Estes Stratoblaster (F and G powered) build thread

[mr_matt_II]

The next step is tedious too. The ailerons have to be hinged to match the wing trailing edge then beveled to allow up and down throw. I use double sided tape to stick them flush to the edge of a piece of glass, then blue tape as a guide. I use the permagrit sanding block very carefully to cut the bevel on both sides. Hard to tell from these pictures but this came out pretty good. Always tricky but practice helps.

 

[mr_matt_II]

In no particular order.

Here is the aileron servo with the mounts installed (the white stuff you see on the servo is melted carnuba wax that keeps me from accidentally gluing the servo in permanently). The servos are bonded in with the 9460F Hysol (now Loctite). This is my basic "go to" long cure epoxy. I don't use the mixing nozzles I just mix it by hand, much less waste.

You can also see the servos installed. The view is of the bottom of the wing, the servo arms go through the top of the wing. There is basically zero clearance with the bottom skin, so the hole will be covered with the ultracote (the iron on covering for the wood parts).

 

[mr_matt_II]

I fish some thread through the holes for the servo wires. I forgot this on my first foam wing many years ago, I doubt I will ever forget it again.

Finally the 2 wing panels are joined. Nothing magic about joining the panels, I used cheap 5 minute epoxy as the real strength comes later when the glass reinforcement comes in (after making room for the motor in the wing root).

 

[iter]

...tool to cut the hinges (works like an old school powered turkey knife)

How do you like the slot machine? I hear different stories about it from different people.

Ari.

 

[mr_matt_II]

How do you like the slot machine? I hear different stories about it from different people.

Ari.

The machine is perfect when it works. Changing blades is a nightmare. If you can't use the blades installed toss it!

i normally use the robart pin hinges, but I don't normally run small wood wings with these small hinges, most of my stuff is bigger. This is my next smallest plane.

 

[iter]

That's a good-looking Stingray! What I want to see is one of them on an I59. 8.5 seconds of burn time.... Mmmm...


Ari.

 

[mr_matt_II]

That's a good-looking Stingray! What I want to see is one of them on an I59. 8.5 seconds of burn time.... Mmmm...


Ari.

LOL well it has about 60N of thrust now but it will go for 5 minutes, so what is that, 18,000 Ns? An M60? (long burn for sure!!)

I have actually thought about a scale V-1 with a turbine, launching with a rocket booster, but I am not sure I have the nerve and I certainly don't have the time to build it!

Back to building.

The mold at this point is sealed up (no access to the inside). In order to gain access to the inside to glue and seam the 2 fuselage halves together, I open up an access hole in the back, were the original 18mm motor mount hole is.

This is the quickest way to do it, a cleaner way would probably be to make a separate mold for the canopy, cut the canopy out and then have that large canopy access for the seaming. In my case I am not going into the stratoblaster spare fuselage business, I just want spare in case (and that plastic fuse seems very brittle and hard to repair this fiberglass fuse is a cinch to repair). BTW the last 2 complete kits I have seen went for 180 bucks....ouch.

Next I coat the inside of the mold with 5 coats of wax and then the same polyvinyl alcohol (PVA) I used to make the molds. I used this sprayer and if I had to do it over again the one thing I would do is properly thin and spray that PVA. The runs in the PVA really made the finished product sloppy, but it is easy enough to sand them smooth so no harm no foul, a good learning experience for me.

I am using the same West system, 209 hardener IIRC, I start by mixing a slurry about mayonnaise consistency using cabosil. This goes into the corners, the nose, anywhere the cloth would have a hard time getting into and not leaving bubbles.

 

[fyrwrxz]

Holy cow! I recognize that flying field! Went there two weeks ago to see what I needed to join up. I really love that pic of the Stingray and the moon-how cool is that!! Thanks for sharing. Still learning from your thread. You've got some mad skills there buddy!

 

[iter]

LOL well it has about 60N of thrust now but it will go for 5 minutes, so what is that, 18,000 Ns? An M60? (long burn for sure!!)

I wonder if 60N is your peak or average thrust :=)

Ari.

 

[mr_matt_II]

OK now to mold the fuselage. In my experience it is pretty much a best guess on the layup schedule for things like this. I do know it is easier to lay up several thin layers than one thick on. I guess that 6 ounces total weight would be enough, so I used 3 layers of 2 ounce satin weave E glass.

Resin is the standard west system.

