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Bungee to Sail & Endcap Mods


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#1 makatakam

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Posted 28 August 2011 - 06:19 PM

If you look at the recent gallery posts you can see what I've done. DutchRev and Revflyer noticed and E-mailed me regarding this mod. I don't have it fool-proofed yet, but will post detailed pics once I thoroughly field-test and feel its a worthy mod. At this point there is a significant reduction in weight and tip snags.

NEW 014.jpg NEW 015.jpg
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#2 katrina

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Posted 29 August 2011 - 08:40 AM

So tell us more about your button doohickey, Mark! :blue_smile: Looks much cleaner. One question, though, does it afford tightening?

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#3 stroke survivor

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Posted 29 August 2011 - 08:56 AM

I'd like to see a couple of pics showing the back side of the sail and button assembly!!! Posted Image

wayne from portland
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#4 makatakam

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Posted 29 August 2011 - 08:06 PM

Ok, I see I've garnered some interest here.

I'm going to explain the entire mod here in general, still working on durability issues, so go ahead and ask questions, but don't get ticked if I don't have an answer yet.

First of all, since I'm replacing "two" strands or call it a "vee" if you will, one strand will have to equal the tension of the original; therefore I use 1/8" bungee.
The endcaps are drilled from the inside, lengthwise, through to the triangular hole where the bridle and bungee attachments are normally made, but not all the way through the distal tip. In other words, stop when you hit the triangular hole.

I use a 3/16" bit to drill the hole so the bungee can be pushed through easily.It doesn't matter if the hole is "dead-on" centered; actually if its a bit "off", it makes feeding the bungee through it a bit easier. Tie a knot in the bungee and draw it extremely tight with pliers. Feed the unknotted end of the bungee up the endcap so that the knot is inside the end cap. Flame the end of the bungee and roll between your fingers so it is about the same as the original diameter.

I won't tell you how long to cut the bungee. That will depend on the sail and whether you like 'em tight or sloppy. Experiment, experiment, experiment!!!!

Here's the fun part. For this step you'll need the "buttons" (#6 hinged screw covers, Home Depot) and #6nylon washers (Home Depot), or Ace Hdwe or anywhere. Feed the bungee through the back of the sail to the front, through the hole in the screw cover (button), and through the nylon washer. Flame the end of he bungee and "mushroom" it. I usually flatten it with my finger (if you don't have calloused fingertips, use a piece of wood or whatever). Now push the washer as far as it will go to the end of the bungee. Apply regular crazy glue (not gel, you want it to soak in) to the front and back to stick the washer to the bungee. Allow to dry. Flame the end of the bungee again and flatten again. Pull the bungee from behind the button into the button and snap the button closed. The washer will take some "convincing" that it wants to be inside the button, but just push it in there any way you can.

the buttons should be on the front of the kite (facing you when you're flying), except for the inner LE ones. I don't use bungee on these; instead I use 1/8" braided Dacron and create a loop that I can slip through the sail and over the encap (the tighter, the better). This forces the LE to roll back, similar to the Rev Speed Series, giving the kite increased forward and reverse speed. It also brings the tips of the endcaps down almost flush with the LE. All other aspects of control remain pretty much standard.

Once I have this down pat, I'll fill you in on bridle change to accompany this mod (extremely minor, just tie one knot).

P.S. -- Losing the vinyl sand caps, 20-some inches of bungee, etc. = 22grams = my sle flies in 2mph or better.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#5 makatakam

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Posted 29 August 2011 - 08:17 PM

So tell us more about your button doohickey, Mark! :blue_smile: Looks much cleaner. One question, though, does it afford tightening?



It can be tightened, but not loosened, which is ok, since your sail will stretch over time, not tighten.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#6 makatakam

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Posted 29 August 2011 - 08:20 PM

I'd like to see a couple of pics showing the back side of the sail and button assembly!!! Posted Image



There's nothing to see on the back side except the bungee coming out of the hole in the sail.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#7 makatakam

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Posted 29 August 2011 - 08:23 PM

Oops, forgot to mention one thing -- tips snags -- what are those??????
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#8 goestoeleven

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Posted 29 August 2011 - 08:28 PM

Oops, forgot to mantion one thing -- tips snags -- what are those??????



I'm going to have to see these in person . . . you going to Two Rivers? I'm not 100%, but maybe . . .

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#9 makatakam

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Posted 29 August 2011 - 08:36 PM

I'm going to have to see these in person . . . you going to Two Rivers? I'm not 100%, but maybe . . .



