Hurricane Mk103

Working on joints etc atm. I'm leaning towards foam shear webs in the H.S. I could use Coro ones, but my joining options other than rivets are limited to well below the Coro strength. This isn't a problem for air loads, but hidden hangar rash damage worries me. Divinycell H45 has the same specific strength, specific modulus and yield strain as Coro, so that's one option, if a bit pricey. I'm trying to find values for XPS but not getting far there. It's also hard finding a supplier for the denser grades of XPS. If you only want one sheet, you need to find someone who stocks it. If anyone has some scraps, I'll happily pay postage so I can test them. I have scraps of the low grade dow, 25psi, I think. One of the local big boxes has pink stuff and the other the green stuff I forget the name of. I am lacking in the higher grades. I suspect that the yield strain is going to be a poor match.

 

In order to pep up the rolling speed that will be crippled by flying at ultralight speeds, I'm going to enlarge the ailerons. Hinge them at the rear spar and extend out to the tip. This also simplifies wing construction and makes them a bit heavier to operate. Scale ones will be stupid light. I'd prefer plain ailerons, but I'd like to lose some of the adverse yaw, somehow. Don't worry, I'm not expecting to win dogfights against anything but other 103s.

 

Here's some info I had in my hard drive. "Mark" refers to Professor Mark Drela of the MIT Aero Astro Dept, the Daedelus airplane project, fastest human powered hydrofoil and the double bubble airliner! We're lucky enough to have him in our model airplane club, though we haven't seen much of him for quite some time now. My guess is because of that airliner. If he every gets free of that, and the FAA doesn't shut down our model flying, I expect he'll be underfoot quite often.

 

It will respond better to larger rudder at 30mph. Maybe more rudder percentage less vertical stabilizer percentage, to keep the profile looking more accurate.

 

Awesome, some numbers!
I'm pondering how to turn my electric hand plane into a mini thicknesser. Once I've done that. I can make uniform test pieces, as well as Eiffel props...
I've now found another adhesive that may make coro shear webs practical.

It looks like I'll be getting a fair bit of overtime at work for the next month and I also have immigration paperwork to do when I'm not working. So progress won't be great for a while.

 

Not a problem. Making progress on a project is not common here!

 

I'm not sure if there are any lessons to be learned from this or not, but here is a video of a 1/2 scale WW II fighter project...ME-109. It uses what appears to be a direct drive Hirth F-23 engine and weighs 264 lbs.

https://youtu.be/Q1BkdsIWaiU

 

That's a flying scale model, not a piloted replica, quite a different beast even if you can find a 1/2 scale pilot to fly it.

 

Sounds good with direct drive. But needs a three person assembly crew.:gig:

 

Of course it is. But the step from 1/2 scale to 2/3 scale isn't all that great. Knowing how a 1/2 scale at 264 lbs gross weight with 40 hp flys might give an insight to how a 2/3 scale Hurricane at 450 lbs gross weight and the same HP would do. The real question is that if a 1/2 scale WW II fighter weighs 264 lbs can you build a 2/3 scale fighter and make it lighter and yet still strong enough for safe flight?

 

Nice plane, but the construction method is too heavy. Look at all that lovely wood...
I prefer my removeable wing panels idea with a just tolerably big fuse and centre wing assembly. Javaprop thinks that a 7'2" 2/3 scale prop will give me lots of thrust on 40hp.
The take away from that video is don't try building a giant RC model.

 

I spent around two hours up close and personal with a Hurricat sans all its removable panels today. Fun and educational. I also picked out the closest Sherwin Williams 'Vinylsafe' colours to Battle of Britain camo colours. The BoB Hurricane was elsewhere so I improvised with a handy Spitfire and some old gloster gladiator fabric samples.
Paint testing can start when I get back to the USA.

 

Were you at Duxford? How does the renovated USA hangar look?


BJC

 

Shuttleworth. My sister lives 3 miles away, so it is a compulsory part of visiting her...

