[photo]

Anthony's Lifting Messenger

up Back to Anthony's Kite Workshop

The following is a discussion and plan for a messenger for ''lifting'' parafauna, candy, and other 'heavy' loads up a kite line.

Just for those wanting to know what a messenger is...

Kite Messenger or Ferry(n): A device which is pushed or pulled up a kite line, usally by use of sails or parachute. When it hits a 'stop' previously attached to the kite line at an appropriate height, a set of rods are pushed which releases the sails and drops the 'load' carried by the messenger. The messenger, with the sails now folded or parachute droped with the 'load', then slides back down the kite line, where a new load can be attached.

The messenger detailed by this plan will actually lift goods up vertical lines! I did this as an experiment fully loaded. The design also requires no adjustments are is typical of many messenger, or produce a lot a wind drag. These factors were the is the goal of this plan, and in this respect has been a total success.

Index



Discussion about Traditional Messengers

The impatient can skip to the next section if they want!

I had decided to get into parafauna, and had even found the perfect parachutist for the job, a small koala named Tuffy, a few months before. The problem was that I did not want to pull the kite down each time I wanted to drop my 'friend' or some candy, as I would with a ''pull-line'' or timer line dropper device.

The only other solution other than a messenger is a manual pulley system, such as Art & FlyWork's Pully Dropper. But this seemed to me to be prone to problems, particularly in unsteady and turbulent winds, and still requires a good deal of work. Ok so I'm lazy, what else is new!

As such a messenger was the only real solution I saw as acceptable.

[photo] I have built messengers before, for example my Mintie Messenger is still a big hit with kids on the field. It is however limited in the weight it can carry, such as a small number of minties, ribbons, paper planes, etc. It also does not like the steep slope of most good kites preferring the 30 degree slope of UFO kites. And finally the wind needs to be really blowing really strongly, right down to ground level, for it to work well.

The mintie messenger and all the other messenger plans I have seen used basically square framed sails and as such were basically reasonably heavy framed, relying on the wind to 'drag' it up the kiteline. I thought this was most unreasonable considering that the users were basically kite flyers, who I thought would have more sense. The more I thought about it the less reasonable it became that messengers should rely solely on drag to lift the load.

Then while surfing the net I came across a short mpeg of a teddy bear drop, which showed a small bear being lifted up a near vertical kiteline. The mpeg movie, now offline, showed a small and very oddly shaped winged messenger carrying the bear up the kiteline. After some discussion it was found the wind was quite strong and the messenger has two adjustable release lines to set the sail angle.

More discussion followed from this on the rec.kites newsgroup during June 1997, but with no real final result. Typical of a newsgroup.

Well I thought long and hard and theorized that a 'kite like' sail must surely provide more lift than drag in a messenger. Finally I got round to building a messenger to experiment with and try out ideas. The following plan is the result.

Hint and Tip Ground winds are essential for launching messengers however I have found that if the wind is not too high up, you can pull the kite line down, a short distance down-wind from the tether point, moving the messenger along the line to this point. When you release the kite line the kite lifts the kite line, and the messenger into the wind. It should then be out of the low ground wind and continue its journey up the kite line as normal, then return to the tether point for re-loading.

Messenger Body

The goal is to build a 'lifting messenger'' and that is achieved though the sails of the messenger. The body of the messenger is not as important as the shape and style of this has become reasonably standard. I did however make a few small changes to the messenger particularly with regard to the sail hinges. More about that latter.

The messenger body is basically a variation on a originally plan published by Thomas Dorf Nielsen. The original plan is offline, but a mirror of the plan is available from Kite Ferry. This plan was one of the first to appear and became a standard plan in ferry messengers.

The plan uses carbon fiber (or other) rigid tubing to form the main body of the messenger, through which 3mm fiberglass rods are inserted to provide the release mechanism. The body of the messenger should be about the same length or width (the longer) of the sail. The sail, when attached, will be positioned around the forward 1/3 mark of the messenger body while the load should be somewhere in the rear 1/3 section of the body. This is not critical and can be adjusted as required for proper working.

You are free to use other components for the body, Aluminum/plastic tubing, dowel rods, whatever. Weight is NOT critical, and can be compensated with a larger sail.

The other parts of the messenger is attached using clear vinyl plastic tubing of various sizes from the local hardware shops. No glue required. The use of plastic tubing in the messenger makes it very easy to assemble and disassemble the messenger, which in turn allows you to quickly try out new ideas. I often create a few different sails, with my sail hinge (see below) built in. On the fly day, I can then quickly and simply dis-assemble the messenger, and re-assemble with a different sail to test out, ON THE KITE FIELD. As such is this messenger design is perfect for general experimentation.

