Estes Tercel build thread

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mrichhcirm

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Hi all. I've never done a build thread before but I figure it's my turn to contribute. Also, I wasn't able to find a Tercel build thread on TRF so it seems like an unmet need.

This is also my first boost glider, so expect to see my rookie mistakes! I did study up on boost gliders in the Stines' Handbook of Model Rocketry, Apogee's online publications, etc. so I don't think I'm completely in over my head. The Tercel is a simple, old-school design: a no-nonsense free-flight glider on a pop pod.

My first observation is that the Estes instructions are a bit on the terse side, so I definitely recommend doing your homework like I did...I learned enough to know that it's not listed as a skill-level 3 kit for nothing. I also learned enough to know that some of the things I learned building flying model airplanes as a kid won't work for a boost glider, especially trimming for boost and glide.

The first step is to sand the wing before removing it from its sheet. Next is to cut out the paper template and use it to trace a line across the top (the side without the cross-cuts) of the wing. Although the instructions don't explain this, the purpose of the line traced from the template is to mark the thickest part of the wing along the span, as a guide to sanding the airfoil section.

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Next step involves a lot of sanding with medium and fine emery cloth (I like emery cloth because you can easily wrap and bend it around a block...it won't crease and create ragged sharp edges like sandpaper does, and you can wash and reuse it).

I think I have a passable airfoil section at this point. Leading edge is on the right...the wing is like a bit like a Spitfire ellipsoid, only with the leading edge swept back.
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The wing is then turned bottom-side up, and the panels are separated by gently slicing through the pre-cut slots. The cut edges are then beveled with sandpaper to give the wing some polyhedral. The triangles (marked "K" and "L") will be used shortly to set the correct angle between the inboard and outboard wing panels, as well as the center panels.

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Now trying to glue together the outer and inner panels of the left wing. I have to say this part was a bit nerve-wracking for me:

1. My beveling of the edges was maybe just a bit rough...significant gaps there.

2. The Estes instructions specified medium CA...and the stuff seemed reluctant to bind the cut and beveled edges. I was used to the quick curing of water-thin CA; the medium stiff was more reluctant. I eventually figured out that I needed to spread it thinner and use the double-glue method to get it to grip the panels together. The Estes instructions explained this...but not until after the wing-assembly section; they got around to describing the correct technique during the joining of the horizontal and vertical stabilizers.

My fault for being unfamiliar with the ways of Medium CA. I intended to practice on scraps of balsa first, but got caught up in the excitement and went right ahead to wing assembly.

3. I used painters tape to hold the parts down while the glue dries...the tape lifted strands of the fibers in the wood, so I need to do some finish sanding later.
I guess next time I should use weights or magnets.

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Joining the left and right wing after both tips have been joined to the inner wings. Sheesh...my glue joints are messy. Using the medium CA to fillet those gappy joints. Oh well, so it won't win any beauty or duration contests. My goals are more modest...I'll settle for safely recovering the thing.
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The underside. More glue to sand off later. Note the empennage right behind the wing.

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An overview of the build as CA fillets dry on the wing and tail joints. Body tube for pop pod is on the left....it got slightly flattened in shipping, so it's been stuffed with spent Estes mini-motor casings to hold its shape.
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Looking good. Suggestion is swap out parachute for streamer, I found that chute way too tight for the small body tube.
It's a pretty good glider, so go with a small engine and windless day.
 
Looking good. Suggestion is swap out parachute for streamer, I found that chute way too tight for the small body tube.
It's a pretty good glider, so go with a small engine and windless day.

I was thinking about that too...I'm also planning to swap out the standard Estes tea-bag shock cord mount for some Kevlar thread, tied around the motor and taped. I'm not crazy about having any kind of bottleneck in such a small tube.

And yes, I already went out and got some half-A motors because I'm too chicken to try it on an A3-4T...:)
 
More progress on the build (I know, I'm slow). This is the fuselage boom assembly: There is a piece of Tyvek sandwiched between the two sides of the main boom and trimmed away with a #11 blade. Then the two cheek pieces/glider hooks are added to the nose. The whole thing is laminated together with medium CA, which I'm becoming a little disillusioned with.

I struggled to get the CA to grab properly (I tried to squeegee off the excess with a piece of scrap wood but I think I spread it too thin) and there were points along the boom where I had to dribble in some thin CA to try to relaminate it...which resulted in my gluing my forefinger to my thumb (fortunately, the females in the house had acetone nail polish remover handy). I think it will hold together after those false starts.

