David Gladwin

Well put me down for a set of mouldings for my next Hawk, due soon, build of that will be MUCH quicker. .

Couple of points:

The stab cover plates in the kit are quite basic. I have reworked them to have scale tracks etc. but they cannot be completely scale as the pivot axis of the stab is too high, it should be about 1 cm lower. This can be and will be corrected on my next Hawk to have EXACT scale plates and tracks but will require a few hours work.

As a start, I suggest arcs of 5.2 cm from the kit stab pivot axis will define the edges of the plates and the flanges which go under the tracks will be additional to that. The result will be about as close to scale as one can get with the stab. in the kit posiition.

Final task is to make the incredibly crude rudder trim tab hinge, what were the designers at BAe thinking when they made it, there is more refinement on a Piper Cub, but it has to be modelled and I am using thin glass board and aluminium tube.

Finally anyone know how to do:
The louvres on top of the engine bay and the MDC on the canopy. Tommy's was excellent but I can't work out how to do either.

Well Gazzer I will soon have three Hawks including my Skymaster version so a three ship in Australia looks go !

Had a nice letter from Dicky Patounas the other day, leader of the Reds, following my visit to Scampton, wishing me luck with the Hawk (I am doing one Hawk as his aircraft, the other will be in the markings of one of my former instructing colleagues, S/L Brian Hoskins, leader of the Reds during the first year with Hawks ) and I also have scale three views coming but in the meantime the drawings in the book, Red Arrows are pretty good, being BAe drawings, but even THEY have some errors such as showing the flanges on the wing fences on the wrong side.


Regards, David Gladwin.

Francois

Hi Guys

Well i have finally got going on mine(great plane and kit)I have managed to finish the stab,speed brake and rudder assembly
enjoying the build immensely so far
Thx David for your hints thus far i have copied your mods(at the rear of the plane)and they are well thought through
I have weight balanced the stabs aswell-no mention of that from anybody yet,do you guys think it was unnecesary(i needed to add about 110grams per side)?

Cheers

Francois

schroedm

My Feedback: (1)

Francois,

I thought about doing this but that's a total of 220g or nearly half a pound and half a pound added to the tail at that. Will that not cause you a bit of a headache when it comes to balancing. It looks like most stuff will need to be up front as it is. I think half a pound about 4ft behind the CofG is going to take quite some balancing.

Rgds,
Mark

Dave Wilshere

Guys

Stab does not need counter balancing..

Regards

Dave Wilshere

David Gladwin

Stab balancing: It really depends on your approach to control surface design, almost ALL control surfaces can benefit by mass balancing . It may be that full mass balance of the stab. is not ESSENTIAL but some mass at least is good practice if (a) You wish to minimise or even reduce the possibilty of flutter and (b) reduce the loads on the servos. You will probably get away without balancing the stab but some balance will be of help. The problem with the model is that the entire stab. structure is of uniform construction whereas on the real Hawk the structure aft of the pivot will be of lighter structure than that forward of it.

Some SM Hawk operators have reported serious stab. problems, even losing the aircraft as a result. My SM Hawk has SOME mass balance and TWO powerful servos and I have experienced no problems whatsoever.

Very few AW Hawks have flown, lets hope no one runs into flutter problems as the fleet grows.

Regards, David Gladwin.

Regards, David gladwin.

mick15

Surely the principal of balancing is to do with servo load in high "g" situations, the hawk tail is already aerodynamically stable because the largest part of the area is behind the hinge, the problem might occur in a high g turn if the larger proportion of the weight is behind the hinge the g force will tend to force the elevator down against the servo?

mick

David Gladwin

I'm afraid that is not the case. Mass balance is really to do with flutter and minimising the control forces at a wide range of speeds and G loadings.