IF I had a slicker mold, or was stupid enough to try painting in the mold, I might have started with 1 ounce on the first layer to avoid pinholes, but this one is going to be so messy from the poor PVA coat that I will be sanding and priming a lot so it does not matter. Another tip might have been to put one or more layers on a bias to get more torsional strength but I wimped out as I did not want to make the bias cut on the expensive glass.

Anyway, 3 layers of 2 ounce, no waiting.

 

[mr_matt_II]

Holy cow! I recognize that flying field! Went there two weeks ago to see what I needed to join up. I really love that pic of the Stingray and the moon-how cool is that!! Thanks for sharing. Still learning from your thread. You've got some mad skills there buddy!

Hi Dave,

What were you doing way up in the valley? Anyway the field is public so you just wander in and do what you want, if you want to learn the local club has trainers and can set you up if you want to join.

That Stingray is beat to death I have crashed everything else and with no time to build I should not complain.

www.valleyflyers.com

 

[mr_matt_II]

There are many ways to join these fuse halves, and since I don't really know what I am doing, I went with what seems like the most straightforward.

I waited until the glass went green (just past the tacky stage but not fully cured) and then trimmed the edges all around.

One trick here is the launch lug mount (the little protuberance hanging under the belly of the fuse). I did not think this could be wetted out, going over the tight bend. So I just cut that out completely. I plan to cast the lug into the fuse when I join the halves.

 

[mr_matt_II]

Once it is trimmed, you prep for joining the fuselage together. Several things to do here.

First, if you wait too long, the glass itself has to be sanded and cleaned before you can bond it. Laminating resin has some sort of amine or wax in it that propogates through the layup as long as it is wet. When it dries this stuff stays on the final surface till it is cleaned off. So I roughen about 1/2 to 3/4 of an inch on each side of the joint and clean with acetone.

I am using some cloth tape from CST I had laying around for years. Nothing special here but it does not unravel like it would if I cut my own.

I messed up when trimming the flange and scarred the release film, as a precaution I painted melted paraffin over the mold joint, taking care not to get any on the fuselage glass to be joined.

I then painted both sides of the fuselage with resin and laid in the tape. I took a bit of resin and mixed a thick batch or cabosil and milled fiber for strength, This should go into the nose and also would pot in the launch lug. For the lug, I filled both ends with melted paraffin. I then laid tape and blobbed in the cabosil mix. Heavy but no other method popped into my head.

The last shot shows the 2 halves ready to join, with the tape exposed and the launch lug installed.

 

[mr_matt_II]

This shot shows why I had to put the hole in the back of the mold, you put a long stick or brush down the hole and smooth that tape out for the joint.

Anyway you put the halves together and bolt them up. press all of the tape down then wait and pray (if so inclined).

 

[mr_matt_II]

Unbolt the mold and then pry the edges with a plastic wedge, and if you have been living right the mold comes apart.

I had to learn some new words when getting the fuse itself out (there is very little draft angle on the aft end of the fuse so especially on one side the mold tends to trap it).

All in all it turned out OK, except for the ugly pattern the PVA left.

 

[fyrwrxz]

Hooray! A star, er, um, Stratoblaster is born! Nice job!

 

[mr_matt_II]

First, I washed off the PVA mold release off the fuselage.

Next I cut out the front and back of the launch lug whole and waiting for me inside was that little wax plug. I pulled it out and the lug is fine.

Now I open up the 18mm motor tube hole to 32mm for the AT RC motors I plan to use. Use a moto tool for this, I have a bunch of mototools

Went ahead now and cut out the canopy with a zona saw (smallest kerf), should have waited, sanding would have been easier if it all stayed in one piece.

 

[mr_matt_II]

canopy pic

 

[mr_matt_II]

The last major cut outs on the fuse are for the wings.

On this build, I am doing everything I can to get weight into the nose, as the new radio I am using is much lighter and placed further aft than stock. To that end, I am moving the wing back as far as I can. The wing root is molded on the side of the fuse, and from my last plane I know the incidence is OK as is, so I just copied thing wing root and moved it back an inch.

That saves about 20 grams in the nose, all else being equal.

 

[mr_matt_II]

Estes has a somewhat tricky was of mounting the wings, but it is simple and robust. You slide the whole fuse over the wing from one wingtip in.

IT is a very tight fit trying to get the center section through the cutout and I have not added any reinforcement yet.

With the 18mm motor mount, there is no interference with the wing. With the 32 mm mount, I had to sand a relief into the wing root to clear the motor. I just wrapped some 18 grit over the mount and sanded it. The motor will slide in after the wing is mounted.

 

[mr_matt_II]

The original 24 mm motor fit over the stock wing, with the 32mm "big block" you have to relieve just enough to fit the mount. After sanding the wing fits tight. I will glue it in the glass it with unidrectional later, top and bottom.

