In really strong winds, like 25kn, it was obvious that the single boom V-tail design was still too flexy. So here's the next version.
I doubled the tail boom and changed to a conventional cross tail. At this stage I have no rudder, which works fine for speed runs. If I wanted more aerobatic performance from this glider a rudder would be essential.
I've added balsa fillets at the tail join for a bit more strength.
It's all much stiffer and is working well. So far I have only flown in a 15kn breeze, can't wait for a decent blow.
For the last 2 weeks the wind strength has rarely dropped below 20kn. To keep flying I needed to
design something that could handle strong winds. The obvious candidate was a speedy slope racer.
The balsa-pod version of my Ultralight Sloper was available because it was superseded by the mad-flipping Fusion. Here are the mods needed to transform it into a high wind speedster.
V-Tail 1
Many slope racers use a V-Tail, and I had never tried one, so that was my first mod. I used tape covered 3mm balsa, hot glue and guessed the dimensions. The tail servos are down on the tail, which is not ideal. Not so much for the extra tail weight but the added aero drag.
It flew OK but did not track well at all, drifting and wandering side to side. This prototype V-Tail did not provide enough vertical area.
V-Tail 2
Further reading here suggested that my V angle should be sharper, about 110ยบ and the area needed to be increased.
That improved the tracking heaps but I noticed my tail boom was twisting alarmingly when operating the rudder, as demonstrated in the video below.
Rudder function on a V-Tail is not as effective as a conventional vertical rudder because the control surfaces are acting at an angle to the airflow. Most of the force goes into twisting the tail rather than moving it sideways, and the twist is in the wrong direction, a bit like adverse yaw from the ailerons.
Seems like V-Tails prefer more bank and yank style flying.
V-Tail 3
To increase the stiffness I shortened the tail boom by 150mm, cut 20cm off the 1.5m wing and 30mm off each tail section.
The shorter tail boom and smaller tail reduced the flex nicely resulting in much better speed and tracking.
In strong wind you can add ballast to give more momentum and penetration, which results in more speed. With a 2200mAH Lipo plus an extra 50g in metal washers it could handle 30kn flying crazy fast.
These photos show the final dimensions.
Flying weight with 1300mAH Lipo - 500g
Add ballast to taste
Wing - RG15 160mm chord
XPS foam hot wire cut
Covered with document laminating film
Servos - TGY9018 x 4
Strong wind V-Tail sloper overview and flights
Future design for more speed
For more speed I'll need to increase the tail stiffness further and reduce the drag.
My next high wind sloper design will have two tubes glued together for a stiffer tail boom and a conventional tail for less twisting. With a stiffer tail boom I should be able to place the servos in the fuselage for less drag, and run long push rods to the tail.
Weight is not a problem with these slopers, in fact more weight means more speed.
This design was inspired by a friend who wanted to take one of my "retired" planes to learn how to fly. So I gathered bits and pieces together and tried to come up with an easy to fly, crash proof trainer.
It only has rudder elevator and throttle, no ailerons. I wanted it to be as light as possible for slow and easy flight with a big energy absorbing nose and a tough fuselage.
The fuselage was shaped from a 50 x 100 x 370 block of XPS insulation foam and the tail planes are 8mm panels of the same foam. The boom is a Skyshark P4X 7.6mm tube.
The hotwire-cut 170mm clark y wing comes from rescued sections of the drowned Fokker (which now has new wings) Three x 360mm sections were glued together with the tips each raised 120mm. No spars are needed to hold the polyhedral due to the tape covering and large join surface area for gluing.
The nose is soft packing foam covered with tape and completely encases the 1300mAh Lipo battery.
The motor is the original Bixler 2, servos are cheap 9g HXTs, and it has a Plush 18A ESC and HobbyKing 3 channel receiver.
All up weight with the battery adds up to 550g, giving a slow continuous cruising flight time of over 30min.
This plane is very smooth and stable and with correct trim will fly hands off.
At this stage the nose, fuse and wings are almost bullet proof, but the tail planes are a bit too delicate. Thinner sheets of XPS foam are quite brittle so some kind of reinforcing is needed. Both the elevator and rudder have cracked during the test flights so I have added a 0.5 x 3mm CF spars.
Might be better to use depron or corflute for the tail.
Dimensions
Flight video - motor slope soaring
Build video
UPDATE 30 March 2016
After some tough flight testing by my dedicated student test pilot it became apparent that this tail
design was not crash proof enough.
So here is the new tougher tail design made from depron. The tail to boom join has extra foam fillets either side for more gluing area and to raise the elevator a little.
The new wing has more area and less polyhedral for smoother flight.
Two wings on the Tigermoth worked so well I had to take the next step...three wings.
The most famous triplane is the Red Baron's Fokker Dr1.
My wings are stiff enough not to need inter plane struts so I decided to stick to the familiar rubber band mounts. That meant I had to come up with a method for creating a rigid mount for the top wing. I recorded detailed build videos along the way.
SPECS
Top Wing - Top 1.1m, iron-on laminate and packing tape. 0.5 x 3mm CF spars
Middle and lower wings - 950mm and 900mm. packing tape. 0.5 x 3mm CF spars
Airfoil - 170mm Clark y
Fuselage - 6mm depron, 3mm ply nose, packing tape.
I have never been much interested in scale model planes apart from the Tigermoth biplane. Tigermoth World is nearby and for my 40th Virginia and I went for aerobatic joy flights...great fun.
I already had enough practice hot wire cut wings laying around for the build so I decided to have a go. I gathered scale measurements from tiger moth photos and made the adjustments needed for a 1.2m wingspan model.
The fuselage is 6mm depron covered with yellow packing tape to mimic the plane I flew in. I added 3mm ply under the nose to take landing impacts and a 5mm ply motor mounting firewall.
The motor is a Hextronic DT750 which had plenty of thrust, especially with a 4S battery. Prop is 11 x 5.5", ESC 40A Plush. 3000 mAH 3S or 4S Lipo gives 20+ minutes of cruising.
Here are build and flight videos of this great looking vintage biplane. It flies just like the real thing, slow and steady with just enough aerobatic capability.
My much loved Versus DLG has been crashed and repaired many times and is looking a bit rough now. But it was a great intro to DLGs. Hobby King's big sale came along at just the right time. The updated Versus, now called the V2, dropped from A$450 to $280, couldn't resist that price.
The V2 has a disser construction wing, crossed CF ribbon reinforcing, and a kevlar pod but otherwise is identical to the Versus.
I bought the Plug N Fly version which is OK, but might have been wiser to get the ARF version and add my own servos.
Here are my detailed build videos showing strengthening and control mods.
After a few weeks the V2 is going well, feels like a better Versus. I wouldn't pay full price for it because there are many better alternatives available, but for the sale price it is excellent.
Ages ago I came across this article by John Gallagher on wax paper bagging DLG tail surfaces, and ever since I have wanted to give it a go.
I'm working on a Fusion style pod and boom sloper designed by Leadfeather on RCGroups and thought bagged balsa tails would suit. My foam elevator is proving to be a bit delicate for repeated rough landings.
2.5mm x 75mm balsa sheet. Elevator will be 100mm wide so an extra strip needs to be glued on.
I'd probably use thinner balsa for DLG tails or sand down the 2.5mm.
Later I realised 100mm wide balsa is also sold at Bunnings.
