The main feature is the snap ring that pops into a groove on the inside of the sleeve. This ring is easily visible in the attached photo. Unlike the typical snap rings used on the Kosdon style motor hardware, no special tools are required to install or remove this ring. One end is notched and a small screwdriver is all that's required. This internally mounted ring allows the outer diameter to be thinner than other quick-release retainers do, which is important to reduce aerodynamic drag on minimum diameter rockets.
To install the SLIMLINE, you mount the motor tube so that its protruding behind the aft centering ring. The sleeve is made to fit all motor tubes and should be test-fit for both tightness and spacing. If you don't test fit it with your motor hardware, you may not have enough room between the motor tube and the snap ring to accommodate the motor's thrust ring - this would be a show-stopper! If it's too tight, you sand the tube a bit. If it's too loose, you add small slivers of tape 120 degrees apart. It fit my LOC motor mount tubing just right. As with most bonding applications, the tube should be roughed up. No processing is required on the inside of the sleeve since it is grooved. To glue it on, you slather some heat resistant epoxy such as JB-Weld onto the exposed tube, and twist the retainer on.
The retainer is advertised to work with AT, Kosdon, Ellis, and hybrid motors. For motors with integral retaining rings, you just slide them in, insert the notched end of the snap ring, and then press it in with a circular motion. For motors that don't have a rear thrust ring, the instructions say to glue in a section of coupler tubing at the depth of the longest motor, and then cut additional sections of coupler to form spacers when using shorter motors. You then insert the motor and spacer washer (really more of a retaining ring), followed by the snap ring.
A note on spacing: I was concerned that I might mess up and make it so the snap ring wouldn't fit once there was a motor installed. In addition to checking and double-checking my work, I also inserted the spacer washer, which isn't required for AT hardware. This provided provide a small safety margin.
I used this retainer on my Upscale Big Brute. Although I have only flown it once, I have inserted and removed AT casings several times and have formed my opinion: this retainer is pretty neat, but I like the screw type (i.e. Aero Pack) retainers better. The SLIMLINE is a easier to use than "Kaplow" style retainers (I re-use a couple of sets from rocket to rocket, so I have to install and reinstall these every time). The snap ring is very easy to remove, but I'm all thumbs and have to work at getting it on. I don't mean to imply this is really tough, but is not as easy as screwing on a cap. Maybe I will improve with more practice.
In summary, the SLIMLINE is a just a tad more difficult to install and use than an Aero Pack retainer. Still, if you're building a minimum diameter model and want to minimize drag, this is the way to go. The final factor is cost. The SLIMLINE currently goes for $20, with its competitor costing $28. However, you can reuse the latter's cap and buy additional housings for $15. You can do the math for your application and needs. I probably will not buy many of any of these machined units, as they are all more expensive than my homegrown or reused clips. But, those boat tail adapters sure look cool...
Hartle Engineering - Solid Resin Nose Cones
JonRocket. Thanks John!. Hartle offers three styles of BT-5 cones and one BT-20 cone. You can see all of them on JonRocket's nose cone page. This review will describe the cones and the rocket I built from the longer BT-5 cone, the Mini-Toobah. The name is a homage to Dave Weber's Toober, which has logged over 200 high power flights.
The parts list:
* Hartle NC-5B cone
* BT-5, 6.25"
* Estes 1/8" launch lug
* Spent mini-motor case (could use a real motor block)
* Thin Kevlar®, ~ 12"
* Thin elastic, ~ 4"
The Hartle cones are solid cast and their outer surface is perfect. The cone-to-shoulder transition was clean on the longer cone but was rough on the shorter one. The later was easily cleaned up with a sharp hobby knife. The attachment point appears to be a paper clip...works as good as anything. I found them to be a loose fit in the Estes BT-5, which is easily fixed with a little tape.
The cones are, as expected, heavier than the typical hollow plastic or balsa. However, unless you're building a MicroMaxx model, the added weight shouldn't be an issue. I had kicked around building a micro but decided to go for a 13mm design instead. The shorter cone would make a great micro-Fat Boy or Big Bertha but I opted for a downscale of my El Tubo Loco.
This was a trivial build. From BT-5 stock, I cut one 2.5" body section and six 5/8" tube fins. These were glued together in pairs and then to the body tube. I used Aleene's Tacky glue throughout. A 5/8" long lug is mounted in one of the fins. I cut a motor block from a spent casing. This was notched and the Kevlar® was tied around it. There is not much room in the body minus the motor and the cone's shoulder. It was all I could do to pack the shock harness.