The plastic tubing I have also found can take a huge amount of punishment, especially in the sudden stop as the messenger returns at break neck speeds down a near vertical kite line. The tubing just absorbs the impact without breaking.

Having said that, I used "Dorf's Ferry: as the basic style of construction, the following diagram details the new design developed from Dorf's version. I have also gone into more detail than the original plan, which should help with your own construction.

[Diagram]

Load Support and Release

First thing to note is that I bound a group of carbon fiber tubes (each 3cm long) together to provide the support of the load and release rod. I did this for two reasons. By binding the load support strongly like this means a stronger and more secure connection to messenger body. Unfortunately it means that this part is permanent and the sails can only be removed buy slinding the hinge off the front of the messenger body.

ALSO NOTE: In my experimental messenger I found that when loaded, with the hook far too close to the lower end of the messenger (as shown in the diagram above) caused the front of the messager to lifting from the kite line. So in the new one I extended the release rod to move the load away from the line line support at the lower end of the messenger body. That is I moved the release point position further along the body of the messenger.

Kite Line Attachment

The Line support of Dorf's Ferry has also been modified. Instead of using a brass ring with a cut in it, I have carefully bent thick coat hanger wire for the connection of the messenger to the kite line. This makes it very easy to attach and detach the messenger from the kite line without having to fiddle with the spilt rings. Similar wire arrangements can be used for release line hooks for parafauna, or candy sacks.

I am still not happy with the 'slipperyness' of the coat hanger wire, especially as I have found it gets a thin layer of rust after exposure to salt sea spray and being put away for a period of time.

I would love to use graphite rings used in fishing rod rings. These rings are ultra smooth and slippery, unfortunately this same bonus means that these rings can not easily have a notch cut into them allowing a line to be inserted. The fishing rod rings to hold the graphite rings are also quite complex and can't accept a kite line in the middle without weakening them considerably. These items are only designed to be threaded by the end of a fishing or kite line, and not for attaching the messenger in the middle of the line (once the kite is flying) which is a important feature of the kite line attachments I am using.

UPDATE: A better alturnative is to use Stainless Steel Cotter Pins I found in a marine shop. A little extra bending in a bench vice and you have a very good and slippery, rust proof, line attachment.

UPDATE: 10 years later and I am still using those same cotter pins. They are just great, and no complicated clips, wheels, line jams, and they never rust.

Messenger Stops on Kite Line.

Not only does a 'messenger' need to be attached to the kite line, but also two 'stops', need to be added. An upper 'fixed' stop that the messenger will hit and thus cause it to release its load. And a lower 'brake' stop.

These should be attached at appropriate moments while the kite is being launched. The upper stop should be at leasy a few meters (yards) from the kites bridle point, as you do not want to have the messenger getting tangled in the kites bridle lines.

Also if the messenger gets too close to thge kite it can cause weight and wind disturbances to upset the kite, and that is not good either. Keep them apart.

[photo] The upper 'stop' should not 'slip' along the kite line, and as such the line should loop back on itself, as part of the attachment, so as to prevent it slipping. Remeber that line also can have a lot of pull so make sure the stop is strong enough.

I find a cork that is 'ladder knotted' onto the kite line is good enough without being too fancy, or costly if 'lost'. The ladder knot ensures the cork cannot slide, and does not fall off if the kite line becomes loose on the ground.

UPDATE: Peter en Marleen Simons showed on his messager web pages a much better stop, providing a good surface for the messenger to 'hit'. Note however that if used as showm, the 'stop' can slip along the kite line. A better attachment to the kite line is recommended.

In contrast the lower stop should be able to slip along the kite line to some extent. This lets the fast decending messager slow down to a stop, without suddenly jerking the line or hitting whatever it is you have tied your kite line to.

For this a cork with a slit cut into it works well. The cork will slide down the line when the returning messenger hits it, slowing it to a stop. Afterward you can slide it back into position for the return from the next run.

Being loose, also allows you to move the lower stop qickly, when you need to let kite line in or out, which can happen on days when the wind is light, changes direction, or otherwise varies.


Sail Support Hinge

The final and MOST IMPORTANT change to Dorf's Ferry, is that I have used two short segments of carbon fiber tubing to hinge the sails 'double spine' (see below) to the messenger body. The use of a double spine is one of the inovations of this experimental messenger. By doing this I find I have absolutely no need of the elastic retraction line used in Dorf's Ferry. As the sails are freely hinged, the wind will easily fold the sails up and away, allowing the messenger to return (unless drag from sail flap becomes a problem on a low angle line).

