highflyinguy

This is my first post on the sailplane forum, as I just purchased a Sig Riser kit. I have flown R/C and C/L for about 40 years but never giders. I chose the Riser for a trainer and relaxing sport flying.
After reading the Old Buzzard Soaring Book, the author did not have much good to say about balanced vertical fins which the Riser has. It is simple to modify the fin to a regular configuration. My question- Is it worth changing or is it no big thing to keep the balanced fin?
Also any opinions about adding the optional spoiler if I'm not planning spot landings
Any other suggestions about building the Riser would be greatly appreciated
Thank, Jerry Bohn

gldrgidr

The balanced fin adds drag and worse it makes it more difficult to get a decent hinge. It should be easy to modify it to eliminate the balanced fin - just glue the balance tab portion to the top of the fin. The balanced fin is more difficult to line up and tends to get caught on things, both in transport and if you happen to put the glider in a tree. I think the balanced fin is more difficult to build right.

Don't think you will need the spoilers for such a slow flyer.

The two meter Sig Riser has a flat bottom airfoil so it is a light wind flyer. So avoid flying on windy days. Something a beginner should do anyway.
Move the radio gear as far forward as possible. Hs81 servos have plenty of strength, are smaller than standard size servos, and they are easier to fit in the forward fuselage.
Cover the tail with lightweight covering material. Econokote is good but the lightest is Ultracote light transparent. The more weight you save in the tail, the less lead ballast you will need to add to the nose to balance it.

rscarawa

As far as the spoilers go, I would build them into the wing , setup the linkages and cover over them. If you ever elect to use them in the future, the will be there with little weight penalty. I would hate for you to have to build another wing just to experiment with spoilers. Is your area for landing confined? If so, the spoilers will make life easier. If not and you do not need spot landings, then you will probably not need them.

rogerflies

My Feedback: (3)

I'm concerned that you won't take the time to get the spoilers installed correctly if you just plan to cover over them. Then when you find you want them, they won't work very well.

So take the time to install them carefully. Small magnets positioned so they don't quite touch when the spoilers are closed work very well. There's nothing worse than having a floater like that float right on by the perfect landing spot out into the rough.

Build them right, and there's little downside to having them on the plane and usable.

Roger

highflyinguy

Gentelmen, Thanks for the advice, will build fin in a standard cofiguration and add/cover spoilers for future use. My landing area is a large farm owned by a soon to retire farmer who I work with as a custodian at a local school. He is getting a hoot out of learning to fly my powered R/C plane, and when I learn to fly the glider, he will get a few lessons on it. It is my plan at this time to switch over to sailplanes exclusivly.
Thanks for the replies, that is exactly the information I needed.
Jerry

BMatthews

Jerry, if you truly have no aspirations to fly this glider in contests and have lots of room to play with where you fly then you may want to save yourself the trouble of spoilers until the next glider. Granted they make for easier landings where and when you want but that is pretty much only needed for either tight areas or for contest work where you must land ON the target and ON time. And by the time you want to try your hand at contests you'll also realize that a model with a higher speed range and more slippery shape is the way to go so you can deal with higher wind velocities and search through more air for lift using the better models cruise speed. And that contest model will also be the one you WILL want to set up with proper flaps or spoilers.

But if you don't mind the extra work to put in the spoilers in this one for later then it will open up future options.

highflyinguy

Bruce, You are correct in that I don't really need the spoilers. I am going to put them on for future training and learing what their all about once I get the Riser and myself flying properly.
Then on to a more advanced plane. Gotta start somewhere, might as well learn all I can with a simple plane.
Thanks, Jerry

BMatthews

Wise decisions all around.

And welcome to model aviation's easiest to get into but at the same time more demanding facet. The glider itself is probably the ultimate trainer being easy and predictable to fly. But to learn to use it as a tool for finding and flying thermals of all sorts is probably one of the greatest ongoing challenges of any area of this great hobby.

