|Jul 02, 2005, 02:14 AM|
Mini F-15 Eagle Park Jet Build
A couple days ago I saw the video of the Hobby Lobby Icarus SU-27 Shock Flyer plane. For those of you who have not seen it, here is a link to the thread over in the foamy section
Link to SU-27 Shock Flyer
If you scroll down to post #8 there are 2 videos to see. The first is a group of stock SU-27's flying in a gym. The second one is a modified SU-27 with a hopped-up brushless motor setup. The motor sounds like it is spinning about 40,000 RPM in this video.
Anyhow, seeing that gave me a big idea!
I had downloaded Steves F-15 Park-Jet plans in PDF format a few months ago. Since I have access to a 36" wide HP InkJet Roll Paper Plotter at work, I can print as many plans as I want.
I looked at the SU-27 and thought, "I could do the same thing with the F-15 If I scaled it down a little bit. So I fired up the computer, grabbed my calculator, and went to work. I figured that if I scaled down the original drawing to 60% of the original size, it would be about the same size as the SU-27. At 60%, the F-15 has a fuselage length of 25 inches, and a wingspan of 17 inches. I will build the plane from 3mm Depron and do a profile fuselage on it.
I picked up a few supplies at the LHS yesterday including:
2 MPI Speed 180 Motors
A couple 3 x 2 pusher props
2 micro 5 Amp speed controller
2 Li-Po 480 mA 2-cel battery packs
1 13" x 39" sheet of 3mm Depron
Plus a few misc. building supplies
My plan is to mount the motor in the same location that is used on the SU-27, in between the LE of the rudders with the prop turning in a slot in the top deck.
I put the 480mA battery, motor, prop, speed controller and 2 GWS Naro Servos on my digital scale and measured 3.7 ounces. The entire sheet of 3mm Deprom weighs 1.6 ounces, and I will probably use a little over half of it, so figure 1 ounce for the airframe, plus a few pieces of carbon fiber and some glue, I should end up with and all-up weight of between 5 and 5-1/2 ounces.
The motor turns the 3 x 2 pusher prop at 17,000 RPM, giving a pitch speed of 32.2 MPH. It is putting out a fair amount of thrust, so It should have enough ummph to fly well.
I will post some build photos after I get going on the project. I have to cut out some templates first.
|Jul 02, 2005, 08:43 PM|
Why go with a profile fuse? Sal C has built a few micro sized parkjets at about 60% scale if I'm not mistaken, and been very successful using the full fuselage design. That is unless you want a profile like the Ikarus SU-27.
|Jul 03, 2005, 03:00 AM|
I could build it with a full fuselage, but for the first one, to keep it simple, I was going to go with a profile fuse like the SU-27 shock flyer. I bought 2 motors and 2 speed controllers, so I may build a full fuse one as a second version. The weight penalty for the extra foam will only be around 1/4 of an ounce or less, so it should not impact the flying characteristics much. In fact, a full fuse one may be more aerodynamic than a profile one, plus you will be able to completely hide all the radio gear as well.
Good food for thought!
|Jul 04, 2005, 02:40 PM|
Mini F-15 Park Jet Build (Part 1)
Well, I got some build time in last night finally. My sweetheart informed me on Friday that "We" were going to clean all the carpet in the house over the weekend. "WE?" I think we all know what "We" means!
So Anyhow, last night after I finished cleaning all the carpet, I got some bench time in. Oh, she was good about it, she let me take a couple hour break after I finished the downstairs to "Rest Up" before I moved on the the upstairs. This gave me time to cut out all my templates and mark and cut out the foam.
For any of you that have posted a build thread before, you know all too well that the documentation process, (IE shooting all the photos, editing them in photoshop to get them adjusted and reduced to the proper size, uploading the photos to your web server, and finally, writing the article on R/C Groups) often take longer that the actual building of the aircraft!
For those of you who take the time to read this, and other build threads like it, please understand that they are really labors of love for the enjoyment and education of the other members of R/C Groups. So if you read a thread, and you like what you see, take a couple minutes and give a small comment and thank the author for their work!
So, here we go with the construction.
Just to bring everyone up to speed, I took Steve's plans for the 3DFoamy F-15 Park Jet and scaled them down to 60% of the original size. This gave me a wingspan of 17" and a length of 25".
Here is a photo of the plans with an 18" ruler layed accross them for reference.
I took the plans, cut them up, and glued them to a piece of posterboard to make templates to cut out the parts. Here is a shot of all the pieces glued to the posterboard.
After I got all templates cut out, I traced the patterns onto a 13" x 39" piece of 3mm Depron as shown below.
And here are all the pieces after I gut them out with an X-Acto knife.