Same here, want to but not 100% sure. Of course, you don't have to drive 280 miles to check it out. Get off the Rev site and go to IKE or just call me.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#10 REVflyer

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Posted 30 August 2011 - 02:53 AM

epoxy has much more "give" than that brittle crazy-glue stuff, one hard shock on the seawall could dislodge your adhesive component, the overall look is nice and clean Mark.

#11 makatakam

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Posted 30 August 2011 - 07:59 AM

epoxy has much more "give" than that brittle crazy-glue stuff, one hard shock on the seawall could dislodge your adhesive component, the overall look is nice and clean Mark.


The adhesive is there primarily to prevent the dacron braid that's over the rubber from sliding by glueing it to the rubber. It also sticks the nylon washer to the dacron, but what actually keeps the bungee from slipping through the hole in the washer and button is the dacron beyond the washer that is melted and mushroomed. Its bigger than the hole and can't pass unless you pull hard enough, harder than the normal forces exerted on the bungee even during unintentional contact with the ground or other objects.I originally just flamed and mushroomed the bungee inside the button without using the washer, and the connection failed repeatedly.

I suppose epoxy can be used and more than likely would be more durable, but would add mass (weight). This mod is still in the very early experimental stages, so I'm definitely open to suggestions and viable alternatives.

I have also considered and played with an aluminum crimp around the bungee that's flat enough to fit inside the button. The crimp, when I tested it absolutely refused to let go, but I had to fabricate my own and couldn't get it to fit inside the button. Still looking for a commercially made crimping method that will work.

Thank You for your input
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#12 makatakam

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Posted 30 August 2011 - 09:49 AM

Just had a new thought. If the dacron is stuck to the rubber with crazy glue, perhaps the nylon washer is an unnecessary addition. In the original version, which kept failing, I didn't glue the dacron to the rubber. The dacron would slip beyond the end of the rubber and pull through the hole in the button. With the two glued together this may not happen. Will try it and post the result.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#13 REVflyer

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Posted 31 August 2011 - 03:37 AM

weight savings of the adhesive shouldn't be a consideration unless you're building an indoor dedicated kite (then you could still put micro-bubbles into the epoxy mixture to make it less dense). Durability vastly outweighs any potential savings in micro-grams. We've tried too light many times locally, it equals too delicate as well Mark. You wouldn't make the weld miniscule (trying to save weight) if you were fabricating sheet metal, right? You can't possible need much glue for your purposes. Slather on the 2-part, 5 minute epoxy and see if it will work using that material instead.

Mushroomed caps occasionally let go too, YES you've gotta jerk it substantially, but some of us like to fly with that style. Tensioning the sail has gotta' be extra tough/durable and focusing on lighter weight in other locations is possible. For example, you could run a Skyshark 3P Black Diamond tapered down spar and pick-up those extra micro-grams in that location. The sail has more surface area at the top leading edge compared to the bottom triangles anyway, so a tapered spar is actually a logical application to investigate. You need less strength down there! You're also moving the weight balance overall more forward (towards the leading edge) which gives a better glide ratio.

Try to stay away from Crazy-glue applications unless you want it to fail in one particular spot consistently,... .. . If it has to crash hard, bust this piece off {crazy glued} ~ not these parts over here {epoxied}! Rubber-band powered competition indoor aircraft use both techniques. Adhesives are weight-reduced by installation of micro-bubbles. you might want the wings to break-off, but not dislodging the rudder and tail section.

If competition model builder planes don't break on impact with the floor they were built too heavy to begin with! (credits: Bill Bigge's influence upon Harold Ames)

#14 makatakam

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Posted 01 September 2011 - 08:28 AM

Just tried a welded steel o-ring, sized so you have to force the bungee through it, as crimp. Used a pair of pliers to test it and broke the button, but the crimp held. That was in excess of 40# of force, and at 90 degrees to the face lof the button. The force on the kite (assembled) is parallel to the face of the button, so this should effectively increase the force necessary to make it fail to over 50#. The sail will rip before this lets go! Also looking at those flat push-on speed washers, you know, the ones you remove from smooth shafts using many expletives. If these work, you can skip the plastic screw cover buttons completely. Six of these weigh in at about 1 gram.

I prefer the button because it has a more "professional", finished look, but the shaft retainer is field-adjustable without having to recrimp; simply grab the end of the bungee with a pair of pliers and pull out the desired amount af slack and trim the bungee, but if you have pliers and crimps in your bag, you can adjust the button-style almost as easily.

