Monday, June 29, 2015

Watching the Super RC Sailplanes Saturday

Last Saturday June 27, 2015 the weather forecast looked very favorable for a radio control sailplane contest hosted by The Minnesota Radio Control Soaring Society so I decided to compete even though I did not have a very high performance sailplane available to compete with. It is always fun flying model aircraft with other people having a common interest and I wanted to take pictures with a new digital camera that I had recently purchased.  

The unlimited class of sailplanes in which the majority of the pilots flew; were very large model sailplanes constructed with the latest composite materials. There was also a RES class which stands for Rudder – Elevator – Spoilers most were partially built of balsa wood. I flew my trusty 2-meter wood Gentle Lady glider which has only rudder and elevator control, normally this glider flies well for me when the wind was light like on Saturday but after the very last flight I discovered the stabilizer of the glider was broken in several places.

Watching the sophisticated unlimited sailplanes was a big reason why I attended this contest. A typical sailplane of this type might have a wingspan of over 12 feet yet only weigh around 4 pounds.  The pilot pulls the glider up hundreds of feet high with an electric winch which puts a huge force on the center section of the wing.  For the contest the goal was a task of flying for 10 minutes from the launch and landing as close as possible to a spot marked with a landing tape.  In some of the rounds staying up with these efficient sailplanes was easy in thermal air currents for 10 minutes but at times it was difficult for everyone.  At times several airplanes could be seen circling in the same general area as that was where the thermal lift appeared to be. 

Following the pack was not always the best strategy as I remember on one round all the gliders had landed while Tim had found thermal lift in another section of the sky and continued to circle upwards.  In another round gliders were way downwind behind a tree line at a rather low altitude, it appeared Brad just barely cleared a tree in coming back to the landing area. The large size of these sailplanes makes it possible to see farther away which is a real advantage.  Larger airplanes are more efficient aerodynamically also.   

The sod field we flew from had some neighbors that were rather close who seemed really interested in what we were doing. At least a couple of the club members did a really good job of explaining just what the hobby is about when they came out to watch. 

Bill Kuhl

Monday, June 22, 2015

Slope Soaring Heavy 2 Meter Glider on Small Slope

Adapting model airplanes and available flying sites I have available has been a challenge that I have been pursuing lately, particularly flying from small slopes with radio control gliders. I have been flying smaller lightweight gliders mainly because of less cost, available as a RTF, maneuver in small spaces, and in most crashes there is no damage.

Side View Shadow 2 Meter Glider

Several years ago I purchased a heavy 2 meter glider used that looked to be aerodynamically clean. The entire stabilizer pivoted with no external controls and the rudder horn was enclosed as well, only control horns and short pushrods were exposed for the ailerons and flaps.  My thought was to fly the glider from a big slope but when I finally installed radio gear I thermal soared the glider and found at times it climbed in thermals pretty well. Because of some battery issues it gained additional weight through repairs and it was already over 3 pounds. 

Super Scooter Foam Glider and Shadow

Last Friday evening there was a south wind forecasted at 9 mph. I thought this would be a good chance to try slope soaring the Shadow 2 meter from a relatively small slope.  The grass is really tall on the slope to cushion hard landings and there is plenty of open area with no obstacles to hit.  I launched the Shadow and it was flying but not very high.

Shadow Front View

After a couple of short flights to get the feel of the glider I made a couple of flights that were probably 5 minutes long. I had to keep in a pretty narrow lift zone and turn very smooth but it would stay up. I thought doing a comparison with the foam Super Scooter would be interesting. Repeatedly I launched the Super Scooter after the first turn on the slope the foam glider had landed on the slope. Switched back to the Shadow and it was again staying aloft.  Saturday I returned to this slope but was too late for the south wind and the Shadow would not stay up. Traveled to a larger slope for SW wind and had some flying with the Shadow but the wind was switching to almost west. 

