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Gary Hinze's Squirrel Adventure
I recieved a lot of information and pictures from Gary Hinze of San Jose, California.
Here's a video of his Squirrel in the gym:
Darcy, I communicated with you when you first went on the Internet several years ago.
I just built my first Squirrel. I have always had a lot of trouble following directions. I made some changes. I hope they are improvements. You can see them all in this picture.
1. I used a 1/8" x 1/4" stick. Even this is heavier than necessary.
2. That necessitated a 1/8" x 1/8" x 1/2" shim block so the Sig prop hanger would be a snug fit.
3. The stick tapers to 1/8" thick in the last 2 3/8" to make the tailplane parallel with the prop shaft.
4. The paper parts were cut out with cardboard templates. This wastes a lot less tissue. No scissors are necessary during construction. All wood parts are self locating on the paper patterns. (Several sets of tissue parts can be made at one time by stacking several sheets of tissue on top of each other.)
5. There is no center rib in the wing. The hold down stick does that job. It is glued in two places, to the wing leading and trailing edge spars, not to the paper.
6. There is no wing saddle. The hold down stick straps directly to the top of the stick with two dental bands, doubled to make them pretty tight. The top ends of the hold down stick are sanded to 45 degree tapers to make it easier to roll the bands on.
7. The wing and tailplane papers were folded in half to make center line creases to locate the hold down stick on the wing and the tailplane on the fuselage.
8. 1/16" square wood was used for the wing trailing edge, tip ribs and winglet spars.
9. The winglet spars were located 3/4" back from the leading edge.
10. The wing was mounted with the paper on the upper surface. That gives the wing 2 degrees of effective incidence. Added to the 3 degrees of downthrust, that is 5 degrees attack angle. As designed, the wing has about zero degrees of effective incidence and 3 degree attack angle from the downthrust only.
11. No wing incidence shim is necessary.
12. The winglet spars are glued to the outer faces of the wingtips, due to the wing being "upsidedown".
13. The fin spar is extended 1/4" below the bottom of the stick to hold the motor. I may file a round indentation in the back of the spar to hold the motor in place. With the motor I intend to use, the motor will never come loose, unless it gets into a thermal, and in that case your motor dethermalizer will come into play. No toothpick or thread are necessary for the motor hook.
14. The back corner of the tailplane aligns exactly with the end of the stick. The root chord of the fin is 1/8" longer than the root chord of the tailplane so it too aligns exactly with the end of the stick, but the fin spar can go directly in front of the tailplane spar. The bottom edge of the fin paper aligns exactly with the bottom edge of the stick taper.
The finished plane weighs 5.9 grams. I used 11# wood for the stick and 14# wood for the spars. I also used a Japanese paper that weighs 26 grams per square meter because the unsupported tissue edges seemed rather fragile in fine tissue. The distance between the hooks is 9 1/2". I will use a handy 20" loop of 1/16" Tan Super Sport to fly it.
It could be made quite a bit lighter with lighter wood, thinner tissue with thread reinforced edges and a North Pacific 5 1/2" prop assembly. That prop assembly weighs a gram less than the Sig unit because the prop is much thinner.
I moved the wing until I got a slow, steady descent. The CG was at 13/16", about a third of the chord, pretty close to the winglet spar position.
There are 18 parts in this Squirrel.
1 1/8" x 1/4" x 12" balsa motor stick
1 1/8" x 1/8" x 1/2" balsa nose spacer
1 1/16" x 1/8" x 12" balsa wing leading edge
1 1/16" x 1/16" x 12" balsa wing trailing edge
4 1/16" x 1/16" x 2 1/16" balsa wingtip ribs and winglet posts
1 1/16" x 1/8" x 2 1/2" balsa fin spar
1 1/16" x 1/8" x 6" balsa tailplane spar
1 1/16" x 1/8" x 3" balsa wing hold down stick
1 tissue wing
1 tissue tailplane
1 tissue fin
2 dental hold down bands
1 5 1/2" propeller assembly
1 19" loop of 1/16" rubber motor
I have not had an opportunity to fly it under power, finished it after dark, been warned by the police about being in the park after dark. I expect to have a chance to fly it tomorrow and report results.
Gary Hinze
Close up of the front end showing nose block, wing mount, wing spars, CG mark. With the paper on top, there is no need for the shim block. The shim block gives 1.68 degrees of incidence to a -2 degree airfoil incidence, resulting in an effective -0.32 degrees incidence. This arrangement gives 2 degrees incidence. Add to those incidences the 3 degrees of down thrust to estimate attack angle.
