Anyone for a Tiffie?

[Biggles' Elder Brother - Moderator]

Hi Linds,

Near the top of the previous page you'll see me establishing the fuselage datum line (which I marked inside and out), so all alignment - tailplane, wingseats and thrust line are all locked back to that. - I've been caught like that before!

BEB

Edited By Biggles' Elder Brother - Moderator on 07/09/2013 22:39:50

[Chris Bott - Moderator]

Hi BEB

That cowl mount is looking good, nice invsible screws.

I'm just wondering if you could improve it further by enlarging the holes in the former into keyholes?
That way you could undo the screws a little and then lift the cowl off, leaving the screws in situ.
Allen bolts are best, as they have the smallest head.

I did similar on the DH88, but in that case made it twist to lift off, and used magnets to keep it in place as I had no access to screws.

[Biggles' Elder Brother - Moderator]

Thats a cracking idea Chris! I have been thinking that, while putting the bolts in when the cowl is empty is very easy, how easy is it going to be when we have motors/batteries and sound system (possibly!) in there? Its going to get very crowded! Your idea certainly simplifies that. Thanks!

BEB

[Biggles' Elder Brother - Moderator]

Not good flying weather - had a few flights this morning - but eventually came home and got on with the Tiffie. The job of the moment was finishing the shaping sanding of the fuselage - well, basically we 're there!...

Here's the basic fuselage down to shape. There's the back end fully reinstated like I'd never butchered it in the first place!...

And here is a shot of the cowl fit - quite pleased with that,...

So, this isn't completely finished by any means - lots of final smooothing, cleaning up and general fettling. But we can claim that the basic construction of the structure is now complete. So we can put that on one side now and get on with the wings, so up on the rack it goes!...

Its quite a good day to reach this point in the build - the project has been running for exactly one month today. So one month in and the fuselage basically finished and it's time to make a start on the wing centre section.

You may recall that we have already done the frameworks for the port and starboard outer wing panels - so we just need the centre part to make up the completeted wing,...

The wheel wells are of course in this section and this is how the wheels will fit in,....

The wells are not quite deep enough as you can see in the picture below. The pencil represents the oleo leg of the undercarriage - its just slightly proud of the level of the tops of the ribs. Its touch and go if, once the skins are on, there will be room for the leg without having to lower the wheel slightly - we'll see...

Tomorrow I hope to install the hardwood bearers for the undercarriage units.

BEB

[Danny Fenton]

The fus looks cracking BEB, Nice one
cheers
Danny

[Tony Bennett]

nice job beb.

[Ian Jones]

Drooling, looks great BEB.

[Biggles' Elder Brother - Moderator]

Time for episode 7 in the Tiffie story!

We're at the run up to D-day. The Tiffie squadrons in 2nd TAF were divided into two roughly equal groups - the dive bombers and the rocket armed ones. Squadrons spent periods in training at special camps in Wales and West Country to enhance their accuracy with both bombs and rockets.

The basic techniques for both bombs and rockets were quite similar. The bomb equipped Typhoons (sometimes know as "Bomphoons"!) would commence their dive from approximately 10-12 thousand feet. The angle of the dive was intended to be around 60 degrees. It's funny, but pretty well every pilot describing this dive comments on how sixty degrees feels like a vertical dive in the Tiffie.

The Typhoon's approach to dive bombing was fundamentally different to that used previously by say the Ju87 Stuka etc. These previous exponents had used airbrakes to limit their speed in the dive, the Typhoon in contrast simply went through the dive fast as possible - frequently hitting speeds well in excess of 500mph.

The Tiffie had no bomb-sight and so a little improvisation and ingenuity were called for. Pilots were told to hold the aircraft steady in the dive, wait for the target to disappear behind the nose, count 5 slowly and then release the bombs! Simple - but it worked. However it was not without its problems:

1. The Typhoon was starting to encounter compressibility problems in these dives as the Mach number started to approach the critical value for the aircraft - about 0.78.
2. Also ordinance release was done at low altitude; that, combined with the high speed, meant the pull out was often a fairly desperate and extreme high-G manoeuvre. Indeed pilots actually tried to balance the pull out deliberately on the point of "grey-out" - ie as severe as they dare. There were also many instances of pilots putting the aircraft into a high-speed stall on this highG pull out. Obviously such an event so close to the ground was usually fatal for the pilot.

