The Wings by Trevor & co.

In the Bag

Unfortunately we never took photos of the polystyrene cutouts so I will try and explain what we did, after cutting out the polystyrene and giving it a light sanding,we joined the wings together and filed a groove along the wing on the C.G. big enough to put a carbon tube about 8mm in diameter and a length of 20cm along each wing. We then put 3 60g carbon toes on top of the carbon tube and along the whole length of the wings. Once all had dried and before bagging we put microbaloons in to fill in all the holes.

We polished the thicker mylar and panted it in our colours using the Ford Focus Orange and a pearl purple for Trevor, two blues for Wes and a lemon yellow with purple for Kobus.

I was very apprehensive when I bagged the first wing but was pleasantly surprised when it came out the mylar, I think for my first time bagging they came out perfect.

Only the fuselages to complete and will keep you posted.

Chat again

Trevor, Kobus & Wes

The Fuzz by Trevor & co.

Hi Jarters

We started by cutting out the outline of the fuzz from the plans glued two pieces of

polystyrene together and glued the outline onto the polystyrene and took a hacksaw blade and cut a rough outline of the fuzz. After a lot of sanding using 80 grid sandpaper we got agood looking fuzz.

From the picture you can see that we have put on (wing-things) because we are not making the Jart as one piece, the wings will attatch to the fuzz with a carbon wing joiner.

We covered the polystyrene with 180g cloth and put carbon toes down the fuzz for strength. Sanded some more and scimmed the entire fuzz with microballoons and epoxy to create a smooth finish. They will be primed and painted.

Thats it for Today we'll chat again.

Trevor, Kobus & Wes

The Stab by Trevor & co.

Hi Jarters

This is all new to me and will be trying to keep you posted of how we are doing with our build.

We are currently building 3 Jarts and have already bagged our stabs but in a different way and opted to paint the stab after bagging. When we cut the polystyrene it never came out to smoothly so we covered the polystyrene with 0.8mm balsa hoping to create a smoother finish.When we bagged the stab I never had very thick mylar so never painted the mylar, we put a lot of microballons and epoxy on the leading edge and trailing edge. We sanded and made the profile correct afterwards, it has added a little weight but that's ok.

Will chat again

Trevor, Kobus & Wes

To Infinity and Beyond

Lionel came around to the flying field on Sunday to show us his Jart plug he has made.

He has made it out of Meranti and after hours of shaping and sanding it was painted with 2K , sanded and polished and the result is an absolutely splendid paint job. It gleams in the sun and is a smooth as a baby's bottom. Not a wrinkle or orange peel anywhere. The shape is spot on and he has got that pear shaped front profile exactly right.

He will be starting on the moulds soon and has promised to keep us all up to date as he progresses.

He tells me he plans on starting a building group once he has all the bits and pieces ready, so people who would like to build a Jart, but don't have the equipment or skills can join and get help and advice and get hands on experience while building their very own Jarts. I for one will be joining, just so I can get one of those fuselages.

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Unfortunately we did not go to the slope this past weekend as planned so Mike's Jart never flew. But we are already planning a trip for next month. Lets just hope Murphy does not hear about it again and stuff up the weather.

All things Jarty in Cape Town

Hey guys,

Good to hear I’ll soon have some company on the slopes. Was getting a bit bored whizzing past all the other planes.

So far I have pulled 4 fuses from my mold, the first was a test and largely a throw-away, 2 are flying and 1 is waiting to maiden.

These planes are amazing in terms of their momentum and speed and the biggest pain with them is slowing them down enough to land.

I largely fly in the Cape Town area, specifically the southern area where we have some great slopes for all wind directions. I have a bunch of other planes but recently have only been flying the jart as is so much fun.

I have been building mine solid and usually weigh in at about 1.3kg’s and on a strong days I have even considered putting in some ballast. I have also flown in light conditions where I’m not sure I would even be able to maintain a bee or zaggi but the jart once going flies superbly in the light air.

Best advice; throw it off the slope and don’t be scared to dive it a couple hundred meters before pulling it up, takes some nerve in light conditions but once its got some air over the wings it easily comes back up.

Reed calcs for the CG are spot on, if you trim the jart to the specs on the plans then it will fly, guaranteed. My first launch was done with all hands off the stick.
I have recently been busy with other projects and not had much time to build or fly but looking forward to getting some good air time this summer.