Close up of the tail showing fin spar extension as rear rubber hook, tapered motor stick and both papers located at rear end of stick with fin extending 1/8" beyond tailplane. You can see the pencil mark for the end of the taper. I have since filed a semicircular notch in the hook post just below the tailplane. May not be necessary.
Bottom plan view showing smaller wing ribs and trailing edge. Tight dental bands will keep the wing from flopping around. This is a very light airplane.
It glides very nicely, turning left. Too windy out to fly in the park. I will be going over to the Gym this evening to teach and may get time to fly it indoors. I have three other planes and several motors to test.
You should be able to get this one together in under 5 minutes. I expect it will do a minute in the Gym. No telling how long it will stay up outside.
Winding stooge that can be operated using your foot.
c. 1927 ROG from an antiquities dealer in Massachusetts
Gary and I were discussing some design issues in email and he sent me this:
"I also received a c. 1927 ROG from an antiquities dealer in Massachusetts that I am measuring and weighing. I am making a complete material specification and will make a drawing. I intend to make an exact copy for flight testing. It has a boat paddle propeller. I will copy it, then make one with more appropriate blade angles, then make a proper propeller. It had dark brown rubber on it, still flexible except where it was bent around the hooks."
Model Airplane Design
I recieved this picture of a removable winglet from Gary Hinze. We are having an email discussion about which side the winglet should be on. There is some good arguement for either side. The problem with building two models is that they would never be identical. But if we can move the winglet back and forth on the same model that might give us some insight.
(2009-07-31)
" I should have known, it is obvious.
I forgot to pack the 14" loop of 1/16" that I was going to use for the Squirrel, so I flew my NP Sky Master instead. Then I decided to use its 16" loop of 3/32" on the Squirrel. I got some good test flights with the standard wing. Then I put the tipless wing on and put the removable winglet on the right tip. It turned right and flew into the wall. Of course! It was turning so wide, it would not have flown inside the Gym even if I had launched it the other way. Maybe with some right thrust it would have fit in the Gym. This can be useful on very high torque if you want a fast climb, because it will allow more torque without spinning in to the left. The important finding is that it flew level without the spiral dive that the wing without winglets will do.
Next I put the winglet on the left tip, bending the prop hanger a bit right to compensate for the expected strong left. It flew too wide, going up on the stage and hitting the wall. Broke the wing, easily reglued. Next flight with a bit of left thrust, it flew well.
So the Squirrel can be flown with only one winglet, with different effects.
All flights were made with the tailplane on the taper without a shim, as originally built. It flew fine. It didn't zoom on launch or dive as power ran down. I didn't try flying it with any of the shims on the tailplane.
We had only one student tonight, so closed early. I didn't get to go for time. Wouldn't have done very well, without the proper duration motor anyway.
Don Long suggested splaying the winglets out 15 degrees to make the wings stackable. "
Kite Eating Tree
Hi Darcy,
Today we did a demonstration of model airplanes for a third grade class at a school. I flew an AMA Cub in the classroom. Several of the guys showed their RC planes and gliders. We gave the kids paper airplanes and foam plate gliders. We went outside where we had a distance contest for the kids. The kids were allowed to work the controls of a RC glider. One of the guys flew his RC tow gliders.
I flew my North Pacific Sky Master. Then I got out the Squirrel. I had never flown it outside before, only inside the Gym. In the Gym I can't wind the motor all the way up, it will hit the ceiling. I started with 2,500 turns on the 20" loop of 1/16" rubber. It climbed over our heads and gave the boys a good run in circles. Then I put in 2,700 turns and let one of the boys launch it. It climbed rapidly to a high altitude, climbing for a long time. It drifted across the playing field, over the school and toward the neighborhood. I was afraid it would keep going higher and higher out of sight. I ran through the school, the line of tall trees along the sidewalk and across the street. I saw it coming down. It looked like it might go across the street and come down in a yard. Then it started to come down faster and looked like it might land in the street. But it landed right in the edge of a tall tree.
The kids were impressed. The teachers were impressed. The other modelers were impressed. Everyone wanted to know where they could get one. I told them about your web site.
That's the trouble with a great flying plane, they fly away. I was disappointed and thrilled at the same time. Gary Hinze
Relief
Hi Darcy,
I went back to the school today to return a book. Lou lent me his telescoping 50 foot pole. It was just barely long enough to reach the treed Squirrel. I was able to pull it out from the branch. It was then hanging from the motor. I was able to pull it free and it slid down the pole. One of the fin sticks and a small bit of paper were loose, easily repaired with a spot and smear of glue. The hold down rubber bands were slightly deteriorated. The motor knot broke, but the rest of the motor seems in good shape. Rubber under tension deteriorates much faster than relaxed rubber. My Squirrel is back home, ready to fly again.
