Topic: Fei Bao F86 1/6.5 Build Thread

While we are on the fuel side I mounted the y fitting and two new turbine feed valves.
Can't afford another lump at the moment so I have got hold of some valves and pump which means I don't have to rob them from another airframe avoiding the inevitable fuel spills and disturbance, will just have to pull the turbine and ecu.

Time to start looking at marking up and routing the rc cables, I simply use a scriber to etch the plugs and sockets.
Top plate is fittable now with mounting blocks but cannot go in permanently yet, the very last thing will be the air intake but this cannot be fitted at this point as it will have to be cut to fit the bypass when I install the turbine and pipe later.
In fact it's been in and out like a yoyo for checking clearances etc.
Bits slung onto plate to see how it's gonna look.
The only part I am waiting for now is the sequencer which the p.o. have let me down on, that will probably go on the rh centre tray next to the ecu.
I love this job!

Hi Gary, got to say you are doing a lovely neat job of that install, which is sometimes very hard to do, like my Intro, which I found a bitch for space to fit all the stuff in, being that I was using a non conventional turbine for it, unlike the L39's we have, loads of lovely space

Thanks Vince, it's not very neat yet but should clean up ok when finished.
Off to test fly the F16 with new l/gear now so fingers crossed! 
Gary.

So how'd you get on today?

Another disaster. Airleaks on both systems and a fuel cell that won't fill up properly and then won't empty.
What you get when you don't build em yourself! One flight mostly with the doors down.

Major headache finding somewhere to put the fuel vent, why an earth some folk stick the vent out the bottom centre of the fuse baffles me, my Jav is like that and means you can't put a nice tube in for an easy connection to taxi tanks.
Routing it so it didn't get trapped under the base mounting plate was akward but I eventually found a home for it, the pipe on the far right can just be seen and the vent is now fully plumbed which means the base plate has been bolted in permanently.

A steering arm has been made up, I think it will be strong enough, only used one side to drive it.
The retract and front door rams are now attatched.

This morning I decided to get the dremel out and cut the slots for the elevator pushrods, tricky job this to try and visualise the run to miss a former and the angle is very tight, I actually cocked up on the first one and now I have a huge slot, far bigger than intended. The second one is perfect of course as by then I knew where to chop!
Now the rods are in I was able to screw the servo's in permanently after first dabbing the holes with cyno to give the screws a firm bite.
This was a major step forward as now I can install the heat protection permanently and think about r/c lead routing as all the other leads are in laying about making the thing look very untidy. Also I can think about the turbine/pipe install.

The back end servo leads in their protection can now be fitted in permanently.

At last after a lousy job comes a great one!
The Tx and SRS can now be programmed, so I didn't have to mess about putting the wings on I used a couple of old servos so I could map the flap and aileron pairs out, the benefit of using long tails means I can work outside the confines of the fuselage and see what I am doing, looks a mess at the moment as I used extensions to programme the valves etc.

In the meantime I have slapped a bit of paint on the air intake tube and the three equipment mounting plates, these are drying at the moment, I think I may have messed up a bit as what I thought was specky type paint turned out to be Fred Flintstone rock textured stuff which is quite heavy, may have to sand it all back, I'll see when it's dried off.

Ok, the paint has dried enough to come in from the garage now, I think it looks quite good if I do say so myself but as mentioned it has added some weight which is a bit worrying, perhaps I'm getting hyper.
Did the painting outside today, a bit damp but don't have to worry about blooming with this stuff.
Btw, good tip if you are like me, a bit cramped for space is to shove a bit of foam up against the end wall so the nose does not get damaged while you are working and shoveling the fuse about. Can be seen in pic.

Looking good, it can save you some weight if you prime the parts with grey before using the spackle paint.

Mmm, wish I'd thought of that, good job I made the plates out of liteply though.

In the meantime I have slapped a bit of paint on the air intake tube and the three equipment mounting plates, these are drying at the moment, I think I may have messed up a bit as what I thought was specky type paint turned out to be Fred Flintstone rock textured stuff which is quite heavy, may have to sand it all back, I'll see when it's dried off.

 
I know what you mean, I did the same on my Intro and that's the effect I got think I'll just stick to gloss grey in future

Decided to get the scales out today and discover the worst.
FB rather optimistically claim a weight of 18 lbs! I know for a fact that a few in the States are coming out at 26-27 lbs dry so they must be building them out of concrete, but anyway these are the dry weights.
Fuse c/w almost everything loosely chucked in 12 lb 1oz 
Wings each 2lb 13 oz
Cockpit w/pilot 1 lb 7oz
Intake tube 7 oz
Bypass 7 oz
Thrust tube 15 oz
Engine 2 lbs 14 oz

This just leaves the Ecu lipo and a few screws etc to complete.

