Post by sean on Aug 20, 2007 16:34:05 GMT 10
After getting home from yesterday's rain-soaked DSing my Bat was a mess. Large sections of covering torn and lifting in a number of places, elevons broken from weeks back, elevon hinges torn, broken fin..... While it looked OK from a distance there was too much wrong with it to patch up once again. So rather impulsively I attacked the covering and had it all off in a few minutes. Then I stood back and looked at the mess. Oh oh, what have I done! That's not going to be easy to fix! So, it's rebuild number four for this particular Bat!
What have I done??
Getting the strapping tape off proved very hard, the goop made it stick ridiculously well and in some places the strapping tape took chunks of foam with it. Good evidence that goop really does it's job!
Under the covering the Bat is very ugly. It's hard to believe it was such a handy little DSer because it just wasn't built for it! Successive rebuilds mean everything's positioned funny, the extra spars were all crammed in wherever they'd fit, there's no room for a good ballast bay etc. I thought hard about whether it's worth rebuiilding, but I think it is, it'll be much less work than starting from scratch and will cost nothing as I'll use all existing materials, plus the Bat's proven to be a very good DS basher, ideal when the conditions are too ugly for something fancier.
With the covering and strapping tape off it's amazing how easy it is to twist and bend the wing, it's not very stiff at all so the flutter it was getting DSing isn't any wonder. The rebuild will concentrate on making it better for DSing. The list of mods includes:
* Extra spars for spanwise and torsional stiffness.
* More strapping tape this time, layed at a 45 deg bias to improve torsional stiffness.
* stiffer, narrower elevons that don't extend to the tip. Should be much less susceptible to flutter plus more crash resistant.
* A better ballast bay. I want to be able to get it over the 1kg mark to improve DS stability/energy retention.
* A bluto-esqe fin, like the one Andrew leant me for a couple of weeks. It proved much better for DSing than the orginal more upright fin.
More weight means it's gonna lose its all round abilites but that's OK, and I'm not going to try and make this one perfect as it's going to have a hard life when done!
What have I done??
Getting the strapping tape off proved very hard, the goop made it stick ridiculously well and in some places the strapping tape took chunks of foam with it. Good evidence that goop really does it's job!
Under the covering the Bat is very ugly. It's hard to believe it was such a handy little DSer because it just wasn't built for it! Successive rebuilds mean everything's positioned funny, the extra spars were all crammed in wherever they'd fit, there's no room for a good ballast bay etc. I thought hard about whether it's worth rebuiilding, but I think it is, it'll be much less work than starting from scratch and will cost nothing as I'll use all existing materials, plus the Bat's proven to be a very good DS basher, ideal when the conditions are too ugly for something fancier.
With the covering and strapping tape off it's amazing how easy it is to twist and bend the wing, it's not very stiff at all so the flutter it was getting DSing isn't any wonder. The rebuild will concentrate on making it better for DSing. The list of mods includes:
* Extra spars for spanwise and torsional stiffness.
* More strapping tape this time, layed at a 45 deg bias to improve torsional stiffness.
* stiffer, narrower elevons that don't extend to the tip. Should be much less susceptible to flutter plus more crash resistant.
* A better ballast bay. I want to be able to get it over the 1kg mark to improve DS stability/energy retention.
* A bluto-esqe fin, like the one Andrew leant me for a couple of weeks. It proved much better for DSing than the orginal more upright fin.
More weight means it's gonna lose its all round abilites but that's OK, and I'm not going to try and make this one perfect as it's going to have a hard life when done!
). Started taping lead to the nose and after many more disastrous tumbling flights finally got it going OK with about 100g taped to the nose. I'd set the CG at 22% MAC, turns out on this plane it needs to be about 19%. The lift was marginal and it didn't like that one bit, kept tip stalling, spinning etc. AUW is now 1KG and this combined with very small tip chord and low slope lift meant tip stalls were the order of the day, on one occasion, before the CG was properly sorted, it spun all the way to the bottom of the valley resisting my attempts to recover, and it's a long walk back from down there 
! By the end of the day it wasn't flying too badly but I'll have to wait for better lift before I can get it properly sorted. Looks like it's going to be a big air machine only.
.
The fixed tips should be stronger with any end impacts/cartwheels. Did you put them in neutral, or with a bit of reflex?