"The Heart Of The Gnat"

[Mike Bull]

Quick question..................

In the above photograph, where the tail rudder is in bare alloy, would the top of said rudder be at the approximate height of K7's tail?

Yup, the T.1 tailfin was cropped in height level with the top of the rudder. The rudder itself was discarded and replaced with a sheet ally fairing, as was the bottom forward root (Both being damaged in the crash) The top of the fin was faired in to house the pitot. There's an excellent photo of the fin minus all the fairings set up on top of the boat during the conversion work, but not being sure whose photo it is, I'd best not post it.

[Renegadenemo]

Yup, the T.1 tailfin was cropped in height level with the top of the rudder.

No it wasn't... 691 wasn't a T1 it was an F1. Single seat fighter derivative with a 701 engine and a smaller canopy and therefore a smaller fin. The orange one above is a T1.

[orgster1]

691 wasn't a T1 it was an F1. Single seat fighter derivative with a 701 engine and a smaller canopy and therefore a smaller fin. The orange one above is a T1

It's doing a good impersonation of a two Seater here
So by derivative you are saying it was cut and shunted into a single seater with a few bits nailed on and a new paraffin heater shoved in its bum?

[Mike Bull]

No it wasn't...

Oh yes it was!

I've been accused of getting this one wrong in the past, but I'm more sure of my facts now. Sorry Bill, but XM691 was the first T.1 prototype.

The Gnat first appeared as a fighter in 1955, and then came the trainer derivative; 'our' aircraft was the first of 14 pre-production Gnat T.1s, first flying in 1959.

I think the confusion may arise from the fact that this first batch of T.1 prototypes had a shorter nose, though still not as short (or as pointed) as that of the F.1, which also had a considerably shorter canopy and different wings. (Subsequent production T.1s had a longer and thinner nose, which is the more typical 'look' for the type.)

Here's '691 in flight with an F.1, illustrating the different noses-

xm691a.jpg

It's true though that '691 at least had the 701 engine whereas production T.1s had the 101 unit, but nonetheless a T.1 it was, with the same tail fin as all subsequent T.1s. You'll find endless sources online re. '691 being a T.1.

Regarding Gnats with different tail fins, the rudder of the F.1 fin was wider and shorter than that of the T.1. Have a shufty at Damien Burke's page here-

http://www.thunder-and-lightnings.co.uk/gnat/walkaround.php

- and you'll see comparison shots of T.1 and F.1 tail fins.

Re. the seating arrangements, check out the caption on this pic of '691-

XM691 landing.jpg

[Renegadenemo]

That's me told...

[thunderer]

now see, look what I done gone did...............

I done gone opened a can 'o' worms.



Sorry lads

[Renegadenemo]

I done gone opened a can 'o' worms.

Cans ' worms are good - means we keep the facts straight. It was whatever plane engine No. 711 came out of that was an F1 if I remember correctly. That's the engine we found in the wreck and I remember researching it way back when. It seems somewhere down the line I mixed it up with 619 but with this distance of time I'd not be surprised if I've cocked that up too!

[Jordangbr]

So if the original Orpheous came from XM691 where did the replacement engine come from after the original was damaged after sucking the intakes shut?

[Mike Bull]

S'okay Bill, it took me years to remember the difference between a 701 SERIES engine, and engine NUMBER 711! Then, there's always my little blind spot of calling a nut a bolt and a bolt a nut, every damn time...

Jordan, Bill, I think you might have got it backwards- Donald purchased XM691 whole along with a second Orpheus; most accounts seem to suggest that it was the loose engine that went into K7 first, and that when he knackered that one, it was replaced 'with the engine from the Gnat'. Can anyone actually confirm that? Steve Holter's book certainly claims that No.711 came from 'the remains of the Gnat'.
(EDIT- there's two of Leo's photo captions in his book that say the same thing, too) Ultimately the salient point perhaps is that there was something rather rare about the fuel system he got, as since proven out by having the thing researched and rebuilt by the original manufacturer.

There are pictures of Donald examining the first(?) Orpheus in it's cradle in the conversion shed, and of the Orph and the Beryl suspended above the gutted boat, though personally I can't make out whether the fuel gubbins is already on the engine by then. The oil tank pictured then is different though- it has a much taller filler neck than the one we see actually fitted in the boat- so there was certainly some swapping about of differing Orph bits from the off.

It's still entirely possible that the first Orph came out of an F.1 though, as F.1s used the 701 series engine, as did the first 14 T.1s.

[sheppane]

S'okay Bill, it took me years to remember the difference between a 701 SERIES engine, and engine NUMBER 711! Then, there's always my little blind spot of calling a nut a bolt and a bolt a nut, every damn time...

Jordan, Bill, I think you might have got it backwards- Donald purchased XM691 whole along with a second Orpheus; most accounts seem to suggest that it was the loose engine that went into K7 first, and that when he knackered that one, it was replaced 'with the engine from the Gnat'. Can anyone actually confirm that? Steve Holter's book certainly claims that No.711 came from 'the remains of the Gnat'.
(EDIT- there's two of Leo's photo captions in his book that say the same thing, too) Ultimately the salient point perhaps is that there was something rather rare about the fuel system he got, as since proven out by having the thing researched and rebuilt by the original manufacturer.

There are pictures of Donald examining the first(?) Orpheus in it's cradle in the conversion shed, and of the Orph and the Beryl suspended above the gutted boat, though personally I can't make out whether the fuel gubbins is already on the engine by then. The oil tank pictured then is different though- it has a much taller filler neck than the one we see actually fitted in the boat- so there was certainly some swapping about of differing Orph bits from the off.

It's still entirely possible that the first Orph came out of an F.1 though, as F.1s used the 701 series engine, as did the first 14 T.1s.

The book will reveal all on this. Not long to wait now....