So, auw comes to a tad under 24 lbs so with a P80SE shoving out about 22lbs we should be ok.

The twin tanks hold just under1.5 ltrs each so flights should be good for around 9-10 minutes with a bit of throttle management.

I remember with my Sprint carrying 2.5 ltrs 10 minutes was never a problem.

I trial fitted the equipment plates today so to complete the front end I just need a sequencer to install (more weight) and a tidy up.
The ecu is mounted and the fuel fill system is in now.

Remaining is the turbine/bypass/feed tube installation, final fitting of the control surfaces to the wings and some slotting for the c/surface horns. I think I'll leave these jobs until February otherwise I'll get bored again.

Final job for the day, SRS cables roughly routed to see how it will look, the top tray has to come out now for engine etc. fitting.

The twin tanks hold just under1.5 ltrs each...

That's about 5.35 lbs then!   

6.75 lbs per US gallon is a good general figure to use(the weight can change from batch to batch etc).

Looks very tidy Gary!  Nice work. 

Hi Gary

Just managed to catch up on this thread, nice build mate!  I'm pleased to see your becoming a proper 'tart' with regard to the internal finish. I remember you once saying to me you didnt understand why I went to the effort of painting the inside or trays etc....   I'm jealous I havent touched a model in over two months 

Just one thing I noticed, can you see the UAT once the duct is in place?  On the larger one I built I cut a window into the top tray so I could check for air.

Cheers, Alex

Thanks guys.
Alex, good to hear from you, how's the training going?
As I pinched your idea of the shelving I thought the least I could do was to paint them like you did. 
Earlier in the thread I made a comment along the lines of bearing in mind that the duct was going in at some point later and make allowances for it: you are quite correct I will not be able to check the uat so a window it will have to be! 
Thank you for pointing that out I had overlooked it.

Elevator horns fitted.

Now I need some advice as I have never used a full bypass before.
It's a pia mainly because of the use of a JetCat with it's offset mount.
Question is, do I need a full bypass? The incoming air is ducted straight to the front of the turbine by the inlet tube so nothing internally will get buffeted by the breeze.
To get the tail pipe in the correct place I have had to move the turbine fairly well forward so it's fingers crossed cg wise.
The pipe has no bellmouth but the 18mm gap is allowed for.
So what purpose does the bypass serve other than keeping some heat away from other components? Do I really need it?
Your thoughts please would be appreciated.

My view only as I am not a fan as I like to see the turbine at startup, and one reason I would'nt buy a jet that needed the wing removing or bottom hatch to see the turbine.

Bypass will make the system bit more efficient due to the ram air effect (turbine dos'nt need to suck as hard) but wont increase the thrust as many people think, and probably will be a bit quieter.

I personally dont see the need for one, as above I want to see the turbine when it starts, and be able to get at it without having to screw off a load of covers.

Hi Gary

Each to their own on this one...

I think the general misconception as xairflyer suggests is that a full bypass increases thrust.  This obviously isn't true but it does reduce drag through the system making the model fly faster at a given thrust setting which is more noticeable at the top end.  Some models benefit greatly others not so... I always install a full bypass where possible.  Its a fiddle but it only involves cutting the bypass down to suit and adjusting the height of the mount.  I also use the bypass as support for the pipe but do use screws onto the ply rails for extra security.  I take it out and do a half a days flying without then put it back in and do the comparison.  I tend to install them all like this...

Thank you both for that, so I really needn't worry if I don't fit it then.
I have seen people rig out F86's without even using the inlet duct and they all look a mess. I wouldn't want all that air ramming into the front of my fuselage trying to rip everything out and attempting to explode it so I will definately use that.
The bypass supplied is a bit big and clumsy, in fact the JL one I did not use in my large L39 is a much nicer size and the quality is better also so I may fit that, even if it's only the bottom half.

Seamus & Alex, very interesting information on bypass's as the Avonds F15's I have also have this feature, my friend Ron Burnett has always had his fitted in his 13 year old Avonds F15, which uses an AMT Pegasus air start engine.

Gary those ball links & rods on your elevator are nice, did they come with the kit? Your still doing a nice job mate and as you say, "keep some jobs back for the winter months so you won't get too bored!" 

I just like to see what is going on when I am starting up, latest internal kero start turbines I suppose dont need looking at, but last year I had a Airworld L39 in for some work which had all the bypass covers on plus on the AW L39 the turbine access is from underneath which means you cant even see a covered up turbine with the top hatch off.
When I took all the cover's off a lot of the wood was burnt, obviously had a wet/hot start and nobody knew! could have been fun if it kept burning.
This turbine was also gas start and from the work I had on the bench if you have a blown plug while out flying you are going home.