To make sure it is stable, I weighed the components and made a RockSim model. The cone alone is 0.24 oz and the entire rocket is 0.34 oz. It is quite stable.
I first scuffed the cone with fine sandpaper and shot a coat of PlastiCoat primer. I anticipated this will be hard to find in the grass, so I went for a bright finish using Rustoleum day-glo orange. I added two vinyl strips to snazz it up a bit.
There wasn't much prep as it uses tumble recovery. It flew nicely on an A3-4 and I could even see it recover!
The Hartle Engineering cones are nice to work with. In this case, their solid construction and weight helped with stability.
I like the design of this little rocket but, being small, it could easily disappear into rocket eating grass, shrubbery, or trees.
Roachwerks Custom Turnings - X-20 Dyna Soar Nose Cone Kit (BT-60)
This is a review of Gordon's Dyna-Soar nosecone kit. He describes it as 'goof' scale. Nevertheless, the cone looks awesome and I don't worry about scale points. Although he provides some application ideas, using this is on a stable model is up to the builder.
This is a simple kit as you'd expect. It consists of the Dyna-Soar body, 2 wings, 2 stabilizers, a transition from the body to a BT-60 tube, a screw eye, and a decal sheet.
The parts come packaged with instructions (9 steps) and two sheets which provide drawings to show the placement of the decals, an outline and color scheme for the X-20/Titan-II, and some other concept drawings. The latter are merely simple views with no detail.
I found the transition didn't seem to mate all that well with the body, but the pre-formed angles made it easy to sand to fit. Gordon provides contact info if you have questions, but I just proceeded on my own. In a move that is certainly not the norm for me, I attached the parts before filling (built upstairs in front of the tube where sanding is taboo). As I was sanding, I got the feeling that the wings might be a bit flimsy to be on the tip of a cone that might end up being quite heavy to ensure a stable flight, so I added some extra fillets on the top and laminated the base with cardstock.
The last step recommends using this kit atop of a FlisKits Deuces Wild, an Estes Big Bertha, or an OOP Titan III. The final photos are atop of a in-process rocket that I'll eventually review. It's kind of a Titan variant.
I used PlastiKote primer and Rustoleum flat black paint. I was excited to get the decals on, then...you should imagine the sound of a record player scratching to a halt (younger readers may have to search this on Google). Take note that these decals MUST be clear coated! I didn't and they were ruined. 'Nuff said.
Matt's Railbuttons (railbuttons.com)
I have been using a BlackSky Standard Rail for some time, mostly for mid-powered rockets. Although I used rail buttons them on a couple of modrocs, I quickly decided that they were overkill and just too costly for that application. Well, around a month ago I saw a post on r.m.r. from a fellow named Matt Stum. To promote the use of rails, he is producing, on a limited basis, nylon rail buttons that are compatible with the BlackSky rail system. The *really* good news is the price! At a quarter a piece, these buttons are now attractive for modroc applications.
Matt's buttons are composed of two washers and a spacer, and come with a zinc-plated steel screw. They come in black, white, red, and blue and the colors can be mixed and matched. I like the look of red, white, and blue buttons against the shiny surface of my Estes Mercury Atlas. The buttons' reflection on the mirror finish gives the illusion of additional tiers of washers, an effect that wasn't noticeable with a solid black color. (The attached pics show this reflection, but the look is much better in-person.) These buttons come in a plain zip lock bag with no paperwork. He provides instructions on his site and, if you have used any other rail buttons, they are pretty much self explanatory. Although the nylon is not as tough as delrin, I can't imagine this being an issue for model or mid powered rockets. They have certainly worked well for me, having used them on my Atlas and my Mean Machine. I have also installed a set of them on my Public Enemy 3" Ultra Fatboy.
Update: Since this review was written, I've used the standard 3-piece buttons on most of my many mid- and high power rockets, flying up to 'I' impulse. I use the larger buttons on 'J' powered birds. My general guideline are as follows. I try to install the lower button as far aft as possible and generally abutting (occasionally in) a centering ring. The upper button usually also abuts a ring unless the spacing is less that ~1.5 calibers, at which point I place them between the CP and CG. I drill a hole, treat it with CA, and install the button. I haven'tused any backing except on cardstock models.
