Gordon Mc

My Feedback: (11)

Once the glue dried sufficiently, I just clamped the dowel in the chuck of my lathe and made lots of wonderful white poly dust as I turned the block down to the size and shape that I wanted.

Two coats of fibreglass later, I'm now just waiting for the finishing resin to completely harden so that I can sand & polish it.

WhoDaMan

My Feedback: (164)

Hi Gordon:
Whats that part for? Also what state is the field in?????

Dave R

Gordon Mc

My Feedback: (11)

It's a plug for making up the front and rear sections of the drop tanks. The part with the rounded nose is the front ; the part with the pointed end is the rear.

It's still there, and last heard, the county wass still fighting the issue of additional cleanup needed for the "unexploded ordinance" that was found.

Gordon

Gordon Mc

My Feedback: (11)

While waiting for the plugs to dry completely, I've moved on to the wing control surfaces. For the ailerons, I elected to install three hinges instead of the two that Mick calls for - as long as this decision is made before closing out the aileron, it's trivial to add

WhoDaMan

My Feedback: (164)

Thank you Gordon.
Better they found that puppy instead of one of us[X(]

Dave

How far out are you on completion

Gordon Mc

My Feedback: (11)

I also added corresponding hardpoints in the appropriate places of the wing's TE for both the aileron and flap hinges. (Note that Mick shows the flap hinges just being screwed into the side of the 1/8" lite-ply rear spar - I just wanted a bit more meat for the hinges).

Here's a shot of the tiny flap hinges - that's a Du-Bro hinge next to it for size comparisson, and a shot of the hinged flap.

In it's up position, the flap TE came up further than desired, so obviously some kind of 'stop' was needed. If you look closely you will see a strip of polyply (about 1" wide) that I have glued inside the TE of the flap pocket - I put some Aeropoxy on the half-ribs, stuck the strip of polyply to the inside of the flap with double-sided tape, then just lowered the flap until it sat perfectly flush. Once the glue dried it held the stop-strip in the perfect position.

Gordon Mc

My Feedback: (11)

No idea. I'm not spending a huge amount of time on the aircraft right now - too many other things going on. To be perfectly honest, I'd be content to have it done by the middle of next year. In addition to the basic building that still has to be completed, I want to put in a fair effort at doing a nice from-scratch cockpit, plus I still have to figure out how I want to do some things - e.g. how do I want to get access to the wing-bolts. They are inserted from above, and are easy to get in when you don't have a cockpit in place (just reach in through the canopy opening) ... once that option is not available, thngs become a bit tougher. I have a couple of options in mind, but am keeping an open mind at this time.

Gordon

WhoDaMan

My Feedback: (164)

I can understand that completely.
I think Kenny in the jet thread may have hurt his F-18.. How do you like the skins you are using.

Dave

Gordon Mc

My Feedback: (11)

They do result in a lightweight and very stiff structure - but as I mentioned earlier, I don't like the fact that you have no room for sanding out minor imperfections as you would on a balsa sheeted wing.. also, I'm a little concerned about preserving the integrity of the wing structure. When I sheet a wing with wood and then put a 3/4 oz cloth over the top of it, that cloth not only gives a nice finish, integrity - like an eggshell, even though it is thin, the fact that it creates a "monocoque" kind of structural layer does add a non trivial amount of integrity; with poly-ply sheeting glued to the ribs and 1/8" leading edge, and then a separate LE cap glued on front of the wing, I'm just slightly concerned that the polyply stuff may flex a little over time, cracking away from the LE just a little, and then if forced air gets in under that crack.... it would not be pretty

I'm considering whether I want to do something like lay a 3" wide strip of 3/4 oz cloth over the LE and wrapped over the front of the polyply, then fair that in to the wing surface. The overlap would be reassuring to me.

Perhaps I'm being unnecesarily paranoid, and the structure as designed is adequate - but there again, who knows ? Mick lost his prototype model very early on, and I don't know of anyone else flying the MR Hunter kit yet - so there's no reassuring "empirical" data out there showing that my concerns are groundless.

Gordon

AsiaSRC

Hi Gordon,

Being a Junior to this forum, and late reader to this thread,
But from now on, I will glued closely behind this thread!

Keep it your effort! we will back you up from this corner of the world....I mean MENTALLY.
[img][/img]

Best regards

albert /AsiaScale RC

IB

Hello Gordon

I obtained the MR Hunter last year but am just about to start it now. I ordered it without the pro skin as I felt it to be an unknown product and am re-profiling the ribs etc so I can sheet the surfaces in 3/32 ins balsa. I have a P120 to provide the whoomph and am undecided yet as to whether I use MR's own retracts for the Hunter or ask Tony at Unitracts to knock up a set ( he's keen as he did a set for the Westbury Hunter ), By the way, the main wheels Mick supplies are superb, really impressed.