Hand Launch Comparison

When I was first flying the Shadow 2 meter I had done a hand launch comparison with my Gentle Lady wood glider.  Consistently the Shadow glided much farther down the field. A hard concept for people including myself to comprehend is the L/D (lift over drag) is not related to weight. The heavier glider will just glide faster down the glide slope. One factor related to the L/D is the wing aspect ratio, the longer wing with narrow chord has less drag. No doubt a stiffer none-foam air frame makes for higher efficiency as well.

Bill Kuhl


My Small Slope Soaring Webpage

Comparing Two 2-Meter Gliders

Tuesday, June 16, 2015

Guillow’s PC-6 Porter Review

Lately I have been thinking about what really holds my interest in the model aviation hobby, there are several types of model airplanes but it comes down to a couple of factors; the challenge of getting good flights and the flying sites I have available. Unlike many people that enjoy only free flight or only radio control, I enjoy certain aspects of both. My radio control flying is mainly gliders which have the constant challenge of staying airborne by flying in air that is lifted by thermals or deflected up from a slope. 

For free flight airplanes I am normally restricted to small flying sites so I normally fly cheaper rubber powered sport models that I can stand to lose or fly scale-like rubber models that for my skill level stay within the confines of a smaller flying site. I have built these same types of models with electric RC but after they are flying well, I quickly lose interest. Flying the fragile free flight model powered by strands of rubber without control just seems more satisfying. 

Guillow's PC-6 Porter in Flight

Guillow's DHC-2 Beaver Electric RC 

The last scale-like rubber free flight model I completed was the Guillow’s PC-6 Porter which is modeled after a Swiss utility plane designed in 1959. I know this by reading the review article by accomplished free flight modeler Don DeLoach in the October 2013 Model Aviation magazine. In the article he gives some tips and rates the kit fairly high even in regards to the weight of the balsa which in older Guillow kits could be very heavy. This is also a laser-cut kit and many of the pieces are interlocking. You do have to be careful in fitting the pieces together as I pushed too hard on some fuselage pieces and broke several pieces.

Another reason for me selecting this particular kit was the full-size airplane has a rather long nose which should make balancing the airplane easier without adding weight in the nose. I left out some of the stringers in the fuselage to reduce the weight and covered with Esaki tissue instead of the supplied tissue. As of yet I have not added any of the decals or color trim but I might yet.

For my first flights I started with a single loop of 3/16” Tan Super Sport rubber which was adequate to fly the airplane but there was little climb. When I switched to two loops of 1/8” rubber, the airplane had a slight stall right after launch because of the power burst. Adding some right thrust appears to have fixed this issue.  The airplane looks rather realistic in flight and if it does stall the recovery is pretty quick.

For future challenge I plan to try a larger Peck propeller and longer strands of rubber. As it is, the airplane is flying to the edge of my tiny flying field.

Bill Kuhl

Check Out my Building and Flying Guillow's Model Aircraft webpage

Additional Info 6/17/2015

Thread on Hip Pocket Aeronautics from Designer or Porter and Beaver Kits

As noted Don DeLoach has won a contest in 2014 with his PC-6 Porter and placed high in another.

My Blog Post on STOL Aircraft 

Monday, June 8, 2015

Testing New Water Rocket System

Water rockets have really been a popular activity that I have done with a large number of students, from the start I invested in a good quality water rocket launcher which has worked well. Considering how cheap water rockets are to construct, I feel it has been a good investment but I have been looking for a cheaper launcher. I spotted the Quest Water Rocket System priced around $40 and purchased it, I failed to buy the corresponding Water Rockets set thinking I could use my water rocket design.

My Water Design on Quest Launcher

Water Rockets and Launcher Needed

Quest Nozzle Adapter

Water Rocket Box Contents

Rubber Washer Inside Adapter

Closeup of Latching Mechanism

String to Release Rocket

Launcher Tilted

When I put the launcher together I discovered that the opening in the Quest launcher would not fit the plastic pop bottle opening, I theorized that the rockets must have a special adapter for the bottle. I purchased the 6 rocket set and sure enough there were 6 adapters for 6 rockets. As soon as I got back from the hobby shop I put one of the adapters on my 24 ounce bottle water rocket and did some launch testing. Unless you had a funnel with a really small outlet, it will be necessary to take the adapter off the bottle to fill it. The adapter has to be on tight or it will leak, by design it should leak after 80 psi to prevent putting too much pressure in the bottle.

