RE: .40 SIZED FLYING WING

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RE: .40 SIZED FLYING WING - 8/27/2009 7:49 AM

iron eagel

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Like I said...
"I can not wait to hear how this one performs!"
You can always tweak the design/construction if you see any real potential.

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RE: .40 SIZED FLYING WING - 8/27/2009 7:55 AM

iron eagel

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quote:

ORIGINAL: combatpigg
I can't see this thing clearing the hay unless it goes on a diet.

I think you will have no problem dialing this design in
Northrop and a few others thought it had potential...

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RE: .40 SIZED FLYING WING - 8/27/2009 8:13 AM

combatpigg

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Dave, the head did take a little abuse, all the fins are still there, though.

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RE: .40 SIZED FLYING WING - 8/27/2009 8:18 AM

combatpigg

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IE, imagine trying to do this stuff back in the day before there was RC models!
With Hitler breathing down your neck to get something going.....[>:]!!

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RE: .40 SIZED FLYING WING - 8/27/2009 9:02 AM

iron eagel

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quote:

ORIGINAL: combatpigg

IE, imagine trying to do this stuff back in the day before there was RC models!
With Hitler breathing down your neck to get something going.....[>:]!!

Now there is a scary thought...

No reflex and the cg can shift aft a bit, the sweep has got to have something to do with that...
Obviously the weight of the torque rod setup is not all that much of an issue, considering she flying nose heavy for you.
I really like the idea of shifting the motor a bit aft, shifting it into the wing will also cut down on some materials as well.
Is there enough room to still provide for a larger fuel load if you do that?

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RE: .40 SIZED FLYING WING - 8/27/2009 10:48 AM

combatpigg

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IE, we'll have to make room. If there's a will, there's a way

. The elevon servos will have to be relocated somehow to accomodate the longer fuel tank plus the engine setback. The setback will probably allow me to substitute that huge 1500 mah pack for something lighter. The model should handle even better without having all that dead weight sitting back there in the stern.
After sizing things up tonight, I don't think it's going to take that much work.
I weighed the model tonight before tearing it down and it was 4 lb 2 oz. It can only get lighter.

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RE: .40 SIZED FLYING WING - 8/28/2009 6:24 AM

combatpigg

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First thing this morning I loaded the fuselage into the chopsaw and took 1.5" off the front end.
The next step was to take a bite out of the leading edge of the wing. The wing dowels needed to be redone. The servo mounts were hacked out and the cavity was enlarged for the wing servos to lay flat. I used GOOP to glue them to the fiberglass skin of the wing.
The rest was just redoing the firewall, front wing mount and throttle servo+linkage.
The plane wont need the big battery or any lead to balance now.
The last big detail will be making a new cowl.
This set up is going to be much lighter than the original, maybe 6 ozs. We'll see after the new cowl gets done.
The biggest drawback to this layout is the muffler has to come off before the wing can come off.

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RE: .40 SIZED FLYING WING - 8/28/2009 7:58 AM

Mike Connor

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cp, what are you using to hold the servos in place and can you get them out with out tearing up things? My wing will need a similar setup.

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RE: .40 SIZED FLYING WING - 8/28/2009 9:35 AM

combatpigg

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Mike, I'm relying 100% on the GOOP. To get the servos out, take a wood chisel and pry with steady pressure. I've used GOOP in less strenuous servo applications. Slowly but surely the GOOP will give with steady pressure. I'm not 100% sure this will last for the long run, but the weight saving and time saving advantages are too good to pass up. I know a couple of F-1 pylon racers who used the same idea with their servos in fiberglass fuselages, but they used GE silicone.
Always clean the mating surfaces with MEK or similar before gluing.
If I was REALLY sold on this [gluing] idea, I could have chopped the mounting lugs of the servos off to loose 2 more grams of weight.

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RE: .40 SIZED FLYING WING - 8/28/2009 6:09 PM

iron eagel

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Wow talk about a remodeling job...

When you do the new cowl try to blend it into the wing if it is not too much of a pain, I think it will reduce the interference type of drag caused by the cowl/wing joint.

For what it is worth...
I have used GE silicone in a couple of airframes myself and I have not had an issue with the servo pulling out either. In most cases the servo mounted that way outlasted the airframe, and even held up during one of those hard landings where the servo gears gave up but the mounting held.

