COTTON Swimsuit Elastic?

Current kit elastic shock cord (when you get elastic in a kit) is probably more synthetic than cotton. 

Cotton has a higher melt/burn point than most synthetics.

Parachute shroud lines now have a higher synthetic composition.

In my Odd'l kits, I use cotton embroidery thread for shroud lines. It is much stronger than most lines in other kits. Years back, Estes and Centuri sold a stronger high content cotton Button and Rug thread for shroud lines.

Regarding the Cotton Shock Cords - 

On YORF, Bill S may have found the answer. 

"I've been using 1/4" SWIMSUIT ELASTIC - its cotton covered and braided. It holds up to the ejection charge just fine; I haven't had to replace one yet due to melting, unlike the less durable 1/8" synthetic covered elastic. I get it from Joanne Fabric. 

I've also got a bit of 1/4" elastic that was supposed to be cotton, but turned out the seller was wrong and its synthetic. Bleh... 

I'd love to have cotton covered 1/8" FLAT elastic, but haven't found any yet.

Here's a link to the 1/4" wide Cotton Elastic: CLICK HERE

There are others listed, but look for the Swimsuit Elastic to get the cotton product.

ASP D Region Tomahawk Build, Part 2, Shock Cord & Engine Block

That craft stick is used to apply glue inside the body tube.

Mark the depth for the glue bead. Apply a drop of glue and rotate the stick end in the body tube.
It'll probably take a few applications to get a line of glue all the way around the inside.

The supplied yellow tube is used to push the engine block in.

For strength, both ends of the tube got a wipe of CA glue using a Q-tip.

After it dried, the glue was smoothed with some 400 grit.





The Kevlar is tied to the elastic like in the old Quest kits with a  simple overhand knot.

The loose ends were cut together clean with a wire cutter.

The BIG Fix, Gyroc Elastic, Part 2

The elastic is double knotted on one end. Feed the elastic through the wing flap from the underside until the knot rests against the flap.

Slide the open end through the rudder notch. When the flap is pulled up against the rudder, mark the elastic at the notch.

The second elastic piece is cut using the first one as a guide for the length.
These turned out to be around 1.15" long between attachment points.

Feed the elastic through the wing flap hole again.

Tie a knot at the mark made earlier.

Slide the end knot of the elastic through notch in the rudder. Notice there is enough of the loose end to each grab it with fingers.







Loaded with an A8-3, Ready for launch this weekend!

Between flights, remove the elastic from the rudder notch.

The BIG Fix, Gyroc Elastic, Part 1

Semroc (ERockets.biz) has brought back the Estes Gyroc. The reissue kit has a 13mm engine mount with streamer attached. The big change is replaceable elastic on the fin flaps.
Balsa Machining Service (BMS) also sells a Gyroc clone kit that uses standard 18mm engines. The BMS kit has the original elastic ties on the flaps.

The illustration to the left (From the ERockets website) shows two notches on the rear of the flaps. A rubber band is set into the notches and over the rudder fins on the wings. This arrangement allows changing the rubber band if it looses elasticity.

The problem with the original Gyroc has always been the weakening (over time) of the flap pull elastic. Even with an engine out of the model the elastic is still under tension. Here's a simple solution allowing removal of the elastic between flights and a change if the elastic stretches out.


Here's my Gyroc with the stretched out elastic. The elastic is weak and doesn't pull the flap up to the rudder fins.

On the right is the elastic looped through the rudder hole. This hole will be cut through to the leading edge making a notch.


The old elastic was cut off.
Using a thin razor saw, a narrow notch was cut into the rudder fin from the leading edge down to the original hole.

The hole on the flap fin was cleaned out (but not enlarged) with a small rat tail jewelers file.

More in next post - 

Estes Scissor Wing Transport Build, Part 16, Elevator Elastic

The notches in the elevator were filled and painted. I looked close at the instruction illustrations and marked the locations.

First a shallow notch was cut with a knife.
A razor saw made the cut about 3/32" deep.

