New scratch-built project

[bearcat]

If you've been following my other threads regarding the overweight and underpowered J3 Cub foamy, then you'll know I've ordered a new power plant to soup it up.

But the old motor is a perfectly good brushed inrunner. It's just that it doesn't have a whole lot of power to swing a huge prop. The 9x6 did increase thrust on the J3 Cub, but the motor didn't have the torque to be able to increase rpm.

SO...I'm going to build another plane for it. It is meant as a small glider and the plans are from one of my modeling magazines from earlier this year. It's got about a 3 ft wingspan and is a tailfeather glider, no ailerons.

BUT it is very much lighter than the Cub foamy.
So if I make it a powered glider, I would like to use the Cub's motor, prop, and speed control. The battery's a NmH, so it's a little bit heavy. But I have a Lipo that's close to the same power rating.

So I'll have two planes on the workbench at the same time, this little guy, and the Sophisticated Lady. I don't have a decent pic, but I will photograph the pages of the magazine later and post here.

[bearcat]

Here is the pic:


I have blown up the centerfold plans 20%, giving it a 44" wingspan. It's just 8 inches larger than the original version in the magazine. Just call it an "altitude adjustment".

The way I figure, I'm going to have about 7.4 ounces per square foot of wing area. It should fly fine. Even though the Cub foamy's motor that I'm using is weak and has a small prop, it still flew a 24 ounce airplane with 18.5 oz/sq ft wing loading, albiet barely.

All a sailplane has to do is be able to get up there. So with the lighter wing loading, it might do just fine. And if it doesn't, then I'll stick an outrunner in it.

[bearcat]

The project has begun. The biggest thing is making enough copies of the wing ribs and stuff, which I did on the Xerox machine at work, enlarging everything 20%. Then I cut them all out and glued them to a sheet of balsa with elmer's glue. Elmer's is wet though, so I had to weigh the sheet down because it wanted to warp while the glue was drying.

This isn't a plane I'd want to have transparent covering on the wings because it doesn't look as good with paper glued to one side of each rib. I've got some monocote in silver, but I do want to save most of that for the 2-meter sailplane project. There's probably enough to cover this and that plane too. I was really saving the silver to do a nice P-51, but that's okay.
I could use Japanese Tissue, which makes a really beautiful finish, but it's so fragile that landing in Gavilan Field would definitely rip it up.

I really would prefer a different color. I don't have anything orange, so maybe something in orange would be cool. I also don't have blue, but for a beginner's plane, I think I want something that's going to stand out against a blue sky. I'm passing through Albuquerque next Friday, so I'll buy something like that (and stock up on supplies).

I'd like to be totally finished building and only have the skin left to do next weekend. We'll see. I'll photograph my progress and post updates here.

[bearcat]

I'm probably about a third done with this project. I've got the starboard wing all built and the fin. I've enlarged it from 36" to 44" wingspan for our thinner air and also to help keep wing loading down for the motor.

The biggest modification is significantly strengthening this plane. It doesn't add that much weight to use spruce and bass wood. The ribs are thicker than called for, the spars are basswood, and the leading edge is a spruce dowel. I want this thing to be more survivable than your typical all-balsa plane.

The motor is kind of weak, but I'll try it. If I keep this down to about 12 oz or so, I think the motor will do fine, because all it really needs to do is get this plane up there to soaring altitude. But if it turns out to be significantly underpowered, then I'll throw a small outrunner in.

Here's a pic of the progress so far. Sorry it's a little out of focus. It's kinda hard to take with my cell phone this close in.

[bearcat]

A quick update. Progress is continuing and this is turning into a quick build. The inner port wing panel is done and the horizontal stab is done. Tail surfaces are built mostly of basswood for strength and also to help balance a motor in the nose. Next step is to join the port and starboard wing sections together and set the dihedral angle. I'm using a lot of epoxy glue on this, with some CA. I've never used mostly epoxy to build a plane before and I'm trying it. It's a little messy, not as neat as CA gel. But it provides one hell of a strong joint.
...I got a piece of dried epoxy in my eye when I was sanding some "over-flow" down with a dremel tool, so that hurt, and did a little scratching, until I fished it out. Guys, safety glasses are a good idea with dremel tools. That goes for me too.

