Estes Sweet V

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Jan 17, 2009
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I bought My Sweet v like 6 years ago. its been sitting on my shelf. I got a wild hair and I think its time to build.

Has anyone ever built one of these before? I'd like to discuss some of the techniques used to build this.

My big one is the Wood covered foam wings. The instructions recommend Epoxy to layer them together. what would be wrong with using Styrofoam safe spray adhesive? I don't think it was made back when the kit was designed. at least not styrofoam safe. I think it would be a lot easier and lighter.

The second question is the motor mount. I'm thinking 32mm. weight would be the main problem. but I have a micro receiver that weighs less than half what the kit recommends plus a way lighter battery pack. that should make up the difference.

If I make those changes does anyone know where the cg should be?

I'm new here, but as a 15 year veteran of many R/C aircraft I've built my fair share of foam wings. I'm assuming by spray adhesive you mean spray contact cement, 3M77 or similar? I've tried this stuff before, and I've gone back to epoxy. The difficulty with skinning wings with contact cement is that you have no ability to wiggle the skin around - Once it's down you're done. With epoxy you have the luxury of time to make sure you're happy with how the wing skin is sitting on the core, and to make sure that the wing is straight and warp-free. (I hate trailing edges that do "the wave".)

If I make those changes does anyone know where the cg should be?
I'm not sure if I'm reading you right, but I believe the correct answer is "exactly where it shows on the plans". I'm going through the same exercise right now with an Aerotech Phoenix - the radio equipment available today weighs about half of the equipment it was designed to use, but the finished aircraft's CG will remain the same because this is dictated by the geometry of the wings and the fins. The new lighter equipment will need to be shifted forward in the radio bay or you'll just wind up making up for the lost weight with ballast to get the CG back to where it needs to be. YMMV

Thanks Kevin.
That helps out a bunch.
Being able to move the skin might be a plus. I guess its time to get some more west systems... needed it for other projects anyways.

I guess i read the plans wrong. it does not say "CG" is here.. it says finished
it should balance at about here... guess that the CG.. der on me LOL
I don't think I am going with 32mm but maybe that bives me way more choices for motors to put it up on.

I also have an electric motor that will fit in a 299 motor mount. I am thinking I might be able to rocket boost it OR slap the motor in and fly it on battery power!
I agree with everything Kevin said.

Remember that the CG needs to be set for glide conditions, not for launch conditions. (Although hopefully when it is set for launch the CG won't be too far off - because if it is.... things could go badly).

I have a Sweet Vee in the build pile, and I intend to install a 32mm motor mount as you are planning to do. You can also easily build an adapter that will allow the use of 24mm motors in the 32mm MMT. An Aerotech 24mm F12 reload would give the Sweet Vee a pretty good ride. I've also seen a Sweet Vee launched on an Estes E9-P (if you can find any - I'm not sure Estes is still producing that motor) and that worked well, too.

One other thing - if you need to add ballast, my preferred way of doing that is by using a heavier - and higher capacity - battery pack. If you have to add weight to get the CG set correctly, you might as well get something for it. The Sweet Vee is capable of thermalling, so having extra battery capacity could be useful.

Would love to see build pics if you have time.
SS23 - Some people may disagree with me on this, and you are certainly free to try anything you like, but you might want to reconsider putting a 29mm motor mount on the Sweet Vee. I think most 29mm motors would produce more thrust than a Sweet Vee could handle. About the only 29mm motor I *might* try in a Sweet Vee would be an F22.

Also, if you put a 32mm MMT on it, you can also make a 29mm adapter for that, and that would still provide you the ability to try 29mm motors to your hearts content. To adapt a 32mm mount to 29mm, all you need is a piece of 29mm tube. A little masking tape around the front and rear ends to snug it up inside the 32mm tube, and you're set.
Good point.

I could do the same with the 29mm
Build it 29mm then adapt down to 24mm
fly it a few times on the 24, Then if I think it can handle it go up to the 29

I Cant remember all the reloads for the 29 RC I bet there are some small ones.

I also DO EX, and end burning or "D" grain Sugar motor might work out well to. Really low thrust long burn. :D
Good point.

