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Member postings for John T

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

Thread: Why RC? Why not FF?
29/08/2020 09:21:05

Hi FFPete,

I used to fly FF and CL before I started flying RC. The main reason I don't fly FF nowadays is simply because the local club field I fly from isn't suitable for free flight. The large open flying fields of my youth are becoming a scarce commodity and I suspect this is the main reason for the decline in FF.

Thread: Sticky casing on Watt meter
25/08/2020 09:25:06

Yesterday I thoroughly cleaned the casing with IPA.There were one or two small patches that remain slightly dull, but all the stickiness has gone smiley Only time will tell if it lasts.

I see from the photo that Captain K posted that Rain X contains IPA. Perhaps that is the magic ingredient.

Perhaps now is the time to break out the other sort of IPA that PatMc was referring to to celebrate.

23/08/2020 17:01:09

Thanks for all the replies so far.

I can't remember exactly when i bought the meter but I think it's probably 5 or 6 years old, so probably not quite ready for the V & A yet. It won't have been in contact with methanol as I don't use glow engines nowadays, although it may have shared the car boot with model diesel fuel at some point,

Although I find the thought of a varnished plywood Watt meter strangely pleasing, I thought I would try a few of your other suggestions first on small patches of the casing.

A damp cloth had no effect. I don't have any Rain X but I have got some RAC Clear View, which I thought might be similar. While it did remove a lot of the gummy stuff the surface still felt tacky to touch.

The last thing I tried was IPA. Without wanting to temp fate this appears to have worked! The surface now looks and feels like new again. If it still seems ok tomorrow I'll clean off the rest of the meter with it.

23/08/2020 10:06:42

Hi Guys,

I don't know if anyone out there has an answer to this one, but I've got a Watt meter with a hard rubber style plastic case that seems to be slowly decomposing and leaving a sticky residue on my hands or anything else it touchessad. At the moment I've cut up a plastic bag to put it in so I don't have to wash my hands whenever I use it, but I wondered if there was anything I could paint the case with to stabilise it?

I know new ones don't cost very much, but I don't like binning what in other ways is a perfectly good bit of kit.

TIA

John

Thread: Electric power for KeilKraft Gaucho.
05/08/2020 15:02:53

Jeff,

My memory must be going or something. I just had a look at my Gaucho and remembered that I'd initially had similar issues with stalling. I resolved mine with a 1/16th ply plate under the tailplane LE. I know it was 6 years ago that I did this, but I fly the model every couple of weeks or so and have to band the tail on each time!smiley

gaucho_t-mount.jpg

05/08/2020 09:40:38

Hi Jeff,

Glad the maiden flight went ok,

The C of G on my Gaucho is 4 3/8th" (or 112mm) back from the LE, which works out as about 70%. If yours is no further back than that I would try packing up the LE of the tail a touch. Don't forget the original free flight design would have been trimmed to glide in a large circle on the glide, which would have tended to kill any slight stalling that might occur in straight flight.

I normally use the dive test to check the C of G. If you dive the model at about 30 degrees and let go of the elevator, the model should gently nose up on it's own. If the dive increases, the C of G is too far back.

Have fun trimming.

John

Thread: build to remember
27/07/2020 11:19:20

Hi Martin,

The size of the KK Gypsy should be fine for the mills, but by the time you've strengthened the nose a bit to mount the engine you might find it a touch nose heavy. Just make sure you can move the radio equipment about a bit to compensate if need be.

As Jim said, go for it!

Thread: Tissue over Doculam covering for undercambered wings
23/07/2020 11:38:09

Love the Amigo Pat. I'll definitely try the Wilco varnish at some point, although I think I'll use cellulose dope on the Chief, mainly because I've got a tin open and I know it turns a bit murky if you leave it too long.

I'm guessing you need to use a reasonably high wet strength tissue such as Esaki or Model Span with these water based varnishes. I've had trouble in the past using Eze Dope on cheaper tissue as it just disintegrates.

22/07/2020 12:22:30

Interesting link PatMc. Slightly off topic, but I was interested to see "Eze Dope" or "WBPU" mentioned. Although I quite like the smell of dope it might be worth a few extra brownie points if I could use Eze Dope instead smiley

I'll perhaps give it a go on an old wing to see what it does.

21/07/2020 18:31:13

Thanks for the offer Nige, it's very kind of you.

However, I think I'll use the film I've got, now I know how to apply it and what iron temperature seem to work ok. I don't want add more variables into the mix.

21/07/2020 11:41:03

Nigel, I take your point about running a few test samples. This is the stuff I've got.

doculam.jpg

The wing is a 30" span "Wee Snifter" before I applied the tissue with a couple of coats of thinned dope. If anything, I think it may have ended up lighter than just tissue and dope alone as I didn't need so much dope.

21/07/2020 09:14:18

Thanks for the replies. Following the example of PatMc I think I'll try without any extra adhesive, but I'll add cap strips to the ribs so that the Doculam has a bit more area to stick to.

20/07/2020 12:38:55

Nice idea. I've used this method years ago using Nylon covering. I'm not sure what glue would work with Doculam though...