At this point I was curious how much all the airframe parts weighed. I had weighed the entire sheet of Depron before I started cutting, and it weighed 1.6 ounces. After I had cut out all the parts, I piled them all up on my digital scale to see what it said. 0.9 ounces
Next I thought I would weigh the servos I was going to use to see how much they weighed. 2 GWS Naro servos, 0.7 ounces. Almost as much as the entire airframe!
I had some other servos that I had purchased at the Ontario, CA AMA show, so I threw them up on the scale to see how much they weighed. 0.4 ounces! Much better! 0.3 ounces may not sound like much, but when the entire plane will probably only weigh 5 ounces, that is 8% of the total weight! Every little bit really helps on these micro planes.
To begin the construction, I started with the wing. I cut an 1/8" wide slot in the wing, 14" long, to put a 1/8" diameter carbon fiber rod for reinforcement.
Here is the carbon fiber rod being test fit into the slot. Looks pretty good so far!
For this build, I picked up an accessory pack from a GWS Slow Stick, (Part #AS1). This kit contaoned two 20" x 1/8" dia. Carbon Fiber rods, two 10" x 1/8" dia. Carbon Fiber Rods, two pre-bent music wire pushrods, soms double sticky tape, and 4 little sheetmetal screws. The entire kit was $5.95, and it contained enough CF and Music wire to build 2 of these planes, so it seemed like a good deal!
Next I took a 15" long piece of Scotch Satin Finish tape and placed it over the slot I cut in the wing on the bottom surface. This was done to keep the epoxy from leaking out when I glued in the CF wing spar.
Next I flipped the wing over, mixed up some 5-minute epoxy, and spread a thin coat in the slot. Then I put a thin coat on the CF rod and dropped it in the slot. while the epoxy was still wet, I took another 15" long piece of Scotch Tape and put over the top of the CF rod and rubbed it down into place. This gives a nice smooth surface of the top of the wing after the epoxy cures.
Once the epoxy had cured, I cut out the ailerons from the wing. I measured in 1-5/8" from the straight part of the trailing edge of the wing, and extended this out to the wingtips. I cut the ends about 3/16" out from the fuselage sides, and then I trimmed about 1/32" off the end to provide a little clearance for the end. Here is a shot of the wing with the spar in place after the epoxy had cured, with the ailerons cut out.
That will be it for this installment. Next I will start on the fuselage construction.
Stay tuned for Part 2!
|Jul 05, 2005, 03:02 AM|
I'll be following the build. Looks straightforward so far, and I like how you mounted the part templates to posterboard. I need to start doing that myself on the parkjets.
|Jul 05, 2005, 09:16 AM|
Yeah as Paul said I've built a few of the full fuse versions (jetset44's designs) and they've flown very well. One thing to keep in mind is to BUILD LIGHT! (not that you don't have that in mind). Naro's are way too big, I've used Pico's with good success. I've even went with flat carbon (2mm) turned sideways for spars and it's very strong.
Good luck, here's a pic of a couple of mine...
|Jul 05, 2005, 09:56 AM|
Thanks for the feedback guys! I am making mine more like the SU-27 shock flyer with the motor mounted as a pusher inside the fuselage just in front of the rudders. I will have a 3-1/2" x 1/2" slot in the top deck for prop clearance. I also went away from the full-flying stab in favor of seperate elevators. I was going to try using coupled ailerons/flaps & tailerons on this one like the shock flyer uses.
They built a new conference room at work that is about 40 foot square with a 12 foot ceiling, so I was going to take this one in after I get it done and try flying it on my lunch hour!
I will post some more build pictures tonight.
|Jul 05, 2005, 01:40 PM|
|Jul 05, 2005, 04:38 PM|
but I´ve bought a new lamp for ~300 $ some years ago
.. I´ve placed the beamer under table and our kids were playing. BOOM.
|Jul 06, 2005, 12:01 AM|
Mini F-15 Park Jet Build (Part 2)
The next part was to move on to the fuselage. I decided to go with a profile front end to save weight & building time. I cut a front fuselage piece and a cross piece to go through it. At first I was just going to extend the wing forward to create the "top view" of the profile fuselage, but it would have come out right at the bottom edge of the canopy instead of the front of the fuselage. Then I thought of angling it down to meet the front, but then I would end up with "Down elevator" acting on the front end all the time. I finally came up with cutting a second piece that went in about 3/4" below the wing and went out to the front, and extended inside the jet intakes under the wing. Here are the 2 pieces that make up the nose section.
Here they are test fit together to see how they look.
I glued these 2 pieces together with a little bit of 5-minute epoxy, and while the glue was curing I went back to the wing. I epoxied the front part of the wing on that forms the top of the air intakes as shown below.