Quest Launcher in Action Note Smaller Stream

Adding Weight for Balance

Comparing Length of Nozzles

Rocket Landed  Out in the Weeds

Lucky to Find Rocket in the Weeds

Another thing I really hadn’t considered was how the stability of the rocket would change as the thrust nozzle was now farther down on the rocket. First couple attempts at launching and the rocket was doing spirals in the air, sure sign that it was not stable. The only thing I could think to correct at the field was to cut a slot in the top of the rocket and put some coins in through the slot to change the balance point. First I put in a quarter, then a penny, and finally another quarter. It did really help but the rocket was going too horizontal from launch. Changing the fin design might help my design but next I want to try to build the rocket with the included materials for fins and nose. The distance was pretty good on the last launch but it landed in really tall weeds and I was lucky to find the rocket.

Aquaport Launcher Larger Stream

Aquaport Launcher Clamps bottle in Three Places

As a comparison I took out my PITSCO Aquaport launcher and the same rocket launched near vertical. The stream that comes out the Quest launcher is smaller but still accelerates my rocket design really fast. If the included rocket is used I think it will be slower because of the greater drag in the rocket design, which might not be a bad thing. I plan to report on this again after I have new rockets to try but I am optimistic it will work well as designed.

Large Parachute Rocket

Parachute Fails to Deploy

Pieces Shatter from Crashing into Road

Since my testing was over tall weeds, I brought out my latest rocket with parachute recovery. This rocket was based on another one that had worked well but this one crashed on the first launch breaking the fins off.  As my luck would have it this rocket went darn near straight up except a little behind the launch spot and did not drift with the wind at all. The parachute did not come out and it looks like it was going to hit my parked vehicle but crashed on the blacktop directly behind it. This time the fins didn’t come off but the rocket broke in several other places. Rockets aren’t always easy.

Bill Kuhl

Monday, June 1, 2015

Dynamic Soaring Goal - Raising the Bar

For me my model aviation hobby is much about new challenges; that is what keeps it so interesting. After finding a slope with a ridge that is fairly close to me I have been determined to improve my success in dynamic soaring of a radio controlled glider on that hill. It was just the end of the last flying season that I had any success of flying more than a single DS circuit. That was with a DLG glider that I really do not want to break, after that one time I have been concentrating my DS efforts using foam gliders that are not as efficient but can take more abuse.

This past Saturday the wind was close to north which blows against the larger portion of this hill which appears to give greater lift. After flying my Super Scooter on the front side enough to get a feel of flying it again, I dived to the backside and made about three DS circuits before having to land because it was out of the proper groove. This was a pretty good start and I felt I could do better. I reduced the aileron throw because I was over controlling at times.  All my attempts at DS circuits after this I was always getting at least three circuits but I didn’t seem to do any better than that. 

On one particular dive over the hill I made an over correction and the glider was on the ground, it occurred to me that I need to get the path for the dive setup on the windy side and then stay off the controls as much as possible as it came across the ridge.  With more practice that was working well for me and I was using very little control on the bottom half of the circuit and keeping better speed. Now I made six circuits and the glider appeared to be accelerating at times as it was flying the circuits.

My progress hadn’t been linear and I had more attempts with fewer laps but I was building confidence that I could do more. Finally I really had the glider circling in the DS groove, what a thrill this was. I was hoping to make ten laps but as I passed that I was hoping to make at least dozen. It wasn’t to be as after the eleventh lap the glider went off course and landed at the bottom of the hill.  

The bar had been raised on my soaring goal and I had lawn mowing to do so I quit flying for the day. I have a fiberglass glider that I know will work better almost done so hopefully I will get a chance to fly that fairly soon.   If I get the chance to fly on a bigger slope, I think I will have the technique now to do much better.

Bill Kuhl

Check  Out my Small Slopes Webpage : Small Slope RC Soaring

Previous Blog Posts on Slope Soaring