I'm getting close enough to start thinking about the color scheme. I really prefer epoxy paint instead of airplane dope over the wood. The problem I've got with dope is that it's too transparent, and you have to put so many coats on to get good color shading that it seems to me 2 coats of epoxy provides a superior finish and might even be lighter than several coats of dope. And I don't really like using plastic film on wood with tight angles (see fuselage on plans above) because it's a challenge to keep air bubbles and wrinkles out. But looks great if you do a good enough job.

I am pretty much set on opaque orange monokote or ultracoat on the wings and horizontal stab. I am thinking about gold paint on the fuselage and maybe fin. Also would like to use some gold trim on the wingtips. But that depends on what's available at the hobby store when I go to Albuquerque. I kind of don't want to have to order by mail because of the obvious mail delays over the holidays. If they don't have orange, I might change to something else. But I don't have an orange plane, and I think that would be cool, and show up well against either a blue sky or a cloudy sky.

I'm also wondering if I should change the shape of the fuselage so that I can use a folding prop. Not a bad idea and would make the nose not quite so blunt.

I'll post pics again soon.

[bearcat]

Now this is a cool RC plane. Unfortunately, they don't show how you get one. It is an actual peregrine falcon mechanical bird, but it looks very real and even flaps like the real deal. It was enough to get a bunch of other birds VERY nervous. My plane is merely called a "pocket peregrine". This one actually looks like one.

You'll have to pull up this link to watch, since it's not You Tube.
www.metacafe.com/watch/1776921/robot_peregrine_falcon/

[Lt Swiss]

I searched good but only got a few hits on this one... Very cool!...


Cybird RC Robot Bird
www.ukrobotshops.com/cybird-product.html


Micro-Ornithoptère R/C "Wingbird
ovirc.free.fr/wingbird.php


ORNITHOPTER
v3.espacenet.com/publicationDetails/biblio?CC=CA&NR=2348085&KC=&FT=E


Check out this thread...
Gliding ornithopter Falcon F5
www.rcgroups.com/forums/showthread.php?t=977895

[bearcat]

Here are the pics, so far. The wing and tail surfaces would have already been covered by now if the right color of Ultracoat was more available. Turned out the ONLY place in the country that had orange Ultracoat was in Illinois, and it's expected in Hobby Proz in Albuquerque today. Thing is, I really don't want to drive down there again so soon. So I'll have them ship it to me.

The color combo will be orange wing and tail, and gold body. Also some gold trim on the wings. The tail boom is a length of carbon fiber tubing, with the antenna and one of the pushrods within it.

You might notice that the spinner for the folding prop is a little smaller than the width and height of the fuselage, so the prop cannot fold flat to the fuse like it should. I know this, but in order to fit the Speed 400 motor, the fuse had to be this wide. The idea here is that even mostly folded back, the prop will survive landings, whereas a straight non-folding prop will tend to break. The easy fix here would have been to lengthen the fuselage, so that it could be narrowed at the spinner. Problem is, the shaft of the motor is not long enough to allow lengthening the nose. The only thing I can do to improve this in the future is to put a much more modern, more powerful, and much smaller outrunner motor into the plane, and then rebuild the nose to be narrower. For now, I'm just using spare parts, so this is the best I could do with a Speed 400.

Also note that the leading edge of the wing is simply a hardwood dowel. There is a good reason for this. I'm a beginner and a pure balsa wing does weigh about as much as a butterfly, but also cannot withstand even a single crash landing. I sacrificed an ounce or two for massively increased strength. The tail surfaces are almost completely built out of basswood.
(And in case you're wondering, the center joint of the starboard and port wing halves is sheet mahogany with fiberglass in the center).

This was originally a 36 inch scratch built 4-oz 2-channel non-powered glider from a centerfold of Flying Models magazine in March of 2008. I have increased it 22% to a strengthened 44" powered version of the Pocket Peregrine. I am hoping for 12 ounces or less. But the motor and battery are admittedly heavy. Part of the reason for the 8" longer wingspan.