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Having had my confidence in CA shaken (the stuff is tricky and so darn brittle), I decided to reinforce my wing joint fillets with carpenter's glue...much more flexible. Behind the wing are the pieces for the pylon/glider hook for the pop pod...the part that attaches to the pod is also a wood and Tyvek sandwich laminated with CA, but the outermost layers are getting the carpenter's glue.
 
And here's the pylon assembly. I'm glad I switched to the carpenter's glue...the Gorilla brand is just grippy enough to let you get a good bond between your fingers before clamping, without gluing yourself to the workpiece. After this picture, I put some fillets around that launch lug.

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Here's the pop pod. Thrust ring has been glued inside and the pylon was attached with carpenter's glue and a little thin CA to tack-weld in place.

One change I'm making from the instructions is that I won't use the standard "tea-bag" or the rubber shock cord in the skinny tube. Instead, I'll tie a lariat loop in some Kevlar thread, thread it through the tube, cinch it around the motor, and wrap a bit of tape around it before inserting the motor. That should take care of shock-cord mounting and motor retention at the same time. I may add some sewing elastic to the end for a little shock-absorption.

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I managed to CA the wings and tail to the glider and test-glided it in its rough state. After a little trimming with the clay, I learned a few things:

1. I succeeded in inducing a gentle right turn by tilting the stabilizer assembly so when you view from behind, the right tip is up. It seems like it should track a circle of 80-100 feet or so.
2. BABAR, you weren't kiddin' about picking a windless day. She glides pretty in still air but got a little squirrely due to the hot breezy weather here today.
3. I'm really starting to hate CA because eventually the wing popped off the fuselage (again, so brittle!). Have to sand off my sloppy gluing job and try again...thinking of using Gorilla (polyurethane) glue if I can find a way to clamp it without crushing it. But then I'm trading one tricky glue for another...

Here's a picture of the major components. Once the wing is back on and some nice glue fillets are added to the wings, tail and pylon, it'll be ready for finishing.
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I would use the CA to glue the wing in place but then back this up with two or three thin fillet coats of carpenters glue. Do the same to the stabe parts. The wing and tail won't come off after this.


John Boren
 
OK thanks, that sounds more sensible...after all the Gorilla Glue could get messy fast. Got enough sanding to do as it is ;)
 
OK, took JumpJet advice and re-CAed the wing, filleting with carpenter's glue. Added a lighter fillet to the stabe assembly just in case I need to pry it off to readjust the tilt. Then sanded the glider up a bit.

Then I used thin CA to harden the pod tube ends a bit, sanding afterward to loosen the fit of the nose and motor.

Currently sanding the pod hook on the pod pylon and the glider. Question for group: how loose should the hook fit? How do I know before flying it that it's just right?
 
I fly ALL my boost gliders with the pod extremely loose. Even my RC ones I want the pod to fall off if you hold the assembled model straight up by the glider. Now there is a difference between loose and sloppy. The only movement the pod should be able to make is backward then up and out of the notch. There should be no up and down or side to side movement just back and up.

I'm sure others may disagree but "knock on Wood" I've not had a pod stay on for the past 8 years of flying various types of gliders. They come off when they are supposed to.

John Boren
 
"Loose, not sloppy". Got it. I think I achieved that...when this rain stops I'll prime, sand, and paint the pod.
 
Finishing in progress! Will my paint jobs win any awards? No. Am I 30+ years out of practice with waterslide decals? Yes. But I have to say it's startin' to look good. After this picture, the glider got a couple of light dustings of spray acrylic sealer, and the pod got a couple of coats of gloss white Krylon (from the 3-ounce "Short Cuts" cans for hobbyists).

Getting anxious to finish this because windless days are few and far between; need to be ready to fly the moment conditions are good.

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Flying Day! (coincidence that it's the 4th of July...it's been the first day in a while where conditions are clear and dry with mid-single-digit wind speeds)

The model in flying trim:
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3 flights and 3 recoveries!
All flights on 1/2A3-2T motors.
flight 1: nice straight boost, no rolling, clean separation of glider, full deployment of chute. Glider took a long, slow turn right, just missing tree line at edge of field.

flight 2: nice straight boost, no rolling, clean separation of glider, but the pod spit the motor which remained attached by the Kevlar thread shock cord tied around it. Nice glide, scared me a little by heading straight out toward the pond but then finally circled back toward me and landed in the field.

Flight 3: Tried to decrease turning radius with a little more clay weight on the right wing. Boost was nice and straight, but pod spit the motor again (gone this time) and failed to separate, resulting in a Red Baron death dive. Field was squishy from lots of recent rain so the model survived.
 