The hinge is created by punching holes into plastic tubing at right angles (or other angles for further experimentation) to each other. This can NOT be done with a knife. I myself use a cheap leather punch with various size holes to select from. Alturnatively you could sharpen the edges a brass or aluminium tube and use a drill to cut the holes in the tubing. The holes should be quite a bit smaller than the carbon fiber tube to be inserted into them to ensure a tight fit.

The hinge is then built into and becomes part of the sail. When you are ready to you can then slide the center plastic tubing into the messenger body, position it and slide extra plastic tubing around it to ensure it does not move. This can be done on the flying field and different types of sails (in size or shape) can be swapped as required for experiments and wind conditions. Each sail with its own hinge.

UPDATE In one location I flew in, the turbulence due to a nearby building played havoc with the sails. Because of this one side of the sail sometimes falls down against the poor parafauna load, where it stayed. The messager still rose but very slowly, with a lean to one side.

As such I now recommend a loose line from the back of the sail to the top line support piller, to prevent any chance of the sails falling down from bad wind turbulance.

NOTE this line is NOT normally nessary and in a clear field with good winds near the ground, no problem requiring the line develops. It also does NOT need to be elastic (such as the retact lines used in dorfs messager) and does not need to be tight, just present to stop ''sail flop'' due to turbulence.

UPDATE: Later I replaced the vinal platic joining the two carbon fiber tube hinges with a more ridgid plastic tube found in some unknown toy. The more ridge tubing holds the sail spine more perpendicular to the messenger body and seems to work better than the more flexiable vinal tubing. It also does not wear out due to the twisting of the sail spine relative to the messenger body as the previous vinal tubing did.

Messenger Sails

It is the sails of this messenger which is heart of the messenger. And it is here that I am doing my experiments.

There are lots of different sails that can be used for a messenger. But most if not all seem to only provide a drag surface to allow the wind to push the messenger up the kite line. Indeed the simplest of messengers use the parachute of the parafauna, solider or whatever to provide the drag.

The problem with this is that first of all the kite line can not be very steep, otherwise the messenger will not actually climb the kite line, just drag the kite down. Secondly the messenger sail does not provide very much lift, as such all the lift will have to be provided by the kite itself.

You must have then a strong pulling kite which is able to lift the messenger and load. And as the kite line must be at a low angle only the lines tension will lift the messenger. Which means the kite must not only have to be able to lift the messenger and weight, but it must pull the line extemely tightly too!.

Some of the newer messagers have sail angle adjustments. I find these tedious and difficult to get right. By using kite sails, the sail themselves can adjust the sail angle automatically. This is due to the sails I am using extending ABOVE the line line and messager body itself. No more angle adjustments! (See ridge tubing for hinge note above)

Diamond Sail

[photo] For my first lifting sail experiment I decided to go back to basics by replacing the fully framed sail used in Dorf's Ferry, and in my own Mintie Messenger, with a diamond kite sail. This however is not so simple. To allow the sail to fold vertically, I replaced the spine of the diamond kite with a double spine which I used as a hinge for the kite in the manner shown in the messenger body diagram, above.

[sail diagram]

The diagram above shows the shape and dimensions of the first sail I used on the lifting messenger and this works extremely well. The sail folds on some hindges made from carbon fiber tubing. The sail release lines are attached not near the bottom of the sail, but to either side to the cross spars to hold the sail open.

No other lines are attached to the sail. Especially note to the lower part of the spine. This allows the sail to flex along the plastic tubing holding the hinges tubes, and lets the sial set its own angle to the wind.

Think of the sail as a diamond kite which has no bridle, the line being attached directly to the cross piece, and you get the idea of the sail setting its own angle.

As this sail is shaped like a proper kite it will actually lift the messenger and payload up the kite line. It is so good it has lifted 'Tuffy' my para-koala, straight up a vertical line I held tight from a ground peg. The load rose slowly but with a good wind it will do this. I have had it climb up a very tight line angled at 75 degrees attached to a 34 cell tetrahedral kite (design courtesy of TetraLite Kites). It also climbs my 1.5 genki kite with my parafauna! A situation which I can guarantee a older drag style ferry will not do, when It also has no problems with lesser sloping lines like my UFO rotor kites, though with the lower angled lines it behaves more like a normal 'drag' style messenger, with some extra lift.

[photo] [photo] UPDATE, 12th May 1998 :- I just finished my latest messenger using a diamond sail as my messenger sail.

