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May 15, 2007, 11:04 PM
Bernoulli+Newton=Lift
magic612's Avatar
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Build Log

Semi-scale swept-wing F14, approx 1/15 scale


Hi all -

Last year I made the standard size version of gpw's "F-14ish" plane. At the time, I really didn't have the right battery or motor, but it did fly pretty well. Now, I wanted to build something a little more scale-like in appearance, yet maintain that fast but easy-to-fly quality of Glen's design.

So, I sat down at AutoCAD, and designed what I hope will be a pretty nice flying plane. Pictures so far show the glued but not-yet-sanded fuselage and wing, along with the jet engine cowling for each side.

I'm hoping it will end up at about 18 ounces. Plan to use a TowerPro brushless generating about 22 ounces of thrust with a 3S 1250 mAh Lipo. Haven't decided about landing gear yet - might add them, might not.

Hope to post more later...
Last edited by magic612; May 16, 2007 at 09:22 PM.
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May 16, 2007, 06:07 AM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
Cool !!!
Latest blog entry: Lost plans
May 19, 2007, 08:57 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP

Fuse / Wing attached


Some minor progress. Sanded all the foam sections on the fuselage as best I could, and smoothed out the rest with lightweight spackle as filler. Added a carbon fiber spar to the wing, which is embedded in the foam wing in order to be flush with surface of foam. And then I epoxied the fuselage to the wing. So far, it seems to be VERY strong. I'm really only worried about the tip of the nose being weak.

I can't decide yet whether to use 3mm or 6mm Depron foam for the tails yet. I'm leaning towards the 3mm, since I think they'll look more scale-like and add less weight (total weight so far is at 9.25 oz). Also picked up some small retracts - leaning heavily towards using them in the plane. I think it'll really add a great element to it, plus help save the bottom of the engines from belly landings.

Next up: Need to get some lightweight fiberglass so I can strengthen the nose and fuselage sections.
May 19, 2007, 09:04 PM
HappySpringPerson
youth must fly's Avatar
WOW you are really at it, nice job with the nose section.
May 19, 2007, 09:09 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP
Thanks! It's amazing what a little 100 and 220 grit sandpaper will do (and a healthy dose of lightweight spackle).

Hey, I grew up in the Nutmeg State - and I know it's not 6948 miles from Chicago (more like 900)!
May 19, 2007, 09:30 PM
HappySpringPerson
youth must fly's Avatar
hey maybe i set something wrong in my profile dont know

When i read mine it says im 11181km away from you
May 25, 2007, 11:28 PM
Wow, I love how this plane looks.
Probably not a big shock, I know.
May 25, 2007, 11:49 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP
Thanks Tomcat!!

Here's some more progress pics. It doesn't look like much has been done, but there's actually a fair amount of work here. I glassed the entire nose section, and the fuselage from wing-height down all the way back into the engine cowling a few inches. I used heavy glass cloth on the underside of the fuse, since the tensile strength of the glass will help keep the nose area from snapping, plus the glass there will help with scrapes on less-than-perfect landings. It's so strong at this point, I can take the plane from the very front of the nose (first 6-8") and flap the entire plane as hard as I can like a hand-held fan, and there is no flex - it's completely stiff. I'd say it's pretty strong now!!

I also added the tails, opting for the stronger 6mm Depron, seeing as calculations showed that using 6mm would only add 4g of additional weight. I carefully sliced the LE and TE of each tail to a point, to aid in better aerodynamics (I should note that I did this prior to attaching them to the plane). I may still glass these with the 3/4 oz cloth, just to make them a little more ding-resistant. There is some heavy glass added where the tail meets the fuse on the inside of each tail. I epoxied the engine exhausts to be a bit more scale-like in appearance, though I'm not going to worry about trying to make them round, I don't think.

Engine mount was added as well - 3/8" basswood stick epoxied to a 1/32" thick piece of plywood which was then epoxied to the underside of the wing, between the "engines".

I tried spraying some gray primer on a small scrap of Depron, and I like how it looks, so I think I'll eventually be painting the whole plane that color.

More to come later. I should get a chance to work on it more this weekend. I need to determine the CG with some dry-weight glide tests, and then figure out where to place landing gear, battery, and radio gear.
Last edited by magic612; May 26, 2007 at 11:11 AM.
May 27, 2007, 12:03 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP

A bit more realistic-looking


Added a light coat of paint to it last night. Looks quite a bit more realistic now. I'm going to leave the tails black, I think. I've designed the necessary support structures for the landing gear, as well as appropriate locations in the plane itself (see PDF files).