Your theory is not correct as you state because the aerodynamic "stability" of the stab depends on the relative positions of the center of pressure, which changes with angle of attack, and the hingle line, which doesn't. In fact it could be that at high G, which would require relatively large stab. deflection or angle of attack, the C of P is forward of the hinge line and the stab needs to be restrained as it may be trying to increase its angle (overbalance) ( Center of pressure moves forward with increasing alpha until the stall (which is why aircraft pitch nose down at the stall) and aft as it decreases. ) The real Hawk stab,. is very cleverly designed in that the BAe designers have lowered the pivot axis so as to be in line with the center of drag, (because of the anhedral) again reducing any undesirable force trying to move the tailplane. On the kit the stab pivot axis is actually about 1 cm too high.

One way of moving the C of G forward on the kit Hawk may be to make the outer skin of the jet pipe from titanium thus lightening it.

Rudder trim tab complete, no quick way of doing this !

Stab hinge cover plates almost done.


Regards,

David Gladwin.

David Gladwin

Last one for a while. The stab pivot covers are done, fiddly but as near scale as I can make them bearing in mind the Hawk kit stab pivot is a little different to the real aircraft. MUCH better than the simple version supplied in the kit.

Now, how about some more hawk builders showing us THEIR progress !

Regards,

David Gladwin.

Hawk_292

David,

Pictures of another Airworld Hawk being built.

Just waiting for a the nose light cover, windscreen and some plastic parts which Airworld have ready to post to me this week. Also ordered the 1/5th scale pilot, strobe lights and Red Arrow decals which will come in the same order and complete the model.

First test flight planned for first week of April.

TC

schroedm

My Feedback: (1)

just so as to keep things all in this thread, the much anticipated control throws/CofG information collated.....

[link=http://www.composite-arf.co.uk/Hawk/Setup.pdf]Setup[/link]

M

David Gladwin

The canopy of my Skymaster Hawk separated in flight yesterday fortunately with only minor wing damage and the model was landed safely, although the canopy and pilots are in a swamp ! Probably the pin receiving hole was getting worn.

Simply can't have that happen the AW machine, this big canopy will generate a LOT of lift, and the canopy is big and expensive in terms of time to add all the scale straps etc. So, as my AW Hawk has the same catch system as the SM hawk I have revisited the AW Hawk latch to make it more secure.

I removed the pin and trigger from the hatch latch (BVM type) leaving just the bearing block in place. the pin is located in the canopy frame by a brass tube. The pin was replaced by a length of piano wire which runs into the heat exchanger exhaust and has a 90 degree bend, about 1/2 inch long which is inserted into a hole in the side of the HE duct. The natural springiness of the wire holds it in the hole so it cannot move out of the hole. To insert, remove, the bend in/out of the hole will need pointed nose pliers but is very quick and as the canopy does not need to be removed for refuelling etc (all done via the nose hatches on mine) its not a problem.

To remove the canopy, just pull bent wire out of hole, pull back wire, canopy releases, reverse process to replace canopy.

This solution is very quick to do, particularly if you have already installed the hatch latch and tube, is totally secure AND you can fill in the slot previously needed for the latch trigger, 1 less point deduction at the JWM !

Pictures show how, the rear locating bend is shown 180 degrees rotated, its hole is on the other side of the bend.

Regards,

David Gladwin.

Geoff White

Hi there David,

I wasn't happy from the start using a hatch catch so I am using a very similar system as you to hold the canopy on my hawk. the difference is that I am using two wires that protrude into the bottom part of the canopy frame. I drilled two long holes in the canopy frame and then epoxied in two brass tubes in to the holes as the receptacle for the wire. The photos should explain it all. The other advantage is that the wire protrudes approx. 25mm from the fuselage so I think there is no chance of the canopy coming off! As the wire is going through through a big S I am confident it inst going to move in flight.

I have to admit I didn't think of this way to hold the canopy on. It was explained to me by a club mate of mine, Mike G*a*y(can't write the actual surname as it blanks it out, political correctness gone mad!) who used a similar system on his L39.

