F86-HPX-Sabre, By Rossco & IrvineJ

Irvine.J
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"Coming down protocols"

Post by Irvine.J » Wed Aug 08, 2007 10:31 pm

Ok Larry, its very apparent you need spend some time in aussieland. Basically, we do things a little differently around here... :D
So, in the event of a flame out heres how we do this...

So here we go...

I know its not optimal, but its all about having a good time :)
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Step 5: Get mates, hot dogs, marshmallows, and salute the greatest 100% stainless steel PJ aircraft that ever flew LMFAO!
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Step 4: Hope for the best...
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Step 3 : touchdown!
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step 2: Bring her in REAL easy, aim to impact on anything that has a 0% Human factor.
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Step 1, dump as much fuel on the CC as possible, making the most absurdly large tailflame you have ever seen.
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Anders Troberg
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Post by Anders Troberg » Thu Aug 09, 2007 6:38 am

Beautiful wings. Make them straight and put a pointy nose on it, and you almost have an F-104.

It looks sturdy as hell. If (or, more commonly, when) it crashes, it will probably do more damage to the ground than the ground does to the aircraft.

Attach the wings with something that allows them to break off cleanly from the body in a crash, such as shear pins, and it will be next to indestructible, although it may aquire some dents.

larry cottrill
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Beautiful, indeed!

Post by larry cottrill » Thu Aug 09, 2007 11:38 am

Yes, Rossco, that's beautiful stuff you have going there. Looks like something I wouldn't want to have "gliding" into the side of my house, for sure!

But, I live a long way from you, so n'worries. Forge on!

L Cottrill

Rossco
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Post by Rossco » Fri Aug 10, 2007 1:29 am

Bit more done on the design...
Slow going from here on.

Just noticed something is out of line, z CG is off... bugga, next time. Id say one of the materials is out, something has taken on the wrong density.

Next is getting the weight out of that tail. I suppose i cant do it ALL in SS.
Now comes some control surfaces, gear and then tanks.

Rossco

PS, the red cross is the CG im aiming at. Needs to come into line with all the control gear before the tanks go on.
Im also thinking that i have to leave the original look a little with the landing gear... she will have to be a tail drager... bugga again.
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Big, fast, broke, fix it, bigger, better, faster...
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Anders Troberg
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Post by Anders Troberg » Fri Aug 10, 2007 6:13 am

Have you considered moving the engine forward?

It looks like (just a rough guesstimate) the CG will be way too far back in this configuration, and every gram removed from the tail means five grams of ballast you don't need to put in the nose.

Irvine.J
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Saber

Post by Irvine.J » Fri Aug 10, 2007 7:50 am

Well I've convinced rosco not to make it a taildragger, and stick with the tricycle undercarriage. (yes we do disagree on things but in the end we get there) Basically, that CG as shown is without the pylons, fuel tanks, and their appropriate coverings. Its also not including a battery, nose wheel, and the rest of the Rc gear that needs to go in. I still think if we keep it as designed we'll get it spot on the money. We are also assessing the possibilities of CF horizontal and vertical stabilizers if we have to go down that road. The fuel tanks are swept forward on the pylon so it leaves us a simple angle change to move the CG fractionally in any direction easily. Stay the coarse !
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Anders Troberg
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Post by Anders Troberg » Fri Aug 10, 2007 11:17 am

Build it slightly nose heavy, the tail always comes out heavier than expected. Also, there is a saying that goes "A nose heavy aircraft flies badly, a tail heavy aircraft flies once". Always err on the nose heavy side. It's also much easier to correct a nose heavy aircraft.

The fuel tanks, especially for such an thirsty engine, should have their CG in line with the aircraft CG, or flying characteristics my change during flight as they empty.

It's a good thing you dropped the tail dragger, it just looks so wrong on a jet.

Which simulator is the video from?

Btw, I've blocked that horrible picture of the P-51 crashing into a P-38. It hurts my macho image too much if people see me cry... :cry:

Irvine.J
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Post by Irvine.J » Fri Aug 10, 2007 12:04 pm

The fuel tanks, especially for such an thirsty engine, should have their CG in line with the aircraft CG, or flying characteristics my change during flight as they empty.
We know :)
What I was saying the actual pylons are obviously of some weight, we simply move them forward or back, with the fuel tanks we will be carrying, we can actually get nearly 1/2 inch of play to for the actual tanks CG on top of that. Don't worry anders, we do kinda sorta know what we are doing ... maybe :)

As for being tail heavy, yes, thats bad.
That simulator video is taken with xplane, when designing the plane, we had to get everything to just perfect to make her fly like that in the sim, changing airfoils, everything. Its not just a matter of slapping on some wings and taking it for a fly, we had to design it from the ground up for our particular specs, alot of work went into I promise you.

Its then simply a matter of using that data to make the real thing now. I've used this method before, and strangely enough, if something happens thats just completely weird in xplane, it does happen in real life. Oh, my poor 4 engined bomber, which now lies in a heap of ruins that rosco is pilfering the electric motors off, learned the hard way that if Xplane says don't invert roll and give full rudder at the same time, you just don't do it!
How are those motors going rosco! LOL!

