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Member postings for Martin McIntosh

Here is a list of all the postings Martin McIntosh has made in our forums. Click on a thread name to jump to the thread.

Thread: Ever wanted to get into or improve your aerobatics?
07/12/2013 23:19:35

I`ll second all of the above, hard sticks and all. The heavier the better. I am at a loss to know how mode 2 flyers ever manage an eight point roll.

05/12/2013 23:28:07

I questioned this with Danny Fenton and he reckons that they are to scale otherwise he would nd not have built one.

05/12/2013 23:22:25

On the differential theme, many of us added a little of this by putting the horn slightly in front of the hinge line (small ammount of positive wing incidence used-not zero-zero) in contrast to what I read in the mag by someone who suggested that it should be behind. On paper that would seem right but in practice it does not work.

In my opinion it is best to start with this configuration mechanically, as everything else on the model should be, then use the computer tranny to fine tune. This way you maximise the servo torque and centring.

05/12/2013 23:00:47

Interesting about the scale factor. When I first flew a comp. I had a `Clipper` with about 63" span then upped the basic design to 67 or 69" when I started to use retracts, same motor used. The result was a much better model even though it weighed tons more.

I have built the Tony Nihuis 44, 62 and 72" Spits. The 62 handles just as you would expect a Spit to do and catches me out occasionally. The 72 is much better and flies round loops rather than being dragged by the motor.

The puzzling thing is that the tiny 44" outflies both on miniscule power (OS26FS) despite a weight of 3lbs 10oz with retracts and a four servo wing with two of them (heavy MG) behind the cg against a plan weight of 2lbs 6oz and is almost impossible to stall even with full up applied. It just mushes like a delta and a spin is difficult to induce. The cg is as per plan.

This defies all the theories.

04/12/2013 16:29:02

As an afterthought to the above just look at the enormously long rudder servo arms on almost any top 3D model. Modern metal geared digi servos will find that centre no matter what, which is why they `sing` and are of course necessary on these to cope with the load but are not favoured or required for F3A.

My Curare replica is fitted with quite cheap nylon geared analogue servos just for authenticity.

Thread: Precedent Stampe 1/4 Scale
04/12/2013 16:10:53

I tried some of those wheels on a Spit and despite glueing the covers on they popped off on every landing.

Thread: Ever wanted to get into or improve your aerobatics?
03/12/2013 23:45:42

I have just started to look at this thread and have read most of it with interest.

There are some very good points here but also some which require questioning.

As a former twice F3A team member and once Btitish champion I feel that I am reasonably qualified to comment.

I do not attempt the current schedules because (a) I do not like them and (b) I am now too old but I still enjoy the manoeuvres which I used to do.

The method of trimming wing balance is sound but only works if you are truly flying directly downwind and push to a half outside loop on low throttle. Insides do not seem to work for some reason. This is the way I do it.

CG and thrustlines are not difficult to set up. Starting with the thrustline, with the canopy towards you pull to the vertical and see if it remains that way. adjust as necessary and a good starting point is 2deg. right.

I try to set CG so that at the end of a spin the model should stop after exactly one half turn when the controls are neutralised. Forget the climbing/ diving, if the model is set up to tail 0 deg., wing +1 deg., motor - 2 deg downthrust then this will be a good starting point for most. If using a very large prop, say on electric. then the right thrust may have to be greater.

I must totally disagree about using the inner servo hole and have seen much written about it. If you do this, then to get the required surface throw you must use an inner horn hole so any play/slop will be amplified. Try it and you will see what I mean. I once got a tip from Mike Birch which was to make the (then used) quick link connection loose so that the feeble servos of the day had a chance to centre. This is still viable since no matter what you pay for your servos they are only able to centre a surface if there is no resistance in the linkage. It is the slop here which is amplified by an inner hole, not the servo gear play. I now only use ball links (cheapo snap on at one end and screw on at the servo works fine). Quick links just grab the arms/horns and give a lot of resistance usually.

Don`t use snakes on controll surfaces since unless they are dead straight and are pinched along their length they will be sloppy. Use hard balsa or cabon tube.

Thread: Martins i/c Mustang
29/11/2013 14:58:39

The inner main doors are now done. These have been constructed from 1mm alloy with 0.2mm GRP epoxied to the outside to give flexibility. The CSK screws go into a thin brass plate to which M2 nuts have been soldered. I drilled and tapped the plate then held the nuts with stainless screws whilst soldering so that the screws would not also get soldered on.

