Vale Gliders
|
|
Span : 60"
Wing section : D7016 root blending to D6515 at the tip
Root : 200mm
Tip : 110mm
Weight : 42ozs
Wing loading : 15.5ozs sq ft
Length : 960mm
Ballast : 28ozs
I designed the Nitro to be a fast but adaptable plane, and intended it to fall half way between the Dynamite and the Jart, kind of like a half ballasted 60 pylon racer, and tough, very tough, to take some extreme landing action. In reality, it is not a new design, the planform being identical to the flitter and dynamite, the differences being the cosmetic change of fuse shape to cope with my desire for a ballast tube, a much heavier layup, and a change of airfoil. The fuselage is fairly adaptable, and would suit wingspans from 40" up to 68", even a plank wing maybe, so will be trying a few different versions out over the year to come, the larger span with four servo's particularly appeals. It is neat when you can get more than one type of plane out of the same mold, it adds to its versatility and makes all that work you have put in a little more worthwhile. With trips to the coast and maybe a visit of the Welsh mountains mapped out for this year I wanted a plane to cope with lots conditions, but mainly fast, not acrobatic or fast in a pylon racing way but fast in a stall turn climb and dive way, which is what I understand Don Ayers designed his foils to do, and have gone for a medium thickness at 7% and a medium camber at 1.6% hence the 7016 numeration. I am not really sure just how accurate vac bagged wings are, but imagine that one swipe with the sandpaper may give you a different foil than you intended, so at least with this foil I will not be sanding out any intricate concave complexities as there aren't any, all I can do is alter the thickness or percent camber slightly, so should end up with a foil pretty close to the one intended. Lots of other airfoils will fit also, so plenty of scope for experimentation. check out the Don Ayers foils for yourself.
I made the wing for this plane some time ago, just before I bagged my first Jart wing, as it was a test of a technique I thought up to add carbon spars without cutting the foam cores about, ie/ less to go wrong when you have to stick them back together and seems quite simple to carry out, just sand some channels on both sides of the wing to suit your carbon spar thickness, then glue them in on one side. When cured flip the wing over and cut out a groove with hacksaw blades glued together, fill with end grain balsa, saturate with epoxy and stick the other carbon spars on top. Having a tapered main spar and a sub spar made this wing really strong, and that was before laying up any wingskins, so made the Jart wings the same but left out the sub spar, and they have survived some horrendous crashes that have broken the fuselage several times yet only have a couple of small cracks in them, definitely tough wings. With 6oz twill bias cut carbon and a 2oz glass veil the Nitro wings weighs in at 15ozs and are very stiff for their weight. Paint was applied to the mylar, its not as good as it looks, don't have much success using masking tape on mylars, so in future will do any masking work after the bagging process.
The fuslage is again very tough, but only has carbon around the wing saddle area as I am fed up with carbon induced glitching. It has a 32oz glass layup and my first one weighed 12 ozs, have done a few more layups from the molds, but with an added gelcoat to avoid all that filling and sanding, they weigh a couple of ounces more at 14ozs. I expect my first one weighs about the same now its painted and filled.
V-tail is 1/4" balsa sanded to an aerofoil shape and bagged with 6oz twill carbon and 2 oz glass veil, cant get on with foam v-tails, they develop a droop in the vac bag, just one of those things I need to practice as it is just a technique issue. Using balsa as the core material does make them a fair bit stronger but more work is involved.
Putting it all together was fairly uneventful, the only challenge being what type of ballast carrying arrangement and how to fit it. Tried a few different mock setups and settled on a long tube made from glass rolled round some 16mm chrome pipe, and bodged up a temporary mold from foam and tape to form a loading chamber, it was all glued into the fuse using epoxy and a filleting mix to bulk it up. then a hole cut on the underside of the nose boat to access it. Works a treat, except too much filler make it higher than I intended causing me to go for one servo in the fuse rather than rudder elevator as I intended, still, know what to do on the next one, and will make up a proper mold for the front end of the ballast tube. I have balanced her out at 76mm from the leading edge, (same planform as the Dynamite remember so c of g should be the same too), and only needed 2ozs of lead in the nose and a tightly fitting AA 4cell battery after a bit of jiggery pokery, quite chuffed with that, the extra nose length paid off. There is an sd200 servo for the elevator, linked up with a carbon tube and ball links. Ailerons have 2 futaba s3150`s, my first digital servo`s. Just setting them up I could tell the difference, very smooth and accurate. Now just need the wind to blow.
