Olympic II Tips?

[surfimp]

Just yesterday I placed an order for an Olympic II from Skybench Aerotech, and I'm wondering if you thermal luminaries wouldn't mind sharing some advice with me? My very first sailplane was an Olympic 650, so the Oly II has been on the list for a long time. I mainly fly slope in light lift conditions so the Oly II will be a fun plane. I also plan to get a hi start and do some real thermalling as well.

My questions are:

1. I am going to include spoilers, but what is the current thinking as to single servo with a pull system (and magnets or springs to close spoilers) versus a micro or submicro servo directly connected to each spoiler? I have a number of HS-55s, CS-10s and CS-5.4s on hand so the servos are not a problem...is this a preferable way to go, assuming you've already got the servos?

2. I know the Skybench kit is improved over the old Airtronics kit, but are there any specific tips for building it? This will be my first all wood plane in a long, long time, so any suggestions are much appreciated. I'll probably go with CA because I'm a bit impatient, but I'd love to hear arguments in favor of slower setting glue if there are some purists who would care to opine.

3. Covering. Monokote? Something else? I mainly deal with packing tape and Solartex so I'm totally out of the loop as far as thermalizer coverings go. I have a 21st Century iron so I think I'm pretty good to go, but any suggestions most appreciated.

4. Ballast. I know the 10% flat bottom foil on the Oly II doesn't provide for best penetration, but what about adding ballast? I happen to have access to a bunch of lead that I am well accustomed to melting down into ballast slugs and nose weight for my slopers, so is this something I should consider to improve the upwind performance of my Oly II, especially as I intend to fly it on the slope at least part of the time? Suggestions for reinforcing fuse to take ballast?

OK, that's all for now. Any suggestions most appreciated! :)

Steve

[Ollie]

The Olympic III is a great light air soarer but it does have a few limitations.

The open bay wing structure is not inherently torsionally rigid. It can flutter in torsion at high speeds. To minimize this speed limitation some you should use the stiffest covering film which is Monocoat and carefully attach it to every rib, top and bottom as well as the leading an trailing edges. Also, all wrinkles should be completely removed and the covering well tightened. A heavy leading edge material and light trailing edge material will also help to raise the flutter speed some.

Don't ballast the Olympic II so heavily that you are tempted to exceed the flutter speed.

The best arangement for spoilers (assuming a programmable transmitter) is to put a micro servo under each spoiler and rigidly couple the spolers to the servo. Assign each spoiler servo to a different channel and mix the channels together. Then you will have the ability to coordinate the open and closed positions of the spoilers so that the servos are not under load when closed and open the same amount. This is much easier to do with transmitter programming than with mechanical adjustments of any kind.

It is best to locate the spoilers well aft of the spar where the boundary layer is thicker. Say at 55 or 60% of the wing chord. That way any imperfections or gaps in the wing contour will have less detrimental affect when the spoilers are closed. The less gap around the spoilers the better as long as they don't rub.Mount the servos as far forward in the wing as you can in order to improve flutter speed. The object is to come as close as you can to mass balancing the wing about the spar.

There are four advantages of aliphatic (yellow carpenters) glue over CA. Its joints are more resilient so that it will absorb more energy without failing. It is much less likely to trigger an alergic reaction, It is easier to sand. It costs less.

The tow hook mount is a good strong, hard point in the fuselage. If you use sheet lead for balast, you can drill a hole in the lead to fit over an extended tow hook thread in the fuselage and tie the lead down with a wing nut. Be sure that the position of the ballast doesn't shift the CG.

Use enough rubber bands to hold the wing down in high G maneuvers.

Be conservative and keep the air speed under about three times the stalling speed (13MPH) of the unbalasted model and you won't have wing flutter problems. That would be a red line of 39 MPH if you have taken all measures to torsionally stiffen the wing. I wouldn't fly it in winds over about 20 MPH.

[kingbee]

Great choice for a floater surfimp. Prepare yourself for some tranquil flying!

Ollie's advice is right on as usual. I'd add two other things: First, reduce the built-in decalage by about half. Do this by trimming the area where the stablizer sits on the fuselage, about 1/8" at the TE of the stab, tapering to nothing at the LE of the stab. Second, eliminate the "balanced rudder" design by making the hinge line straight all the way to the top.

Both these mods will improve the "high speed" (well, high speed for an Oly) handling.

Also, it's gonna handle like a pig compared to what you've been flying so give yourself some real estate to land the sucker.

Cheers,
Dave

[surfimp]

Thanks Dave and Ollie! As for sloping, our typical conditions at the one site where I'd be realistically flying a glider like this are about 7-12mph...so, light lift for sure! Normally I fly my Weasel but it's always nice to have something different, and I suspect the Oly II will fly in almost no wind at all. When we have really dead days at Ellwood, the only things that fly are the large "old school" floaters.

Thanks for the tips! I don't plan to fly this plane in such a way that I'll flutter it, but I'll build it as well as I can to prevent it.