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RE: .40 SIZED FLYING WING - 8/28/2009 7:37 PM

combatpigg

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IE, I'll see what I can do to blend the cowl to the wing. I look at this plane as the guinea pig. The wing is massively over built. I'm afraid to knife into it at this point, I think it would do more harm than good. The next one will be blue foam, but there's going to be a lot of foam removed before glassing and skinning. Without even using a scale, you can hold this plane now and it seems within reason weight wise. With a lighter wing, it's going to be great....hand launches with speed props should be no sweat then.

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RE: .40 SIZED FLYING WING - 8/28/2009 8:45 PM

iron eagel

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Cp,
It looks great, and the current engine mounting may be a bit easier on the head.

I really think that this has design has real possibility to evolve; it obviously has a lot going for it as far as potential when looking for flat out speed.

Looks like you need a Jett .46 with a rear exhaust and pipe…

You would have to go inverted but it would be interesting to see what would happen with out the trash can hanging out the side.

Problem is the cowl would have to be done in such a way as to shield the head from ground contact, as well as ducting the cooling air out the back.

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RE: .40 SIZED FLYING WING - 8/28/2009 10:09 PM

combatpigg

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The engine hasn't been tried yet with open exhaust, there's the aerodynamic answer if power isn't hurt. A bladder tank to feed it would further reduce weight and allow a bigger intake....possibly.
This muffler really does give the engine a boost though, you can see the rpm jump and hear that resonant tone as you adjust the needle. This muffler sure is load...louder than some full piped engines.

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RE: .40 SIZED FLYING WING - 8/28/2009 10:33 PM

iron eagel

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I love those Jett Mufflers they really can give a boost to even the tamest motors by themselves. The scavenger effect is still well worth the penalty of the added drag of the muffler, and like you said you can hear the engine respond to it. And I would be willing to bet their tuned pipe setup is even better.
I have got to get me one of those Jett engines!!!

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RE: .40 SIZED FLYING WING - 8/29/2009 6:17 AM

combatpigg

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Here's a look at the cowl.

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RE: .40 SIZED FLYING WING - 8/30/2009 4:24 AM

iron eagel

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Nice!

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RE: .40 SIZED FLYING WING - 8/30/2009 5:45 AM

combatpigg

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Thanks IE.
This morning's flight testing went OK...for awhile. The 1st flight was with a 11x6 and it launched and flew real nice, just like a pattern plane. The Jett turns this prop as well as any .45 I've seen.
The 2nd flight was with a 10x8. The engine was loaded down a little bit....the speed of the plane improved and the flight lasted longer with the lower rpms. 6 ozs still burns pretty fast.
3rd flight with a 9x8......never happened. The plane shot straight up after release and wallowed around swapping stalled wing panels until it crashed. It was a combination of less thrust and tail heavyness that caused it. If the plane had more flying speed before takeoff, it probably would have been easier to save. Landing gear isn't an option, though...this field is too rough and no club field around here would allow this type of plane. I never considered that the 9x8 prop is light enough to make a big CG difference...but this plane was probably already at the aft limit.
I've made a couple of changes to lighten the plane a little. I'm heading back out to see what happens.

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RE: .40 SIZED FLYING WING - 8/30/2009 7:42 AM

combatpigg

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Too bad the Sun had to set tonight. Finally, I think I can say this thing is dialed in. The launches still tend to baloon straight up unless you make a real effort to aim low when you release. You basically have to aim at a spot 30 feet in front of you.

I was able to remove 2 ozs of wing material by drilling 32 holes. I had to add some of that back with a new front spar. The original cracked on the last bad launch...so the net result was -1 oz there. The biggest improvement was swapping the 4.4 oz battery for a 1 oz pack [300 mah].
I also left off the cowl tonight [1 oz]. The total weight loss was 5.4 ozs, so the dry weight RTF is 3 lbs 10 ozs now.
The landings are still like dropping a bucket of bolts for this hay field. The real solution will be making a wing with white foam, or doing the same wing out of wood. So far the Jett has only been run on 5% nitro and only has an hour on it. It ran a 9x8 up to 17,200 which isn't exactly awesome, but it's still early in the game. This fiber-filled-plastic Dave Brown engine mount is too rubbery. After a nice engine run the mount feels like it's broken. After it cools off it firms up again.
About the only thing that is left that I can think of doing to increase the speed would be to clip the wing. I kind of hate to do it because this thing really flies great now.....but it's only doing 120 mph by my best estimate.

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RE: .40 SIZED FLYING WING - 8/30/2009 12:46 PM

Strykaas

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quote:

It ran a 9x8 up to 17,200 which isn't exactly awesome,

What would you call awesome ?

