MJD

My Feedback: (1)

Maybe you could fill in the nose and put 3/4 pound of lead in there, and fly it as a dynamic soarer..? Then you could go 300.

I never did and maybe never will, but at one point I had the idea of reworking the nose to fit a RIRE big block, and stuffing the pipe in the turtle deck best I could. But in the end I realized it would be completely reworking a Magnum into a fast but heavy and ill-tempered aircraft, and got happily distracted by deltas and other ideas.

A honking RE .50 or pylon engine, faired in neatly and with the pipe buried in the turtledeck would move it along smartly. The pipe tunnel RI setup as an option is a missed opportunity on this aircraft IMHO, with that big empty fiberglass canopy and turtledeck. I realize for marketability regular old FISE is the way to go.

MJD

mk1spitfire

Put another tank in the empty canopy, injector in manifold, use crankcase pressure and smoke fluid, its been done before.


Weston have a prototype mini magnum, which is electric.

2w-25 5s i think.

john josey

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john josey

I only managed an hour or so today, but managed to make up the snakes to their final lenth and set up the travel on the TX at the recommended 10mm throw, although if it`s like westons suggested CofG location and claimed top end speed it`ll be way out !

MJD

My Feedback: (1)

Are you going to seal that rudder hinge line? According to the scale there's about a 1.3-1.5mm gap there.

You'll only ever use that throw on the last stages of flare. Are you setting up dual rates, or mucho expo?

MJD

evan-RCU

This thread makes me want to build a new Magnum and retire my old one....

john josey

Thats a phrase you dont hear much. quite reasuring !

As for the rudder gap, it`s not glued in yet , my intention was to fly the model first and then fit it but the more i think about it i think i`ll just fit it and fly.

The eventual gap will just be the width of a modeling pin, i`ve put a large enough chamfer on the leading edge to have next to nothing gap and plenty of movement

I have a 3 position swich on my TX for the dual rates, so my intention was to have the total movement the same on all 3, but different amouts of expo, something like 15, 30 and 40%. and then go from there. The good thing about my TX is you can quite easily adjust them in flight.

evan-RCU

It's one of the very first that came into the US about 10 years ago. Still flys great though it is showing it's age after at least a hundred flights. I built a second one about 5 years ago, stripped off the covering taperd the T.E. and enclosed the motor better, turned out real nice but on the first fligh I had a radio problem (range tested fine a few times) and she flew off at full power never to be found. What makes me mad is that new Weston .50 is out there rusted away.....

mk1spitfire

I found it pays to have extra elevator for flare as a second rate.

john josey

Are you saying i`ll need more total throw than i have showing for landing ?

mk1spitfire

no, thats fine but will most likely be your high rate as in flight you need very little elevator at high speed, expo to if you need it, so you could use less for low rate John.

john josey

Ok cheers

john josey

Oh ouch ! at least with a crash you get most of the debri back, i feel your pain !

MJD

My Feedback: (1)

No that's lots. But you'll want to stay far away from that much travel at speed.

It's strictly personal, but my temptation would be to knock down the travel on low rate and do something like this:

- high rate full throw with 25-30% expo
- medium rate either full throw with 40-50% expo, or 65%-70% throw and 25-30% expo as per high rate
- low rate 50% throw and 25-30% expo

I'm not sure the expo levels you are suggesting, coupled with that elevator throw, will be smooth enough at top speed. But, you do have a throttle if things get hairy after all.

This is just $0.02 from a guy who prefers rate changes to more expo, so bear that in mind before swearing by what I suggest (but go ahead and swear at it). I just don't like rapid throw change at the higher end of stick travel, not on this type of stuff. I prefer a more linear response in case I react a little too quickly and energetically to something that needs reacting to.


MJD

john josey

I agree it is personal preference, but it makes sense what you say my TX has a possible 5 D/Rand expo settings so i have plenty of options, the hard part is trying to remember what you`ve put where !

john josey

Now i know most modelers know how to set up their throttle properly, but some wont, so i`ll give a quick explanation of how i go about it. It`s more important in helicopters because it means the throttle curve values correspond to exact barrel openings on the carb :afro:

First thing to do is throttle trim to low if it`s an analog trim (JR) or in the middle if it`s digital ( futaba)

The next thing is make sure the throttle stick is exactly at 50% !

The next thing to do is fit a servo arm that will put it at 90deg to the linkage, use subtrim if you have to but only as a last resort :afro:

After that you need to adjust the lenth of the linkage to get the throttle arm 90deg with the linkage. it`s not critical how much the throttle barrel is open on the carb at this point. Roughly half way is fine.

The next thing to do is adjust the ATV`s on the TX so that the barrel just opens at full stick and just closes and no more at low stick. In this case it`s 130% at high and 88% at low stick. if it comes out at an odd number just add 1% to make it an even. it makes the next bit easier :afro:

Now a bit of simple arithmatic.
130 - 88 = 42
42 divided by 2 = 21
130 - 21 = 109
88 + 21 = 109
Which means we set the ATV`s to 109% you get the idea :afro:

All thats left to do is move the throttle stick to full and move the barrel on the carb to fully open and then simply tighten up the throttle arm on the carb.