Carry on with the build, I am looking at it with great interest.

Gordon Mc

My Feedback: (11)

If you decide to pursue the Unitracts path, lemme know what Tony would be charging for a set, and what difference there would be between his and Mick's. If they come out as a higher quality drop-in replacement for the MR parts, I may consider a set myself. So far, I have taken Mick's retracts apart and am reworking them a bit. I've made up some spacers to take up some of the slop that the various parts had, and have slightly reworked one of the frames on each of the main gear retracts (Until I did that, the angle that the strut sits at meant that the gear could not come all the way up - there was interference between the top of the strut and the frame).

Yes, the wheels really are nice. I would have preferred to have much harder tires though - with the rough surface that we have on some of the runways I fly from, I don't see these soft tires lasting more than 10 or 12 brake applications. At some point I will probably be looking to either cast new hard rubber tires, or find a manufacturer who will do it.

Gordon

IB

Hi Gordon

I'll be seing Tony from Unitracts this weekend at the British Nationals and we'll be discussing the retracts as I've prepared drawings for what I want. I know from past units I have had from Unitracts that the quality is superb and beats everything I've seen from other manufacturers. I'll let you know what price we come up with for the nose and main units.

Regards

Ian B

stumax

Nice build, gordon. I love Hunters (who doesn't?), and some day when I'm rich enough to afford a turbine I'll have to have one. The glass skin on the wings looks interesting. How do you think it compares weight-wise with a foam/balsa wing? I'm thinking that the skins could be layed up over a (flat) mould which had all the panel details, rivets etc, perhaps with a coat of silver sprayed on the mould first. The LE could also be moulded so there's no need to shape it to match (as long as the ribs are accurate). I know the beauty of the skins for a manufacturer is that you can layup a huge skin on a sheet of glass and cut a whole bunch from them, but the above method may have merit also. Any thoughts?

Gordon Mc

My Feedback: (11)

If I get lucky and the surface is ultra-smooth, it will probably be a tiny bit lighter than balsa plus glass ; if there are any imperfections, then it may end up heavier - because instead of sorting those with a combination of sanding the balsa and using lightweight filler before glassing, I'd have to put a filler on top of the glass. Typcally the kinds of filler I'd use on top of glass are denser & heavier than the ones I'd use under glass.

I imagine you could get away with that on a simple wing design; for anything with more complex shapes,it could be pretty tough.

Gordon

stumax

I guess you just can't beat a cnc machined wing mould and sandwich skins!

Gordon Mc

My Feedback: (11)

I've had the main gear fitted in the wing before, but that was before both sides of the wing were sheeted. Now that the sheeting is on, I realised that the gear (when retracted) stick out past the bottom wing skin.

Obviously that is not good, so I'm looking at several ways to fix the issue. The first step involves recessing the gear mount slightly to allow the rubber grommets to be pushed in further, allowing about 1/8" more room. Since the gear plate is only 1/4" ply, obviously that weakens the gear plate, so in addition to recessing the mount, I've also added additional plywood on the top surface (bottom in the upside-down picture) of the plate in order to restore strength.

I also had to gring out several of the wing ribs to allow the strut to move closer to the top surface of the wing.

That is probably still not quite enough, but at least I'm now pretty close, so I shouldn't have to do too much more to get the gear fit right. (I hope!)

Gordon Mc

My Feedback: (11)

The doors on the main gear involve separate pieces that will move. In addition, to allow access to the retracts I will need one "fixed" panel as well.

Attaching the various moving parts to the strut could be tricky, so I wimped out and started with the innermost door since it is attached to the fuselage instead of the strut / wheel.

I simply cut the required shape out of the fuselage using a dremel cutoff wheel and an Xacto saw blade, then used two Usher offset hinges per door, and finshed by using Proskin to create a "lip" for the door to sit on. Note that the door that is hinged on the fuselage should actually be wider than the fuselage (as shown on the plan pic), so I will still need to glue an extension onto this door section.

Door actuation will be by means of air cyliners that I will mount in the bottom of the fuselage.

BTW, the small wooden strip on the door is simply a "stiffener" that I added to ensure that the door does not flex & bind while it is opening.

Gordon Mc

My Feedback: (11)

I've also now added two wooden blocks per wing for the anti-rotation dowels to fit into. Being a numb-nuts at heart, I of course screwed up and glued them in place without setting the incidence of each wing panel correctly, so I'll need to rework one side.