As for the spoilers, what's a good spanwise dimension? I know on the Skybench site, there's a recommendation that they don't need to be particularly large, spanwise or chordwise, to be effective. Also, I'm a bit unclear as to how to get the microservos underneath the spoilers so that they are rigidly coupled to the surface, but still in front of the spar for the mass balancing. Should I use some kind of flexible pushrod system?

Thanks again for the help, it is most appreciated!

Steve

[shoe]

Originally posted by surfimp
Also, I'm a bit unclear as to how to get the microservos underneath the spoilers so that they are rigidly coupled to the surface, but still in front of the spar for the mass balancing. Should I use some kind of flexible pushrod system?

Thanks again for the help, it is most appreciated!

Steve

Check out the way Jim Bacus did his AVA spoiler setup, very clean. Here's the URL
http://www.jimbacus.net/blog/2004/images/avaspoilertop.jpg
http://www.jimbacus.net

[Ollie]

You could mount the spoiler servo in front of the spar and run a rigid metal or carbon rod through a small (3/32) diameter hole in the shear web. As long as the hole is centered from top to bottom it won't cause any structural weakness to speak of. Spoilers cause drag two ways first by their frontal area and second by the vortices at each end of the spoiler. The frontal area drag goes up as the square of the airspeed and th extra induced drag goes up as the square of the coefficient of lift. This covers both ends of the speed range. As long as the spoilers are at least as long as a wing chord they will work well, especially at slow speeds. The maximum glide ratio of the Olympic II isn't all that high so you don't need exceptionally big ones.

Another thing to note about spoilers is that they reduce the maximum lift coefficient of the wing and that increases the stalling speed of the model. Spoilers will slow a fast flying model but, the minimum speed will be higher than without spoilers deployed.

[charlie tasto]

Hi Surfimp, my Oly II I followed the plans pretty closely and it flys great. I did place a single gusset at each rib and trailing edge intersection, and I tapered the nose of the fuselage compared to whats shown on the plans. To make up for the reduction of material at the nose I glassed the front end back to where the trailing edge of the wing sits. With the glass front end this thing can really take a beating.
Terrific kit!

Charlie

[charlie tasto]

Oh yeah, one more thing...I used CA glue for everthing and then went over EVERY joint with titebond. The titebond forms a tiny gusset everywhere and really makes durable frame without any noticeable wieght gain. Oh and forget those curled up tips shown on the plans, glue on the soft balsa blocks and bevel up 45 degrees.

Charlie

[surfimp]

Thanks for all the good info, gentlemen! I really appreciate it! I think that answers all my questions for now, I will save the rest for when I get to work on the plane. Many thanks!

Steve

[surfimp]

Kit arrived today, well packed and seemingly in perfect order. Man, i'd forgotten what a box o' balsa looked like! Looking forward to the project, it will surely be a learning experience! :)

Steve

[TLyttle]

My Oly11 went for ~13 years before I sold it: VERY reliable model. I D-tubed the leading edge and capstripped the back of the wing, that put paid to any flutter; I could stand it on its nose and not overspeed the wing. I also replaced the fuse sides with 1/16 ply with no monstrous increase in weight, and used pine for the noseblock (you have to watch me land to understand these mods!) Even with all that, she would keep flying while all the 2m and all-singing, all-dancing standard class models would drop right through where I was flying...

I guarantee you, you will be happy with that model.

[surfimp]

Thanks TLyttle! I'm getting a bunch of great suggestions, they're going to be awesome once I get to building my plane.

Steve

[SpiritQuest]

Every preceding suggestion has been accurate. I built mine in '79 and accidently flew it out of sight in 2001. 22 years! It stays up long after all the others can't. My only suggestion would be to add a "Philips entry" on the leading edge. This was suggested to me for my Super Questor kit that I was lucky enough to find. I had/built both Airtronics kits in '79. Loved both of them. Building an Airtronics kit back then was akin to working with a masterpiece. That kind of quality was unheard of before that. I really remember the parts fit was was like working with a Swiss watch. They slide together with absolute precision. I feel like a lucky man to have original Airtronics kits of BOTH still unbuilt...waiting for my loving caress. He he, as a sidebar about mine, I was told that putting the tinted canopy on mine was an abomination, heresy, sacrilegious! I still thought it was pretty cool. Still have never seen one like mine. I guess thats why I did it.

[surfimp]

Sweet, thanks SpiritQuest! Does the Philips entry help penetration? Any other details? I'm somewhat ashamed to admit that I don't know much about a Philips entry, nor how exactly to apply one to this model (or any other).

Your Oly II looks cool, but I think I'll stick with the "boxy but good" look for mine. No offense! :D

Steve

[SpiritQuest]

Try this link for more info and/or do a google search on "Phillips entry" or Oly II mods. Skybench also has a good deal of info and testimonials. No offense taken. I want to build my next one the same way and still be the only one!http://www.charlesriverrc.org/articles/kitmods/peteyoung_olympiciihintstips.htm

[surfimp]

Thank you! :)

Steve