Author Topic: RW materials question for the Whiffverse:  (Read 10523 times)

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: RW materials question for the Whiffverse:
« Reply #25 on: January 05, 2014, 01:29:39 PM »
Going back to all aluminum, are there ceramic coatings that adequately deflect/absorb heat that can be used on leading edges and other high heat areas?
No, n ot really. Ceramics are too brittle and don't bond well enough in thin coatings to stay with the structure as the aluminum flexes. You're better off with titanium.

The problem with titaniun is not corrosion or CTE (although that one can be a problem), it is cost, density and, worst of all, formability.

Aluminum forms easily and then can be heat treated to get the strength you need. Titanium is too springy to form worth a d@mn. To get it to smoothly curved shapes requires either machining it from billet (= $$$$$$) or superplastic forming (= $$$$$). While it is stronger, for most aircraft structure, it is stiffness that counts, so you really can't reduce the thickness of the material to counteract the increased density, thus whatever you replace with Titanium instantly becomes 60% heavier, which is a bad problem for an aircraft that is supposed to go fast.

In thinking about a super fast Phantom, your real problem is that the aerodynamics really aren't there to go a whole lost faster than the Mach 2 that the design is rated for. The Phantom really is as aerodynamic as a brick and would need a huge aerodynamic clean up and reshaping to hit much faster than about Mach 2.7 even with higher thrust and lighter engines.

Paul

Offline Daryl J.

  • Assures us he rarely uses model glue in dentistry
Re: RW materials question for the Whiffverse:
« Reply #26 on: January 05, 2014, 01:38:42 PM »
I randomly chose 10-15% slower than the RF-4x.   Why?  Why not!  ;D :D :D
kwyxdxLg5T

Offline GTX_Admin

  • Evil Administrator bent on taking over the Universe!
  • Administrator - Yep, I'm the one to blame for this place.
  • Whiffing Demi-God!
    • Beyond the Sprues
Re: RW materials question for the Whiffverse:
« Reply #27 on: January 05, 2014, 01:56:24 PM »
What I have in mind is a pre RF-4x.

In that case I would probably go with the brute force/simple solution..i.e. standard RF-4 + rocket booster ( possibly two - mounted in aft Sparrow points) + some ablative coating applied to wing and empennage leading edges, front canopy and nose.  The bright white (or scorched, depending upon at what stage you show your model) coatings plus the rockets would certainly constitute enough of a difference so as to be able to achieve your goal of giving "the educated Phantom fan a double take".  Maybe also give it an appropriate code name and say it was planned for China overflights or similar?
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline elmayerle

  • Its about time there was an Avatar shown here...
  • Über Engineer...at least that is what he tells us.
Re: RW materials question for the Whiffverse:
« Reply #28 on: January 05, 2014, 02:19:35 PM »
One little problem there, Greg, the US RF-4's had all their Sparrow wells closed and faired over.  Still, I could see a twin-booster installation using that structure that remains internally or just a single centerline-mounted booster with the fuel in a conformal underside pallet.

Offline GTX_Admin

  • Evil Administrator bent on taking over the Universe!
  • Administrator - Yep, I'm the one to blame for this place.
  • Whiffing Demi-God!
    • Beyond the Sprues
Re: RW materials question for the Whiffverse:
« Reply #29 on: January 05, 2014, 02:36:33 PM »
Maybe convert a centreline fuel tank to have a rocket in the rear end then.  This would allow the rocket system and its fuel to be kept separate from the rest of the airframe...and also be jettisonable if need be.

To be honest, I actually prefer a single rocket solution since that has less risk.
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline elmayerle

  • Its about time there was an Avatar shown here...
  • Über Engineer...at least that is what he tells us.
Re: RW materials question for the Whiffverse:
« Reply #30 on: January 05, 2014, 02:40:33 PM »
The conformal pallet could pick up the pylon attach points and be just as jettisonable.  I'd rather go with a conformal pallet to keep the interference drag down.  Too, the pallet allows you to better spread out and arrange all the components and tankage.

Offline Daryl J.

  • Assures us he rarely uses model glue in dentistry
Re: RW materials question for the Whiffverse:
« Reply #31 on: January 05, 2014, 04:42:24 PM »
Would said pallet allow for the doors in the Phantom's aft belly?
kwyxdxLg5T

Offline Daryl J.