Gary Hinze
Jig!
Hi Darcy,
I made a jig for cutting multiple Squirrel sticks so kits of parts may be quickly made up. I also have cardboard patterns made from cereal box material for cutting out multiple tissue parts.
The stick cutting jig was made on a table saw from a piece of 3/4" pine, 1 3/4" wide and 13" long. A channel 1/4" deep and 1 1/4" wide was cut down the center of one face with multiple sweeps of the blade. A 1/4" x 1/2" x 1 1/4" stop block was glued in at one end. Slots were cut across the rails with a hacksaw blade, using a block of wood to guide the blade and keep the cut vertical, with the inside face of the cut at the length of each stick required. Ten lengths of 1/8" stripwood may be put in the channel, with their ends butted against the stop block, and a razor or razor saw may be used to cut ten pieces at once. Twenty pieces of 1/16" wide wood may be put in the slot. Five pieces of 1/8" x 1/4" may be put in to cut the fuselage sticks.
The jig block could also be made by gluing together three 13" pieces, one 1/2" x 1 1/4" for the bed and two 1/4" x 3/4" for the side rails.
Gary Hinze
(2009-10-09)
In future I will cut the cross cuts with the table saw. The hand saws were too much trouble. The saw kerf will be wider, but it is the inside face of the cut that guides the blade. It doesn't need to be a snug fit.
I cut out parts for a dozen Squirrels last night. I took pictures of each step. I had a request for one from a parent, so I will be teaching it this evening. I plan to use 14" loops of 1/16" rubber for the motors.
If you want to precut many paper parts, consider hardening the edges of the cardboard template with CA, use ply hardened with CA or even sheet metal.
(2009-10-11)
Hi Darcy,
I had two third grade kids build Squirrels tonight. Both about 8 years old, younger than we usually take. One boy and one girl. I made enough parts to make 12 Squirrels, but had only three propeller sets. None available at the local hobby shop. I made one as a way to show the kids what to do, step by step. Another kid came in later and wanted to build one, but I said "No" because we were close to finishing and flying and I could not divide my attention between two places, classroom and gym floor. I forgot that I had only three props, but I could have given the third to the kid if he had wanted to start with the others. I could have "borrowed" the prop off one of my other planes for mine.
We used Ambroid in the narrow tipped bottles because that is what we use in the class. Lou likes it because it helps the kids apply the glue more precisely. Didn't take me long to regret that decision. I use water based carpenters glue that is a lot more tacky than the solvent glues. They don't seem to stick until completely dry. And it quickly forms a dry skin on the surface so it never makes a good bond with the paper. And it dries in the tip, so you are constantly struggling to squeeze glue out and having to poke the hole open with a pin. And you are constantly pulling gobs of semi dry glue off the tip, so getting glue all over your fingers. I usually dilute the Amberoid with acetone a bit to make it more runny, but then it takes even longer to dry. OK when everything is pinned down to a plan. I usually put a puddle of carpenters glue in a bottle cap and apply it with a stick. So much easier.
The boy glued his wing sticks on with gaps, so the joints were weak. I put lots of glue into the corners. It took a lot longer to dry. He broke a trailing edge and a wingtip, pressing too hard applying the glue. Getting the tailplane on was tough. The glue just would not hold the parts in alignment long enough to get everything in place. I thought I had the stick on, tried to smooth out the paper and the stick fell off. Then the fin came loose. Several times. The hardest part was the wingtips. The way I make them is to fold the paper up away from the stick, not around the end, then glue the tip stick to the outside of the rib and paper. The glue oozed out around the rib stick, forming a ridge that did not permit a sharp fold, so it was hard to get good contact between the wood parts. Again, gobs of glue to fill the gap took a long time to dry and make a weak joint. This step needs more thought. The girl misaligned the wing hold down stick, she got it on right, but the glue didn't hold it in place when she put a weight on it to hold it down, so the wing was canted slightly. This made the plane crab slightly. I softened the glue with acetone and reset the piece. I started each with two 7" x 1/16" pure rubber office rubber bands linked together, but one broke at 1,100 turns. I was aiming for 1,400 turns. We got a couple trimming flights in, just enough to see where the wing needed to be moved. I replaced the motors with 14" loops of 1/16" Tan Super Sport. Couple more trim flights to get the wing position marked. 1,800 turns gave some pretty good flights of several circuits above our heads. You can work up to almost 2,000 turns if you wind slowly at the end. We ran out of time before we got to work up to the turns required to graze the ceiling. No timed flights. Both Squirrels spent a lot of time in the repair shop with a couple AMA Cubs. I hope they survive the trip home.