The most common cause of loss of Typhoons was without doubt flak. The requirement to hold the Typhoon steady in the dive made them a relatively easy target for the flak gunners - despite their great speed. The normal format for an attack by a flight of Typhoons would involve the group of aircraft moving into line astern at 10-12 thousand feet and then the leader calling the attack. He would then half roll into a "reversal type" manoeuvre and move into the dive. His number two would follow, then three and so on. This attack in line astern formation was the most effective method - but it did put the aircraft towards the back of the line in great danger, the gunners were going to have an excellent opportunity to line up their aim onto these rearward aircraft because their flight path was highly predictable. In my view these pilots were men of great courage. To fly straight into such a hail of concentrated and well aimed flak, without being able to jink or take any avoiding action, whilst watching comrades in neighbouring aircraft getting hit, required enormous bravery.

So what exactly were the Tiffies attacking at this point? There were a number of different types of operations all exploiting the accuracy the Typhoon could achieve in targeted attacks and its exceptional low-level speed:

1. Squadron sweeps - on these the whole squadron would fly into occupied territory to attack a designated target - usually communications (railway junctions, bridges etc), specific military targets (headquarters buildings, storage depots, troop rallying points etc.). One famous example of such an attack was the sortie against Rommel's staff headquarters in which the building was completely destroyed by a single squadron of Typhoons - over 70 staff officers being killed. Unfortunately Rommel himself had left the building a few minutes earlier.
2. Escort duties - usually providing top cover for Mosquitos - the Typhoon was one of the few fighters that could keep up with the Mossie at zero-feet.
3. "Noballs" - Allied intelligence was becoming increasingly aware of V1 launch sites being built all along the northern coast of France and the low countries. Noballs were the code-name given to Typhoon attacks on these installations.
4. "Rhubarbs" - these were the Typhoon pilots' favourite! They could be flown by day or night. Day versions normally used two aircraft whilst night time Rhubarbs often involves a single aircraft. The idea of a Rhubarb was to simply fly out over occupied territory and attack "targets of opportunity" - basically anything "fruity". Trains were a favourite and one squadron destroyed over 130 trains in one month! "Soft-skined" military vehicles - particularly in convoy were another popular target. Goods yards, road junctions, airfields,.... all were fair game. The objective was to make a thorough nuisance of yourself, and the Tiffie was always good at that!

So, the Typhoon squadrons were being kept busy with a wide range of work - all at low level, were it excelled. This was all great practise and preparation for the major role the aircraft was soon to play in the invasion of Europe.

BEB

Edited By Biggles' Elder Brother - Moderator on 08/09/2013 09:39:27

[Biggles' Elder Brother - Moderator]

Thanks for the encouraging comments lads! Much appreciated!

BEB

[Biggles' Elder Brother - Moderator]

Well went flying yesterday - naughty me! - so didn't get much done. But tonight I've completed the structure for the wing centre section,...

Which is quite a piece of engineering! This was actually proving to be a bit of a handful to build using my usual aliphatic resin as the adhedsive of choice. In the end one or two bits could only really be done by dry fitting and wicking in CA. I think TN is a big CA user - maybe it shows in his structures! But you have to admire it, its light but very strong and with the sheeting will be emensely strong.

Mind you the model has a lot to live up to - the full size had wings of phenominal strength,...

No one ever pulled the wings off a Tiffie!

Anyway, back to business, as you can see the hardwood bearers for the retracts are in place now so the next job is fitting them! Exciting!

