Louis9624

I have a Great Planes Spirit.I like to modifythings. I just don't have a way around it.So, back into rc gliders after a 20 year gap, so much has changed, I haven't exactly figured out what to pursue. And after my third flight, slope soaring isstill my favorite. Withenough wind,the instuctions say adding weight is okay,but Ilike slow landing speeds. So, to make the best of both worlds, I figured out how to atach a door in the bottom of the fusalogewhich when opened, a bay inside storing 3/16" pebbles will empty and the plane has become light and easy to land. I am using a standard Hitech servo forward of the bay. The door is hinged from the front and is about 5 inches long. The bay is directly at the center of gravity. A little fuseloge reinforcement is needed around the bay. I am about halfway done.I would like to hear if anyone has tried this before. I'll postsome pictures and flight results soon.

Lnewqban

Full size gliders accomplish the same with water tanks and a valve.

skylark-flier

Outstanding idea! If I might, instead of loose stones do it with an actual box container with measured weights. You could have several different weights for different wind conditions on the slope and still drop the thing - but as a single piece and "standardized" so the plane flies the same way with the same weight.

BTW, welcome back to gliders!!

(me & my Spirit-100& BoT)

cfircav8r

My Feedback: (1)

Please be careful where you dump the weights. Even small objects can cause damage (maybe no real injury but could chip a windshield or dent a hood) when dropped from a plane, but as long as your careful it should work great. If your using pebbles you might consider sand, sand would provide more weight by volume and be safer.

BMatthews

A hearty +1 on the sand. It'll "flow" better through the door as well. And it SHOULD be more dense than a similar volume of pebbles. But measure it to check. Either way dropping some sand will be far less dangerous to people and property. Yeah, I know it's a remote slope site. But if you mistime a turn or the dump it could well direct the payload onto the flight line or parking area.

I honestly don't know of anyone first hand that's done this. But the idea is very valid. My only thought, with a whole lofty ONE DAY of slope soaring experience is that sometimes it's hard to fight through the back rotor or surface tubulence to plop the model down in the right spot. Waiting until you're within 5 to 10 feet high from touch down before flicking the dump switch might not be a bad idea. The extra weight and speed should keep the model more controllable right to near the end. But by dumping the ballast before touchdown you'll still have the reduced inertia needed to land slower and do less damage in the event of a less than ideal "arrival".

Of course much depends on the conditions of your slope site. You're in the best position to know the best time to dump the ballast.

stick man

I think this is a pretty good idea, which gave me another idea- what if you attached a lead weight to a long servo arminside the fuse? that wayyou could adjust the position of the weight fore and aft to find the sweet spot? just a thought.

Louis9624

I am almost finnished and there are a few problems. I originaly wanted sand but I think it would seep out of the smallest holes. Thereare so many things to consider, I never thought it would be so complicated, but it just drives me harder. First off, the spirit just does not have enough room to fit a decent amount of pebbles. There is a servo in the way, that cost alot of space. I filled the bay with pebbles and opened the door, they fell out really quick. But then the door would not close; there were pebbles jaming it at the hinges. Now, of course, after I built it, I have a much better idea about everything. The lever from the door exits the fuselage and the pushrod bends in after it. I could put it inside but that would reduce the area for the sand. There just is not enough room to really set it up the way I like it. My next glider will be much better. It will be able to drop sand, without worring about sticking in the hinges. It will have really cushy foam around the entire door. It will be tall because the servo will not be on top of the bay, and the arm andpushrod with be completely internal. So, for now, I really like the idea of droppinga lead weight.That is something I think my current setup can do very well. It will have a neon greenripstop nylon parachute, so It will be easy to find. The lead fits easy in the small bay, I willglue foam in the bay to keep it from moving around. I am going to fly it tommorrow, wish me luck.

cfircav8r

My Feedback: (1)

Good idea with the parachute, that should reduce the danger issue. Let us know how it works out.

Louis9624

I had great success todaywith the lead tied to a streamer. The parachute did not fit into the bay.Once again, my next plane will fit a large parachute. There was not much wind, I had one succesful flight, which ended in a bit of a crash. Not to bad. A little glue fixed it. Second flight, although still not much wind, I had the weight in the glider this time. I was waiting for a couple hours for the wind to change direction and strengthen.The wind did this sometimes but it never held. I got tired of waiting and threw it as hard as I could. It liked to go down. After a few times across the bowl, (near Livermore California) and it was losing 20 ft. altitude every time.I dropped the lead. It fell out and the streamer wipped the air for a second. I think this noise would turn heads (which I think is good; more people will see where it went) Suddenly the wings were lifing the glider up, but it was too late. It crashed into a tree, then fell onto a barbed wire fence, and then onto the ground. Oh, I was thinking about what plane to buy next. When I got to it, the wing had came off, but no damage. The fuselage , no damage. I must have got lucky, or that plane holds up very well.A Great Planes Spirit. I simply need a little more wind. The parachute I made was out of ripstop nylon. Ripstop nylon comes in many different styles, weights. I need to find the lightest one, I think it is .05 oz.. Even at this weight it is overbuilt. Does anyone know of a lighter material? The lighter it is the larger I can make the parachute. My next plane will have more space but I don't know when or which plane that might be.

cfircav8r

My Feedback: (1)

If you like the Spirit try the Spirit 100, I have one with flaps and ailerons and had a blast flying it out at Torrey Pines (SoCal) in the early 90's. It has a decent sized ballast box and is very sturdy as well, I once cartwheeled it down the cliff and only had to re-glue the vertical.