The black elastic was fraying on the end.
I tied an overhand knot to stop the fraying. White glue was rubbed in the loose end. After the glue dried the string was cut off clean.


A second knot is tied at 3 1/2".

Here's how the elastic is placed to lift the elevator when the pop pod is ejected.

The inset picture shows how to store the elastic between launches.

The last two red stripes go over the ends of the elevator.

On the left shows the stripe right off the sheet, still on the backing.
On the right shows the stripe trimmed for a even white border around the ends.

Estes Skydart II #3229 Build, Part 18, Elevon Hinge

It's hard to turn the adjustment screw with your fingers. I used a Allen head jeweler's screw driver. Line it up with the trailing edge angle of the stab to reach the screw head.
Raise the screw almost all the way out to tie on the elastic.

Tie an overhand knot and feed it through one side of the elevator and through the stab hole.
With the screw raised all the way up, lift the elevator and pull on the elastic. Mark the spot where the elastic touches the elevator hole.

Tie a single overhand knot and leave it loose as you slide it towards the hole. I used some tweezers to work the knot close and tight against the elevator.

Cut off the excess elastic. Hang onto it, you can use the excess to replace the line if needed down the road. The kit gives you more than enough for a replacement.

Here's the finished assembly with the pop pod in place. The elevator is being held down by the retainer.

A Better Shock Cord Knot? Tips, Part 2

Tie an over hand loop knot in both the Kevlar and elastic cords. The loops should be about 3/4" long. (Left side picture)

Pass the Elastic loop over the Kevlar loop. The elastic loop can pass over the Kevlar knot. (Right side picture)

Pass the loose end of the elastic through the Kevlar loop. (Left side picture)
Pull the end of the elastic almost completely through the Kevlar loop.
Pass the elastic knot and loose end up and through the Kevlar loop.
Pass the Kevlar knot and loose end down and through the elastic loop. (Right side picture)

On the left are the loops after the knots and ends are passed through, before cinching up the knot.

On the right is the finished and tightened knot.
The new knot is cleaner, stronger with less stress on the elastic.

You may not get it right the first time. All new knots take practice.

Estes Gyroc Build Part 11, Elastic

After this step I remembered having the same problems with my first Gyroc build in the 1970s. There was a lot of tweaking to get the elastic to fully pull the flap against the rudder fin stops.

Enlarge the picture an you'll see where the instructions recommend setting the elastic holes. I marked the hole positions with a pencil dot.

The holes were made with a needle before threading the elastic.
TIP: Find the thinnest needle that you can still thread the elastic through. You want the hole to stay small!
The lower hole (near the hinge) didn't give enough pull on the flap. I had to go higher on the flap.
Now I'm stuck with an extra hole on the flap - Oh well!

Behind the flap is a double overhand knot. Over the rudder fin the elastic is looped and sewn through a second time.

The flap had to be trimmed at the root edge (Below the "A" in EXPERIMENTAL) so it couldn't bind when pulled open by the elastic.
If I were to build another Gyroc, I'd make the root edge of the flap a hair shorter so it couldn't rub against the body tube.
EDIT: Check the previous post for corrections I should have made!

When the elastic is tight enough the flap should lightly "click" against the rudder when released.

When all is right, put a small drop of white glue at the thread holes.
TIP: Never use CA (Super Glue) on shroud lines, shock cords or the elastic used here. The CA glue will run up the lines and harden it.

The white glue helps hold the elastic knot tight. Use just enough to hold it but also allow replacement of the elastic if needed later on.

Knots? Part 3

 

On the left is the Duncan (Uni) Knot tied with 135 lb, Kevlar.
Refer to the knot HERE

Looking at the animated tying instructions, you loop the line four times after making the "S".
This Kevlar tie has the four looped turns.

On the right is 1/8" elastic tied around a plastic nose cone eyelet.
The elastic is thicker than the Kevlar so I only did 3 loops before pulling it tight.
I prefer to keep the loose tail end about 1/2" long, not cut short as shown in the animation.

Both lines feel very tight and aren't going anywhere!