After a little fudg, - er, fine tuning the doors fit OK and I am confident that when eventually linked to servos they will work just fine. Not really as much work as it may look.

martins ic mustang 087.jpg

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28/11/2013 19:34:40

Thanks again for the comments. The jamming has been overcome by repositioning the tubes. The ones on the first side have now been sewn on since Liquid Weld is not strong enough by itself. The second hinge pins will be permanently fixed when the model is complete.

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27/11/2013 22:22:43

On the face of it this looked to be on par with a Spit for complexity but it is turning out to be far from it although I could have simplified a few bits. The wing is now complete bar the LE fairing and the control surfaces ready to sand.

martins ic mustang 076.jpg

The tailwheel doors have consumed much time and more than a little scratching of the grey matter but I think that I have come up with a workable solution. Just need to add stops and find a way to keep them from sliding backwards or forwards to avoid jamming. The closing `springs` are Tesco elastic hair bands which are temporarily taped in place. The tension needs to be just right otherwise the retract could stall. Much fidely bending of wire and careful soldering involved here. Hope that the following pics explain this. It is a system which I have previously used on a Lanc.

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Thread: Hanno Prettner Magic
25/11/2013 23:10:08

Regarding making moulds, a problem reared its head a few years ago. I always used to tissue and dope the balsa plug but all of a sudden they all well and truly glued themselves to the resin. I can only think that the dope formula must have changed so I now glass cloth the surface using epoxy. Problem solved.

24/11/2013 21:30:53

Just had a look at this - great job. Regarding molding, I have done quite a bit (amateurishly). I use Fibretech (now Bucks Composites) release wax. Five coats allowing 20min drying and buffing between each works well. I understand that PVA is really only for polyester resin, not epoxy.

Martin Mc

Thread: Martins i/c Mustang
24/11/2013 20:53:54

Why bother growing up? We all still build toy aeroplanes and why not?

martins ic mustang 075.jpg

Just a tad more tonight. The upper sides of the remaining control surfaces and fin with peel ply applied to absorb the excess resin. Once removed there will be very little sanding to do. These will be coated with very thin clear dope to seal the dusty surface and provide a paint key so that masking tape will not pull the finish off.

24/11/2013 19:04:05

Don`t try this at home!

24/11/2013 16:12:44

martins ic mustang 073.jpg

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Found them now Colin.

24/11/2013 15:42:14

Long time no post but I have been far from idle. I have made the airscoop from GRP which has taken well over a week. It is by far the most complex one piece mold to date but I am wondering if it was worth the effort. However, it only weighs 25gm. The pics show it placed roughly in position; also my effort at the cockpit dash. This is almost invisible with the canopy fitted.

The little guy in charge has been ordered from `The Pilot People` at 1:6 scale and 28GBP so I hope he fits. 28 days lead time on these.

The tail has been glassed prior to fitting as have the fin, ailerons and flaps. Just doing the wing tips then the wing can be glassed also.

\

Thread: oh no a hobby king thread again..................
17/11/2013 22:19:59

I have received some sixty orders from HK (sorry UK LMS`s) and the contents have always been correct but I had an issue with three out of four Donkey b/l motors which were described as not pretty but very robust. Within seconds the windings fouled on a protrusion and two broke. They said `OK, please send photos` Ever tried photographing a broken winding inside a motor? Got a $5 credit for one of these after much effort. Not worth the trouble.

Also advise not to buy their Nanotech high C lipos since they all soon swell up. Cheaper TGY ones are fine.

Thread: Rewinding outrunner
17/11/2013 22:00:39

Tried this myself once just for the hell of it with an iffy motor and got about the same results as you. Probably due to a turn or two cutting into and shorting on the stator. Not worth the bother now that they are ten a penny.

Thread: Crane Fly Light , Autotogyro Trainer , For experienced pilots trying autogyros for the first time.
15/11/2013 20:55:24

Yes please Tom. Not had chance to get out with mine again yet but you know that I am interesred in ROG with this.

Martin Mc.

Thread: Martins i/c Mustang
13/11/2013 00:04:11

Wow! Beats my feeble efforts. Good luck with it.

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