I could do the same with the 29mm
Build it 29mm then adapt down to 24mm
fly it a few times on the 24, Then if I think it can handle it go up to the 29

I Cant remember all the reloads for the 29 RC I bet there are some small ones.

I also DO EX, and end burning or "D" grain Sugar motor might work out well to. Really low thrust long burn. :D

Of course, there's the 29mm Apogee F10 with its 8 second burn. Kinda pricey, though.
Of course, there's the 29mm Apogee F10 with its 8 second burn. Kinda pricey, though.

Very true, Its a 1" blue propellant. I am sure I can EX something like that together too.

I also believe there is a 24mm E-6 from apogee. great suggestions.

Instead of Spray adhesive. I ended up getting a water based brush on contact type cement. its used for skinning counter tops. I am going to test that on some other foam I have and see what it does. Why? well im not sure. but the epoxy thing just seems like way over kill and very pricey.
I built a modified Sweet Vee for Ed LaCroix in 1996. Among the mods was a 32mm engine mount.

To get the 32mm mount to fit right, and to be at the proper thrustline as the 24mm mount was supposed to be, I had to cut a gouge into the top of the wing skin. So I added extra fiberglass cloth to the top center section of the wing to help to reinforce it some more.

Also, I think I used at least 2” wide, if not 2.5” wide, glass cloth on the center section joint. The glass tape in the kit is only 3/4” wide, but that seemed to be too wimpy even without the need to cut into the top of he wingskin.

The wingskins are Obechi. It is stronger than balsa (per thickness), and also cheaper than balsa. I think they chose the Obechi mainly because it was cheaper (particularly since the surface area of this wing is so much more than the Astro Blaster and Strato Blaster kits). I learned the hard way on another project that Obechi soaks up epoxy like a sponge. I kept applying more epoxy, and the skin looked “wet”, then a few minutes later the “sheen” was gone, and the skin just looked “damp”, the epoxy had mostly soaked inside of the skin.

I learned from someone else what you do about that, when I made the Sweet Vee. Use some clear dope, and apply the dope to the inside of the skin, and let it dry. The idea was to use the coat was a barrier to help keep the epoxy from soaking thru the Obechi. It worked. When I did that then applied the epoxy, it was like working with balsa, it did not soak in like a sponge.

If I did it today, I would still do the same. I do not trust spray contact adhesive to bond the wing skins.

Something else I did was to reinforce the inside of the skin a bit. I used some 3/4 ounce glass cloth for the first 6” of the wing, staring from the root. It did not add much weight. I applied the epoxy first, squeegeed most off but left it “wetter” where the glass cloth would be. So when I laid the cloth in place, the epoxy soaked into the cloth and there was still enough epoxy left to bond to the styrofoam cores.

BTW- I like to use some dry pigment to dye the epoxy. I use red, and when mixed it looks red. But when applied and then squeegeed thin, the thin layer looks pinkish. That is very useful for seeing where the epoxy has been applied and how much epoxy since the pinker it looks the more epoxy is there.

I will attach a photo showing a wingskin for a very special Cuda wing (reinforced and built for a flap to be cut out), after the epoxy, fiberglass cloth ,and thin .003” graphite spar had been prepared and was ready for the skin to be applied to the wing core. You may take note that on the root side at the left, the pink is darker, partly at the very root, then for about 1/2” along the first 6” of the leading edge, and for about 1.25” of the trailing edge for the first 6”. The pink is darker because that is where I added fiberglass cloth. The stock Cuda did not need that, but since I modified the wing for a flap to be cut out of it, the rest of the wing in that area had to be strengthened. On the core side, the other wing skin had already been applied (same exact layup) , plus a balsa insert I shaped and added to the core, where the flap would be cut out and hinged. Actually in that pic you can barely make out about a 1/16” gap between the facing trailing edges of the wing skins, where masking tape was used for “hinging” the skins along the trailing edges to keep them aligned.


I built the Sweet Vee wing to fly on, at most, a G12 reload (The Cuda wing above was built only to hold up to an E6). And the Sweet Vee flies so well on an F13 reload that a person might be pleased with “just” an F13 most of the time rather than a G12.