Never got to fly mine. Typical. ;-)
Camera didn't work, so no pictures. Viewing screen went blank about halfway through the evening.
Gary
ROG Squirrel!
Squirrel with Sleek Streek landing gear.
With a 14" loop of 1/16", it did not climb. With an 11" loop of 3/32", it climbed well, but flew straight into the wall, no turn. Balanced at the midpoint of the wing chord.
I have been having a problem with consistency of the turns. I think the loose trailing edge of the fin makes for inconsistent turns. I am thinking to try a 1/16" square trailing edge on the fin. A rectangular tailplane will improve recovery after collisions with ceiling obstacles.
My method of attaching the wing with two dental bands is weak. When the plane hits ground obstacles, the prop torque twists the stick away from the wing mount. Doubling the bands to make them tighter may help. It is not a problem during flight.
I used Lou's camera to make this picture on my memory card. At home, my camera was used to download to the computer. I will pack my camera tonight to send it for repair.
Gary
Squirrel Stick Cutting Jig and Tissue Cutting Templates
Squirrel stick cutting jig and tissue cutting templates.
The jig may be used to cut many sticks at the same time. With a 1 1/4" wide bed, it can cut 10 pieces of 1/8", 20 pieces of 1/16" or 6 of each.
The 1/16" square and 1/16" x 1/8" sticks were cut from 1/16" sheet using the strippers on either side of the finished Squirrel fuselage.
A razor blade may be used to cut the sticks. You can see the piles of different parts.
All the wood parts for a dozen Squirrels are quickly made.
Cardboard templates are made for each tissue part.
A razor blade and cardboard pattern are used to cut out 6 tissue wing coverings at a time.
It didn't take long to make a dozen sets.
The tailplane tapers are cut one at a time.
The end of the stick is marked 1/8" from the edge.
Another mark is made 2 3/8" from the end.
A cut is made just outside these marks with a razor saw.
It may also be done with a razor blade and straightedge.
It is backed up with another piece of wood and sanded to get a flat, square face.
All the parts for 12 Squirrels are in this box. Except the glue.
Gary
Serious production of Squirrels
OK. Here are some pictures of the balsa strippers in use. I cut the 1/8" x 1/4" sticks from 1/4" sheet on my table saw, but sticks are more available than table saws with smooth cutting blades.
The 1/16" square and 1/16" x 1/8" sticks are cut from 1/16" sheet balsa. First check that the edge is straight against a straightedge.
This sheet was not perfectly straight, so the edge was trimmed against the straightedge with a sharp razor blade. Be careful that the straightedge does not move during the cut. Check the edge again when done.
The 1/16" square was stripped with this home made stripper. Similar strippers may be bought. This is a 5/16" x 2" x 6" pine plate with a 1/16" square groove down the middle. Two 5/16" x 1/2" x 1" blocks are screwed down over a short piece of thin razor blade laid across the top of the slot. The entering faces are beveled slightly to facilitate entrance of the balsa sheet. The balsa sheet must be kept in firm contact with the entire length of the slot to insure straight, uniform cuts. Keep the pushing hand over the slot and cut with many short pushes. Do not let the hand go beyond the middle 2/3 of the slot.
This is particularly important at the end. Hold the edge of the balsa firmly against the base of the slot, but be careful to not crush the balsa. It is easy to let the balsa droop over the end, making a curved cut.
This is a Master Airscrew balsa stripper, available at some hobby/craft stores and on the Internet. The knob at the right adjusts the distance between the guide face and the knife at the left. The space has been set to 1/8".
I am cutting 1/16" balsa, so I space the sheet up from the table top with a 1/4" sheet of balsa so I can withdraw the knife blade. The shorter blade is less prone to wander with the wood grain as it cuts. I set the blade point height by placing a thin piece of paper on top of the 1/4" spacer sheet.
The stock projects a tiny bit beyond the edge of the spacer. We want the stripper to be guided by the edge of the stock, not the spacer. At the start, assure that the lead half of the guide face is in uniform contact with the edge of the wood. It is easy to push the back inward too much, putting the stripper at an angle.
Pause and move the other hand along as the stripper is moved along the wood. Always keep both hands together to ensure firm contact. Do not press overly hard, especially with soft wood, because the wood can compress.
At the end of the cut, insure the back end of the stripper stays in firm contact with the wood. Otherwise it is easy to rock the stripper around the corner, making a curved cut.
Gary
(2009-10-19)