Estes Stratoblaster (F and G powered) build thread

[fyrwrxz]

And the plot thickens...
Looks really good right about now, I can hardly wait for the 'pod' cloning.

[mr_matt_II]

Now you take glue the fuse pod to the parting plane. The gap gets filled in with clay and smoothed with a razor (hard to see in this view).

[mr_matt_II]

Now you have to hit this whole assembly with wax, pure carnuba is best, no silicone. 3 to 5 coats, buffed in between.

After that a couple of coats of Partall. Partall is a brand name for polyvinyl alcohol, a water soluble plastic that creates the barrier release film. I have heard of people using hairspray as well as hairspray is just water soluable plastic (!)

I did not want to get any spray equipment out so I brushed it on (mistake). The looks worse than it is, when partall dries it is very thin and I hope this won't leave a ugly pattern on the mold.

[mr_matt_II]

First layer is surface coat, does just what the name implies. Very thick but it self levels. This forms the hard inner surface of the mold.

From this point on it is a continuous process. You can't stop with epoxy, if you do you have to sand and clean off the amine blush that forms when it hardens. If you keep putting the layers down before the last one fully sets you won't have a problem.

[mr_matt_II]

I had some OLD epoxy and when it gets this old the hardener turns dark amber, it still seems to harden OK so what the heck.

I thicken it up to paste consistency with cabosil and put it in all the corners, the cloth will not get down in there by itself.

[mr_matt_II]

Cloth goes on over the surface coat just after it tacks up (still sticky but wont lift onto a dry brush).

I go with 4 layers of 2 ounce bi directional fiberglass (very flexible) followed by 4 layers of 6 ounce. The mold should be 3 times as thick as the finished part so I should have put another couple of layers of 6 ounce but I got tired.

[mr_matt_II]

All the layers are down. I trim the edge at the green stage (tacky but rigid, very easy to trim at that stage).

[mr_matt_II]

I popped off the parting board. In the first shot you can see the remains of the sulfer free clay I used to fill in the gap on the parting board.

The next shot she is cleaned up and the waxing begins for the second side.

[mr_matt_II]

After waxing the reverse side I cut out the old parting plane to have something to rest the mold in while working the other side.

Next, partall. For my finished parts I swear I will find a way to spray this thick stuff, for now the ugly brush routine again.

[mr_matt_II]

Surface coat, thickened resin for the corners and then resin and 8 layers of fg cloth, all in one shot.

[mr_matt_II]

Molds separated clean, good enough for this effort anyway. PVA comes off with soap and water.

I think it is back to the wing for now.

[kjohnson]

Thanks for documenting the mold steps. I've read a lot of threads about mold making, but your photos really help make them click.

kj

[mr_matt_II]

No sweat this is the first rigid 2 sided mold I have done so when I go to join the halves it will be a first for me.

The area that the guide tube goes in will be tricky, I am tempted to go with rail buttons and get rid of the tube, but then I would have to drag my rail launcher to one of the local launches I go to, hence I want to work on the wings while I think about it.

[fyrwrxz]

Matt- How about the old dowel/wing guide type launcher? No lugs, no buttons.

[mr_matt_II]

Not a bad idea, of course this is how the Phoenix launches. I tried Mk1 in the Phoenix launcher but it does not fit, making a new one would not be too big of a deal. Also, the angled launch is great to build up speed, on the Stratoblaster keeping it vertical will help keep the speed down!

The more I think about it, rod launch capability might be good to retain in any case. I like the possibility to launch it with the club launch rods. The rail buttons really took a beating on my Gamma Star landings.

... decisions....

[fyrwrxz]

On my first SR-71- I moved the LL to the top and 'hung it' to launch. Kept from scraping off during landings or plugging it with dirt. Buttons would be better maybe as the lift would reduce the friction but you have to cantilever the rail mass and bird with a counter weight. I should get off my duff before making any suggestions and start building things with wings again. Maybe during the hiatus. Nice thread- am enjoying the journey immensely. Your experience shows. Nice tools too!

[mr_matt_II]

Re: top mount LL. That might work, I thought about doing that on the gamma star by switching to a twin tail, but the plane did not last that long (dead battery after trying to light one of those new Estes igniters for the 5th time). I would have to check if the launch rail would fit between the bottom of the tail and the top of the fuse.

by "hiatus" I assume you mean OTL? When does that debauchery normally end (or at least move off the island)?