You can't see it here but the aileron wires go through the front of the wing and not around the motor, I did not want them to get hot.

 

[mr_matt_II]

This kit had much better wood than my first, not as good as my Phoenix but at least most of it was usable.

I use this slotting tool to cut slots in the 1/8 thick balsa trailing edges. I then embed 0.014 in uni carbon prepreg into the grooves. This will let you sand razor sharp trailing edges.

 

[mr_matt_II]

The tail group goes together pretty easy with titebond. I use a ceiling tile over a plate of glass for all of my wood biling, use regular T Pins. Same with the booms.

One mod (major mod) was to change the elevator linkge. The original stratoblaster has the elevator servo up in the nose running through a snake all the way back through a slot cut in the upper wing skin. NOT for me.

So I planned to mount the elevator servo right on the stab. This is why I have had to go to lengths to get other weight forward, to minimize the balance weight I will eventually need. Well there is no where to run the wires so I cut slots in the leading edge of the surfaces, less drag that way.

 

[mr_matt_II]

The carbon fiber trailing edges worked out OK, I am not sure these would work on a normal rocket, too fragile at the aft end.

 

[mr_matt_II]

The tail goes together quickly. I put triangel stock on the tails between the vertical and horizontal stabs, this increases the strength greatly, I am not sure why they did not have that in the original kit.

You can see the trough that now runs arcross the leading edge. This is where the elevator servo wire will end up.

 

[iter]

I like your CF TE trick. Thank you for sharing that one.

A slightly off-topic question for you since you also fly fast jets. I'm using nylon horns on Vulcan's control surfaces (https://shop.dubro.com/products/productdetail/part_number=107/101.0.1.1.5161.5791.0.0.0). Their size is just about right, but they seem way too flexible for my comfort. I want to replace them with with something stiffer, perhaps metal. I wonder if you have a recommendation.

Ari.

 

[mr_matt_II]

These modern servos are really amazing, there has neveer been a better time to build small models. This servo is about 1/2 the mass and twice the power of the original
submicro servos. This one is mounted on small maple standoffs. I could have used servo tape and it would be lighter but I don't like using tape for servos. And since the wires cant really be changed out I could have just glued the servo on. I might do that if I need to get the tail weight out (every gram taken out of the tail is 3 grams out of the whole plane due to the nose weight you can take out)

These are digital servos too. I have switch completely, if it is worth putting a servo on it should be digital, in my book.

 

[mr_matt_II]

OK the elevator servo wire goes down the trough. I added a forward lip to the horizontal stab as I wanted a bit more area (I ended up cutting about an inch off the booms so I wanted more area). The wire then turns the corner down the vertical stab and gets covered with balsa filler.

It ended up being a major pain having the servo flopping around while covering the tail, and another several feet of servo wire hanging from the front of the vertical stab

 

[mr_matt_II]

Ari in all honesty they should be fine. If you are going fast enough to have a problem with them, the rest of your linkage will probabaly have shredded already. In any case I know the nagging feelings, so the next step up is usually carbon fiber horns embedded into the trailing edge, but they are usally embedded into a composite surface, but there is no reason you could not use them in balsa with good workmanship. I almost used them myself as they are usually lighter.

https://dreamworksrc.com/catalog/airpower-carbon-control-horn-type-p-1316.html

Any idea how fast you are getting your plane up to? Congrats on getting a delta to fly so well, I found it challenging to balance boost versus glide CG and trim.

 

[iter]

Thank you for your encouragement Matt. One key decision in Vulcan's design is that it's completely symmetric on the way up--a NACA 00xx airfoil makes it easy to set zero-lift trim, even if it's less efficient in glide. The thrust is exactly inline with the airfoil's centerline--and consequently with the drag vector. So while the CG does shift--thrust, lift and drag stay in alignment all the way up.

I'm working on an electronic nose with pitot tube and proper telemetry, then I can tell you the speed for sure. The sim says about 100mph on the baby Hs I fly now. It holds up fine to that. What I want to do if put bigger motors in it, like an I49, and that sims to well over 150mph at the top. An I59 pushes 190mph according to the sim.

I'm not sure how I can attach these thin CF horns to balsa. I imagine I'd need a second CF plate to form a T profile like traditional plastic horns, then I can glue it to balsa or screw it down.

The horns seem to be the weakest link currently. I use ball links everywhere, I use solid metal pushrods, and the servo horns (although nylon) seem to hold up pretty well.

Ari.