Original laminated block of foam for the wingroot section of the fuselage.
Tuesday, September 18, 2007
The Fuselage and Wings are in final stages.
9/18/07
I left you the last time as we were beginning to glue 2 inch foam sheets together. EPS insulation foam comes in 4’ X 8’ X 2” sheets and they are prescored at 16” intervals. Lengths of blue EPS insulation foam were cut to fit between the bulkheads. Since the fuselage is 11” wide, we did not trim the 16” dimension. 4 layers of foam were glued together with milk based carpenter glue ( Elmer’s carpenter glue). One section of the fuselage had to be 5 layers. Wing panels were easily contained within the 2” dimension of the foam sheet.
Several common types of glue were investigated. Only the milk based water soluble glues were appropriate. (They did not dissolve or melt the foam). Polyester resin based materials damaged the foam surface. We did not determine if the effect was the result of solvent action or the huge amount of heat generated by the curing process. Some of the glues were quite effective at turning the foam into jelly or a puddle.
The fuselage was composed of 5 sections. Each section had a fore and aft bulkhead section to determine its conformation. Each wing panel was composed of six sections.
A hot wire cutting tool was manufactured from poplar and single strand wire fishing leader. The wood was cut into a bow shape with and extended handle, similar to a tall hacksaw. Heating the wire caused it to expand and lose tension. To accomodate the expansion of the wire, a shaped block of wood was pinned to the handle with a short length of dowel rod which acted as an axle and allowed the combination of the grip and the block to be squeezed to tension the hot wire. Power was derived from a 15V 15amp Radio Shack power supply. This was sufficient power to effectively cut the foam mass but there was no excess power.
I left you the last time as we were beginning to glue 2 inch foam sheets together. EPS insulation foam comes in 4’ X 8’ X 2” sheets and they are prescored at 16” intervals. Lengths of blue EPS insulation foam were cut to fit between the bulkheads. Since the fuselage is 11” wide, we did not trim the 16” dimension. 4 layers of foam were glued together with milk based carpenter glue ( Elmer’s carpenter glue). One section of the fuselage had to be 5 layers. Wing panels were easily contained within the 2” dimension of the foam sheet.
Several common types of glue were investigated. Only the milk based water soluble glues were appropriate. (They did not dissolve or melt the foam). Polyester resin based materials damaged the foam surface. We did not determine if the effect was the result of solvent action or the huge amount of heat generated by the curing process. Some of the glues were quite effective at turning the foam into jelly or a puddle.
The fuselage was composed of 5 sections. Each section had a fore and aft bulkhead section to determine its conformation. Each wing panel was composed of six sections.
A hot wire cutting tool was manufactured from poplar and single strand wire fishing leader. The wood was cut into a bow shape with and extended handle, similar to a tall hacksaw. Heating the wire caused it to expand and lose tension. To accomodate the expansion of the wire, a shaped block of wood was pinned to the handle with a short length of dowel rod which acted as an axle and allowed the combination of the grip and the block to be squeezed to tension the hot wire. Power was derived from a 15V 15amp Radio Shack power supply. This was sufficient power to effectively cut the foam mass but there was no excess power.
Friday, September 7, 2007
Well we started
As previously commented, the aircraft we are endeavoring to produce is an autonomous aircraft that uses artificial intelligence (AI). Basically, we wanted a plane that is big enough and stable enough to be airborne for an hour with monitoring equipment. We would prefer the monitoring data to be streamed real time to a ground station. The monitoring equipment could be cameras of various capabilities (movie, still or filtered), air sampling devices, weather instruments or other devices that fit in the payload compartment.
The final design is a high wing canard configuration. Fuselage dimensions were dictated by the plan forms of the projected cargoes. Consequently, the fuselage is slightly ellipsoid. I'll give particulars in another post and some insight into the design process (3 1/2 months from the concept to a final CAD drawing) as we go along and the milestone corresponding to the different design criteria are reached.
Let's look at the engine requirements, because this is a large contribution to the weight and performance of the final product. We discussed the design concepts with an electric motor manufacturer and the recommendation was 2 -4 Kilowatts of propulsion power. Evaluating electric motors and battery requirements for a 1 hour flight resulted in a cost of approx $12,000 just for the propulsion. NOT able to be done!!!! The other option was either 2 or 4 cycle piston engines. 2 stroke glow engines which meet the power requirements burn 2 or more ounces of fuel a minute. This is possible in our design, but a lot of weight and volume for the fuel. 4 cycle engines meet the power requirements burn approximately 1.1 to 1.4 ounces of fuel a minute. The 4 cycle engines are larger size and weigh more but the reduced fuel load makes up for the weight penalty. We now have a good estimate of fuel weight and volume for a 1 hour flight.
Bays for forward electronics, general purpose volume (which include the nose gear), computer area, fuel compartment and engine were configured in the final design. Airfoil and wing area requirement guesstimates were evaluated using the NASA freeware FoilSim II v1.5 found at:
http://www.grc.nasa.gov/WWW/K-12/freesoftware_page.htm
Design and 3D rendering was performed in-house (my garage) using a 3D CAD program.
Bulkheads for the fuselage cross-sections were determined at locations suitable for the necessary instrument bay volumes. Bulkhead outlines were printed from Cad drawings onto paper and the outline was transferred to 3/16 inch plywood.
We are laying up foam blocks to carve.
The final design is a high wing canard configuration. Fuselage dimensions were dictated by the plan forms of the projected cargoes. Consequently, the fuselage is slightly ellipsoid. I'll give particulars in another post and some insight into the design process (3 1/2 months from the concept to a final CAD drawing) as we go along and the milestone corresponding to the different design criteria are reached.
Let's look at the engine requirements, because this is a large contribution to the weight and performance of the final product. We discussed the design concepts with an electric motor manufacturer and the recommendation was 2 -4 Kilowatts of propulsion power. Evaluating electric motors and battery requirements for a 1 hour flight resulted in a cost of approx $12,000 just for the propulsion. NOT able to be done!!!! The other option was either 2 or 4 cycle piston engines. 2 stroke glow engines which meet the power requirements burn 2 or more ounces of fuel a minute. This is possible in our design, but a lot of weight and volume for the fuel. 4 cycle engines meet the power requirements burn approximately 1.1 to 1.4 ounces of fuel a minute. The 4 cycle engines are larger size and weigh more but the reduced fuel load makes up for the weight penalty. We now have a good estimate of fuel weight and volume for a 1 hour flight.
Bays for forward electronics, general purpose volume (which include the nose gear), computer area, fuel compartment and engine were configured in the final design. Airfoil and wing area requirement guesstimates were evaluated using the NASA freeware FoilSim II v1.5 found at:
http://www.grc.nasa.gov/WWW/K-12/freesoftware_page.htm
Design and 3D rendering was performed in-house (my garage) using a 3D CAD program.
Bulkheads for the fuselage cross-sections were determined at locations suitable for the necessary instrument bay volumes. Bulkhead outlines were printed from Cad drawings onto paper and the outline was transferred to 3/16 inch plywood.
We are laying up foam blocks to carve.
Wednesday, September 5, 2007
The Starting Point
We are initiating this blog to share our experiences, trials and tribulations during the construction and flight testing of our UAV.
The initial design criteria included carrying a 5 to 10 lb payload (cameras etc) and an unrefueled flight time of 1 hr.
The initial design criteria included carrying a 5 to 10 lb payload (cameras etc) and an unrefueled flight time of 1 hr.
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