Instrument question

KRA 0804K

I found it listed as fitted to RNZAF Sunderlands

Thanks for that. It was last serviced by Fokker, so a Hunter or Sea Hawk would be a suitable candidate.

Hi there mate. This should give you all the answers you need 🙂

http://www.ebay.co.uk/itm/Rate-of-climb-indicator-Mk-3A-P-6A-2966-Hunter-Vulcan-etc-/190744149022?pt=UK_CPV_Aviation_SM&hash=item2c693cbc1e

Just to bump this one up, I’ve just acquired a turn and bank indicator which I fully intended to use in the Spit, but was wondering whether “any old t&b indicator” will go, but if not where can I get the instruments that I need?

I think (but can’t be certain) that he originally envisaged a gross weight of 1,000lbs, but revised that later.

I’m hoping to build as per the original, and intend not to let any extra weight creep in!

well, at least the first question IS answered!

Weight awareness is going to be part and parcel of your build. Is the figure quoted what John designed or what the Spit actually was?

Most aircraft of this size and weight are going to be subject to the same considerations. Let’s face it, weight is an issue with a beast like the Rearwin too.

You’ll be OK.

MH

Looks as though what I thought would be a simple answer to a mundane question is totally the opposite!!

So, given what we now know (that the Spit + me + 72lbs (thanks Mike!) of go-juice = 1102lbs), does that mean I **should** be OK to fly the Spit as it is?

Working out the weights for the Rearwin included us (her indoors and my good self) full fuel and 1/2 lb of baggage. Since the weights we were using for ourselves were, let us say, in the morning (that would be barefoot to the chin – not a pretty sight), the bottom line was if we had full fuel we could just about justify underwear!

The other thing that limits things is the c of g. I am lucky that the range in the Rearwin is wide enough that if you DO go overweight you still remain inside the limits. I ca go 170lb overweight and still be in balance. I used to fly the Old Sarum Citabria and that could not have more than 1/3 fuel and two people. I have flown it with half tanks and me (fat) and her indoors (thin) and it was not pleasant.

MH

Melvyn the only reason I know that off the top of my head is that I enjoy reading flight tests and when I come to the data on the Aircraft I like to work out whether I could use said machine for myself with one or two passengers and full fuel and still be able to take at least overnight baggage. A prime example of a machine which would not be much use to myself and No 2 son is the Bolkow Monsun (Bo 207?) as the two of us and 20 lb of baggage would leave no room for fuel, even discounting baggage we’d be down to 1/2 fuel to stay inside the limit IIRC.

Thanks, as always, for the hints and tips. I guess I can forget about the strobe lights in the wings…!

The way people are talking about weight gains (not that I’m disagreeing with them) I think you’d best forget the wings as well to be sure of staying within the limit 🙂

Daz, Avgas is 7.2 lbs/imp gal =72 lbs for a full tank, any help?

Ah, my widdly circular slide rule thingy worked it out wrong. Still that only leaves you two pounds overweight. Better develop the weeing up the rudder trick!

Well, from memory…

Empty weight – 805lbs
Gross weight – 1100lbs
Fuel capacity – 10gal

My weight (roughly) 182lbs

So, empty Spitfire + DDM = 987lbs. Add fuel (weight of which I’m not sure of)….

Daz, Avgas is 7.2 lbs/imp gal =72 lbs for a full tank, any help?

The Isaacs Spit (as far as I can remember) has no electrics – swing that prop, baby!!

Quite right Daz, BBJI has no starter motor, I swung that prop a few times.

Radio was a very small handheld unit.

Just as a guide,

Spruce is hard to get and v. expensive. It is possible to substitute Douglas Fir and in my experience the quality of Douglas Fir far outstrips the spruce we get for a fraction of the price. However, the powers-at-be have decreed that fir and spruce have the same structural strength and therefore get used at exactly the same sizes. The problem is that fir is 10% heavier (partly because the quality is that much better and it is denser than the crappy spruce we sometimes see).

So, you could try using fir for your spars and hey presto an extra ten pounds has crept in.

As for radios, I have the Microair 720 panel fit one that is about the same weight as my old Icom and is a very, very nice piece of kit…

Melvyn

The Isaacs Spit (as far as I can remember) has no electrics – swing that prop, baby!!

talk to people who have built them before to get an idea of what they have fitted and how the weight pans out in reality.

So far there has only been one built and flying!!

Thankfully the inspector in my local strut knows what I’m going to build!!

To go back to your original question about usng instruments. As you are going to build a Permit to Fly aircraft, there is no need to get certified instruments, so you can save money (if not weight). An uncertified altimeter can be got for £179, the same one certified would cost £359, (weight for either 600g). An ASI: 375g, £100.

I don’t know the specs for the Isaacs Spitfire, but do you actually need electrics? That could save weight too – no battery or alternator. But it would mean hand swinging it to start. The radio could be a handheld transceiver weighing about 500g. (Built-in radios would weigh between 1-1.5Kg + the electrics)

A friend of mine built a Europa, and was obsessive about saving weight wherever he could, without compromising structural strength and integrity. It’s surprising how much a coat of paint weighs, for example!

When you start to build, you’ll have to have a PFA Inspector on board to sign off your work as you progress. He’ll be able to give you steers about where you can save weight. Also talk to people who have built them before to get an idea of what they have fitted and how the weight pans out in reality.

YR

Thanks, as always, for the hints and tips. I guess I can forget about the strobe lights in the wings…!

After many years in the car industry, I can safely say that the amount of effort put into keeping weight down (and monitoring the design activities) is immense. And the cars still gain weight in mysterious ways despite all that… (in one case at a previous employer, 200kg appeared between prototype and production).

Weigh everything (even glue, nuts, bolts and washers), and if possible weigh each sub assembly as you go. Set up an excel spreadsheet to give running totals – ball ache to be sure but not as much as trying to figure out where to save 5 – 10kg at the finish of the build!

John C

Blimey!! Time for me to get on that diet, then!

Well, from memory…

Empty weight – 805lbs

That will go up, trust me.

Gross weight – 1100lbs
Fuel capacity – 10gal

80lbs of fuel

My weight (roughly) 182lbs

with or without clothing? Add in headset, packed lunch, hostess etc.

So, empty Spitfire + DDM = 987lbs. Add fuel (weight of which I’m not sure of)….

OK, so empty weight plus a very modest 5% allowance for homebuilders weight gain = 840lbs or thereabouts.
DDM 182lbs plus a bit of equipment and baggage (headset, maps, hand-held GPS) 190 lbs
Fuel 80lbs
Total 1110lbs, or ten pounds over gross.

Already you need to have an eye on making to the exact weight stated (this WILL NOT be easy) and you will be close to the limits.

It don’t arf add up quick!

I got offered a share in a Turbulent yesterday (as if!) and there is no way I can get in and put in ANY fuel!

Melvyn