The larger sail (tyvek, with a dragon motif painted on) is 1 meter long and 1 meter accross, to allow Tuffy to ascend in very light winds. The cross piece for the diamond has been moved downward so it is 1/4 the distance from the top (25cm) instead of the 1/5 measurement (used above). This change of the cross piece position was the the result of further undocumented experiments, and lets the wind set the messenger sail angle better.

Also I added two small holes at the very top of the sail so I can tie a short pice of string, or clip, across the kite line gap in the sail, after it has been attached to the kite line. This reduces the bend in the longerons due to the need for this gap, especially when the sail is full of wind.

The new body of the messenger is also 90cm long with the load support 'hook', 20cm in front of the lower line support post. In my experimental messengers before this, with the hook so close to the lower end of the messenger, the load weight and sail lift caused the front of the messager to lift the front load support from the kite line. So in the new one I extended the release rod to move the load away from the line line support at the lower end of the messenger body.

Also I added a set of lines between the sail and a large rubber o-ring (I happened to have handy) which I throw over the front line support piller to prevent 'sail flop' in turbulence, or when behind a wind shield at ground level.

Sail Flap

One final point before you go and try your own experiments, I used thin garbage bag plastic for my prototype sails above, and have found that the wind flaps the trailing edge of the sail so much that often the messenger comes down extremely slowly.

To stop this flapping I have taped some pieces of BBQ skewers I had handy on the kite field to the sail. This is a bit like the battens used in sails such as those in sail boats, windsurfers, and hang gliders. After adding them the sail will no longer flap when released, allowing the messenger to descend more quickly.

Also I found that adding a link across the very top of the sails, stops the two spines bending back with the wind, and stops the lower part of the sail from becomming too loose. But make that link detachable so you can remove the kite line from the slot in the sail, so just a bit of telephone wire, hook, or clip will do.

[sail flap]

When I later upgraded to a larger sail made with Tyvek the BBQ 'battens' were not needed, allowing the sail to roll up easily. But the link at the top (stop spine bending) is still nessary. As such to release teh messenger from the line I have two attachment hangers (stainless steeel cotter pins) and a clip at the tp of the sail.

Triangular Sail

[photo] When ''Tuffy's Parachuting Adventure'' was released on the WWW I was emailed by a fellow Australian, Graeme Poole <graeme.poole@unisa.edu.au> and we talked about our experiences. The photo to the right is of his messenger which was built by Graeme's friend Esben Collstrup <ecoll@geocities.com> from Denmark.

According to Graeme, his messenger's sail dimensions are approx. 1.5 metres across the top and the vertical spar is cut at 70cm. The spars are 5.5 mm carbon fibre.

This looked interesting. First the sail is hinged horizontally instead of vertically and was released by a single line attached to the spine. The sail as such does not fold in half as the other sails. Instead the sail remains open as the messenger descends, which in turn slows the descent somewhat and may require a heavier messenger body to descend in high winds and lower angled kite lines.

The following is a diagram of my version to attach to the messenger above. I however only used 3mm fiberglass spars (as I did in the other sails and I sized the sail so that the sail area will work out to the same as the diamond messenger above (this is an experiment remember).

[sail diagram]

This sail worked, and flew up the kite line well. Unfortunately it could not lift Tuffy. This was probably due to my use of 3mm fibreglass for the cross spar, which as it did not have any sail support in front of it was bent very heavy backward by the wind. This in turn loosened the sail, destroying any lifting ability the sail may have had in my first trial.

I replaced the leading spar with carbon fibre tube and while the sail now lifts it did not seem to lift vertically as well as a diamond sail of the same size (which was smaller for storage as the diamond folds in half). For low angles of kite line the sail has no problem but for higher angles it seems to be very particular about the length of the release line to set the angle of sail into the wind.

Also I don't think a plastic sail worked well due to the way plastic streaches. Ripstop verions of this sail would probably do better.

Genki Sail

With the success of the diamond sail above I decided I will next try a really high angled kite sail which should give even better lift. The following sail is basically a genki kite sail (see this traditional genki kite plan), but without the center section.

[sail diagram]

This sail did not work!

When I tried this sail I found that the sail tends be unstable, wanting to spin and twist around the kite line. The problem I think is that the lift provided by the sail is just too great. As such it wants to not only climb the kite line but raise the kite line higher! As it can't do this and remain stable (center of forces is behind and below the kite line) it will instead spin around and around and around the kite line.

