F-8 crusader profile Parkjet - RC Groups
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Jan 27, 2014, 01:53 PM
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F-8 crusader profile Parkjet


I've been going through my old designs/plans and slowly re-doing them for public consumption, originally I did an F-8U-III super crusader which was basically a similar design except for the nose and intake. I decided to make it a straight crusader this time. You could take these patterns and make a pointy nose and curved intake snout and re-do it as a super crusader. There are slight wing differences but probably not enough to notice. On the super crusader you'd have to figure out a way to model the ventral fins which are either horizontal or vertical and quite large, on mine I just created some ventral strakes that sort of modeled them from the side view in takeoff position.

I used a center piece with tail and then two doublers on each side to give me enough thickness to give a nice rounded nose and intake.
It would be easy to add some formers or pink foam and add thickness to make it fully 3-d.

Originally I mounted the wing on the top of the fuse with some tabs and glued a fairing cover over the top. On this version, since the real plane has some airfoil thickness, I decided to pick the most forward point of the wing leading edge and use that for the slot location. I think it looks ok like this and allows some foam above the wing to hold it in place and model the fairing that is on top of the wing. In order to lock the wing in place, I'll drive some 2" pieces of 1/8" carbon rod down through the top of the fuse through the wing and into the body and CA them in place.
In the photo of the wing, i took it an an angle, so the wing tips look angled in, they are in reality parallel with the centraline.

I placed the motor thrustline as far up as I could in the tail cone. I did need to reduce the size and placement of the ventral strakes so that the full flying tail tips would clear them. On the full 3-d fuse the ventrals are low on the plane and the placement of the horiz stab is further out so they clear naturally. I also added a bump on the side to model the refueling probe area.

I ran the servos as far forward as I could and supported the pushrods via carbon outer tubes. I cross mounted the servos in the fuse so I could get them as flush with the body as possible so that the pushrods wouldn't hit the tips of the surfaces when moving.

The ventral strakes are placed so that they provide somet feet for the model to lean on when landing, I reinforced the tips with .04 styrene sheet to take the landing load. If you don't have these in place the model will tip far enough that it will hit the tips of the stabilators on the ground before the wingtip makes contact and could damage them.

Dry with motor and serovs is 11 oz, still need to add rx, esc, battery, and finish, expect it to be a similar 15-16 oz as the phantom.

I'll show some construction photos. I also posted a photo of the color scheme I like.

Update 1/28: Did the painting last night, unfortunately I completed the painting and removed the masking in the garage and the gray looked much lighter there, now it looks dark to me but I'm commited. I finished the wing/tail panel lines and right side, ran out of a few letters/numbers, will do more tonight.

Here is a good site with lots of side views of different color schemes...http://www.crusader.gaetanmarie.com/...20drawings.htm

Here is my CG calculation point, I used about 20% of MAC, 6% stability margin and about 20% of a flying wing CG position:

http://wingcgcalc.bruder.com.br/en_U...d6=0&sweep6=0&

Plans can be found at www.dynasoarrocketry.com go to the plans pulldown and then select parkjet plans
Last edited by burkefj; Nov 10, 2017 at 01:21 PM.
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Jan 30, 2014, 12:09 PM
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Maiden result....


Maiden went really well, the CG at 7.5" as shown on the plans was very good. I needed about 4-5 clicks of up trim, and some right, but that's pretty normal. Slow flight was very good, I wasn't able to induce a true stall, it just short of mushed with power and full back and would then drop the nose just a bit. Very tight loops can be done, flies like a heavier plane, tracks really well. Handlaunch at medium throttle was nice, just keep the nose level till you get a bit of speed and climb out.

Rolls were pretty axial, wanted to drop the nose a bit, but could be counteracted by a bit of down when inverted, split esses were very easy, as were barrel rolls. Inverted flight wasn't bad, did require down elevator to be held, but was nice and controllable and didn't want to flop over to right side up.

Glide power off wasn't bad, but it is not a floater without some throttle...