[fyrwrxz]

The debauchery NEVER ends on Fiesta. Been there, done that! Burned the shirt afterwards!

[mr_matt_II]

The trailing edge stock needed to be razor planed down toward the tip. This is a terrible job, probably the hardest step next to lining up the booms. Fortunately I have no pictures of it so I don't have to relive the horror. You can see the amount that had to be planed down, and the trailing edge at that point goes down to about 1/16th or less.

[mr_matt_II]

Now the servos holes have to be cut, I used the same template I used to place the kevlar under the top skins. The servos are mounted from the bottom of the wing with the linkages going through the top. The stock estes uses torque rods...no thanks.

You can see the kevlar under the top skin. I am using some hitech servos, using a flat mounting system, this ends up dead flush (or should be) with the bottom skin if you do it right.

[R&R Model Aircraft]

[/QUOTE]

The more I think about it, rod launch capability might be good to retain in any case. I like the possibility to launch it with the club launch rods. The rail buttons really took a beating on my Gamma Star landings.

... decisions....[/QUOTE]

What were you landing the Gamma Star on?!! There are screws on the bottom that protrude, even if you were landing on pavement.

David

[mr_matt_II]

What were you landing the Gamma Star on?!! There are screws on the bottom that protrude, even if you were landing on pavement.

David[/QUOTE]
LOL pavement would have been perfect! The places I land on are like the surface of mars.....actually it was not as much the rail bottons but the blind nuts/mounting plates holding the rail buttons in. If I had to do it over I would glass them from the inside.

[fyrwrxz]

Now the servos holes have to be cut, I used the same template I used to place the kevlar under the top skins. The servos are mounted from the bottom of the wing with the linkages going through the top. The stock estes uses torque rods...no thanks.

You can see the kevlar under the top skin. I am using some hitech servos, using a flat mounting system, this ends up dead flush (or should be) with the bottom skin if you do it right.

Matt-stupid question #1- why is the wing servo canted? I really don't understand the geometry. Thanks

[mr_matt_II]

Matt-stupid question #1- why is the wing servo canted? I really don't understand the geometry. Thanks

Good question Dave. It is really force of habit. I normally fly turbine RC planes that are pretty fast and I like to run the linkages parallel with the airstream for lowest drag. For best mechanical advantage, they should of course be normal to the hinge line.


Servo drops in OK, a little sanding on the case and it is flush. Next step is tricky, you have to route a channel into the wing about a foot, without punching through the skin. This is for the servo lead. Second shot shows the drill bit poking through into the servo pocket.

[R&R Model Aircraft]

What were you landing the Gamma Star on?!! There are screws on the bottom that protrude, even if you were landing on pavement.

David

LOL pavement would have been perfect! The places I land on are like the surface of mars.....actually it was not as much the rail bottons but the blind nuts/mounting plates holding the rail buttons in. If I had to do it over I would glass them from the inside.[/QUOTE]

Sounds like you need a landing skid in front of the rail button to avoid shearing!

[mr_matt_II]

Sounds like you need a landing skid in front of the rail button to avoid shearing!

yes I had them on the front and back, the back one kept breaking off. If I did it again I would slot them into the fuse and tie it them a larger ply plate for the blind nut. Here is the front skid (you can barely see it) and the martian landing site.

[mr_matt_II]

Sweet plane, hauled on the F blackjack RMS

[R&R Model Aircraft]

yes I had them on the front and back, the back one kept breaking off. If I did it again I would slot them into the fuse and tie it them a larger ply plate for the blind nut. Here is the front skid (you can barely see it) and the martian landing site.

You weren't kidding on the Martian landing site! Jeez!

I think the larger plate idea is good in your situation. It is sometimes amazing what people do with (or how they use) a product you design. You think you have all situations covered and think "There, that is really robust and should hold up to regular use" and then a guy comes along and shows you that he lands on a aggregate field with small boulders.....

[mr_matt_II]

OK back to the wing. The servos are flush mountable. I carefully placed the servos as far outboard and as far aft as I can get them in the wing. The pockets were reinforced before the skins went on and now. The servos are held in with small pieces of nyrod. Once the glue dries you can remove these servos pretty easily.

As for hinging, I hate this job. I use a tool to mark the center line on the tapered trailing edge and then another tool to cut the hinges (works like an old school powered turkey knife)

[mr_matt_II]

As I said these are not typical servos but made to be mounted flat. They are going in their 3rd plane now! They are waxed so they want get glued into the wing.