BEB

Edited By Biggles' Elder Brother - Moderator on 09/09/2013 22:31:30

[Trevor Crook]

BEB - another cowl fixing idea. What about holding the top with magnets, and the bottom with screws going forward through the firewall from the wing cutout, into captive nuts in the cowl. Locating dowels would keep it all lined up. No need then to try to get a screwdriver past the motor. My (wooden) cowl is held on like this, without the magnets, and it works fine.

[AlexJ]

Hi BEB,

This is looking good! Love the tiffie as I do, I always think it has the appearance of a bar brawling thug but that fuselage looks so elegant with such great curves! This is probably due to a bit of great carving on your part though.

Just an observation, wouldnt the sound unit drown out the engine ? (I would have put a wink in here but the emoticons will not work)

Alex

[.]

Looks a very nice project, loved reading through it so far, cant wait to see the finished result.

[Broken Prop]

Fantastic work BEB! Can't wait for the next episode.

Pete

Edited By Peter Ward on 10/09/2013 10:28:03

[Biggles' Elder Brother - Moderator]

Trevor - thanks for the suggestion on the cowl I'll certainly look into that. Anything that saves me from having to poke a screw driver etc in past what is looking like being a very crowded cowl space, as I try to get as much weight forward as possible, is a good idea.

You're right Alex - the Tiffie does have that "no nonesense" sort of appearence doesn't it - like a guy who's drink you wouldn't want to knock over! Re the sound system - I'd not thought about that - yes there may be some conflict between the synthetic sound and the engine, not mention oil and vibration effecting the electronics - I'll just have to look for a work round on that one!

Craig - you and me together mate!

Right, progress. Well as I mentioned above work is going through one of its busy phases and I must admit it took a bit of will power to stop dosing in the armchair last night and get out into the workshop! But get out I did, and we had something of a "watershed" moment - the Tiffie now has an assigned Rx and a slot in the memory of my Tx called "Typhoon" - what else would you expect me to call it? I always think this is the moment that an assemblage of wood" becomes "a model" - its now part of the fleet - albeit an as yet an unflyable member!

This step was taken of course in order to test the retracts. I did this first out of the model - all was fine, they dutifully went up and down following the switch I'd assigned.

I then proceeded to fit the units into the wing centre section. Some fairly serious "trimming" of wing ribs was needed as the E-Flite units are clearly significantly deeper than the Unitract mechanical retracts the kits was designed for - but it was all managable.

The real problem came when I tried to take the ready fitted piano wire legs out of the units in in order to fit them to the model. The supplied legs are 5mm piano wire and are held in by two grub screws acting on a ground flat. The first one was very tight and the grub screws needed a lot pressure on the supplied Allen key before loosening. The second was impossible to move! I was putting so much pressure on the Allen key that I was seriously worried about snapping it! In fact eventually it actually jumped a 1/6th of a turn! Bad, very bad. Too much of that and I'll round the socket and end up drilling the grub screws out!

At this point I decided on a "time-out", a cup of coffee and a think. I applied a very small amount of WD40, as there did appear to be some kind of "packing grease" on the grub screws I had removed from the other unit and I thought that maybe this had solidified and was the cause of my problem. I wasn't very optimistic about that - but hey it was worth a try! I also found that my own Allen keys were a tighter fit in the grub screw socket, and stiffer, than the somewhat "cheesey" one provided by E-Flite. So I left the screws to soak for a bit while I installed the other unit.

The basic installation of the other unit went fine. No problems.

Back to the problem side. Tried again - no joy. Both grub screws simply would not budge. As a last resort I dug out some long shaft hex-drivers that I have, pushed one very firmly into the grub screw socket and twisted with all my might. There was an almight "crack" - at first I thought I'd snapped either the driver or the screw! - but no it was alright and in fact now "loose" if still rather stiff! Another Herculean effort on the second screw with the hex driver produced a similar result. Phew!