The J Fleet

How to land a jart :)

Jart finishing

Well the Red Baron would approve of the colour scheme, I really needed to add the stripes so that it is easier to tell the top from the bottom and to find if it goes down in the rugged terrain of the slopes.

The yellow colour has proved easier to spot from a distance than the darker colours, I have helped find several gliders at Volksrust by looking back up the slope from the bottom with binoculars and orange/ yellow and to a lesser extent white stand out well.

The canopy is starting to fit ok but still needs some work I have added two ply-wood tongues,

and may now attach it with small cap screws, (dont want anything comming adrift as this beast comes screaming past)

The radio gear I am going to use is as follows.

elevator servo Hitech HS 125 flat wing metal gear (this fits nicely and screws down into ply- wood blocks from the top)

Wing servos HS 85 metal gear servos(HS125s would have worked, but I have 85s MG available. )

The receiver is a Futaba ppm 5 channel but on one of the less popular 53mhz band frequency which reduces the risk of a shoot down.

Battery is a 4cell 1000mah NIMH.

One of the last tips which I have noticed is often overlooked, is to label your plane with your name and telephone number, On Volksrust gliders often get lost and recoved later ...if your name is on it your chances of getting it back improve greatly.

Mike

Mylar prepertion - Evan - Post # 2

I mentioned in my previous post that I wanted to experiment with a paint technique. The Mylar sheets were cut out so that they match the foam cores exactly on all but the TE, which is cut about 15mm oversize. Then the pattern is marked on the reverse side, then turned over and masked with newspaper and clear DC fix shelf paper before spraying with 2K paint.

I used a special water based release agent on the mylars before masking. The DC Fix sticks okay and releases easily. Time will tell if this is going to be successful.

I will be laying up with Uni-directional Carbon, so the areas I want black will not be painted. The pattern is white and black on one side and white and orange on the other. The masking is removed when the white paint has dried and the orange areas are then sprayed.


The painted mylar sheet are then put aside and left to dry.

The next job is to reinforce the LE of the wing before bagging. To do this I cut two strips of 106 gm glass cloth at 45 degree, laid this on the table and put 4 x 12K carbon tows over them and wet them out and squeegeed the resin through the carbon and into the cloth with an old credit card.
These strip are carefully laid onto the LE , wrapped around and brushed down with a little more resin. A little resin is brushed onto the foam before the strip is added to help hold them in place.

This is left to go to the green stage before bagging.

Next post will cover the bagging.

An Airfoil Plotter for AutoCAD

In the February 2005 R/C Soaring Digest I discovered an airfoil plotting program written for AutoCAD users.
Above is a screen shot of my AutoCAD at work. The Airfoil selection dialog box is open and my Jart drawing is in the background.

It sounded very interesting and as I use AutoCAD I thought that I would give it a try. I am no computer boff but I managed to get it all working without any problems. I just followed the instructions and installed the program and am extremely happy with the results.

No more manually inputting coordinates. It is done automatically for me. Phew!
I even went so far as to create my own button for Airfoils, so I don't even have to type anything. It's just a click away.

Below is the article as it appeared in the R/C Soaring Digest, with links to where you can download the program. If you use AutoCAD and want to draw airfoils then this program is an absolute must for you.

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An Airfoil Plotter for AutoCAD
by Dennis Mead


R/C Soaring Digest - February 2005

I have an airfoil plotting program written for AutoCAD users who design their own planes using that program.
This is a routine written entirely in Autolisp, so it runs within AutoCAD without depending on any external resources. It can be installed or removed almost as easily as moving or deleting a folder. No fancy installation/removal steps are needed.
When designing a model plane in AutoCAD, the routine can call up and draw airfoils directly into the drawing without having to use any other programs or intermediate steps. After the program is loaded, just type the word “airfoil” any time you desire and the routine is running. An airfoil can be selected and drawn to any length of chord and thickness desired. All that is needed is the airfoils’ X & Y coordinate data. The data files may have any extension: .dat, .cor, .vec, and even .txt.Very fast, very simple.
For more info, see the “Airfoil.readme.txt” file. Airfoil.lsp is also a text file so it may be scrutinized easily if you wish.
The original program was downloaded from the web back in 1995 and was deficient in several ways. I re-wrote some of the code and added to it in order to make it work easily. The original author is noted at the beginning of the file, but so far all efforts to find him have been futile. I assume that since the original program has been in the public domain for quite some time, that the original author won't mind the improvements.
The “AIRFOILS.exe” file contains the program, the “readme” file, and also several folders of airfoil data. The airfoil data files were gleaned from a number of web-based resources.