Check out the sanding job on this fuselage. This is a day's worth of sanding by hand with 320 grit. And it's almost a shame to cover it with a coat of paint. Stain and varnish would be a LOT prettier. Yeah, this thing is going to get a skid, because soft balsa won't stay this nice after too many landings. The original Pocket Peregrine had the body made out of plywood and I think basswood. I had to save weight in the nose where I could, so the entire thing is balsa, except for ply fuse braces.

[bearcat]

Canopy's done. The entire top of the fuse will be open, and the area in front of the wing covered by a canopy. I'm going to work on it today and make a little handcarved pilot for it. I painted the fuselage gold and it looks good. I cut some vents on the side for motor breathing and I'm tempted to have some kind of air cooling for the speed control too, but haven't figured out where to put everything inside yet.

I am forced to rearrange things. The weight of the Speed 400 motor requires that the lipo battery be placed as far to the rear as possible. I can put it directly under the CG but then there isn't room for the two servos to control tail feathers. I can move the servos to the compartment just forward since they weigh very little, and they might have to reside as far forward as the other side of the firewall, so that I have room to pull out the battery from the rear compartment.
It's a little unconventional, but it'll work fine.

I cut the carbon fiber rod to 18 inches (about a fourth larger than original scale) and mocked everything up yesterday with the battery in place and found that I needed about 3/4 of an ounce of lead in the tail. Once the servos are in place and with all paint, prop and spinner, I might end up with an ounce of lead in the tail. But it is still fairly light and noticeably lighter than when these electronics came in the foamy Piper Cub that I bought.

But is it light enough to fly this glider? I think so. It flew the 23 ounce stock Cub foamy, albiet extremely underpowered. So in a glider with 8 inches more wing and half the weight, I'm sure it will get me up into the thermals. And if not, maybe I'll retrofit the nose of this plane for a 125 watt outrunner, which would give this plane 3D ability.

Because of Christmas, I am afraid I will have to forego buying the Ultracoat until payday next week. So I'll be dead in the water in a few days anyway. I sure hate not being able to finish the plane. I could use Japanese tissue, but I really don't like that stuff. It's so fragile that even handling the plane could put your finger through the skin. If I had silkspan, that's a little stronger, but I'd prefer to wait until I get Ultracoat. Besides with all the chicory brush and sage brush here in New Mexico, the first landing will shred the wings if I use tissue.

I'll try to post pics later.

[bearcat]

At this point, I'm so close to finishing that I might as well wait until it's completed, which may be later today. The cockpit is finished and painted gold. The electronics are installed and have been tested. I had a bad servo, so I swiped one out of my foamy Cub wreckage. Now everything works. The folding prop and spinner is on and it works perfectly. The fuselage is not too wide afterall. And it's beautiful, how it turned out.

I finally got my Ultracoat in and have coated the tail surfaces and started on the wing. That stuff is really good and is a step above Monocoat. It feels like it's actually tougher than Monocoat. And provides a very nice finish.

I had to move out of my workshop, because the "man cave" got flooded due to a bad boiler inside the furnace. I had to get the furniture out of there and pull up the carpet. Saved the carpet but now I have furniture all over the dining room. On top of all that, now a friend of mine needs rescuing due to car trouble and so I have to turn around and drive back down to Santa Fe and bring him back. And I'm supposed to be smoking a ham on our charcoal smoker this afternoon and installing an electronic fence for the dog.

Boy, for a day off, I sure am busy!!!
Maybe tonight I'll be able to work on finishing the skin on the wings. Should be ready to fly this Peregrine by Sunday. And it's going to be gorgeous.

[bearcat]

Well, it's basically done. But it really is as they say, the devil's in the details. I'm getting the last final things done. Got the tail mounted to the tail boom and the boom mounted and aligned on the fuselage. The ultracoat is done and the orange looks fantastic with the gold! That's a neat color combination, but it didn't photograph well in the house this evening. I'll try and take a better pic in the sunlight tomorrow morning and post the pics.

Will it be ready for flight by tomorrow? Wow, I don't know. I sure tried! There isn't much left on it, and it's really close, but maybe I'll bring it out, if only to show it off.

I ordered a scale on ebay so I can make sure it didn't end up overweight. It feels okay, but it might be sitting at about a pound. Hopefully less. Scale's not in yet though.

Mitch, do you want the honors to take it up for its first flight and trim it out?