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RE: .40 SIZED FLYING WING - 8/30/2009 3:57 PM

combatpigg

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I was expecting better than 18,000.
Look at it like this, a OS .32 turns a 8x8 @ 18,000 and will fly a small enough model to 130 mph on 15% nitro sport fuel. They have set the bar for my expectations.
What I need to do tomorrow is mix a batch of 15 - 25% nitro and put the HowFast? gizmo on this plane and then see what we've got here. Maybe even bring the razorsaw out there to prune the wingtips?.....

Also get an aluminum mount for the poor engine.
Might be better off to make another wing with less span in mind, make it lighter throughout.

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RE: .40 SIZED FLYING WING - 8/30/2009 6:28 PM

Mike Connor

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quote:

ORIGINAL: combatpigg

I was expecting better than 18,000.
Look at it like this, a OS .32 turns a 8x8 @ 18,000 and will fly a small enough model to 130 mph on 15% nitro sport fuel. They have set the bar for my expectations...

Keep in mind that a 9x8 is about 60% more load then 8x8. My SJ50 would turn a 9x8 around 18,000 rpm.

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RE: .40 SIZED FLYING WING - 8/30/2009 7:17 PM

iron eagel

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Nice to hear it is starting to come together.
I don't know as I'd clip the wings, it would probably be better to build a new version that is a little less rugged.
I bet that motor mount is also costing you some performance. I recall HP making a comment about how motor vibration reduces speed, and his suggestion that a sidewinder type of mounting is far superior when dealing with the speed as the span of the wing damps out a lot of vibration, that flexible mount is probably not helping you out at all.
Besides you have only run the engine an hour, wait til you have it broken in.

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RE: .40 SIZED FLYING WING - 8/30/2009 8:52 PM

MJD

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quote:

ORIGINAL: iron eagel
Besides you have only run the engine an hour, wait til you have it broken in.

There are plenty of comments posted here and there on how folk's Jett engines just run better and better as they get a bit of time on them. Not 50 hours I mean, but through those first couple of hours of accumulated running time I guess. I recall the difference in the first three flights of my SJ50 as being pretty evident. I recall a comment from someone who tried out the Demon when I had the SJ50 on it, using the throttle a lot but also doing high speed passes - his comment was "man, is that ever a nice engine..". Sure is. It's going back on #1 until #2 is finally finished and also until I sort out why the West.50 is running relatively feebly at the moment. No use diagnosing it on the aircraft.

CP, you noted how rpm pick up with channellocks clamped around the head. What about vice-grips - you could leave those on. Or maybe, plug the intake, glow plug and exhsut outlets, then pot the engine into the cowl with filled epoxy..?

MJD

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RE: .40 SIZED FLYING WING - 8/30/2009 9:31 PM

combatpigg

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MJD, if I send the engine back in for service and it's totally encased in casting resin..or if the upper cylinder has big visegrip chew marks on it....he might try to "squirm out" of the warranty?
For an engine that doesn't have more than 2 speeds, it sure has a lot of barrel throw at the carb. Having a rubbery mount for the first ugly test crashes worked out OK but for now I'm going to glue some CF to the mount as a stop gap until I come up with aluminum.

Mike, I don't have the thrust calculator any more...could you tell me what the thrust and HP is with a 9x8 at 17,000? About your flying wing....take my advice and don't take ANY of my advice, except keep it light, light, light. I didn't factor in the wingtips on this plane because it complicated the CG locating process and I ended up noseheavy for the first flight. If you don't factor in the forward strakes on your plane, it could end up tail heavy. I ran into a guy at the LHS who claims his CAD [Auto CAD?] deal factors all that stuff if you enter the outlines.........I know nothing 'bout that stuff.

IE, yes this poor wing has suffered enough, no hacking today. Here's what the core templates look like. The outboard template is so small it has to be tack glued and screwed to stay put.

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RE: .40 SIZED FLYING WING - 8/31/2009 12:15 AM

Mike Connor

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For what it's worth, ThrustHP says 1.842 hp and 5.69 lbs of thrust using an APC 9x8 at 17,000 rpm. I find a large difference when using the thrust #'s from some of the electric motor calculators but you can't just plug in the rpm numbers.

I finally got a complex shape CG calculator from a guy in "aerodynamics" and someone else confirmed it using a "real" CAD program. My TurboCAD Learning version lacks some of the goodies. Light, light, lilght, I couldn't agree more. I should know for sure soon but now it looks like mine will come out RTF at 2 lbs 12 oz. with 495 sq. in. wing area. I can be happy with that wing loading.

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