Hey anders, any idea how much something like that 51 or the P-38 there would cost, that looks to me like quite a bit of cash getting churned to the wind :) I CRIED TOO! :P
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Post by Anders Troberg » Fri Aug 10, 2007 12:41 pm

Don't worry anders, we do kinda sorta know what we are doing ... maybe
I didn't mean to offend, I was just rambling about the subject in general. I do that a lot.
That simulator video is taken with xplane
Aha, that's why I didn't recognize it, I looked for simulators specifically made for model aircrafts. Xplane is, I think, mainly a simulator for full size aircrafts (not that it matters, it's the same laws of physics)?
Its then simply a matter of using that data to make the real thing now.
Simply? :shock:
Hey anders, any idea how much something like that 51 or the P-38 there would cost, that looks to me like quite a bit of cash getting churned to the wind
I don't think it's really a matter of cost, it's a matter of availability. Sometimes money is not enough.
As for being tail heavy, yes, thats bad.
Hehe, I have a Tiger Moth, and the first flight was on a windy day (yeah, I know, bad idea) and the CG was a little bit far back. It's harrowing to fly when you can walk beside it going against the wind, but when you turn and get the wings up against the wind it's "SWOOSH!" and it's 300 m away, all at less than one meter altitude since it never managed to get out of the ground effect due to the heavy tail. Flew much better with some extra weight in the nose...

Irvine.J
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Lol

Post by Irvine.J » Fri Aug 10, 2007 1:10 pm

Lol anders, i'd have loved to have seen that tigermoth. I once strapped a camera to the rudder of a partinavia...BAD idea, the thing was a tomb for a good piece of wireless camera gear. but hey, it was fun for the 10 seconds it lasted :)
Aha, that's why I didn't recognize it, I looked for simulators specifically made for model aircrafts. Xplane is, I think, mainly a simulator for full size aircrafts (not that it matters, it's the same laws of physics)?
Yes you are right. It is really designed for larger aircraft, but it seems to handle the small stuff quite well. Though there are a few little things that it "doesn't particularly like" with our model. For whatever reason it doesn't like to be programmed with a hollow fuselage, its expecting if this is the case, to have the compressor in the engine specs to take up the rest of the room so it can calculate drag and "stuff." Since we are using a rocket as our propulsion source, we have hollowed it out an used a miscellaneous body as the engine. This still has a normal and registrable computational domain, but still has the hollow tube around it. We use the rocket as we can specify the SFC that way with a more pj like throttle response I usually use it for Pj plane testing. It doesn't seem to effect the flight model too much at all though, we did try closing up the tail end and noticed very little difference.

Anders you should come over to Australia when its the big day, your welcome to crash here! *No pun intended* :)
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Post by Anders Troberg » Fri Aug 10, 2007 1:46 pm

Lol anders, i'd have loved to have seen that tigermoth.
Oh, you can see it: http://rpglab.net/troberg/gallery/view.php?gid=64

It's still alive and well, currently hanging in the ceiling of my computer room.

Didn't get that flight on video, though.
For whatever reason it doesn't like to be programmed with a hollow fuselage
Hmm, gives me an idea. If the body is kept hollow with a smooth inside, wouldn't it work somewhat like a barrelwing (like the Stipa Caproni)? That might make it more aerobatic, especially knife edges. The body would act as two extra wing surfaces (or, more correctly, one extra, as there's always an outside of the body).

http://images.google.com/images?q=stipa ... s&ct=title
Anders you should come over to Australia when its the big day, your welcome to crash here! *No pun intended*
Thanks for the invitation, but Australia is far away and I just used up my holiday days for this year. Too bad, I've always wanted to see Australia (and take lots of photos which I would put upside down in the album so everyone can see how it looks...).

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Post by Rossco » Sat Aug 11, 2007 8:57 am

Haaaahahaha, that Stipa Caproni is hillarious!.... no.... it will not be anything like that! ha.

Very nice bipe Anders. How does the yellow go for visability? I cant decide if a bight colour like that, or a dark one to contrast with the sky is better? Depends on your flight style i suppose.
I am a little concerned about keeping visual on this one, but thats the least of my worries atm.

OK... more done.
I didnt pattern out the tail planes with the cuts in these parts, as i just didnt know how accurate my mounting piece would come out. Some very delicate trimming to be done this time.
This is the last of the major steel parts done now, so all the tweeking, straightening, balencing, welding, grinding and polishing can get underway. And no... it will not be having any ballast. It should be all designed to come into line as is.

Hopefully my sticky tape will hold up under the conditions! ;)

Rossco
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Anders Troberg
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Post by Anders Troberg » Sun Aug 12, 2007 1:33 pm

Haaaahahaha, that Stipa Caproni is hillarious!.... no.... it will not be anything like that! ha.
I didn't mean it will look like that, I meant that the hollow body can give some of that barrelwing effect.
How does the yellow go for visability?
I have very good eyes, so it doesn't matter either way for me.

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Post by Rossco » Wed Aug 22, 2007 7:36 am

A little more done.
Still havnt worked all the kinks out of the control surfaces yet, so they wont be cut till we are sure.

Ideas are being tossed about for attachment to the stubs. This will be the next step once finalised, locking/attaching points fitted, then glassed/carbon fibred.

These are straight off the cutter, so some finishing is required yet.

Rossco
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Irvine.J
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Lol rossco

Post by Irvine.J » Wed Aug 22, 2007 2:48 pm

A XXXX in every picture uploaded to the forum! Now you've set a standard! Hehehehe.

I love it rossco, your wire cutter did a nice job on those wings and tail section, now all we need is some carbon fiber, epoxy, and whole lotta luck!
Nice job.

Anders that was a sweet tigermoth too btw, I only just now realise I didn't reply to that post, I thought I did. I was curious what size motor it runs, and what airfoil you used on the main wings. I know some friends who have had terrible trouble getting their biplanes to fly properly, she looks really pretty and I bet she flys just the same!
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