I still figure this sail will work and will provide even better lift than the diamond kite, but may require a stabilizing keel, such as provided by the bridle keels of a real genki kite, perhaps a keel like those used in roller kites (See this Pearson-Roller Plan).

Maybe if the genki sail was repositioned so that the center of forces is above the kite line the messenger will not only lift the payload, but perhaps support the kite line itself! Of course the line connections between the messenger and the kite line may also require some revision to handle the messenger lifting the kite line itself!.

Basically I have come to the conclusion that while some sail lift is good, too much is bad. It is only becuase of this conclusion that the genki sail is still shown in this plan.

Sail Design

Guy Reynolds had some thoughts on messenger sail design, after his own messenger experiments....

I have been considering at your Genki sail failure, and come up with a theory that may explain why your Genki sail (in the published design) fails, the diamond works and how many other sail forms, including the Genki could be made to work whilst others couldn't.

I believe that your theory about the sail trying to lift the line as well as itself is partially correct, but necessarily because of lifting power of the kite. My theory is that the problem is to do with the natural angle of elevation of the sail compared with the lifting/pilot kite and the position of the line/messenger body in relation to the sail. One only has to look at man lifting kites where the lower kites run freely up the kite line before hitting conical stops, these kites have a huge amount of lift but remain relatively stable when running up the line. This set me thinking and gave me a clue to the possible causes of the sail instability problem, rather than taking messenger in isolation, consider it as a lower kite in a train, the body of the messenger as the kite line, and assume that the angle of elevation of the line is the same or more than that naturally reached by the design of the kite being used.

Take the diamond; if we extrapolate the kite line beyond the bridle point and through the kite, it roughly passes through the kite at the crossing point of the spars, which is where we bridle from for a train and where the hinges are in the messenger, hence the sail is stable

Now consider the Genki; I don't own a Genki so have no first hand experience, and can find no reference to a Genki train, but looking at photographs and plans and extrapolating the kite line up into the kite, it appears to pass through the sail well below the horizontal spar. Thus what you have with your Genki messenger sail is effectively an incorrectly bridled and thus unstable Genki. What I believe is happening is that the sail is trying to change its angle of attack (lifting the line as you describe it) to reach a stable point i.e. with the line/messenger body passing through the sail below the horizontal spar, but because the line/messenger body position is fixed it is flipping over the line where lift is lost, dropping back and going into a spin around the line. If the theory is correct it should be possible to make the Genki sail work, particularly with your messenger design, by positioning the horizontal spars higher up above the messenger body, so that the line/messenger body passes through the sail where the effective line would be for a properly bridled Genki.

However, following the same thought process, the same problem could occur but possibly to a lesser degree even with the line/messenger body passing through the correct point in the Genki sail if the angle of elevation of the line is less than that normally achieved by a Genki. This is because the sail will still try and lift the line, however this time it is only constrained by the lifting/pilot kite holding the line, and not by its own construction so the instability could/should be less.

I would thus like to postulate three basic rules for messenger sail design, if using a kite design as the basis of the sail.
  1. In its kite form the sail must be inherently stable i.e. must not require a tail for stability.
  2. The line/messenger body must pass through the sail at the point where the extrapolated line would effectively pass through the sail of a correctly bridled kite of the same design.
  3. The natural angle of elevation for the kite on which the sail is based must be less than the natural angle of elevation of the pilot/lifting kite being used.

If my theory is correct the a Delta Conyne Kite should work as the effective line runs through the gap in the middle of the kite, which is where the line for a train is run, and it should just be a case of designing sail such that the horizontal spreader spar is positioned just where there effective kite line passes through the back of the sail. However, it will only work effectively so long as I use a Delta Conyne as a lifting/pilot kite or a kite that has similar or even greater natural angle of elevation.

As yet this is only a theory, I have yet to prove it in practice

Regards
Guy

Future Things To Try

These are ideas and thoughts which I may or may not experiment further with... You are welcome to try them out, and I'd happy to include or reference your own results.

Responses

For more information about peoples experience with building this messenger (or others) and what results they have achieved I suggest you look at the various Responses I have recieved. Many thanks to all who have replied. If like this plan, and/or build one, please mail and let me know what you think. Including any ideas, suggestions or other experiences. That way I can add them to the above so others can read and benifit from your results. :-) Photos especially welcome!

-- Anthony Thyssen.


Created: 10 November 1997
Updated: 13 January 2012
Author: Anthony Thyssen, <anthony@cit.gu.edu.au>
WWW URL: http://www.cit.gu.edu.au/~anthony/kites/parafauna/messenger/