Can't tell from the image of the motor installed in your pod, but you want to also wrap a layer of tape half on the motor half on the body tube. You shouldn't every spit a motor this way as long as the recovery and nose cone are Not packed in to tight. What type of glide times were you getting 20, to 30 seconds?


John Boren
 
In fact, the tape in the picture only helps secure the Kevlar shock cord to the motor. Tape was also used to tighten the motor fit but that was clearly not enough. Next time I'll wrap around the body tube and motor end, or I may do what a fellow club member did and retrofit a motor hook.
 
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As for glide time? Seemed like forever when the glider was headed for the pond and the trees...i kinda lost track in the excitement. My buddy got the flights on video, hopefully I can give you a good answer when I see them. The 2 good flights were long enough to make a wide 180+ degree turn before landing
 
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Nice build thread and flight report. Definitely need to get a stop watch on your next attempt. :) Glide trimming is the fun part; nothing better than getting a nice turn dialed in and laying back to watch for a minute or two.
 
Great thread, thank for sharing this build information. I am finishing up a Semroc Starlight and the next rocket to go on the bench is a Tercel!!!!

Great Stuff
 
Thanks all for watching my rookie effort and for some good advice; maybe others will learn from my mistakes and false starts :) . A few points to follow up on:

On swapping out the rubber shock cord for Kevlar thread:
Good News: Saved space in the crowded pod tube, much easier to pack chute and improved ejection.
Bad news: Tying/taping the thread around the end of the motor didn't work out so well...the ejection charge toasted and frayed the thread where it passed between the motor and the thrust ring. I'm rethinking my attachment method.

Attention to details is extremely important:
1. securely tape the motor in place around the end of the tube because friction fitting may not be enough.
2. if you're using the clay for trimming weight on the nose, make sure it doesn't gum up the mounting of the glider on its hook. This may have been what caused my Red Baron crash.
3. CA glue joints are brittle; fillet them where possible with white or yellow glue which are flexible and more forgiving.

And on boost gliders in general:
1. Study up on boost gliders. Getting a good boost and a good glide represent different sets of problems; you're trying to make a vehicle that does both well. Building, trimming, and preparing for launch are all tricky.
2. This one's a really nice free-flight glider in its own right, so find a big launch site, a day with calm winds (mine were 6mph and I think that's the most wind I want to have when flying this bird), and bring friends to help you track the thing.
3. Don't forget to appoint someone to time the flight--I forgot :facepalm:
 
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UPDATE: this is my final solution to shock cord mount...Kevlar thread tied around front of pylon thru a 1/16" hole, tied in a loop and fed back into tube thru another hole in front of pylon. I also coated the thread and especially the knots with white glue for extra heat protection and to prevent fraying. Everything I wanted: strong without a bulge inside the tube from the mount or a rubber band hairball.

Also replaced stock chute with crepe streamer; I think the Kevlar cord cut the chute on flight 3.

More flights on the 1/2 A-2T:
4th flight: tried running the cord outside the body. No good; the knot gave way and the glider Red Baroned again. Went home and reconfigured the shock cord as pictured.

FLIGHTS 5 and 6: perfect flights! Full deployment, no damage. Glide times 20 and 22 seconds in 3 mph wind. Very minor pitching and stalling fixed with tiny pinch of clay on nose for flight 6, which probably earned me the 2 more seconds.

Update of FLIGHT 1: Slow-motion review of shaky smartphone video reveals glide time of 22 seconds.
The camera missed the landing of Flight 2 but judging by the size of the arc it flew, 20+ seconds seems reasonable.

Looking forward to a calm day at a club launch, where we have much more room and I can send this baby up on a full A.

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Well, after about a dozen nice flights my pop pod got stuck about 30 feet up in a tree last fall. (it managed to tie itself on pretty securely by its Kevlar shock cord). I turned the glider over to my 10 year old who, happily and literally, flew the wings off it. Over the winter, I built a new pod by Kitbashing a Star Trooper kit and cloning the pylon/glider hook, and sanded/re glued the wing and tail joints on the glider. Changed a few things...pictures and details to follow!
 
Design objectives for replacement pod:
1. Make shock cord replaceable and switch to elastic. I learned that Kevlar will burn and may cut the chute or streamer. Better to make the cord easier to replace than to try to make it indestructible.
2. Install music wire motor hook. Tape is a PITA.
3. Make pylon out of 1/16 basswood. A little stronger and sands nicely. Will offset extra weight by skipping paint.

Goofy face courtesy of aforementioned 10 year old.

The music wire shape is my shock cord mount, contoured to fit inside of tube. Another wire loop will be Gorilla -Glued into the blunt plastic nose shown.

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