I've always likened it to fishing. You can see the water (the air) but what it holds in store for you is invisible until you cast your lure (model) out and see what it attracts. If nothing bites in one spot you move around looking for the rich area of the day or even follow it around hour by hour. Sometimes they bite almost before your lure is in the water (model is off the line) and other times you need to scratch incessantly for a nibble at all (light air days that'll really make you sweat to stay up). For me it's that level of the unknown and the thrill of specking out from a little "nibble" just when you think all is lost that keeps me coming back for more and more. The sky, like those rivers and lakes, is a widely varied and ever changing hunting ground that can seldom be totally mastered.

Am I getting too poetic for you all?

highflyinguy

BM. Not too poetic at all, a very good anology of sailple flying. Years ago I built a R/C Buzzard Bombshell 72", and used an old OS35Max engine, once I got it to altitude, I cut the engine to idle or off, that was a hoot, the thought of searching for a thermal or even what one was never occured to me, but I did notice while the engine was off, the glides were a lot long, especially if I kept the plane around any circling birds of pray in the area, now I look forward to searching for thermals on purpose, for a new challange.
Thanks for the welcoming, it's always good to join the ranks of diffrent disciplines of flying model planes.
Jerry

gtmattz

Im not trying to jack the post here, but I'm a little new to the hobby and am not able to get a clear definition of what a balanced vertical fin is. Am I correct in my assumption that it is a fin that is like the attached drawing? (excuse my quickie mspaint drawing ;P)

BMatthews

That's right GT. The balancing part is the bit of the rudder that sticks out forward of the hinge line. In full sized aircraft it was used to provide some releif for the pilot at the control stick by balancing out part of the airstream loads. On our models it serves no purpose generally speaking and has disadvantages to it.

The only valid place I can see for these aerodynamic balance horns or tabs in in some of the super lightweight 3D models where the designers are specifying very small and light servos for moving large surfaces over huge angles. In those cases there's a case to be made for using the balance horns.

But don't get this mixed up with mass balances. Those are totally different. In that case it's about the arms with weights on them so the control surface balances closer to or at the hingeline to help avoid flutter. In some cases the mass balance is hidden inside the aerodynamic balance area so the issue can get clouded and confused. But make no mistake, they are two totally different things with different goals.

gtmattz

Thanks for the clarification. I am a little concerned now however. I just started building a Dynaflite Daydream, which has a balanced rudder. It would be no big deal, but for the fact that I built the tailfeathers before reading your post here . Im just going to work with what I have for now, if I have too much touble with it I will just have to get some more balsa and re-build it I guess.

BMatthews

We're talking probably a couple of % difference and the drag from the extra horn area really only builds at higher deflection angles. It's not that big a deal. Especially when you're learning. Trust me, until you learn to enter and exit turns truly smoothly and with inspired rudder and elevator coordination so you avoid any unwanted pitching up or down and if you're flying with just a hair's worth of travel on the Tx sticks unless you're in a thermal then you won't see a bit of difference.

kwmtrubrit

I built the Riser 100. Is this the same as yours, or do you have the 2M. Either way, take out the balanced rudder and build it as a conventional rudder. It works just fine. Build the spoilers for sure. Speed has nothing to do with this model, but if you hit a boomer of a thermal you will be glad you have them. I used hitec HS81 servo's on the spoilers connected with thin piano wire. WORKS GREAT!! Good luck.

Keith

highflyinguy

Keith, I have the 2M Riser and plan to build a coventional rudder and install the spoiler but not use it untill the plane is trimmed and I learn to fly properly first.
Thank you for the information. My future plans are to eventually build the Riser 100 and information from someone that flys either Riser is very helpful and encouraging.
Do you ever enter competition with your Riser 100?
Jerry

kwmtrubrit

Hey Jerry,

No, I never have entered a contest with the Riser or my Gentle Lady. It's not the issue of not wanting to but more a lack of contests near me. The closest I've seen is Houston (Hawks) or Alabama. Both of these are too far away for me to consider. If you need some pointers on the 100, let me know. It's a very nice plane.

Keith