The inspiration, the philosophy, and the story behind the Jart can be found on the Jart World Web page. Well worth a visit!

Wednesday, August 24, 2011

a jart is born




After polishing the mould and applying the PVA release agent, I laid up 3 layers of 195gsm glass.
This produces a 225g fuse that is very strong. Here is the first one out, a little porky at 300g, number 2 was the winner at 225g, and they have been consistently this weight since then.

I skipped a bit of picture taking, and ended up here with little to no pictures.


Paint trim and servos to go in and then it's ready to fly.

The moulding process



Here is the moulding process I used.



After cutting out the shape of the plug into some chip board, I waxed the plug and applied PVA again. I then filled in the seam line with an epoxy/cabosil mixture from a plastic bag, kind of like an icing bag arrangement. Once cured the plug was removed and the seam sanded flat. This creates a fantastic seam.

A closeup of the seam, see, no gap :)

First layer of tooling coat on. Each coat is light and must not fillet the corners

1 Layer 160gsm glass, 6 layers 400gsm Biaxial glass and then another layer of 160gsm glass, corners were filleted with carbon tow, should have used glass tow, but it was a pain to get so I just used carbon since I had it already.

Mould just opened after second side was done. Needs a little cleanup(bit of paint came off the plug and stuck to the mould, quick scrape with a plastic scraper got rid of it without damaging the mould surface), but otherwise pretty nice surface

So it starts




After reading much about the Jart, I purchased the plans for Reed and got going.




I decided to use a high density polyester foam for the plug, The shaping was all done with a razor saw and sandpaper. This stuff sands very nicely, but what a mess!
Basic shaping done.


Fin Shaped and epoxied on. Starting to look the part now

First Layer of 160gsm glass on the plug
All sanded down and looking pointy
Canopy mould being laid up. The plug was polished 8 times with Ram wax and them buffed out. Then a layer of PVA release agent was applied with a sponge.

Monday, June 21, 2010

The New 70" AFR JART - News from Reed

Folks, I gotta tell you, I'm so happy with this thing. It's been a challenge, it's even been a little scary, but we have finally given birth to the new 70" ARF composite version of the JART design. Have a look at the YouTube channel, or just go to JARTWorld and check some of the latest posts to see video of the process and to watch the prototype fly on a mellow day out at the coast.




Use the PayPal buttons below to purchase your kit (or go to the Kits page on the website). You can use a credit card or your PayPal account, either will work. Production kits will be arriving here in a few days and I will begin inspecting and shipping immediately.



So this is how it goes: you hear that people want a rudder and flaps and a bigger version of the design and you say, "uh, ok!". To be honest I never needed all of that, I designed the plane as it was because it was all about me, me, me and I only wanted a simple plane that would fit in my car. Besides, I had to build them myself and didn't want to spend the extra time and money to fit flaps and rudder.




But here we are, 6 years later, and I find myself standing on a ridge, holding a 70" molded version of the plane with all of these bits and pieces wagging around, up down left right and all over. Just after launch I can already feel the size of the thing. Obviously I'm very familiar with the 56" wingspan, so having those big wings driving through the air is fascinating. At 72 ounces (yours should be lighter by 6 ounces or so) I'm surprised that the plane flies almost exactly like a 45 ounce standard-size JART, though I shouldn't have been. The extra size has a more than proportional affect on the airframe's efficiency so the numbers and the experience do match in this case.



For the first few minutes I flew with aileron and elevator only, just to get a feel for the handling characteristics. I certainly enjoyed it, and all of the maneuvers in the "teaser" video are with that setup. After a few minutes I decided to add flaps to the aileron movement and suddenly the plane felt more like a standard-size JART - very crisp and decisive in lateral control and overall very tight and neutral.



Then came the biggest surprise of all: the rudder. Honestly, I only added this to the design because a lot of people seemed to want it. For a 56" version I still wouldn't bother, but for this 70" version I thought the rudder might come in handy for inland "slermal" conditions where the pilot ranges out and looks for bubbles of lift away from the ridge and could use a flatter turn. It was a shock to me, though, when I pulled some rudder in on a racing turn and the plane came leaping out of the corner with unexpected energy. What I thought would be a fairly ineffective control surface is actually a very useful tool for keeping the nose straight through the turns and creating a "grippy" feeling, especially coming back from the downwind leg.



Landing this thing is just a breeze, especially if you already know how to land with flaps and/or crow. Once I got the elevator compensation figured out, those big flaps just bring the plane down to a crawl and you can land it on a dime in reasonable conditions. Being new to the flaps game it has taken me a few flights to get it dialed in, but I have a good technique now where I set the plane up behind the ridge and then pull in aileron reflex to kill some energy. Once the plane begins to settle down toward the LZ I pull the flaps in also and pilot the plane down to about waist-high where I pull the flaps out and let the plane sit right down. I missed a bunch of landings trying to learn this method and the poor plane took a lot of abuse dealing with my learning curve. But despite all of the bashing about, I never broke anything and was able to launch immediately every time - she's tough.



There will be many more flights and I'll post my impressions as we go. Can't wait to get her out to one of our DS spots to rev her up on the dark side!



Thanks

I just want to take a moment to send a special thanks out to all of you who trusted me enough to send advance payment for your JART-M70 kit. You have helped me more than you know and you have made it possible for many others to fly this cool plane. You may not have meant to be so helpful and beneficent, but you were, and I deeply appreciate it. As I've said before, there is blood money in this endeavor and that can be a scary thing, especially when things don't go exactly as planned. Now, however, we are finally enjoying what we have all worked to see.



As always, a thousand thanks to all JARTists!

Monday, January 4, 2010

EPP mini Jart




The Jart was maidened on Friday at Tamatieberg, Volksrust. It fly beautifully and for sure a keeper. It was instantly my favourite model. At 600g I was not sure if it would go in the light lift, but it climbed out and after some trimming was zooming up and down the slope face. It is not as slippery as I thought it would be and actually can land slower than I envisaged. With more wind I will add ballast.

I resized it to a 1.2m wingspan to fit easily in my cars boot. I cut the wings and fuz on my CNC from EPP. She looks very sexy Hey!

Pity the weather turned to mist and rain on Saturday , so I will have to go back soon.

Cheers
Gert
TRMC Secunda

Sunday, November 22, 2009

Double Trouble

The terrible twins are finally complete with thanks to all that contributed to the build. WELL DONE !!!
We are ready to take on the slopes of Hermanus next week. So watch out!

Sean on the left and myself on the SW Slipper face.



Flying Jarts in formation is not for the faint hearted

Filming Jarts ai'nt easy eather!

Give the file a moment & enjoy!
video

Wednesday, November 18, 2009

Baptism of fire

Yesterday, with the South Westerly wind blowing 80km/h, Sean and I decided to give the Red Bull Jart her baptism of fire and went up the Lady Slipper. The site is located on the highest peak in our area and generally works best on a South Westerly or North Easterly wind. The height above sea level usually provides ample lift.
80km/h winds are overkill to say the least!

One of a few landing attempts

Typical Jart Profile

Sean surprised that the plane was still in one piece


Wind speed indicator


Holding the camera in the wind was almost as bad as flying the plane, so look past the shakes!

video