  • Assures us he rarely uses model glue in dentistry
Re: RW materials question for the Whiffverse:
« Reply #32 on: January 05, 2014, 04:46:08 PM »
Secondarily, what would be a maximum velocity for the factory stock alloys?   Mach 2.4-.5?
« Last Edit: January 05, 2014, 04:51:40 PM by Daryl J. »
kwyxdxLg5T

Offline PR19_Kit

  • Likes to brag about how long his...wings are.
  • Made it at last!
Re: RW materials question for the Whiffverse:
« Reply #33 on: January 05, 2014, 10:06:54 PM »
The three IDF F-4E(S)s, which grew out of the F-4X project, retained their Sparrow bays as they were build from F-4E airframes IIRC.
Regards
Kit

--------------------------
Any aircraft can be improved by fitting longer wings

Offline GTX_Admin

  • Evil Administrator bent on taking over the Universe!
  • Administrator - Yep, I'm the one to blame for this place.
  • Whiffing Demi-God!
    • Beyond the Sprues
Re: RW materials question for the Whiffverse:
« Reply #34 on: January 06, 2014, 02:06:16 AM »
Secondarily, what would be a maximum velocity for the factory stock alloys?   Mach 2.4-.5?

Apart from some key areas such as radome, windscreen, engine faces,,,and paint ;), I think you will find that most of the materials would last until at least 2.7/2.8 unless of course you were doing extended runs at high speed and thus temperature.  That is without the suggested ablative coatings though since adding these would alleviate the problem regardless of the materials below.
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline elmayerle

  • Its about time there was an Avatar shown here...
  • Über Engineer...at least that is what he tells us.
Re: RW materials question for the Whiffverse:
« Reply #35 on: January 06, 2014, 08:16:08 AM »
Would said pallet allow for the doors in the Phantom's aft belly?
It would probably need to be designed around them for routine servicing but major maintenance would likely require removing the pallet.

Offline elmayerle

  • Its about time there was an Avatar shown here...
  • Über Engineer...at least that is what he tells us.
Re: RW materials question for the Whiffverse:
« Reply #36 on: January 06, 2014, 08:19:50 AM »
Secondarily, what would be a maximum velocity for the factory stock alloys?   Mach 2.4-.5?
ISTR that the Phantom had a max. limit of Mach 2.8, though that generally required component replacement afterwards.  For your purposes, I could see the use of ablative material and possibly a special engine build allowing this somewhat more regularly.

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: RW materials question for the Whiffverse:
« Reply #37 on: January 06, 2014, 10:53:22 AM »
I could see the use of ablative material and possibly a special engine build allowing this somewhat more regularly.
Ablatives have the disadvantage that as they ablate they create a rough surface, increasing drag.

Mach 2.7 in a Phantom might be the "do not exceed" speed, but it's not somethiing that could be maintained for more than a second or two, much less minutes. And probably not obtained in level flight. You probably needed to be in a serious dive, with a tailwind, to get near it.  :)

Offline Daryl J.

  • Assures us he rarely uses model glue in dentistry
Re: RW materials question for the Whiffverse:
« Reply #38 on: January 06, 2014, 12:24:08 PM »
I'll have to ask Bill, my co-Dr. at work how fast they got their F-4J to.   High altitude, shallow dive, full AB.  1750 is what comes to mind but will ask again.   
kwyxdxLg5T

Offline Daryl J.

  • Assures us he rarely uses model glue in dentistry
Re: RW materials question for the Whiffverse:
« Reply #39 on: January 06, 2014, 12:31:23 PM »
Same questions apply to the Starfighter.   And presumably the same answers. 

I just prefer the Phantom.  ;D
kwyxdxLg5T

Offline GTX_Admin

  • Evil Administrator bent on taking over the Universe!
  • Administrator - Yep, I'm the one to blame for this place.
  • Whiffing Demi-God!
    • Beyond the Sprues
Re: RW materials question for the Whiffverse:
« Reply #40 on: January 06, 2014, 02:38:46 PM »
Mach 2.7 in a Phantom might be the "do not exceed" speed, but it's not somethiing that could be maintained for more than a second or two, much less minutes. And probably not obtained in level flight. You probably needed to be in a serious dive, with a tailwind, to get near it.  :)

That's where the suggested rocket helps...
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline tankmodeler

  • Wisely picking parts of the real universe 2 ignore
Re: RW materials question for the Whiffverse:
« Reply #41 on: January 07, 2014, 12:08:25 PM »
That's where the suggested rocket helps...
Generally, when you exceed the "do not exceed" speed, the wings fall off immediately, they don't take the time to melt. :)  DNE speeds are almost always structural limits.

Paul

Offline elmayerle

  • Its about time there was an Avatar shown here...
  • Über Engineer...at least that is what he tells us.
Re: RW materials question for the Whiffverse:
« Reply #42 on: January 07, 2014, 09:28:03 PM »
Not necessarily wings, the DNE speed for the XF8U-3 was, so I've read, set by where the canopy started melting.  So DNE values are set by reality, the Mach .82 DNE for the Learjet is set by where the wing is almost at a Mach tuck condition where the flow over the wing goes supersonic and generates a severe nose-down pitching moment.  There were some cases in the early 1980's where Learjets made big smoking holes from 45,000 ft. and it was found that the pilots had prevailed on the maintainers to put in an over-ride on the Mach limit function on the autopilot to allow them to go faster; unfortunately, this got them into this range.