I am an UAS Operations student at UND and this is my current project, not school related. This is a Giant Telemaster (12ft wingspan) that was built from a kit and flown for a few years. The previous owner then converted it to a twin but never completed the project. With so many other projects to finish, he decided to give this to me. The plan is to put 2 ryobi weed eater engines (fully converted for use on a plane) on the wings and an APM. With this set up the payload bay will start at the nose of fuselage (which has been stretched for CG purposes) to the aft of the wing. I estimate a 15-20lbs payload capacity. This is loosely based of the fact we built a Senior Telemaster with a MicroPilot Autopilot and electric power plant, and it can lift 6lbs for an hour endurance. I built that aircraft to use for research projects within the university (I work for UND Aerospace flying sUAS). With the small 33cc engines and plenty of room for gas the endurance could easily be setup for over 6hrs. In order to handle the extra weight and the multi-engine setup there are a few modifications to the air frame. In addition to the original wing mounting spars there is also an aluminum tube running from one nacelle to the other. Also the inner part of each wing half has been sheeted with ply to prevent flexing due to the weight of the engines creating torque on the wing. The struts and landing gear have also been replaced by stronger versions. The tail now has 3 vertical stabilizers and rudders to help in the event of a engine failure. There is still a lot of work to be done but I am trying to finish it before the first snow. Thoughts, ideas, suggestions?
I would revert back to a single engine. If you have two engines you're twice as likely to have an engine failure, have increased system complexity, weight, and expense.
It's a little to late for that as you can see from the photos. It may be more likely to have an engine failure but I rather lose one engine and still have another providing power. (You dont see many commercial aircraft with a single engine, obviously there are other factors but multi-engine does provide redundancy. Even a 747 can lose a couple engines and still fly.) It may not be enough to hold its altitude indefinitely but it will help get it home. The complexity of the system does not increase much as the APM does not know there is two engines. There is a synchronizer that controls the engines from a single input. In case of an engine failure it will reduce the power to the good engine to prevent a spin. The good engine can then be returned to full throttle by the pilot by reducing the throttle then increasing it (and correcting for the asymmetrical thrust) , similar to a cutoff in an ESC. One issue with a single engine up front is it can create issues with payloads. One of the payloads we carry at work measures atmospheric variables, which a gas engine would contaminate. While this plane wont be used as a UAS (since it will be operated for sport/recreation and not commercially/research) and may never see a scientific payload like that, it is something to keep in mind. Plus that nose is just begging for a nice camera and pan tilt mount. The weight will definitely increase but this air-frame can more then handle it. As far as expense it was actually cheaper to go twin engine since I dont have 60-80cc engine on hand. This is a joint project and someone already had the converted ryobis sitting on a shelf.
Bottom line this project is for fun and we wanted to make something unique.
Well I would certainly be adding some carbon to the wings to help cope with all the extra load. Looking forward to seeing it fly.
an aluminum wing tube was added through each nacelle transfering the weight to the wing box on the fuselage. The inner wing was area was sheeted to help with the torque placed on the wing since all the weight is out in front of the wing. Also the wing struts are heavy duty aluminum. They are actually jusry struts found on ultralights, a little over kill :) I dont have any pictures of the struts on the plane yet.
Things left to complete: Mount engines, throttle servos, gas tanks, aileron linkages, and finally covering the beast! The wing struts stiffened up the wing nicely.
This is an awesome plane!! Keep up the good work!! I look forward to seeing this beast in action!
Well I decided to save a few pounds and gain twice the static thrust by installing DLE-30cc gas engines instead of converted Ryobi's. The 3 bladed props look great on the plane. Today was the first engine run and they both ran like champs. I have not powered up the APM or the Twin-synce but the engine rpm's match well with out any adjustments. I am planning to maiden it next weekend if all goes to plan. A few items left to complete is covering the tail section, the ailerons, control linkages, and programming everything. I am starting to get excited and a little nervous... I think it needs a sticker saying "to big to fail" for good luck haha.
I recently acquired this pan tilt system: http://servocity.com/html/tube_servo_power_gearboxes.html It will be carrying a sony HD handycam that has image stabilization, which should help a little. I will also have a GoPro HD mounted near the tail so if something fails it will capture all the glory. There will be a video switch on board to changes sources in the air. The video will be piped through a 5.8gHz transmitter to a custom built ground station. The pan tilt will be mounted underneath one of the two massive payload bays, depending on CG. I will work on camera tracking at a later date since priority in setting up the APM and associated systems.
I fly a senior telemaster with APM. One thing I've found very useful is to setup flaperons using a mixer, with flap angle controlled by a knob on the transmitter via channel 5. I've found that really useful during takeoff and landing, and for slow photo flights. The senior telemaster handles flaperons really well, keeping stable even with full flaps, but lowering the stall speed a lot.
We had considered flaperons to allow steeper approaches for the senior telemaster I use at work, University of North Dakota. Unfortunately the autopilot we use, MicroPilot 2028g, does not allow for manual flap control and I am not sure about flaperons. Instead flap deployment is based on airspeed. So we deiced to not to use them for now. Because of the two engines and large nacelles this one should slow down nicely. I love the senior telemaster, including the new version, so I was ecstatic when I got my hands on this balsa overcast :)