Anyway to the photos.

-JC-

My Feedback: (26)

Here is a little inspiration for you Hawk builders to get them done.

First in a series of two new AW Hawks being built by Henry from HVN Models.

-JC-

My Feedback: (26)

And... it flies too



The oter one Henry is building will be ready in two weeks. That one will be in the Saudi Airforce camo.

mick15

John

I have a kit which I hav'nt yet started, I'm curious looking at the scale flaps, what mods were made to the wing. Was the interior vertical webbing in the back of the wing just removed and if so was the skin reinforced in any way to help support the flap hinges?

Mick

schroedm

My Feedback: (1)

I'll second that! Any chance that Henry took any pics of the flaps mod on either this model or Ali's??

Cheers,
Mark

-JC-

My Feedback: (26)

No modifications needed for the scale flaps.

Henry made molds for the parts, and they fit on the flaps and under the wing without modifications. All you have to do is to sand 5 plywood pieces as stand-offs and glue the strips on. All done in a day.
I am sure Henry can be talked into laying up a few more pieces for a fee (After Top Gun) PM him... He is HVNmodels on RCU

mick15

John I was actually asking whether any mods were made to the actual wing, cause the rear web must be cut away to alow the new flap to retract in?

M

David Gladwin

The flap vane on the real Hawk cannot be reproduced on the AW Hawk in exact scale as there is insufficient room in the rear of the wing, they will have to be semi scale, still, better than nothing. The Red Arrows book I mentioned earlier, has very detailed BAe drawings of the flap and vane in quite large scale, there is room only for a compromise. That is unless the latest kits have had the rear structure of the wing moved forward, on mine the leading edge of the flap is almost up against the wing structure and on the real Hawk the vane is almost entirely in front of the flap leading edge. Its the last job to do on mine and I will make a near scale section from two laminations of 1/64th ply with small ribs to create an airfoil section to create a near scale section but the vane will have to be mounted further back than on the real machine.

Regards,

David Gladwin.

hvnmodels

Hi Mick,

As John already stated, there are no modifications needed for the wing at all. There is room inside the wing in front of the existing flaps. I will post some photos when I have time, but right now I need to concentrate on getting two Hawks ready for Top Gun.
The flaps look 100% scale when comparing them to the full scale photos I have. If it looks scale it is OK with me

David Gladwin

Here is a BAe drawing of the vane configuration. I agree with Henry it can be made to LOOK scale ! Moving the internal wing structure is TOO big a job.
Regards,
David Gladwin.

Two other issues. How to do the MDC in the top of the canopy and how to do the grilles on the top of the fuselge (I thing they are air intakes for the GTS). It would be nice if someone can do them, laser cut from thin glass board just like Philip Avonds did for his F15 kit. Any ideas?

hvnmodels

Hi David,

I have not made the MDC's yet, but I will cut them from light gray vinyl. It will be almost impossible to paint, so vinyl is an easy solution.

The intake grilles I hand cut from 1/64 ply. Took about 2 hours per plane.

hvnmodels

Here is a photo of the full scale Hawk flaps. Compare it to John's photo of the model. I think it looks pretty scale. I just did the flaps on Ali's Hawk, and the whole process took 30 minutes on each side.

Henry

hvnmodels

Here is the flaps process explained.

I made a splash of the top portion of the existing flaps. That way I have a smooth strip with all the rivet detail that already comes in the Airworld kit.

10 plywood spacers are cut from 1/8 ply.

The fiberglass stripp is positioned on the model and the spacers are tack glued in place.

The the whole assembly can be sanded to fit. Very simple. Once fittet, I glue the parts together with 30 min epoxy, glue on balsa end caps and primer.

mick15

Thanks Henry
Thats an excellent answer to my question, although I may try and see if its possible to get the scale flap to retract in. Obviously this will mean modifying the back of the wing.
I'll contribute more to this thread when I start my Hawk

M