BMatthews

Lead is just too expensive both to buy and in terms of time needed to form to fit the model and frankly just too dangerous to be dropping around the area. I'd stick with pebbles or sand or just learn to land with the higher wing loading.

wyowindworks

What is the wing loading of the glider when its fully ballasted? Most slope gliders have a wing loading of 15 oz/sq. ft. or better. If you are under that then you really just need more practice on your landings.....or a plane that is designed specifically for slope soaring. Many slope gliders are above 30 oz/sq. ft. and land fully ballasted. Most people only use a Spirit type glider for when the lift is very light. Here the ballast isn't needed.

Adam

Louis9624

I think sand is by far the best method of dropping balast. The bay on my next plane wil be larger and have soft foam around it, with external hinges. The spirit instructions suggest 6 to 8 oz. ballast should work fine, and some more canbe added if needed. My lead weight is 9.6 oz. The flying zone werewhere I fly is relatively safe for a lead weight to be dropped.But what if I accidently flipped the switch, that makes me cautious. I amgoing to switch to sand one way or another.Thanks for your concern,and I think this is a great idea. It needes improvement, especiallyfor safety reasons. That would ruinthe whole day andmaybe worse.

BMatthews

Yeah but 6 to 8 is the sort of ballast you would install for some extra penetration on a somewhat windy thermal day. To get a model to fly well on even a moderate wind slope day you want to load it up a lot more than that.

Just looking at the GP website about the Spirit shows that it's got 676 sq inches of area and with a published 30 oz weight it's flying at 6.5 oz/sq ft. To get the Spirit to fly on a slope in anything other than light to moderately light winds you'll want to increase the wing loading to somewhere around 8 to 10 oz/sq ft. To go up to 8 from 6.5 will need (676/144) x 1.5 = 7 oz. That's not bad and quite doable with sand or small pebbles. But to get up to 10 if the model is being tossed around would require 11.7 oz. That's going to need a fairly big box for sand or pebbles.

If you're new to slope flying you are likely going to find that if you need to ballast to 10 oz/sq ft that you won't want to dump the whole thing for landing. Some speed is still needed to aid in punching through the back rotor turbulence. You may find that 7'ish oz of dumpable ballast combined with units of 4, 6 and 8 oz of fixed lead ballast works out better. That'll let you get rid of the 7 oz but still retain some fixed ballast.

In the end result you're soon going to find that once you get to where you need to add 10 or more oz of ballast that the Spirit just isn't the model to use though. At that point you'd be far better off and get more fun out of a proper slope model that uses ailerons and elevator and is more solidly built to deal with the nature of slope flying... and landing.

Louis9624

About the aileron with no dyhedral wings, or rudder, I have seen lately, they look easier to land because the wing keeps it level through the whole grounding part of the landing.  I have trouble with the rudder planes landing.  No matter how hard I try, one wing will overpower the other and spin around and turn upside down. I think it's because of all the dyhedral in the wings.  I have increased the size of the rudder, and elevater, like a lot of poeple do with this plane. It flys better but does not make much difference landing.  Almost all planes where I fly are ailerons, with straight wings. They sometimes spin around, but the wind does not go under the plane.  Is there a trick I don't know about?  I don'tn want to gradually ruin my glider.

BMatthews

There's no trick. You're just finding out that turbulence affects polyhedral wings more than it does flat aileron wings. It's just the nature of the beast.

Remember that with a rudder/polyhedral model that the rudder yaws the model which pushes one wing ahead and the other behind. This skewing of the wing in connection with the strong dihedral alters the angle of attack of the wings to increase the AoA on the leading wing and reduce it on the trailing wing. The result is a strong rolling action which banks the model. But this same dihedral will also roll the model if you fly it into a turbulent area where side gusts are hitting the model. The side gusts act on the model as if it is yawed and so the model rolls in response to these. A flat aileron wing also sees the same gusts but only responds to the vertical transients instead of BOTH the vertical and horizontal transients. So while it's still tossed around the control and recovery from the disturbances is easier to perform with a flat wing model. Which is why you don't see a lot of true slope soaring models with lots of dihedral, let alone with polyhedral.

Louis9624

Thanks for all the info, It sounds like it takes time to land corectly. I couldn't resist, I went and put flaps on the thing.  Large ones too, finnished in one night.  It didn't work at all. The wingtips were at a negative angle. They weren't doing what dihedral wings do: stabilize to an upright attittude.  So, I thought, why not put flaps on  the wing tips as well as the inner wing has.  I hooked them together with a small rod and fiberglass. It works now. I thought I might have wingtip stall but I didn't. The glider lands now at maybe half the speed as before, with the sand ballast I will now have a fast plane in strong wind, with the ability to dump weight, flaps down and very low landing speed.

wyowindworks

Here is another way to do it:

http://vimeo.com/17565057