4th April 2012, 02:25 AM
Estes Stratoblaster (F and G powered) build thread
I usually take pictures when I build for club newsletters and I am taking enough to do a decent build thread on my second Stratoblaster.
It will be set up to run Aerotech RMS-R/C 32 mm reloads.
As the built up target weight is 13-16 ounces I should be able to keep this under 500 g if I build light.
I thought my first one was in a substitute box but the second came the same way, so this is what you get (or got if you bought it new)
Last edited by mr_matt_II; 4th April 2012 at 02:43 AM.
4th April 2012, 02:31 AM
The problems start
When I opened the box, everything looked good, until I pulled out the cores. I have never seen a set this warped. I hope I can get the warp out. All else is fine except the very questionable wood selection (more on that later)
To give you an idea of how straight a core can be, the next photos are of the nicest cores I have ever seen. These are for a 75% Phoenix, custom CNC cut from Spyderfoam (the stratoblaster uses a pretty conventional expanded bead styrofoam)
4th April 2012, 02:43 AM
I forgot to mention I plan a series of mods for this kit.
1.) A modern radio (everything is better, smaller and cheaper now). 2.4 GHz radios (no interfering with other R/C planes), lithium polymer batteries and digital micro servos. These will save weight and ensure safe operation at higher power levels.
2.) Center of Gravity. Early kits did not take advantage of the new class of micro RC gear available. As such, it can be hard to build them per plans and not have to add nose weight, defeating the purpose of the light weight radio. I will adjust the build to help minimize this by shifting the aerodynamic center aft.
3.) 32 mm motor mount. Option to install 24 mm RMS 24/40 motor with adapters. The stock launch altitude prediction is 300 ft with a D and >500 ft on an E. I am expecting 1000ft plus with F-16s
4.) Aileron/elevator linkages. I will not be using aileron torque rods (especially how Estes did them) and I won't be cutting a slot accross the wing to snake a sloppy control rod to the elevator. I will use direct linkages to ensure positive control and resist flutter at high speeds.
Last edited by mr_matt_II; 4th April 2012 at 02:57 AM.
4th April 2012, 02:51 AM
Construction begins with the wing skins. These are 1/32 balsa and pretty fragile. The grain was decent but the weight vary pretty substantially, so you want to plan a matched set for each wing that will balance out. This has to be done throughout the build to make sure and minimize lateral imbalance.
This is almost the only usable wood from the whole kit BTW. The rest is too heavy or the grain is not right for the application.
6 sheets are used total. This makes 2 wide sheets used to cut the top and bottom wing sheeting from.
I trim both sides straight, tape them together, flip them, fold them and butt glue the sheets with Titebond.
Last edited by mr_matt_II; 4th April 2012 at 02:53 AM.
4th April 2012, 02:56 AM
WOW,HUGE difference !!!!!!!!!!!!!!!
Originally Posted by mr_matt_II
Anywhoo- Ill be watching....
Everything there is to know , is to know what you don't know.
Somedays its hard to stay centered on being eccentric.
I like Fat-Bottomed Rockets
Temple of the Dog
5th April 2012, 04:56 AM
Skins are cut, sanded and weighed. Many use CA for this step but that makes the sanding tough, I find I use titebond almost exclusively now.
5th April 2012, 05:03 AM
I am using HS-5056MG digital metal gear servos. These are about .375 thick. I want them as far outboard and as close to the trailing edge I can get in order to minimize flutter chances. This runs counter to the plan of moving the equipment forward, but I will take the CG hit in exchange for better servo linkages and solid controls.
Once the servo location is set, I make a template to mark the inner skins, top and bottom. I want the strongest skins for the top surface for better compression strength and of course they need to balance.
5th April 2012, 05:11 AM
Laying out the reinforcement
Now back to the cores. The way Estes did these cores, I can't seperate them from the foam shucks, the entire stack has to be bagged at once. I mark the cores/shucks so I can line them back up and fit the skins with a final trim.