When I removed the piano-wire leg and examined it I saw that the grub screws had been so tight that they had actually indented the surface of the locating flat on the piano wire - not just marked - but actually indented! Now, as we all know, piano wire is very hard, it just shows how tight those grub screws were. I simply don't see the point in this. Yes, I can appreciate that E-Flite might be concerned that some folks might just take the units out the box and use them - so they have to be done up tight ready to go - but this was ridiculous. The first lot were tight but OK - the second lot were well beyond just "tight". If I hadn't had access to the long hex driver the unit would have had to be drilled and not every modeller has the facility to do that accurately - indeed I would have had to take it to our workshop at work to get it done. Silly.

Anyway - the long and short of it is that its done, both units are fitted and from what I can see - without legs yet - seem to be lining up well. Although they may be a little low as the E-Flite units have the leg fitting quite low down on the body. But if that is the case its nothing a little packing can't sort. So I'm just waiting for the oleos to arrive now and I can fit them and give the whole thing a proper test. I'll ask my "A.V. tech team" (the kids!) if they will help me make a short video then just to show them working.

Hatches for the aileron servos next I think, while we await the oleos.

BEB

Edited By Biggles' Elder Brother - Moderator on 11/09/2013 12:10:50

[Pete B]

If you could have got a soldering iron tip onto the grub screw without melting anything else, that would probably have made it a tad easier...heat can be your friend in such circumstances

Pete

[Bob Cotsford]

I think there's threadlock on the E-Flite grub screws BEB, you would have done better poking the tip of a soldering iron into the screw for a few minutes to soften the locking compound.

I've used the 90-120 size retracts with great success, but the leads are a bit thin and really need more support where they exit the epoxy encapsulation.

[Biggles' Elder Brother - Moderator]

Very true chaps, a small soldering iron could well have helped - but of course you're there, on your tod, in the darkness of the shed totally focussed on "how the hell am I going to undo this" and the obvious solution doesn't always feel so obvious.

I should have asked on here - an got a dettacted calm view! Still - won in the end!

I did wonder about threadlock Bob, but while I found grease I didn't find evidence of threadlock - but hey that proves little, it still could have been there and the grease applied over the top of the screw? Putting them back I will probably use blue Locktite - but at least I know its there then and I'm not planning on doing them tight enough to indent piano wire!

BEB

[Biggles' Elder Brother - Moderator]

Not a lot of progress at the moment - too much "day job"! But looking at the weather forecast I think there is an excellent chance of getting plenty done over the weekend - a good and bad thing of course!

Well in the meantime let's have episode eight in the Typhoon drama,...

An RP3 rocket with a 60lb warhead packed the same explosive power as a 6" naval shell, so with eight of these (as we have observed) the destructive potential of the Typhoon was tremendous. Add in the four 20mm cannon and you have a formidable weapon!

But over the years there have been questions raised about just how effective the rocket firing Typhoon really was. The Typhoon was not without its critics - indeed these "nay-sayers" damn near finished the Typhoon off in 1942 when things weren't going too well for it. It was only the enthusiaism of people such as Roly Beaumont that kept the Typhoon in the game.

Even when the Typhoon was doing its bit and earning its rations, there were those keen to say that these new fangled rockets were not as good as people made out. So what was the bottom line?

Well, tests by the boffins established two key facts: the accuracy of a typical rocket Typhoon was a circle of radius approximately 55 to 60 feet around the aiming point. This accuracy was then interpreted as meaning that the probability of a Typhoon hitting a tank it was aiming at was about 4%!

Well, the "anti'-Typhoon" lobby had a field-day with that figure! "A 4% chance of hitting the target!!!" But in reality this interpretation of the accuracy figure is very misleading. Consider the following two points:

1. In practice the Typhoon wasn't generally aiming at "one lone tank in a field" - it was aiming at a cluster or convoy. Now a "near miss" on one vehicle is very likely to hit a neigbouring tank. And frankly it doesn't matter which tank you hit in this situation as long as you hit one!
2. Would you sit in a tank in the middle of a 120 foot diameter citcle in which eight 6" naval shells were just about to land simultaineously? No I didn't think so! Well it turns out that the troops in the SS Panzer Divisions would have been in full agreement with you! There is a lot of evidence that mere sight of Typhoons turning into the attack-dive was enough to cause many troops to simply abandon their vehicles and take cover at some distance, leaving the Typhoons free rein. I stated that it took courage to hold a Typhoon steady in the face of concentrated accurate flak - well I think it also took a lot of courage to stay at your gun and put up that fire whilst twelve Typhoons, firing 20mm cannon, apparently made you the sole focus of their rockets attention!