The sides of the fuselage are made up from 2 pieces that also contain the rudders. I needed to glue on a little strip of Depron to serve as a support for the fuselage top deck the fits in between the rudders. Here is one of the side pieces with a guide line drawn on for placement of the Depron support strip.
And here is the piece that will be glued onto the rudder.
Next I glued the support strip to both rudders. After that was done I added the rear top deck that forms the top of the engine nacelles to the back edge of the wing as shown in the photo below.
To install the fuselage sides/rudders I placed the wing assembly on the edge of my workbench, upside down, and epoxied the fuselage sides into place.
Here is another view looking straight in from the back.
Next I test-fit the nose section to the wing assembly to see how everything lined up as shown below.
Just like in the SU-27 Shock Flyer, I am using a centrally located motor in a pusher configuration. The fuselage sides are 3.6" apart from inside to inside. I bought some 4 x 2 props and cut them down to 3.5" so they would fit in between the fuselage sides. The motor will mount inside the fuselage, on the bottom surface of the wing, right below the carbon fiber wing spar. To make room for the prop, I cut a slot 3.6" long and 0.5" wide into the top of the wing.
Here is the motor and prop that I will be using. The motor is a Maxx Products Speed 180 unit. On a freshly charged 2-Cell Li-Po battery, the motor turns 18,500 RPM with the 3.5 x 2 Prop. I have it shown on top of the wing in this photo, but it will actually be mounted on the other side of the wing.
That does it for this installment. Next I will move on to the tail surfaces and starting putting everything together.
Stay Tuned for Part 3!
|Jul 06, 2005, 12:57 AM|
Mini F-15 Park Jet Build (Part 3)
In this segment I will move on to the tail surfaces. To simplify the control linkages, and allow independent taileron control, I cut elevators from the horizontal stabilizers. I measured back 3/4" from the trailing edge at the root, and extended this out at a 90 degree angle to dertiming the cut line for the elevators. After I cut them out I trimmed about 1/32" off the inside edge for clearance.
Next I marked the location for the control servos. I will be using 2 servos, 1 on each side of the fuselage. Each servo will drive both the aileron and elevator on one side of the fuselage at the same time. I will use elevon mixing on my Hitec Optic 6 transmitter to control the servos. Here is one of the servo holes.
And here is the servo being test-fit into the hole.
After I had the servos test-fit, I moved back to the wing. I used 3/4" wide Satin Finish Scotch Tape for the hinges. I beveled the leading edge of the ailerons, with the angle on the bottom side, and attached them to the wing with the tape on the top and bottom. Here is a shot of the pane at this point with the front end glued on and the ailerons installed.
Now it was time to make up the control horns. I have been using blank CD's to make my control horns from for all my foamie planes. They are easy to cut and shape, and they are very strong since they are made from polycarbonate plastic. Most of the packs of blank CD's have these on the top & bottom of the stack to protect the CD's from being scratched. CD's are 0.050" thick, and the blank ones are usually the same thickness, but every once in a while, I get some that are only 0.025" thick. Since this is such a light plane, I decided to use the 0.025" blank CD to make control horns for this plane. Below is a photo of the piece I cut from the CD to make my control horns. The strip in the middle is 5/8" wide.
Next I squared off the ends and scribed four 5/8" squares onto the piece of CD material with the tip of an X-Acto knife. Then I scribed out the shape of the control horns in these reference squares. Here is a shot of the piece after I marked the control horns out.
The plastic is thin enough that it can be cut with scissors, so using the scribe marks as guides, I cut out the 4 control horns to the shape shown below.
Then I sanded the top edges round, drilled a hole for the pushrod, and roughened up the bottom edge with an emery board so the glue would hold better. Here are the 4 control horns ready to be installed into the control surfaces.
To mount the control horns, I cut a slot 1/32" wide by 5/8" long into each of the control surfaces about 1/4" from the inside edge. Here is the control horn slots cut into one of the elevators.
And here is the control horn slot that was cut into the aileron.
Next I put a 1/4" x 3/4" piece of scotch tape over the top side of each control horn slot. This was to keep the epoxy from leaking through when I glued the control horns into place. Then I placed the 2 elevator halves upside-down on my workbench. Then I mixed up a batch of 5-minute epoxy. I used the back end of a #11 X-Acto blade to push epoxy down into the slots in the control surfaces. Then I spread a very thin coat of epoxy onto the base of the control horn and slipped it into the slot. After I made sure they were aligned properly, I waited for the epoxy to cure. Here is a picture of the 2 horizontal stabilizer assemblies with the control horns glued in place.