Found this on RCU


Pro's
1. Less drag, smoother airflow through the inside of the airplane than a non-ducted installation.
2. Cleaner install (if done properly)
3. Less chance of equipment inside the plane coming into contact with the turbine (either fod in the intake, or melting onto the side of the case).
4. More protection for the turbine in a crash
5. Might also help avoid having fuel spray come in contact with hot engine parts in some crashes (less chance of a fire)
6. Easier for inexperienced builders to set up a bypass system that is pre-engineered without making mistakes.

Con's
1. More difficult turbine access.
2. Much more difficult to scratch build using a bypass because the ducting and fuel tanks need to be designed and built to fit the airplane.
3. After engine shutdown the radiant heat from the turbine will be contained inside the bypass, necessitating the use of a fan to help with cooling (yes I realize this is a good idea even if you don't run a bypass, but it is pretty much mandatory with one).
4. Takes up more space inside the airplane.
5. Higher cost.
6. Some propane start turbines are more likely to "BANG" on startup inside a bypass (usually doesn't hurt anything, but it gets everyone's attention).

I don't agree with some of them but the general idea is good


Some will argue all day about static and dynamic thrust differerances but I just like to see the effect once airborne and as I said some models are much better with a fully ducted set up.  I have seen transparent top covers for bypasses which is a neat idea.  If you watch Ali start a ducted install he stands about 5 meters behind looking straight up the pipe with a guy on the extinguisher ready to shoot a load down the intakes if it goes pear shaped.  I think he does this until the turbines set up at least.  I wouldn't recommend that technique though  . I just fly with it off until I'm happy the turbines behaving.

When I took all the cover's off a lot of the wood was burnt, obviously had a wet/hot start and nobody knew! could have been fun if it kept burning.
This turbine was also gas start and from the work I had on the bench if you have a blown plug while out flying you are going home.

Yup your quite right Seamus, blow a plug and it's wasted trip to the field, or the fire aspect!

Thanks for the info , Vince, the ball links came with the kit.
I think I found an engine for the Sabre this afternoon, had a flame out on the Elan. Really strange, the GSU says "low revs" for last off condition but when I investigated the cause the (charged) ecu lipo read 7.6 volts so when I attempted a start in what was left of the fuselage the battery dropped to zero volts. I am assuming that caused the fire to go out.
A strange thing happened which is confusing me, after the f/out I could not get the gear to deploy or flaps but still had flying surface control, anyway the resulting confusion and lack of drag meant that I ran out of runway and finished up in a quarry.
Hey ho.

Oh hell Gary, you've not lost another Elan Jets are bummers at gliding Is it totaled? or is it repairable? Also, on a lighter note, where do you get your nice metal servo arms?

cheers,
Vince.

That's the problem, no gear or flaps so it just floated on, couldn't stop it.
Turns out the engine seized, 10 1/2 hour P80SE!
What stopped the gear and flaps from working when all the flight surfaces did I haven't worked out yet.
I managed to land it flattish which considering I couldn't see it at the time was pretty good.
May be repairable, booms got it bad as it hit a mini tree, everything else looks not too bad.
Horms are HK.

Sorry to hear that garry

Does the Ver 6 ecu go into cool down mode automatically after a flame out ?

It there any damage to the turbine blades or compressor?

Hi Seamus, it would have tried to go into cool down because when I heard a whoomph sound and saw some flame coming out of the back end I hit the kill switch anyway to save a possible fire, I thought it had thrown a blade actually.
It's not seized totally solid, I can turn it and it feels like something is scraping but I cant see any compressor or turbine blades missing.
I charged the battery today, it went down to zero volts when I attempted to start the turbine obviously because of the tremendous load on it, as soon as I saw that I killed it before the starter motor got damaged and then pulled it out of the model.

Like a bearing failure, which probably happened after it shut down, might not have cooled and so cooked them. if it happened when running it would be wrecked.

Any chance the turbine got a bang in the impact? as might also just have knocked it a bit out of line (NGV)

No Seamus, landing was not severe enough to bash the turbine. It sounded as though it just locked up on full power, I was on the early part of a vertical when it let go.

Seamus, I've had a closer look this morning, it's bad.
Compressor ok, I use a fod guard, but the turbine wheel (diffuser?) has two blades missing, all the blades are damaged and bent back a bit on the outside diameter, the NGV is also damaged so they have all been in contact.
The NGV is badly damaged, chopped about and obviously damaged on its inside face where the blades have clobbered it, not sure how this all happened unless a bearing failed but the shaft does not seem to have any play in it, what do you think?
Gary.