[bearcat]

Here is a pic at about 95% complete. All that was left at this point was to do the pushrods and install the subfin. All of that is done now. But this photo is just prior to attaching the subfin.
With the subfin attached, it is perfectly balanced. To offset the weight of the heavy Speed 400 motor, the tail is made out of basswood and there is a section of allthread glued in the middle of the tail mount, not visible from the outside. Then the 3-cell, 1320 mah Lipo, which is also kind of weighty, sits right in the middle of the CG.

I'm not sure what the weight is yet. I've ordered a scale but it's not in yet. To me, it feels like about 12 ounces, but Evan felt it was more like about 16 ounces or a little more. Once I weigh it, I'll post it.

[bearcat]

Here it is, fully completed and ready for its maiden flight. Notice that the subfin is now attached.

[Lt Swiss]

Outstanding! Can't wait to fly it.

Its gotta be 3mph max for her maiden flight. Come early next Sunday around 9:30-10:00 for the best air...

[bearcat]

Sir, yes sir!
I will be there.

I'm going to predict that stall speed on this will be around 15 mph. It might drop out of the sky at 3 mph.
I'm looking forward to it.

[bearcat]

Maiden Flight today!

First time was kind of wobbly because it has such a large rudder and had too much throw. It had a crash-landing as a result. But thanks to Mitch for taking the hot seat to be Chuck Yeager. Oh, it wasn't hurt really. A little bit of cracked balsa on the pod, but nothing to stop it from flying again.

So after adjusting the rudder for less throw, Evan decided to be Chuck Yeager this time. Suspecting that the throw wasn't forceful enough the first time, causing it to be wobbly, I ran with the plane at full throttle and it had a much better launch with more speed.
Apparently that's all it needed.

Excuse my French, but the Peregrine hauls ass. It's a somewhat fast plane. Wind penetration should be excellent. It is extremely sensitive, according to Evan, but it flies just fine. It looked to me like motor-on, it was going about 40 to 45 mph, and with a stall speed of about 20 mph. So, not much of a floater. It's almost a sport plane...with a little bit more motor, it could be. The Speed 400 has plenty of power for this airplane. Considering it came out of the Foamie Cub which barely flew, I would say the Peregrine is significantly lighter than the cub, which was 24 ounces.

So very minor balsa repair on the nose of the pod is needed. But I think I will pull off the rudder servo's control horn and drill another hole for less throw, since the rudder is so large.
I also think I will gear up the airplane factory and build a second wing for the Peregrine.

The second wing will be about 10 more inches of wingspan and a little more chord. I'd like to have a wing for thermaling and a wing for more speed.
And I don't think I should fly this myself yet. A little more experience, but this would be a GREAT plane for the windy springtime here. I'll bet it would even make a very respectable slope soarer...with power of course.

I'll have to see how rough it is on the foamie slope soarers you guys fly first, before I decide to take it out there.

[Lt Swiss]

Sorry to crash your plane today. I hope she's easily fixable. I'm glad it turned out okay with Evan. She flew very good. I hope I haven't lost your trust in my Yeager abilities...

[bearcat]

Hey, my friend. My faith in your abilities as a spectacular pilot is not waivered one bit. The launch for you was simply too soft and it teetered on the edge of stall for a good bit before finally doing a wingover. I think you did okay. Yeah, if it was overpowered, the motor would have pulled it out. Just didn't have enough speed, that's all.

And yes, I have repaired it. I'll use a little wood putty and some spot painting, and it'll look good as new.

[Lt Swiss]

Whew! Thanks...

[bearcat]

Thing is though, 11.1 volts on a Speed 400 may perform well, but it WILL burn up the motor. It is a few volts beyond the range of a brushed 400-type motor. If I only used full power on occaision, it would live longer. But the high stall speed and our thin air means that it needs that full power to fly. Long story short, I need to make plans for an engine swap. And a larger wing still is not a bad idea.

I COULD use one of my 7.4 volt batteries and save the motor. But you saw that thing fly. It needs all the power that 400 can put out. I can't back off to 7.4 volts, otherwise it won't have the balls to fly well.