If a person wants to fly it on a motor with a lot more thrust, just place the kit under the left front wheel of your car, and drive forward three feet. It will save a lot of time and money in the long run to just do that instead. R/C Rocket Gliders are typically NOT built to boost super-fast. I have heard of some people getting away with lying the Strato-Blaster/Centurian on things like an E28, and the Phoenix R/C R/G was actually purposefully over-built to hold up to a G40, but the Sweet Vee is not designed for that, nor should it be (if someone wants a super-hot boost, then beef up a Strato-Blaster or get a Phoenix).

Think of the Sweet Vee as a GLIDER that happens to get into the air on rocket power. Not a ROCKET that glides down.

OK, couple of other things. The kit’s mechanical V-tail mixer design is nice in an engineering sense, but operationally it did not work smoothly enough. You could move the stick for elevator up, then let it return to center, then move the stick down, then to center, but the center would not be at the same exact place. It was biased towards the direction it returned from. Also, this bird needs noseweight and the mount for the servos did not put them as far forward as they could have been. So, I junked the mechanical mixer, and built a custom cradle to hold the two servos side by side as far forward as possible, and used the transmitter’s electronic mixing for the V-tail.

Also, the bare 1/32” music wire was a bit troubling to me. If the model lasts even a few months, music wire pushrods will oxidize. Especially the portions exposed to exhaust gases on boost. And those narrow slits cut into the boom (for the pushrods to slide thru) would then cause the music wire rods to bind somewhat. So, I replaced the music wire pushrods. I used Sullivan’s flexible cable pushrods, with the yellow sleeves that are between 1/16” and 3/32” diameter, with .030” wire cable pushrods. I had to cut out those slits in the boom not only to make them wider, but somewhat longer so the angle thru the boom would be shallow. The pushrod sleeves need to be set up to be very gradual wherever they curve, so that the pushrod cable can slide thru VERY smoothly. Otherwise, there will be the same problem with biased centering as I described for the mechanical mixer.

Try to keep the V-tail lightweight. Every excessive gram you add to the tail will require at least 2 grams, maybe 3 grams, of weight in the nose to balance it out.

For the wing finish, to keep it light, I just gave it a light coat of clear dope.

For the radio gear, put the receiver and battery pack as far forward as possible.

For the CG, try using the forward-most location, at 3”, when a burned out 32mm reload casing is in it. So that will be the glide CG. This means when loaded with a G12, the 32mm reload will cause the CG to be more to the back, but since he engine mount is not TOO far back from the wing CG, this will not be as excessive of a change as happens with models that have the engine farther back, especially in the tail (this was a big problem with the Astro-Blaster, and somewhat of a problem for my SkyDart 2X).

The issue with the CG being aft on boost is that the model will be very sensitive in pitch during boost. At least until a lot of the propellant has been burned off. But again the Sweet Vee engine mount is not too far back, so there is not a huge amount of shift. But there is enough of a shift for me to suggest to trim it for the glide CG to be a little more forward, at the 3” range they mention, as opposed to having the glide CG more to the back, which would then make the boost sensitivity worse.

For flying it on a 24mm motor, I would only recommend the E12 RC reload. Nothing bigger than that, nothing with more thrust than that. If you fly it on something with more thrust and the wing shreds, well, I already have warned about this with suggesting driving over the unbuilt kit with a car to save time and $. At some point a big enough engine will make the model boost fast enough to shred that wing. And with a 32mm casing to enable the use of an F13 or G12 reload, there is no sense in using more thrust than that.

The E6 thrust level is too low for the Sweet Vee mass. And I have something to say farther down about flying on Black Powder D or E engines.

One thing for sure. Never fly it on black powder motors. It was originally designed for the Estes “E15”, which turned out to have a high cato rate and was withdrawn, later re-introduced as the lower-thrust E9. Engine catos would often shoot the propellant grain up inside of the model, burning up the wing, the fuselage, AND the radio gear. Well, a person could risk it by making a 24mm adapter to fit into the 32mm reload casing, so if the black powder engine catos, the 32mm casing would contain the fireball. That is what I do when I make first flights with D and E sized models, using a C6 engine, where I mount the C6 inside of a 24mm RC casing just in case.

The Sweet Vee, on a G12, will boost about as high as high performance FAI S8E models do on an E6 (like the Cuda, Stingray, and modern-day FAI models). There is no need to go for more than that. And I will say that if I put “just” an E12 into an FAI S8E model that was designed for an E6, that the wing would shred on boost.