20/07/2020 11:23:45

I'm planning to make an enlarged version of the old Keil Kraft Chief glider for my next build, and in order to keep the original appearance I intend to use a tissue finish.

I've recently built a couple of small models using tissue doped over Doculam and I've been really impressed by how much stronger the result is, so I'm tempted to do the same on the Chief. However, these other models don't have under cambered sections. The KK Chief has a very pronounced under camber (NACA 6412) and I wondered if the Doculam has sufficient adhesion to prevent it pulling away. Has anyone tried doing this, and if so are there any tips to help?

Thread: The Atom Special
08/06/2020 21:03:14

O.k, tried again today.

Slightly thicker shims and the rotors spun up more quickly than before. There still seemed a lot of lift and I managed a short flight before I got disorientated and ended up with another walk to collect it from the hay field. No damage this time. It's a strong design Rich!

I flew another model for a bit while I had a think and decided to increase the shim thickness a bit more (an extra 0.2mm in total). The next attempt was much better. The rotors spun up quickly in the breeze, and when it was airborne it seemed a little less "pitchy". For the first time I actually managed to land it on the patch smiley. Very pleased with myself! I'd almost resigned myself to another trip to the hay field.

One thing I am having trouble with is disorientation. I think I might put a large orange patch on the outside of one of the fins to see if that helps.

Thread: Electric power for KeilKraft Gaucho.
04/06/2020 17:05:03

The main reason I used a 2S pack was to try and keep the bulk down as much as possible to avoid widening the fuselage much. It's a bit tight in there! If you can cram a 3s pack as far forward as possible it might help with the C of G.

The elevator is hinged at the original rear spar line in the rather optimistic hope that it wouldn't really show up when it was flying (It uses an internal wire yolk which engages in a slotted sliding plate). Both halves are used, but there's only about 15 degrees each way and it's not particularly sensitive.

04/06/2020 11:05:00

Hi Jeffrey,

About 5 years age I made an electrified Gaucho which i still fly regularly, in fact I last flew it 2 days ago.

Gaucho

Mine is powered by an Emax CF2822 motor with a JP Green 8 x 4.5 folding prop and a 2 cell 800mAh LiPo. This gives quite a reasonable climb, although not exactly "contest" level. I'm guessing your set up would be similar or slightly more powerful. As Peter said, somewhere between the Mills and the Sabre.

As for the model itself, I widened and extended the side cheeks slightly so there was room for the battery, receiver and elevator servo. The pylon was also widened fractionally and I've mounted the ESC and rudder servo there. I extended the trim tab to the full height of the fin to use as the rudder, but if I were to build another one I would make it a bit bigger. The dihedral is pretty much as designed. I needed a bit of nose weight in mine so try and keep the gear as far forward as possible.

For a relatively small model it thermals really well, and it will cope with surprisingly strong winds.

Thread: The Atom Special
29/05/2020 10:16:24

Well, my Atom finally got its maiden flight yesterday, though with somewhat mixed results...

On the first attempt I gave the rotors a spin by hand, but even with full back stick while moving slowly into the breeze the rotors seemed a bit reluctant to spin up. After about 50 yards they suddenly seemed to speed up, so I released the back stick and with a bit more throttle it was flying.

There seemed to be plenty of power available with this set up. However, it was wanting to roll to the right despite having about 3 - 4 degrees of left tilt on the rotor. I was also having to fly with a lot of forward tilt.

After about half a dozen circuits I'd managed to kid myself that I was in control, so I decided to try and land it to sort the trim out. That's when I discovered it wasn't a good idea to bank it too steeply as it dropped out of the sky into some long grass. Much to my amazement there was no damage.

Before the next attempt I lowered the left hand control rod slightly, thinking this would give a bit more left roll and also reduce the rotor pitch at the same time. After another long take off run it was airborne again and I realised the boundary fence around the patch was very close. Without thinking I banged the throttle wide open, and before I knew it it was three quarter of the way through a loop.

I wasn't so lucky this time and broke the mast and the prop. Other than that there was no damage, but as I didn't have a spare mast with me I called it a day.

Before I try again do you think it would help to increase the shim thickness at the back of the rotor blades a touch? I wonder if this would help the spin up and also reduce what appears to be excessive lift a bit.

I can see why this autogyro lark is so addictive. It's a totally different ball game from fixed wing flying.

Thread: Shear webbing grain direction. Does it matter?
10/05/2020 11:17:15

Many moons ago one of the magazines had an article where they actually built some mock-up spars with the grain running in different directions. The conclusion was that there was virtually no difference in load before the spar failed.

Having said that, I still use webbing with a vertical grain because it just feels 'right' smiley

Thread: The Atom Special
25/04/2020 09:30:36

Thanks for the reply Rich,

Here are a couple of photos taken in the back garden. As you can see, I've shamelessly nicked the colour scheme from your original article. The tail booms were supposed to be red from an old Wilco rattle can, but for some reason the last dregs came out as brown.

It may be some time before I get the chance for any flying shots...

img_20200422_114913748.jpg

img_20200422_120128257_hdr.jpg

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