Spar

Creaking Door: Wouldn’t that present one huge chunk of metal to mill? What would that cost and how much would it weigh?

By comparison, here are illustrations showing the construction of a metal, aerobatic aircraft similar in weight to the 70%-80% replica Spitfire, maybe a bit on the heavy side. The wings are two piece, like Tom’s design. The spar appears relatively simply in construction but that is misleading. It’s a complicated structure. Look at the massive plates in center fuselage joining the two spar halves.
This aircraft has an empty weight of approx 755kg/1664lbs, stressed to +6g -3g with a max aerobatic wing loading of 109kg/m2 – 33.4 lbs/sq ft.
Unlike the Spitfire’s wing, this wing is a straight taper.

Blown LS7

Here’s Algie’s blown LS7 – some serious HP

http://members.iquest.net/~aca/images/img15.jpg

Pilot Seat

Is that a new build pilot’s seat from Oz?? :0-

VTwelves

In fact the Jag V12 isn’t that heavy… about 220 kgs complete in road trim. The nice fact about it is that you have so much room in the crankcases that you can up the stroke a full 20mm,and bore it 6mm. So from having an engine with Bore 90 and Stroke 70,giving 5.344 liters you can have 96 x 90. Which is 7.817 liters… Or if that’s not enough,they have been pushed to 98 x 94 with deck plates on the block… That’s 8.5 liters.

Or just go here: http://www.falconerengines.com/prod04.htm …that is,if the budget allows.. 🙂

Yeah, the Falconer V12 is the one that was designed for the Thunder Mustang – originally two Chevy V6s mated together. Big bucks. Good ol’ hot rod engine builder.
Or if money is no object, why not the home-grown Orenda V12? What ever happened to that one? Last I heard it was a bit over a hundred grand a copy.

A stroker Jag V12 will do that? What about a PSRU?
BTW, RF769, what do you do with your Jag engines in Norway? Auto or airplane? You sound like a Jag lover – my first one was a ’67 Euro-spec E-Type/XK-E roadster, one of the last of the covered headlight Series 2s that I picked up new at the factory in Coventry when I was stationed in Germany oh so long ago. The most frustrating part was driving back to our base in Germany with no-speed-limit roads but limited in top speed by the break-in rpm of 2500!!!! It redlined at 5500!

Mk1 Spitfire

Mk 1: Thanks for posting the pictures – it’s a pretty airplane! At the risk of dating myself, I can recall building the Guillow’s Spitfire back when it only cost three or four bucks. Some years ago it was quite a pleasant surprise to discover that both my sons were building the Guillow’s Spitfire and FW 190. How many thousands of kits have they churned out over the decades, and how many generations of modelers have experienced those wonderful balsa models?

You’re quite correct about the sound and the practicality of a V8 in a replica warbird, but how about a modern Chevy LS all aluminum powerplant over the Buick/Olds/Rover engine? One, they’re more modern, and put out twice the power that the Buick/Rover does at about the same or even less weight. Secondly, they’re a whole lot cheaper to build than the Rover V8. There are also more companies that specialize in the Chev for homebuilts and a wider choice of PRUs.

Tom, we seem to be butting heads, but to go along with the above post giving you advice on the twisting moments of the wing and spar, here’s a simple illustration on the load vectors acting on a wing.

There are a couple of books available that contain information on sizing the loads and designing the spar. Reading them might not be a bad place to start.

Too Simple A Way

Hey, PP,

That’s what I’ve been trying to tell him!

Why reinvent the wheel when others have already been there?

Ah, but let’s not be too hard on Tom. He’s got a dream, so why burst the bubble? Let him chase it.

If Tom enjoys beating metal, why not let him do it? Ol’Spitty is doing a 100% scale Spitfire. That’s a whole lot of challenge but must also be a whole lot of gratification in the sense of self-accomplishment!

Thoughts on the Concept

Tom: At the risk of aggravating the sh*t out of you, as mentioned in my above post, the spar loads must first be calculated to determine the thickness and width of the spar caps and the thickness of the spar web within the height of the ribs/airfoil.
Otherwise, you can conceptualize all day long and there will be no guarantees that your concept will work. My two cents worth is that it’s virtually impossible to ascertain whether whatever concept you may doodle out on the sketchpad will work until the size of the sparcaps and web have been determined, plus, don’t forget, the width and thickness of the spar carry-through in the fuselage. Don’t forget that important piece of structure.
Any simple C-channel or box spar will work, the spar being no more than a simple I-beam, but the width and height and type/thickness of material will be determined by the calculated loads.
A simple spar consisting of two U-channels bolted back to back to form the web and a mounting point for additional tapered flat plate sparcaps will work. A simple round tube as used on the BD5 will work. A simple box spar will work. There are a number of solutions.
Why don’t you research other metal designs such as the Vans RV series of metal aircraft and the Chris Heintz metal homebuilts? Have a good look at their solutions.
In viewing the photo that Ol’Spitty posted of the bare wing, it seems that the Spitfire ribs are of simple truss type construction – light, strong. Heck, you could build a spar with narrow tubes for sparcaps that would be easy to bend to the wing taper, and use a truss type web…. there are any number of solutions.
In building a replica, as Mk 1 has mentioned, what’s under the skin is not visible to the naked eye. However, regardless of manner of construction, a spar that is not sufficiently sized for the loads may fail at the most inopportune time.
I’ve got a set of Vans RV3 plans that I purchased some years ago for research sitting around somewhere. It’s a terrific, simple, metal design and the plans and manual are excellent. I’ll be glad to sell them to you to at my original cost if you want. The plans will definitely give you a bunch of knowledge of how a metal homebuilt goes together. I’m not pushing the plans but many enthusiasts will tell you that a good start is to obtain several different plans sets of various aircraft for study and research. Over the years I’ve spent a few thousand dollars on research material. Worth the entry price!
And, hey, don’t take me too seriously. I’m not really trying to aggravate you on purpose!