The following is a discussion and plan for an experimental messenger for "lifting" parafauna, candy, and other 'heavy' loads up a kite line. The resulting messenger will lift goods up near vertical kite lines of delta and genki kites, and in fact would probably prefer it. and will not weigh down the support kite itself.
This is the goal and so far the experiments seem to show that it is very possible to do this.
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.
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, and relied 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. and the more I thought about it the less reasonable it became.
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 was titled ``Little Jessie goes aloft'' and shows 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.
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 down, down wind moving the messenger along the line for a bit. When you release and the kite lifts the kite line, the messenger will rise rapidly with the line. It should then get out of the low ground wind and continue its journey up the kite line.
The goal remember 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 the plan published on the WWW as ``Dorf's Ferry'', created by Thomas Dorf Nielsen, <firstname.lastname@example.org>. This plan was one of the first to appear and remains a standard for this type of ferry messenger.
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 whole thing being put together with 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 easier 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, before a fly day, so I can 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 my lifting experiments.
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 am using ``Dorf's Ferry'' as the basic style of construction, the following diagram details the modifications I have made to the design. I have also gone into more detail than the original plan, which should help with your construction.
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 to 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 from the front of the messenger body.
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. :-(
UPDATE 2 May 1998 :- See a Cotter Pin Alturnative I found in a marine shop.
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.
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.
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.
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. 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!.
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 above for the messenger body.
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 the carbon fiber tube hinges vertically when the release lines attached to the cross spars are released by the messenger.
No other lines are attached to the sail to set the angle of the sail to the wind, this was intentional to allow the sail to flex along the plastic tubing holding the hinges and set its own angle to the wind. Think of the sail as a diamond kite which has no bridle, just the kite line attached directly to the cross piece and you get the idea of the self correcting sail 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 sent it 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 static line dropper will not do, when loaded!
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, thoiugh with some extra lift.
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 is 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 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. Some sort of clip or hook here, for fast release, would be a nice furture addition.
The body of the messenger is also 90cm long with the load support `hook', 30cm in from the end of the messenger. In my experimental messenger I found that a heavy load (like tuffy) so close to one end of the messenger caused problems, so in the new one I extended the release rod to move the load away from the line line support at the end of teh messenger body.
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.
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!.
I am still experimenting as this sail while unstable for a angled kiteline should remain stable for extremely high angled lines, theoretically of course. How practical it will be? Well we will see.
When ``Tuffy's Parachuting Adventure'' was released recently on the WWW I was emailed by a fellow Australian, Graeme Poole <email@example.com> and we talked about our experiences. The photo to the right is of his messenger which was built by Graeme's friend Esben Collstrup <firstname.lastname@example.org> 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 was 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 diamond or genki-like messenger sails above. 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).
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 (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 form for this sail works well due to the way plastic streaches. Ripstop verions of this sail would probably do better.
One final point before you go and try your own experiments, I have been using 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.
These are ideas and thoughts which I may or make not experiment further with...
The sail should be a high lift sail such as a genki like sail (see above) or perhaps a delta sail.
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.
-- Anthony Thyssen.
Created: 10 November 1997