5th April 2012, 05:14 AM
Now I lay out some reinforcement. This is probably overkill, but I am really pushing this plane so I need to update the construction.
The plans call for a simple skin mounting, using spray adhesive, stacking books as weight. etc. I will be vacuum bagging. I use 4 ounce unidirectional S glass for the spars (top and bottom) and a bit of kevlar 1.7 ounce where the servo will mount (top only).
I used these materials mainly cause I had this material laying around and I will save my carbon for something that really needs it.
Last edited by mr_matt_II; 5th April 2012 at 05:17 AM.
5th April 2012, 06:04 AM
Please, please, please. pm me the night before you fly. I really want/need/have to see this baby fly! Could you really take some time and pics of your Rx and servo installs? I'll prolly copy this step by step as I haven't built a bird with feathers since the 80's. I even bought obeche wings skins for it. Any thots that way?
6th April 2012, 12:22 AM
Ok will do. Doubt i will make it to fiesta before the shutdown. We will see. I need to splash a mold of the fuse so i can build one from scratch. These things cost way too much for what you get.
Obechi is good. I never used it but it was very popular years ago. The key is vacuuming. You can really reduce the glue content. I bet i will only use 3/4 ounce of epoxy on the wing skins top and bottom.
Last edited by mr_matt_II; 6th April 2012 at 06:29 AM.
6th April 2012, 12:33 AM
Thanks matt- I'll be lurking and taking notes. Think I'll build a trainer with new gear to get a feel for it. Rockets made me rusty. (nice title for a song...hmm)
6th April 2012, 06:30 AM
my 7 year old can buddy box you!
I can bring my radian next time to fiesta and you can fly it on the wireless buddy box if you want.
6th April 2012, 11:43 AM
Snap! Mentored by a 7 year old...hey, you take experience where you can find it! Thanks!
6th April 2012, 06:58 PM
LOL I was just kidding you, he is just learning himself! My point is if he can do it anybody can.
Originally Posted by fyrwrxz
The radian is a great plane to have, everything you need in the box for $250 if memory serves, and the tx and the rx that comes with it are fine for rockets.
I would keep one of these packed in the bomb shelter so i could enjoy the post apocolypse. You can literally take this from the bobby shop and drive to the field, by the time the battery is charged you have it put together and it fits back into it's box for storage. Awesome.
Last edited by mr_matt_II; 6th April 2012 at 07:41 PM.
6th April 2012, 09:17 PM
ha ha-got me! Not only am I naive, but gullible too! I can totally believe a 7 year old could smoke me in an aerobatic competition, even at my peak decades ago! The kids these days have so much more going for them at an earlier age.
I found this out when my 10 year old fixed the sound card on my 286 back in the day after Mr Aerospace messed with it for 4 hours! Hopefully see you on the field!
7th April 2012, 07:09 AM
OK time to bag it
Back to our program.....
I am going with West Systems with 209 hardener, very slow, it gives plenty of working time. I need the time to get that warp out.
I weight this on a gram scale for accuracy. The mix ratios are different by volume versus weight.
7th April 2012, 07:25 AM
The trick with vacuum bagging skins is to get the right amount of glue. You defeat the purpose if you use too much glue.
I scale the amount I need based on what I used on the phoenix, so in this case I will use about 3/4 ounce of resin. You squeegee it on with a plastic scraper and really scrape it, the skins should just barely have a wet look to them. I save some resin and dab that on the reinforcement and a bit extra on the TE and LE to make sure they bond well at the edges of the cores.
7th April 2012, 07:52 AM
I forgot to mention I vacuum off all of the dust and tack rag the skins and cores before the glue up.
I put the stack all together and align with the edges of the foam and the marks I made earlier. Tape the stack and slide it in the bag over a bed of paper towels. I have used all kinds of breather materials but paper towels work fine. I use bags and seals from Aerospace Composite Products.