The next part of the construction was to glue the horizontal stabilizers in place to the sides of the rudders. I drew a guide line on the side of the rudder with a Sharpie marker to line up the part. Then I took the 1/8" wide strip that I had cut from the wing to make room for the Carbon Fiber wing spar, and I cut 2 reinforcement strips from it. These would be glued in place on the bottom edge of the stabilizers to increase the gluing surface and strengthen the joint. Here is the first stabilizer being epoxied into place. I balanced the plane on the edge of the workbench while I glued the stabilizer in place.
Here is the bottom side of the stabilizer after the epoxy set up. You can see the small 1/8" square reinforcement piece in this view. Also notice the epoxy that is left on the mixing board. Just because you mixed it, does not mean you have to use it!!! It does not take much epoxy to hold the parts together, and any more than you need is just dead weight you have to carry!
And here is the other stabilizer being glued into place.
And here is how the plane looks now.
Starting to look like an F-15!!
Well that concludes Part 3 of the build sequence. Next I will move on to radio and pushrod installation, mounting the motor, and installation of the bottom sheeting.
Stay tuned for Part 4 coming soon!
|Jul 06, 2005, 01:58 AM|
Wow Cool! Thanks for sharing the technique for making control surfaces from the CD's.
Looking good. Keep us posted.
|Jul 09, 2005, 11:27 PM|
Mini F-15 Park Jet Build (Part 4)
Moving on to the innards of the plane..........
The next step is to install the control servos. I decided to use some more of the 0.025" thick CD material to make some servo mounts. I cut 4 pieces 1/4" x 3/4" as shown below.
Then I scuffed up one side of each with some 100 grit sandpaper. Once that was done, I used some 5-minute epoxy to glue one at each end of the servo cutouts in the fuselage sides.
After the mounts were in place, I set the servos in the holes, marked the screw locations with a Sharpie pen, and drilled holes through the plastic. Then I used some little sheet metal screws to hold the servos in place. Here is a shot of the fuselage at this point.
With the servo in place, I measured and cut 2 pieces of 0.032" music wire to make the aileron pushrods. Here is one of them in place running from the servo to the clear plastic control horn on the aileron.
Next I moved on to mounting the motor. I am using a Maxx Products Promax 180 motor in this plane. It is a standard brushed motor that turns the 3.5" prop at 18,500 RPM with a 2 cell 480mA Li-Po Battery. My local hobby shop had some little 5A max speed controllers on sale for $10.00 each, so I picked up a couple. Here is a shot of one. All the electronics are inside the red shrink wrap. The circuit board only measures 3/8" x 3/4".
This motor only draws 3 amps WOT, so the controller should work just fine.
Since the prop I am using is a 4" one cut down to 3.5", and the space between the fuselage sides is only 3.6", the motor needed to be firmly mounted in the plane with no chance of shifting. If it were to move more that 0.050" either direction, the tips of the prop would eat a hole in the side of the fuselage and that would be bad!!!!!
To keep the motor firmly planted in the plane, I decided to fabricate a box mount out of 1/16" plywood. Here is the first piece that will be split on the line to make the bottom piece and the motor mount piece.
After I cut out these 2 pieces I cut some notches in the ends with my Dremel tool. Then I cut 2 triangular pieces to form the sides of the box and notched them as well. Here are the 4 pieces that make up the motor mount after they were trimmed to fit.
After I had the pieces cut and test fit together I drilled 3 holes in the motor mount plate. Two of the holes were for the mounting screws and the larger center hole is for the front motor bearing to fit through. Here is a close-up of the piece.
Here are the finished pieces dry fit together just before gluing them. The notches really make this a strong box, taking the stress off the glue joints.
And here is the finished mount with the motor being test fit to check the alignment of the holes.
Here is the completed power assembly ready to be glued into the airframe. I mounted the prop so I could get the motor mount glued in dead center with equal clearance on both prop tips.
Here is the motor assembly epoxied into the plane. The center of the box mount glues right to the carbon fiber wing spar rod to help distribute the thrust loads away from the foam.
For the controls I am using coupled ailerons and elevators with elevon mixing from my Hitec Optic 6 transmitter. To provide independent adjustment of the elevators, I coupled the elevator pushrods to the aileron pushrods with a 1/16" wheel collar. This way I can trim the servo arm to the aileron, then trim the elevator to the aileron. Here is a shot of the pushrod installation.
And here is a close-up of the pushrod adjustments.
Here is the plane with the servos, motor , pushrods and speed controller installed.
And here is a close-up of the radio gear installation.
At this point, All I have left to do is build a battery box to hold the 480mA 2-cell Li-Po battery, install the receiver and glue on the bottom sheeting. After that is done I thought I would take a ruler and a fine point Sharpie pen and draw some panel lines, and then take some wide point Sharpie pens and draw some color on it to make it look nice.
That does it for Part 4. Part 5 will finish up the plane and move into flight testing.
I should be able to get it finished this weekend. I will keep you all posted.
Till next time.............
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