Just tried the speed washer/shaft retainer and it works. Here's some pics:

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Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#15 makatakam

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Posted 15 September 2011 - 03:26 PM

This is the finalized version(s) of my endcap to bungee to sail connections.

IMG_0910.jpg NEW 014.jpg NEW 015.jpg

The components, from left to right:
1. Spar
2. Bungee, knotted end
3. Endcap
4. Sail
5. Screw cover with hinged cap
6. Nylon washer
7. Bungee, flamed end

The assembly sequence:
1. Disconnect the bridle from the endcaps and the bungee from the sail and the endcaps. Put the washers in your spare parts collection.

2. Cut bungee to length. Flame and roll each end between your fingers to keep it about the same in diameter. Four inches should be more than enough. I use two to two-and-a half inches = a very tight sail. I recommend starting with more than necessary. You can always adjust the tightness by shortening it. Its a trial & error process. After you've done a few, you'll develop a feel for how long it should be. Tie an overhand knot as close to the end as possible. Draw the knot as tight as it can be with pliers. Trim the excess and flame the end.

3. Drill a 5/32" hole in the endcap through the end that goes over the spar into the triangular transverse hole where the bungee and bridle are usually attached, but not all the way through the end of the cap. Remove any debris and flashing caused by the drilling process. The hole doesn't need to centered. Push the un-knotted end of the bungee into the cap and out one side of the triangular area. Pull the knot into the endcap as far as it will go. The spar will go into the cap and over the knot during kite set-up.

4. Push end of bungee through hole in sail. From the back if you want the screw cap in front, or from front if you want it to end up in back. I burn new holes in the sail to accommodate the bungee. (See photos for locations) Push bungee through bottom of screw cover and through the nylon washer. At this point you can make approximate adjustments to the length of the bungee. (Hint: you can always shorten the bungee, but you can't make it longer.) Flame the end of the bungee while holding it vertically and let it burn until it forms a nice "mushroom" shape and blow out the flame.

5. Assemble kite and shorten bungees by cutting at the end inside the screw cap, symmetrically, all around until you're satisfied with the tension on the sail. Snap the screw cover caps shut, reconnect the bridle, and you're done.

6. Optionally, you can use small steel chain links to crimp the end of the bungee at the screw cover end. You can find these at craft stores in the jewelry making aisle. If you prefer this option, the nylon washer is not used. Use pliers to crimp the ring at the desired location, trim the excess bungee, flame what sticks out and close the cap over it while it's still hot to flatten it so it fits under the cap.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#16 stroke survivor

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Posted 16 September 2011 - 08:52 AM

Mark - Are you still using a glue to keep the fabric on the bungee from moving or creeping? Or is the flaming doing it well enough to skip that process? Overall it looks very clean!!! Posted Image

wayne from portland
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#17 makatakam

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Posted 16 September 2011 - 05:24 PM

Mark - Are you still using a glue to keep the fabric on the bungee from moving or creeping? Or is the flaming doing it well enough to skip that process? Overall it looks very clean!!! Posted Image


I did not use any adhesive on the last set. I found that the bungee you use makes a difference. That which is supplied on the kites made by Revolution doesn't require any, mushrooming with flame is sufficient. Also, using a nylon washer that you have to force the bungee into keeps it secure.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#18 stroke survivor

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Posted 16 September 2011 - 07:13 PM

Thanks for the info, I'll investigate and see if it's something I want to pursue!! Posted Image

wayne from portland
You have 2 choices - live on or die!! I ain't the dying type!!!  Also known as "portland flyer" on some forums!

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#19 makatakam

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Posted 16 September 2011 - 09:30 PM

Thanks for the info, I'll investigate and see if it's something I want to pursue!! Posted Image



If you consider yourself a "flailer", I recommend the metal crimp and putting the holes for the bottom bungees 1/2" to 1" further from the tip, especially if you like dacron braid instead of bungee at the tops of the verticals.
Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y

#20 makatakam

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Posted 09 December 2014 - 07:00 PM

Bumping this one just to say that these mods have been working now for three years, with only two failures. One with the washer/flame style and one with the metal crimp style. The failures both times were where the button allowed the bungee to slip through, no damage to sail material (which is what I definitely wanted to avoid). Both failures occurred while teaching new flyers, with typical new flyers' hard impact on grass. Intermediate-and-up flyers should have no problems, barring any SEVERE impact.


Mark

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"...it's a fair wind blowin' warm, out of the south over my shoulder, guess I'll set a course and go."
CSN&Y




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