Based on their "bang-for-the-buck", I can't help but give them a rating of 5 points. Finally, I recommend you jump on these fast - who knows how long they will be available at this low a price?!? Here's the URL to Matt's site: http://www.railbuttons.com/rb/
Into the Wind - Nylon Tape
Burn holes in your nylon parachute? Have a tear? Bullet holes? Try self-adhesive nylon tape from Into the Wind!
This self-adhesive rip-stop nylon tape is 2" wide and is available in red, yellow, green, blue, purple, hot pink, black, and white. You can currently get it for $2.00 per yard or $10.00 for an 8 yard roll (as of January 2011).
Although developed for nylon or polyester kites, it works great on most nylon chutes. I just cut a couple of squares to overlap the area and place one on each side of the damage. At first, I was concerned about how well it would adhere, but after several years, all but one of my patches have stayed on. The chute in the photo was in the trees for over two years attached to my Public Enemy 3" Ultra Fat Boy. When I got it back, I was very surprised that all the patches were firmly attached. Unfortunately, the cardboard and wood components didn't fare so well.
The one chute it didn't seem to adhere to is my Rocketman R12. This material is very low porosity and the tape just didn't want to stick. I have used it on many other chutes successfully however. If it sticks initially, it will pretty much last forever. And I define forever as being at least 2 years in the trees.
If you want to keep those old parachutes going strong, this is a great product to keep in the shop. A small amount goes a long way. The best option is not to burn them, of course. But as they say: !#%* happens!
Semroc - BT-60 Baffle
This kit includes three components and a piece of Kevlar® twine. All three parts are laser cut from a small sheet of fiberboard.
As you can see, the gas actually vents at the base of the baffle and then out the top so there isn't anything near a direct path out the top.
The instructions say to install it at least 3" from the top of the body tube. I installed mine 6" down in an 18" piece of BT-60.
I noticed when I read John Lee's review of the FlisKits BT-55 baffle that he forgot it was there and added wadding. I chuckled because I did the same thing. And, like John's experience, ejection was perfect. (I wish I could say the same about the flight as a whole.)
Well, the chute came out as planned and, as you'd expect, was in pristine condition. However, I have to make one observation. I've found the C11 ejection charges to be on the energetic side and this one was no different. The back pressure from the baffle caused the motor to spit and the motor hook no longer is parallel to the motor tube. I don't really how to factor this into the rating, but I'd be cautious with any baffle on a single BT-60 using a 24mm mount.
This is a cool little baffle. It's easy to build and is effective. That being said, I'd like to see comments if you've used this size baffle with 24mm motors.
CEN-TECH - Model 90899 Multimeter
How many times have you forgot to bring a multimeter to a launch and found yourself scrounging one to check continuity or battery voltage? I almost never brought one and couldn't seem to justify buying a second one to leave in the range box. Harbor Freight recently opened a store nearby and I ran across the perfect solution to my problem: a $3.99 DMM manufactured by CEN-TECH.
The CEN-TECH DMM measures 2.74" wide x 5" high x 1" deep and provides the following features:
* Functions: AC and DC voltage, resistance, DC amperage, battery test, diode test, transistor (hFE) measurements
* Fused circuit with diode protection
* Low battery, over range indicators
* LCD readout
* 32" leads with banana plugs
* 750 VAC, 1000 VDC, or 10A DC max input
I know you often get what you pay for and if I was using this professionally, I would opt for a 'name brand' device with more features. I will generally just use the resistance measurements to check continuity and either the battery test or DC volts features to check batteries. I am not sure how much use the battery test feature will be over a simple voltage measurement, but it might be more effective since it verifies the battery under a load. Either way, it fits my needs perfectly.
As of this writing, this meter is still on sale at Harbor Freight. The newer version appears to be $9.99 and has a backlight, which mine does not. However, the point is not the exact model or the exact price. Rather, I wanted to highlight the availability of inexpensive DMMs from Harbor Freight, which are just perfect to keep in your range box.
Note the following possible safety concern.
03/07 - "The Cen Tech meter can burn up under high voltage conditions http://www.bnl.gov/userscenter/Immediate/cen_tech.asp" (rcc)
04/07 - "Thanks for the link, this is something to watch out for. Luckily, mine is used to measure up to 12v DC and for checking resistance/continuity. I wonder if this was standard wall voltage?" (D.S.)