When you have done that little lot whan you move the throttle trim to half (JR) or 3/4 for futaba the barrel should be near enough to the correct opening for a good idle ( you may have to make small adjustments to the trim position to get the ideal idle) It means now your throttle curve will be perfectly matched to your carb i.e if the curve says 56% than you know that the barrel is exactly 56% open at that point and so on.

mk1spitfire

Good stuff, but when you fly magnum, you may only want full throttle!! A swtich instead!

I try and set up mechanically the best i can,followed by radio, that means getting the right resolution, ie same horn length hole as throttle horn and like you said aim for 50% open on carb.

john josey

I agree with you, i usually try and keep to as close to 100% on the ATV`s as a can, but i have found in reality that if you are within 10 - 15% of that thenthats acceptable.

It`s just the amount of people you find at the field, when your looking over their model for whatever reason and you see the throttle ATV`s are at something like 130 at one end and 35 at the other, an then they tell you it`s ok because they get full at one end and it closes at the other.

You normally find that these are the same guys that are bragging about their latest super duper radio with huge resolution and high precision digital servos ! you end up shaking your head and walking away.

john josey

Managed to get the engine and tank fitted today, although i had a bit of an issue with what way up the tank was meant to go 

The first way i tried it seemed good and the pre-bent brass pipe for the vent was right at the top of the tank, but when i screwed the engine to it`s mount, it was so close to the bulkhead that it would kink the fuel lines if the tank was pushed forward as far as it would have to go to clear the front of the wing.

I changed it to the way is shows in the picture, although the vent doesn`t reach the top of the tank now, although not by much !

It should be noted that it fits well both ways untill you fit the engine !

john josey

Not much left in the box/bag now !

I used longer bolts to go through the manifold so i could get a washer and nut on it instead of just relying on the threads on the manifold to keep things tight.

Not much left to do now, fit the reciever, battery and switch then balance and final check of everything.

MJD

My Feedback: (1)

Flight report tomorrow...? Looking forward to it. No knife edge loops on the first flight.

I'm sure you'll like the engine, I found it remarkably easy to handle. It helps that the pipe/header setup is ready to go of course, but the engine itself is a nice piece of work. Mine was pretty squeaky, if I did it again I'd warm the head the first handful of runs just to be extra kind.

MJD

john josey

It`s my daughters birthday on sunday so i think it`ll be next weekend till i get a chance to fly it i`m afraid. I`ll try and organise a clubmate to video the first flight

This is without doubt the 'tightest' engine i`ve ever owned. i fully intended to give it the 'hot air gun treatment' for the first start, but if you think i should do this for the first runs thenthats not aproblem,i trust your judgement

What about the running in procedure, do i just follow it to the letter in the instructions ? The point they make about it being fully run in after one tank is pretty lame at best.

Any advice you can give me on the first few engine runs would be much appreciated.

cheers
john

mk1spitfire

Your engine will be alot free'er after 1st run in. The pinch is tight on 50v1 and 36v1,so i assume the same for 52. Its another debate on how to run it in but basically the quicker the engine can get up to to temperature then the pinch will be less due to expansion and things won't wear out, but bed in! I'm sure instructions will say run rich for 1st tank, or more like 4stroke sound tuning,but its not a ringed engine.
Ohters here can give more tech advice.

What fuel you going to use? Prosynth 10%? Weston say use that because they sell it and thats part of the warranty. My only comment on that is the unknown oil content they refuse to disclose.
I've used it for a season but im convinced the low oil wears things out quicker but performance is good as there is more methonol to burn instead of oil.
I've switched to another synth called propower 18% oil or may try techpower 15% both by model technics. Pro sythn cheaper though.

Watch out for flooding, be prepared to take plug out and turn her over to spit fuel from glow plug hole.

pp7 plug? sometimes 2v gives a better glow for starting.

Your know when its tuned right because it sounds angry. It might pay to get someone to launch it for for first flight until trimmed but after that its very simple to launch. I've found a THIN rubber glove very useful to launch to give grip. 9x7 it will fly out your hand likewise 9x6, with gentle push 45 degrees, watch out for torque to left.

john josey

I`m gonna be using coolpower 10, which has 18% oil.

As for runing in, i was gonna set the needle for pretty much peak power and maybe back off a 1/4 of a turn something like that, and run it for two minutes or so and then stop it and let it cool down, and just do that untill a couple of tanks are through it ?

I have a 9x6, 9x7, 8x8 and 8x10 props for it, i`m leaning towards the 9x6 for the first runs and flights, but the information supplied between the instructions with the aeroplane and their website is a bit confusing.

On the kit instructions they say for maximum speed the aircraft is capable of you need to shorten the pipe/manifold and use the 8x8, but the website says leave the pipe the standard lenth and use the 8x10 ?

But they stress not to use any other prop than the 8x8 if you shorten the pipe/manifold !

I`ve read stories about the conrod blowing on them, but i`m hoping to avoid that sort of thing by warming the head up before the first runs.

john josey

Only managed half an hour or so today, one 4mm hole and three cable ties i`m afraid.

I didn`t like the idea of the cable tie straight onto the pipe so i used a short piece of large bore fuel tubing that i had lying around.