 

Any progress? I see on Youtube Peter Sripol is playing around with Coroplast skins on the tailfeathers of his latest ultralight.

 

He didn't seem too impressed with the weight in the video or at the show, but it does seem to actually make a decent looking final part. That said, I think going with Oratex for wings is more on the right track.

A lite Hurricane with Oratex covers would look pretty good.

 

Spendy but quick, no painting, and light.

 

We're trying it on our control surfaces. Spendy is certainly true, but it's not quite in the realm of insanity. I think we're about $1k in for our plane. Of course we had to get quite a bit extra because of the geometry of our surfaces, I'll be curious how much we have left over at the end. There's certainly other ways to do it if we aren't super satisfied with the results.

 

I've been working a lot, which doesn't leave many clear hours to work on my toy. I've been running numbers trying to get everything ballparked. I have picked a pair of main wing airfoils after some research and playing in XFLR5. As a result, the root is up from 19% to 21% to get a tame-ish stall progression at high (for a 103) speed. I guess I'll just have to eat the weight savings that provides to the main spar . Speaking of which, 7075 caps will save me several lbs and won't be too much more spendy than the 6061 I'll likely use for most of the tubing. I'm currently looking at monocoque coroplast behind the pilot and about the outer half of the outer wing panels. A centre section frame of aluminium much like the full size (which was steel) to take the heavy loads and provide the numerous hardpoints. A sheet Al shear web would buckle unless it was far thicker than needed for shear, so it'll be a truss. I have a lot of other maybe ideas that aren't ready for the interwebs.

Coroplast did look particularly good for control surfaces when I did the numbers. Lighter than my Minimax comparison, yet more rigid. Far less ballooning, too. The 2mm stuff I plan to skin with is a bit awkward to find. I've been playing with 4mm scraps to get a feel for the stuff. At some point, I may have to bite the bullet and order motor freight delivery of a stack of 2mm sheets. I'd prefer to leave that until I can actually use it as it is plasma activated, which will help with bonding of glue and paint. That 'wears off' after some months.

 

Somewhere in the thread you asked about tail feather weights....shown Carbon dragon data, mostly wood all cantilever surfaces. The Aluminum Dragon is close to these weights. All fabric covered.


Flight Limitations:



NORMAL

MAXIMUM

5 G Limit Load

4 G Limit Load

Minimum Weight Pilot and Chute

120 lbs

120 lbs

Maximum Weight Pilot and Chute

155 lbs

190 lbs

Maximum Speed - Flaps Down

38 mph

35 mph

Maximum Ground or Aero Tow

Maximum Rough Air Zero Flaps

50 mph

45 mph

Manouvering Zero Flaps

Maximum Rough Air Flaps Up

55 mph

50 mph

Maximum Smooth Air - Vne

65 mph

60 mph


Data:


Root Chord

61.2" = 5.1 ft.

Tip Chord

22.5" = 1.87 ft.

Span

528.0" = 44 ft.

Area

153.34 sq.ft.

A/R

12.62

MAC(1)

44.4"

DATUM(2)

L.E. of Root Rib(3)

DATUM of L.E. of MAC

4.5"

DATUM to 20% MAC

13.4"

DATUM to 25% MAC

15.6"

DATUM to 30% MAC

17.8"

DATUM to 35% MAC

20.0"


(1) MAC: (Mean Aerodynamic Chord) is the average distance from the front of the wing to the rear of the wing. 20% percent back would be the point at which the glider should balance

(2) DATUM: The datum line is an arbitrary point from which all weight and balance calculations are made. Most often, it is at the very front point of the aircraft (as in the case of the Carbon Dragon). All points back are referenced to this point with a notation such as Former 51.75 (former 51 ¾" back).

(3) L.E. of Root Rib: (leading edge of the root rib) indicates the largest rib at the near center of the wing.



Empty Weight Detail:


Glider Section

Weight in pounds

Wings - 37.5 lbs. each

75.0

Vertical Tail

5.0

Horizontal Tail

8.0

Fuselage

57.4

Total

145.4