Below - Ed LaCroix boosting a Sweet Vee using an E12 reload. And a larger image of the Cuda Wingskin layup.

- George Gassaway


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George, Thank you VERY much for the insight, thats whatI was looking for.
I agree about the low boost 32 and 29 motors that was always my plan.
I was planning on a larger strip og glass down the middle. it just seemed right.

I like the idea of 3/4 ox glass inside the wing seems smart.

I have a older futaba radio, it does not have a v-tail mixer, BUT I do have a mixer I can add. like you said the kit supplied one just didnt look like the best.

I know there is a lot more GREAT info in your post, I will read it a few more times, take some notes, and probably ask many more questions!

A recent build thread--

I built it basically stock, including 24mm motor mount. I've flown some R/C planes, and some rocket gliders, and had trashed two other conversion attempts at HLG's, so really wanted to stick with as-designed construction of something designed to boost and fly fairly well under rocket power.

I've got about a dozen flights on it now, mostly D7's and E7's. Nothing spectacular, but the D7 is an easy motor to train with, gets me high enough to glide for 1-2 minutes, and the E7 is identical thrust curve, just lasts longer. I do eventually plan on climbing the ladder to E6 and F12's, but in addition to higher altitude, those larger motors mean much higher velocity, which means much it reacts to the stick a [heck] of a lot faster and more extremely. My first E7 flight was worse than my typical D7 flight just because I over-corrected and did a lousy job managing the transition.

One other very important consideration in using non R/C motors (even -P's) is that the thrust curve makes a big difference with RCRG's. Gliders need a very short and very sharp spike to gain enough speed to clear the tower and fly, but after that spike you want as long and slow a burn as possible to avoid overly stressing the model and shredding. Very few rocket motors share that thrust profile. A couple different people suggested I build with a 29mm mount, but as I looked at motor choices I found few, if any, I'd be willing to fly that could beat what it can do with an E6 or the F12.

I did vac-bag the wings, guided by a very experienced guru on that front, and highly recommend that over the press-under-a-ton-of-weight method, which results in a much heavier wing. My finished glider, with motor and gear installed, is about 15 ounces.

--Chan Stevens

Thank you for that input.

Question. I don't recall an E7 or D7, what are they? single use, reload aertech estes etc!
D7 and E7 are 24mm Aerotech RMS, for the special 24mm RMS-RC 24/20-40 reloadable casing. The 24mm RMS-RC casing has only an open end to insert the reload, the nozzle, and then you screw on the aft closure. The RMS-RC reloads are designed for applications where you don't need or want delay elements and ejection charges - like rocket gliders, either free-flight or radio-controlled.

The reloads that I am aware of for this casing are the D7-RCT, E7-RCT, E6-RCT, and the E12-RCJ. You can go to and get info about these reloads.

The reloads are designed to have a sharp initial thrust spike to get the rocket glider up to speed for stability purposes, but then have a long steady low thrust burn.

When Aerotech was out of production due to their factory fire for a few years, it was a long dry spell for us few RC rocket glider pilots. To the best of my knowledge, no other vendor makes specialized loads like these.

I keep hoping that AT will make a rocket glider type load for the new 24/60 casing. That would be awesome.
VERY strange. On another thread you said you used to work at Aerotech.

How could you not know about the existence of the D7 and E6?

- George Gassaway

I did very little with the R/C line. Also Aerotech does not move very many R/C motors. I remember actually getting rid of a bunch on the shelves because they had sat too long.

I don't know why they didn't click. just me I guess.
Not a rocket person, but a great admirer. I have just acquired (EBay) a wellbuilt Estes Sweet, minus motor and rc gear. I was planning to add it to my slope-soaring fleet, but am now tempted to fit an electric ducted fan. So this thread, with all its tech detail on CG and more is incredibly valuable. Thanks very much
I find fiberglass is easier than sheeting. 1.6 once glass and a light coating makes a very light and strong wing. Precoat the glassfiber on cooking paper. When you lift the fiberglass, the excess resin is left on the paper. I find it makes it easier to put a making tape heem on one edge for handing.

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