I have a pretty good idea of how to make all the landing gear retract with one servo, using a number of carbon fiber rods and tubes to assist in consistently aligned movement of retract apparatus. Probably won't sketch that out, as I know what needs to be done - just a matter of doing it. I'll take more pictures as I make more progress on it.

EDIT: Forgot to mention that plane weight at present is 11.625 ounces. I'm concerned my AUW will exceed my intended weight of 18 ounces, though in fairness, since I'm adding retracts, those alone will likely contribute to the majority of the weight overage. I think I'll still be in good shape though, because even if I end up on the heavy side at 24 ounces (shooting for 22 or 23 at present), it will be generating in the range of 90-95 watts per pound. Not quite blistering, but should be FUN anyway!
Last edited by magic612; May 27, 2007 at 01:16 PM.
May 27, 2007, 02:18 PM
AMA 42867
callmeishmael's Avatar
Nice looking bird! I like the way you've given it a three dimensional look without the hassle of a fully built-up fuse.
May 27, 2007, 03:53 PM
HappySpringPerson
youth must fly's Avatar
Wow very nice, Glass cloth, looks to me like you plan on flying this model for a very long time

The landing gear, looks like you know what your doing. (Great drawings)

How about that paint camo? any ideas?

Tom
May 28, 2007, 11:16 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP

Land(ing Gear), Ho!!!


Hey, thanks for the kind words everybody - I appreciate the nice things you've been offering. The encouragement helps... a lot!!

Well, I worked on the landing gear. I was kind of dreading this part, since I've never put any retractable landing gear on a plane before, and this one needs not just two, but three retracts - one of which goes the opposite direction of the other two. So it was a bit of a mind-bender for a while, but once I figured it out, it was a matter of just doing it - and then hoping it would work like I thought it should!!

Let's see - built all three of the landing gear rail supports. Those are the plywood / balsa boxes visible which support the retracts themselves. These were needed to ensure the landing gear would lower into a position to keep the propellor high enough up so it won't smack the ground on hard landings.

Next was routing the pushrod for the front landing gear - simple enough, just a carbon fiber tube pushed through the fuse into the front landing gear / battery box area, and clipping it on. Then came the REALLY hard part - getting the rear gear to operate simultaneously with each other AND in concert with the nose gear.

First, I determined where the rear gear should approximately be located. Next, I cut slots into the engine cowling ahead of the gear supports. I slid a carbon fiber bar through these slots, and attached two Dubro Mini EZ connectors at each end. .047 wire attaches from these to the retract pulls. Then in the middle of the fuse, I epoxied 4 CF tubes, each about 1/2" away from the slot. A CF rod was inserted into each of these. Then the CF bar was epoxied to these, and a plywood brace was epoxied on top of that to ensure that the CF bar maintained a perpendicular attitude to the retract pushrods. Another Dubro Mini EZ Connector was attached to the plywood brace, and another .047" wire extends from that to go to the servo.

And amazingly enough - it all WORKS! And smoothly at that!!! (Sometimes I amaze myself...)

I didn't like the wheels I got at my LHS for the rear retracts, so they are just bare wires right now. And I decided to place the rear retracts outside of the engines, for bettery landing stability. I figure I can "hide" them with a dummy missle / rack.

Next up - finishing up underside to cover it all up (and still make some places accessible).
May 31, 2007, 07:18 PM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP

Better detail


I realized that my picture of the rear landing gear mechanics wasn't very good - since black CF against dark grey Depron doesn't show up too well!!

Hopefully the labels I've provided will help the picture make more sense. Note that the carbon fiber rods which extend through the four carbon fiber tubes are about 9" in total length.
Jul 01, 2007, 09:28 AM
Bernoulli+Newton=Lift
magic612's Avatar
Thread OP
Got some new servos - tried them for the landing gear. They're not quite powerful enough to move the gear up / down every time.

Grrrrr....
Jul 01, 2007, 09:46 AM
AMA 42867
callmeishmael's Avatar
Well that's frustrating enough. Are you going to keep working on the retracts or go to fixed gear or no gear next?


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