I got my scale in finally, and the Peregrine weighs in at 18.90 ounces. Lighter than the foamie Cub, but a little heavy for a 44" wing. That's why it flew fast. Slow it down some and that sensitive rudder might be perfect.

[bearcat]

The Peregrine is going back to the airplane factory for some revisions. Here's why.

The original Pocket Peregrine was a 36" wingspan carrying only 4 ounces of total weight. I've totally changed the personality of the plane by modifying it for power. The tail surfaces are large, making it super sensitive at the high speeds that my 44" wing has to fly it. It's designed for lower speeds.

Another big reason is the Speed 400 motor, which makes adequate power running a 3-cell lipo. Problem is, 11 volts will burn up the brushed motor very quickly, and will soon need to make a dead-stick landing.

So here's the goal. Cut the 44" wing in half and build a 10 or 12 inch center wing section for it. The 20" wing end-sections will each attach on the center section then. I'm looking at probably having an overall wingspan of about 56". In order to do this, I will incorporate a carbon-fiber tubular spar which will accept a rod that will slide into it. Haven't worked out how I'll attach the wing panels to the center panel yet. I could even do it like my Gentle Lady, which just uses electrical tape once the panels are slid in.

While I'm at it, I am strongly considering upgrading my power to a brushless outrunner, which can run all day on 11.1 volts and make more power too. Why not? Why do all this work and end up with an underpowered plane that could lose its motor at any time?

I'll work out my calculations and post here. Plus the pics of the revised project.

[Lt Swiss]

That seems like a hell of a thing to do. Crazy!... Cool, but crazy...

Can't wait to see it. You are certainly a builder...

[bearcat]

I have a 125 watt outrunner that turned a 9x4.7 prop on the foamie Cub. With a 1320 mah battery, flight time will be about 7 minutes of full throttle. It provides a power to weight ratio of 100 watts per pound, which would make the Peregrine aerobatic.

However, the Peregrine runs an 8x4 folding prop. Close enough.
Top speed? Should be around 70 mph straight and level. That's a lot of power. However, it doesn't have to go that fast. Most of the time it could be flown at half throttle, or no throttle for thermal-riding. That should extend flight times as long as you can ride a thermal, or 14 minutes of continuous half-throttle.

Not bad for a little 1320 mah battery. This thing should fly like a real falcon.
By the way, I LOVE the falcon pic. Thanks!

[bearcat]

I was going to start on my Peregrine wing extensions this weekend, but got a real lazy bug and just couldn't get to Ace to pick up the balsa. I was finishing up a 240Z model I have been working on. That was a ride. I'll talk about it somewhere else here.

[bearcat]

I spoke to Pat Tritle, the RC plane designer, and asked him about extending the wing and he disagreed. He said if I change the wing dimensions, I have to also change the tail length. His recommendation is to replace the weaker speed 400 with a brushless outrunner and try to lighten the plane. He said the plane is what it is, and suggests reducing the rudder throw and reducing the weight.

I think the 125 watt outrunner will be a little lighter, but I'm still running the same lipo. I think it's only going to lighten up maybe an ounce. So it's going to be a little heavy. But at least it'll have a lot of power. Works out to 111 watts per pound, which is 3D.

Like Pat said, it is what it is.

By the way, the plane appears in this latest issue of Flying Models magazine. I sent Pat a photo and he had it put into the magazine, since he's a contributing editor. Cool, huh?

[bearcat]

Okay it's modified. It lost 4 ounces of weight by switching to the Supertiger 360 outrunner. Would have been more but it was so much lighter than the brushed Speed 400 that not only did I have to relocate the battery as far forward as possible, but had to also add half an ounce of lead to the nose.

I didn't like having to do that but when I first built it, I had to add ballast to the tail because of how heavy the brushed motor was in the nose. So if I had it to do over again, it could be an ounce lighter than it is now. But 18.3 ounces and triple the power should be more than enough.

It was so oversensative that I also reduced the throw on the rudder. Plus I'll switch it over to the Futaba radio, which has a D/R function. Just need a channel 39 crystal and they didn't have any crystals at all at Hobby Proz. I'll have to order that.

It's running a large 10x6 prop and makes 109 watts per pound. So this is a little hotrod now. It tries to pull itself right out of your hands at full throttle.