Since access to the forward one of these blocks was a little tough, I figured now as as good a time as any to open up the air intake. Here you can see it roughed out, and if you look carefully inside you will see a wooden former that has a similarly shaped cutout in it - the intake will be formed by rolling sheet material into a duct that will go from the intake to this former. (This will be clearer once I get to that step and show more photos)

WhoDaMan

My Feedback: (164)

Hi Gordon:
I was not aware of the time involved in this kit. It will be great to see one at the field. So what changed with the sheeting?

Dave

Gordon Mc

My Feedback: (11)

If you mean w.r.t. the problem of the wheel etc being beyond the surface - nothing changed when I sheeted it, it's just that it was only after I had the bottom sheeting on and started looking at gear doors that I realised that the wheel was actually protruding. It had been protruding the whole time, but that wasn't obvious until I tried to door that covers most of the wheel.

I usually work with the gear "unlocked" in the early stages of the build (since I don't have air lines fitted to allow me to swing the gear, I just stop it short of the locks. Doing so means that the gear doesn't use that last 1/8" or so of its travel, and so having the gear protrude marginally past the surface at that stage is "normal" to me. Next - until such time as the tracking of the wheels (toe-in etc) is finalised, it's also quite normal to have the wheel "twisted" slighty such that it sticks out of the well very slightly on one side. Last but not least, the sheeting on any other model adds depth (3/32" or so), but the extremely thin Proskin used on this model does not do that. These facts combined to make me not pay much attention, earlier on, to whether the gear retracted far enough.

It's not a big deal - just one of those fairly typical "nigglies" that crop up with a lot of the lower volume kits.

Gordon

Gordon Mc

My Feedback: (11)

The inlet ducting was interesting to do. When I tried making it out of the supplied material, it kept cracking (dunno if I was doing it wrong, or if the material just hardened withage, or what...

Anyway, I chose to make my own inlets out of plywood. First I just cut some card-stock until I could fit it into the duct area, then traced the correct outline from that. (Mick supplies a template on the plans, but I found it to be slightly off, hence the card approach.)

I then cut the main section of the ducting out of 1/64" plywood, soaked it in water & ammonia, and then bent it to slip into the duct area; after a few adjustments I got it to fit the "V" section of the duct. Then I used a thicker (1/32") plywood side to fit inside the fuselage, to close the duct out into it's extended "D" section. To ensure an adequate join between the two pieces of ply, I actually manufactured some very small "L" sections of hardwood (like "angle-iron" but out of wood) and used that. Unfortunately I forgot to take photos of the parts as I was doing this, so you'll have to just use your imagination a bit.

Finally, since 1/64" plywood is kinda thin, and I've seen a few inlets buckling when power is applied, I have applied Carbon Fiber TOW around the assembly in strategic locations, and secured those to the ducts (using a syringe + gravity to run coating expoxy along the TOW). Only one of the pieces of TOW is shown in the attached photo.

Gordon Mc

My Feedback: (11)

The main hatch needed some stiffening to keep it in the correct shape and to prevent it twisting and being able to come loose.

I made up some very-lite ply formers and a couple of stringers, and now the hatch is absolutely rigid.

Gordon Mc

My Feedback: (11)

The join of the two fuselage halves (front & rear) needed a little bot of work.

First, there were gaps (longitudinally) where the rear slid into the front but did not meet quite right. I fixed that by roughing up the joing area on the rear portion, then spraying mold release on the rear 1" or so of the front fuselage half. That mean that when I joined the two halves together, I could apply polyester putty to the gaps and know that it would fill the gaps without "gluing" the front to the back.
Next there were areas where (width-wise) the front stood proud of the rear and vice-versa. For that I simply roughed up the join area, slapped polyester putty over the join, then sanded the lot down until the parts popped apart again. The result is not perfect yet, but is fairly decent for 15 minutes work.

Gordon Mc

My Feedback: (11)

The rudder is kinda interesting. Mick's plans show that you use only ONE hinge (at the top), and then glue a servo horn into the bottom of the rudder, and push this directly onto the servo. The servo horn therefore acts as both the actuator, and the second hinge.

This may work well, but I just couldn't bring myself to do it. First off, I wasn't sure how secure it would be, but more importantly that meant that the servo would only be able to use about 45 degrees of its travel - and I like having mechanical advantage on my side. I therefore decided to change this too.

My first attempt was to simply make 3 holes in the fin TE and the rudder LE, into which I could install Robart hinges.

Problem ... given the angle at the bottom of the rudder, there was no way I could get the rudder in place whlie the hinges were sticking out. (I had this problem to a lesser extent on the flaps, but managed to work around it. In the end, I took the 3 Robart hinges and drilled the pins out of them. This allows me to install the halves in the fin and rudder as shown, then maneuver the rudder into place and push a central hine-pin wire all the way up the fin from inside the fuselage. The rudder "horn" will be mounted internally, on a tube that the hinge-pin can slide through.