7th April 2012, 07:57 AM
All sealed up with the paper towels. I bag the whole thing over a piece of thick glass. I push hard on the top of the stack to press that warp out as best I can on the glass before the vacuum takes up.
I use an ACP vacuum set up, I have had it for years, it works great on white or blue foam. I am pulling about 8" of vacuum.
7th April 2012, 08:00 AM
At this point you can just hang the bag up or put it anywhere, when under vacuum it can't move. I let it cure for at least 12 hours and I like to keep the cores at 90F or so the whole time.
10th April 2012, 08:06 AM
out of the bag, thankfully i was able to get that giant warp out. kind of hard to see here but this is the sheeted wing trailing edge sitting next to its corresponding foam shuck.
10th April 2012, 10:54 AM
Very informative thread; thanks for doing this.
10th April 2012, 11:19 PM
yes glad to do it. So far there is not a lot that bridges over to traditional model rocket techniques (I am a beginner rocketeer). I think some of the HPR folks use vacuum bagging but to laminate fins IIRC.
Soon I think some of the tools I use will be interesting. And the servos mounting can be helpful to most RC rocket glider building.
17th April 2012, 01:42 AM
Back to work
First the wood. So far I used all of the supplied 1/32 inch wing skins, but the poor wood selection really starts biting me now. The leading edge (LE) and trailing edge (TE) material was not uniform and the wrong grain. The weight variation was over 4 grams on a tiny (3/8 square x 22" long) piece.
I use the heavy wood for the LE pair and balance the heaviest piece onto the lighter wing. I will try to juggle this way throughout.
I chuck the TE material into the scrap box and cut the new TE using a little ripper made just for this task. It can be adjusted for width and is perfect for ripping these strips.
Last edited by mr_matt_II; 17th April 2012 at 02:10 AM.
17th April 2012, 01:52 AM
Glue it up
The LE and TE blanks are glued on with Titebond and held in place with high quality 3M blue painters tape (MUST HAVE)
After they dry the shaping begins. I use nice tools from Permagrit. I think these would be very good for general rocket building and not just gliders and such. They use a tungsten carbide coating and can be cleaned with acetone. 2 different grits on each side. Wonderful tools.
Last time I bought these BVM was the exclusive distributor, not sure if he still is.
I start shaping the LE with the TLAR method (that looks about right)
I put some blue tape about 1/16 away from the edge I want to sand and level it out with the tape serving as protection. I also build over glass, but in this case I have to use the warped foam shucks to hold the wing while I sand. Mercifully I am almost done with them.
17th April 2012, 01:55 AM
The Phoenix kit includes sanding guides for the LE, in this case I don't have anything, these LEs are probabaly a bit sharper than designed but worked well on the Mark 1 so what the heck.
17th April 2012, 02:00 AM
more crap wood.
The aileron stock was abysmal, and actually warped on the thick axis (!). right into the kindling this time.
I cut new parts from my own balsa stock and got ready for shaping the aileron, probably the worse job on the whole plane.
ripper makes quick work on the oversized TE material and then a few quick passes on the permagrit (butted up to the glass) gets a perfect 90 degree angle on the backside.
17th April 2012, 02:03 AM
let the games begin
Glue on the tapered stock with spot glue titebod (very little you have to remove this piece to make the ailerons).
Scuba weights are excellent around the shop, they are like super heavy bean bags full of lead shot. 1 and 2 pounds here I think.
22nd April 2012, 05:55 AM
I lost an SD card with some of the wing building so here is the work on the fuse pod.
This pod is really the only part of the kit that is hard to replicate and I went though heck getting these kits so I wanted to make my own fuse mold so I could make spares. And the stock blow molded plastic is HEAVY, over 3 ounces. Fiberglass will cut this in half.
First, I made a parting plane out of cheap foam core board. This goes around the highest point on the seam, same place the blow mold halves split on the stock part.