Inconveniences: Some airfoil coordinate data is tab delimited. For some reason, Autolisp cannot recognize the “tab” character, so it is not possible for the routine to sort this out. Rather than having to manually edit out tabs in the data files, I have included a handy utility which can take a whole batch of files and convert all of the tab characters in all of the files into spaces and then place these converted files into a new folder. This utility was written by a friend of mine for one of his projects and he kindly modified it for our use here. This takes care of the only real quirk in using Airfoil.lsp.
Other data requirements are easy to check and correct. See the “Airfoil.readme.txt” file.
The “Tab_2_Space.exe” utility takes a whole batch (folder full of) of airfoil data which is tab delimited and replaces all of the tabs with spaces. This is needed sometimes because Autolisp does not have the ability to recognize the tab character in data files. Most all airfoil data is space delimited, so 99% of the time, the utility is not needed... but it's nice to have because it saves so much time and the possibility of making errors when editing data by hand.

For Macintosh OS, too:
The Autolisp routines and data files will work on a Macintosh if someone happens to be running AutoCAD Release12 (the last version for the Mac). The only thing that you Mac users may not be able to run is the “Tab_2_Space.exe” utility... unless you have one of the Mac programs that simulate a PC. An alternative to “Tab_2_Space.exe” is a small text processor, Tex-Edit Plus, which can rapidly exchange the “tab” character for a “space” character and quickly go
through a series of text files.

Final notes:
You will find all instructions/descriptions in the “readme” files as well as in the header of the Airfoil.lsp file. Some of the readme files may not exactly reflect Macintosh AutoCAD usage.

I hope RC Soaring Digest readers will find this program useful. Now off to design that next model! We have to keep proliferating graceful flying objects y'know.
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AIRFOILS.exe (PC) includes the routine, readme file, Tab_2_Space.exe utility, and folders of airfoil coordinates. http://www.b2streamlines.com/AIRFOILS.zip

AIRFOILS (Macintosh) includes the routine, readme file, and folders of airfoil coordinates. http://www.b2streamlines.com/AIRFOILS.sit

Tex-Edit Plus can be found at http://www.tex-edit.com/

Mike's Jart controls

These photos show the silicon hindging of the ailerons and the elevator.



The control surfaces are carefully masked onto the plane and checked for the right amount of free movement, then with something hard (I used the back of the scissors) you get a good seal of the tape to the surface(you can see this in the photo.


Next you apply a bead of good quality silicone (I use the marine type clear)and you half close the control surface, now you make up a scraper from some balsa scrap with a concave shape,
as shown on the left and you smooth the silicon bead down across the hindge line.

The control surfaces are held in the central neutral position with some tape and allowed to cure.



The tape is removed and the silicon checked (add some if there are any flaws) this should give a free moving hindge which is durable but easy to repair if required.
The whole aircraft will now require final finishing , to do this I will waterpaper the exposed carbon on the leading edges , the sealed wing tips the gusset between the wing and the fuselage and the tailplane and fuselage. Then the whole thing will be carefully masked and touched up with red 2k and my airbrush. Thats better all red now, some polishing is next.

I have some vinyl and will add some stripes to the wings for visibility the plain red is a bit boring .

The radio gear goes in next .

Cheers for now

Dear Father Christmas

Please, please, wont you send me the following on Christmas day,

A full house composite Jart like the one in the photo below.

I promise I'll be good and behave on the slope when other pilots are around.

Thanking you in anticipation.

Many thanks

Stevie

MIKE SMART JART

I will put my complete JART build thread with all the never seen before photos on this build thread when time permits.
Here are a few photos in the mean time , in the build sequence.

Sorry not the plane but the tools I use to route out the foam on the control surfaces prior to a coating of resin and aerosil/cabosil

On one of the forums someone asked was it possible to build a jart in a day.

The total time on this project is about 17 hours at present , however that excludes epoxy curing

times and paint and glue curing times...so I guess it is possible to build a JART in one day

(24 hours) I would use fast setting everything but why bother ,current life has more than enough pressure.

Hope it flies as good as it looks watch this space the road ahead is clear of any obstacles.

regards

Mike