So I think that, as the invasion of Normandy was to show and we will see when we get to that, the Typhoon had no difficulty in "dishing it out" to great effect.

BEB

[Martyn K]

BEB

Enjoying your Typhoon History notes as much as the build blog.. I think you should build a Tempest next.

Well done

Martyn

[Biggles' Elder Brother - Moderator]

I'm working at putting the servos in the wing at present. On the plan TN shows the aileron servo's inverted in the wing, sitting on two hardwood bearers that run between the ribs. This arrangement results in the top face of the servo protruding beyond the bottom wing skin - OK that's not that unusual, but I think its less than ideal for two reasons:

1. It leaves the servo top face exposed to all the mud, rain, hale, gravel, muck etc that gets thrown up at the wing lower surfaces on the ground.
2. It leaves quite a big chunk of servo, and the output gear, sticking out below the wing and that doesn't look as smart as it could do.

So to tackle this I decided to make some ply servo plates onto which the servo would be side mounted and only the servo arm would show through.

So here is the view from behind the plate,...

Here we are looking from above. As you can see the servo, which is an HS82MG, is secured to two hardwood blocks which in turn are epoxied to the 2.5mm ply plate. Soon these will also acquire small wooden fillets just to make them as secure as possible. The plate itself has a slot cut in it through which the servo-arm protrudes and is then fixed into the wing via four hard-points one at each corner of this wing cell.

The view from outside, below the wing, is shown here,...

You can see the plate is held in place by four screws into the hard-points.

This method is of course nothing new, its very common on ARTF's. But you don't tend to see it on "plan builds", probably because its actually quite fiddly to fabricate. But I think its worth it for the end result which leaves very little of the aileron actuation mechanism visible outside the airframe.

These ply plates are currently proud of the structure - but of course once the wing is skinned with 2.5mm balsa these plates will actually end up flush with the wing surface (I hope!)

BEB

[Lindsay Todd]

Good move Beb, a much neater installation in my mind too. Does the wing carry split flaps as well, looking at the ribs / rear spar it suggests not but perhaps there is more going on than the photo shows. Linds

[Biggles' Elder Brother - Moderator]

No Linds, no split flaps on this one. You could fit them and it would be more accurate scale-wise of course. But as regards needing them, well with that big fat wing I'm kinna hoping she'll be quite well behaved for me on landing! Ever the optimist me!

Onto the ailerons today,....

Here they are all made up and with their leading edges glued on drying before being trimmed and sanded. There is a 12mm balsa block glued inside each first bay lined up with where the control horn will be fixed.

One thing I have noticed about the Tiffie is that the control surfaces - ailerons and elevators at least - are surprisingly small! I guess this is a consequence of the high speed of the prototype - it didn't need large control surfaces. But of course the model doesn't fly at scale speed - so I guess we're going to need fairly generous throws!

BEB

[Trevor Crook]

BEB

My slightly smaller version slows down fine without flaps. Your "full size" one should be even better, provided the weight is kept down.

[Josip Vrandecic -Mes]

Posted by Concorde Speedbird on 05/08/2013 12:23:21:

Oh no, this is going to overshadow my Spitfire build completely! This should be good, have you made a decision on power, retracts etc?

CS

Don't worry CS, famous Flt Lt John S.B. Wright said : ''Spifire is like Swiss watch...and Tiffie is more like a buldog.

Cheers

Joe

Edited By Josip Vrandecic -Mes on 16/09/2013 13:57:03