Wahhhhoo
It took a few days but the wind finally obliged, not knowing what to expect, first launch was a little nervy, but was fairly confident the 15mph wind would be enough once I was away from the slope and up to speed. It ended up being a very gentle affair, no trim required, thats a first for me, it just flew, guess my bench setup is getting better. It rose a little on launch then slowly moved foward picking up speed as I dove her down and then up into a stall turn, nice height. Flew her around for a few minutes doing big loops and stall turns, its a very fast plane, and climbs really high with all that retained energy, I love it. Landings are gonna be interesting, thinking ahead I had left the elevator/ spoileron channel open on my radio to adjust in flight, (never tried this before), so started practicing landing approaches and fly bys, soon had it all but hovering and landing very gently and under control all the way to touch down, wow. I have never been able to do this and had given up on spoilerons, going for fast flat landings. Tried the same tecnique on the aileron differential next, as that is another thing I have always struggled with, axial rolls, mine always being barrely, requiring very precise elevator control which has been a struggle to master as it happens so fast. Initially the turns were as I expected lots of speed loss when tight, so large sweeping turns to retain energy being a better choice. As I got the differential dialled in, the turns got better and better, up to the point where it almost seems to almost bounce out of a 180 turn with the same energy it went in with, wasn't expecting that! The wind was picking up, though she was coping well with it , I decided to add some ballast, put in 4 slugs to bring the loading up to 19.5oz sq ft, the auw being around 52ozs, and was probably not enough in the 20mph breeze, she could carry more. Certainly took the speed up a notch though. The only plane I have to compare it with is the Jart, being similar weight but a few inches less wingspan. No chance the Jart would keep up with this plane, it is significantly faster and more agile, yes even the rolls, had to tone them down to 70% throw they were so mad. The Jart has a presence in the air though, and retains its number 1 spot in my slope arsenal. With the Nitro carrying ballast I thought the landings might suffer, but as the wind had increased, it still gently hovered down, couldn't land a 4 sevo equiped wing much smoother than that. Overall, very impressed with this plane and its chosen airfoil, no tip stalling , very fast, and far more agile than I had expected, very confident it will cope with sub 10mph winds if the speed is kept up, I love it. Wonder how it will go with all the ballast in?
Update 07/03/07
Have now had a few hours flying time on the Nitro, and it is currently my most flown plane, though I am sure that will change as summer approaches and the wind disappears. The amount of energy it retains when flown smoothly really impresses me, even better when ballasted, but have not tried the full lead compliment yet. The airfoil doesn't seem to like any thermal camber unless it is actually in a thermal, just makes it dragy and slow, but then I never expected it to be much of a thermaler.
Rob has combined a Nitro fuse with Shooting Star wing and v-tail, and called this cocktail Nitro-star. Looks sweet as you can see from the picture, nice neat radio installation and flies very well to boot.
Rob's Nitro-star 8.64mb mpeg.4
Also have some video of the Nitro in action, same hill different day, and carrying 4 slugs of ballast, bringing the auw to 52ozs, and the wingloading to 19.5ozs sqft.
Nitro 1 17.7mb. mpeg.4
28/01/08
Thought I would write an update on this plane as I have been flying it for well over a year now. I take it with me to the slope almost every time so I must like it. It is a real energy plane, with ballast and a good wind it will stall turn up to the limit of my eyesight, and enormous big loops, fun fun fun. Fully loaded up its an animal but 67ozs is stressing the airframe a bit on landings, have come to the conclusion that 50% of the flying all up weight is about enough ballast, any more and the structure seems to suffer, even with gentle landings, so have now got a rule of thumb to adopt to my other planes.
It has survived a lot of abuse over the year, taking nose first stick it in the ground landings no problem, I guess if the wingtip hit first it might be a different story, but I always manage to keep the wings level near the ground, well, most of the time. Flying it this weekend, gave it a pylon turn workout, pulling harder and harder turns, was amazed at how hard you can pull, of course it flicked in the end, shame I was 15 or 20 ft from the ground as it ended my session, but a good lesson learnt, got to really crank that elevator. Back in the workshop I just needed to re-attach the v-tail, nothing else, amazing for a high speed flick type crash, nose cone took some digging out of the ground though.
This site was last updated 01/28/08