I think it is slightly nose heavy at this setting, only thing I noticed was that on power off landing, if you start the flare too early, it will get slow and drop the nose after a bit. Just keep a bit of speed and flare gently. I'll fly it here for a while and then maybe play with CG a bit.

Looks very good in the air.

Frank
Jan 30, 2014, 02:51 PM
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Build Notes:


Print out plans, make sure you print with no scaling and no margins. Double check that the dimensions on the X/Y on the title page match what are marked or somethign got shrunk and things won't align right. Tape them all together and cut out the templates.

Trace the wing and cut it out. Sand the edges if desired, cut a V slot for the main left and right wing spars. Cut the spars to length. Use the end of a spar to drag in the v groove till they sit in nicely without a force fit(or it will warp the wing). Glue them in with foam safe CA+ and tape over using dubro blenderm hinge tape. Cut the cross spar and cut/groove/glue/tape that spare in place being sure to glue it to the other two spars.

Trace the stabilizers. Sand the edges if desired. Cut the aluminum 1/8" ID tubing to make the torque tubes, leave about 3/16-1/4" longer than the foam at the root edge to glue the control horn to. Sand the tube rough, cut a V groove in the bottom of the stabilizers, make sure they are at 90 degrees to the root edge. Use the tube to ream out the groove till it fits nicely but not too tight or it will warp the foam. Use a dubro micro servo horn for the control horn, drill it out to fit snugly over the aluminum tube, and glue it in place using CA. Glue in the torque tube into each stabilizer using foam safe CA+ and tape over, make sure the control horn is facing UP toward the top of the model.

Cut out the ventral fins, sand the edges and bevel the root edge so that it will sit at approx 45 degrees to the side, make a left and right.

Cut out a single fuse center section with vertical fin, Sand the vertical fin and spine round if desired. Then trim off the vertical fin from the template and make four more doublers, since depron has a smooth surface on one side, make the two outer ones mirror images with the smooth side out. Cut a nose reinforcing rod from 1/8" carbon rod to length, and then groove/glue it into the nose/side of the center side, it doesn't matter which side, it will be hidden by the doublers.

Use 3m-77 spray adhesive to glue two side doulbers to each other, then to the other two doublers. At this point, round the top edge where the spine/vertical fit will be, as it is hard to sand this after gluing to the fuse spine. Then use 3m-77 spray to glue the doublers to each side of the center fuse, and sand edges round to shape.

Cut two 3/4" .04 or .03 styrene disks. Glue one disk on each side, centered on the pivot point noted on the plans for the horizontal tail. Drill out a 1/8" hole to fit the torque rod. Be sure this is square to the body and wing. Cut a carbon 1/8" rod to length to fit through the fuse, slide on the left and right stabilator, and leave 3/16" on each end, cut the rod to length.

At this point, mark and cut the wing slot, test fit the wing and make sure it is square to the fuse. You may mount your motor in the tail however you wish, just be sure to leave prop clearance for the tail. The motor wires will need to route on the bottom of the fuse to clear the moving tail surfaces and can be hidden under the right side ventral strake and routed up to the underside of the wing.

Make some pushrods, I used .039 music wire with 1/8" carbon rod slid over and CA'd to stiffen them. I put z bends on each end so that the rod would sit closest to the side of the fuse. Cut the fuse to mount your servos, they sit crossways to the fuse and align them so that the pushrod is fairly perpendicular to the turque tube control horns. You need the servos mounted so the the pushrod is right against the side of the fuse, or they will interfere with the tail surfaces at full deflection. I mounted my servos slightly ahead of the CG location. When happy you can tack glue the servos in place on both sides. Mark and glue the ventral strakes in place keeping them aligned to the centerline of the fuse and make sure that they don't interfere with the tips of the stabilizers at full deflection. I then removed the full flying stabs, and carbon pivot tube.

At this point I painted the individual pieces and applied sig 4" stars and bars, used a sharpie for panel lines using any of the 3-views you can find online, and used some 1" vinyl letters I got from office depot. I cut some trim from self adhesive monokote trim for the cockpit windows and intake red V. You could paint these as well.

Install the torque rod into the fuse, make sure it is centered and apply a very small amount of thin foam safe CA to the rod to lock it in place. You don't want any glue on the rod as it will bind the turque tube, use an exacto to scrape off it the stabilizer is tight. Install the stabilizers and pushrods again and center them using the radio. Cut two 1/8" long aluminum tube pieces. Slide an aluminum tube piece on the end of the torque rod on each side and put a small DOT of foam safe CA+ on the end of the rod/tube piece to lock it in place and hit it with accellerator. Do this very carefully to be sure you don't get any inside the main torque tube or it will lock in place and you'll have to cut everything off and start over. Make sure both sides move freely. I used the third from the outermost hole on the dubro servo horn on the torque tube and the outermost longest servo horn hole that came with my servos. Make sure the pushrods don't interfere with the tail during movement. If they do you can trim the root edge of the surface to solve it.

Mount the wing and be sure it is centered and use foam safe CA+to glue it in place. Once installed I cut some 3" long 1/8" long carbon rod pieces and rounded the ends. I then pushed a hold through the top of the model through the wing and fuse in two places and put in CA+ glue and pushed them in place. This will lock the wing to the fuse.

I mounted two dubro wing skids to the bottom of the fuse to protect it from our conveyer belt landing runway, you will notice that the ventrals help keep the tail surface from dragging on the ground after landing. I inserted some 1/2" wide strips of .04 styrene into the fuse, and along the bottom of the ventral fin and glued them in place to help reinforce that area on landing.
Mount your electronics and tape down the wires using dubro tape. I mounted the esc and rx as far forward on the underside of the right wing, and mounted the battery as far forward as I could on the right side. This helps counteract torque to the left. Be sure the motor wires are not interfering with the tail surfaces. If desired you could slot and push in the motor wires into the side of the fuse to make a cleaner install. Check CG and add nose weight if needed, I added 1/2 have ounce by cutting a slot into the front of the intake and pushing it in place and CA'ing it. You may choose to wait to glue it till after your trim flights. I'm using an eflite 800mah 3s pack which is small and weighs 2.3 ounces. You could use a thunderpower g8 910 pack as well, or something slightly larger instead of adding nose weight. If you are running a pack over 2.5 ounes I'd strap it to the fuse instead of relying just on velcro to hold it on the side, however with my light packs I've never had one come loose in flight. If you use velcro be sure to attach it before painting, or the self adhesive will just pull the paint off with the battery. I'm getting 5 minutes of slightly agressive flight time, half throttle flies it nicely, I usually don't need to go above 2/3 in a nice big loop.

Flare slightly for landing,

I'm using all the roll and pitch throws I can get and I like it that way. If using the grayson V-3 microjet and apc 6x4 launch at half throttle or so as needed to launch and avoid a torque roll as it leaves the hand, once away, keep it level and throttle up and climb out. Trim, check out the throws and adjust to suit you, check stall, loops, rolls, etc and glide and have fun.

I'm right at 16 oz rtf and this grayson motor flies it really well, even with the small battery pack. I'm using a thunderbird 18 but you could use the stock grayson 20 amp esc as well.
Mar 28, 2016, 06:36 PM
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J Bergsmith's Avatar
My Crusader is coming along nicely thanks to the easy to follow planes, and build pictures provided. Fuselage is built up with five layers of depron, so it requires some sanding/shaping. Takes a little time, but it's very rewarding when the finished product turns out well.
Mar 29, 2016, 01:24 PM
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Wing spars are installed and Ailerons are cut, and the wing is fitted in the fuse. The elevator bearing tube and supports are installed.
Mar 29, 2016, 05:50 PM
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Photo of the elevator bearing and support disc.
Mar 29, 2016, 09:31 PM
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burkefj's Avatar
Looks great!
Apr 07, 2016, 10:09 AM
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The Crusader is complete and ready to fly. The only changes I made to the original plan was adding ailerons. Since the fuse was thick enough, I recessed the receiver and battery. Used Testors paint, decals from Stickershock, and added the panel lines that really add a lot to the model. Hopefully will get some flights in tomorrow.

Frank's plans are excellent. His designs are not fun, easy to build, and fairly inexpensive.

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