Topic: hawker harrier jump jet ( large size )

hi all i am new to this and not shore what to do
and may well get things wrong to start with
i bought this harrier with the moulds .
the fuz is a no good and will need a new one.
the moulds will need some work to get ready.
i have started on the left hand side and will
post pic's when ready.
i have my own laser 900x600 so no prob's
cutting out the bit's.
my name is robin and have built planes for 48 years
and will welcome any help.
regards planeking-robin

Hi Robin

I saw it on Ebay and thought it looked interesting but ducted fan or jet is not my thing.  you say you are new to this do you mean modelling or forum, a harrier is not a 1st time model to fly!  Do you have glass experience it would be interesting to see how you tackle building a new fuselage I will be watching with interest.

hi norfolk'n'good ,i am new to the forum game.
yes i am some what of an exspert in glass.
regards robin

oh dear, we all had a good laugh about this wreck last week....

oh dear, we all had a good laugh about this wreck last week....

People were the same with a racing dingy I was given at the age of 13 which was similar to a Mirror dingy and was de laminating and literally falling apart at the seams but after my dad and I (yes I did do 75% of the work) had been on it for a while everyone though it was a new boat so I'm interested to see what magic can be done on this Harrier 

hi cactus, oh dear i like a challenge and you have just set me one.
regards robin

well it seems with a lot of hard work you might end up with a rowboat

well it seems with a lot of hard work you might end up with a rowboat

Don't mind Cactus, he's harmless really

It wasn't clear from what I can see - is this going to be an EDF model in the end? Or IC powered?

I'm guessing from previous discussions that it won't be feasible to make it hover, IIRC the power to weight requirements are too high for any model engines, even turbines. It does look like the ducts swivel though, could be a good scale feature if they get servo'ed up.

hi to all , thanks for the comments and i don't mind cactus a little bit
of bantar is ok.
will put more info tomorrow as i work nights till jan 2012.
catch you all to morrow

hi all. where to start  first job is to get the moulds ready for glass  as they
need cleaning up and reinforcing on a flat serfice so the moulds are flat.
2) once i have made the fuzz sides the i will diesect the old fuzz to see what i
can improve on.
3) at the moment the fuzz with all the engine and rc gear no wings is about
 11 lbs witch i intend to reduce as much as Po's.
4) the engine i think is a os 91 but till i get it out i don't know
 it has 2 fans  1 on the engine fan no 2 driven by a shaft off no 1 .
my idea is to put 2 engines + fans in .
please let me know what you think.
regards planeking-robin

Concerning the two engines and two fans, you mean in series? i.e. one fan will blow onto the next fan behind it?

If so, you need to consider the fact that a commercial DF (regardless of make) assumes it operates at "model flying speeds" and if you then plan to have a second fan that will actually receive much faster moving air, then that second fan (if it is a standard commercial fan) will have its blades at the wrong angles and may prove rather inefficient at best, or also actually foul the flow and efficiency of the first fan, at worst.

Some 25 years ago there was a multi stage DF unit available in the States (I forget who manufactured it) for a very short while, advertising fantastic thrust in those days. I managed to get hold of one unit and with an OS 77VF got maybe 30% of the advertised thrust and certainly far less than the simple single stage fans.

I'd suggest lots of bench testing and thrust measurements with whatever engines/fans setup you plan, before committing a model and dedicated structure to that.

On RC Groups a while back one of the fan designers did some tests putting two identical fans in series and found that there was a minimal increase in thrust. over one fan.
Are you intending to go electric with the power plants?

hi erez & tsr
1st in answer to tsr ? at this time no to electric,
if i can reduce the weight quite a bit then i will think
about it, and as i have ic df units i will try them first.
2nd erez many thanks for your input.
why i said i was going to put 2 engines + fans  is
the Wye the ducting is layed out is , it separated
in to 2 , the front fan feeds the front 2 thrust nozzle's
and the back fan feeds the back 2 thrust nozzle's.
so the front fan will not impede the back fan if you know
what i mean.
i will try to take some pic's and post them at the weekend.
regards planeking-robin

That's quite interesting, does it all feed from a common intake or is the left side feeding one and the right the other. Just thinking there must be a lot of turbulence in the intake if it is working as a bypass arrangement, I suppose it would just need some very careful ducting design. It could be done as two intakes one inside the other so the cross sectional areas were constant.

why i said i was going to put 2 engines + fans  is
the Wye the ducting is layed out is , it separated
in to 2 , the front fan feeds the front 2 thrust nozzle's
and the back fan feeds the back 2 thrust nozzle's.
so the front fan will not impede the back fan if you know
what i mean.

Should make an engine out an interesting situation !

J

hi tsr , if you go to pic no 2 and enlarge it and look
the intakes on the fuzz you will see inner duct, that
feeds the front 2 thrust nozzels the outter part of the intake
passes over and under the first 2 thrust nozzels to saply
the back 2 thrust nozzels.
i wil post a better pic later.
regards planeking-robin

Hi Robin, I had looked at picture 2 and wasn't quite sure what I could see. How does deal with reaction control puffers out on the wings?

hi tsr, that i do not know at this time.
i do know from what i was told it did fly
ok .
the man that built it was a spitfire pilot
but died befor he got it spot on.
this harrier is over 20+ years old
thats as much as i know.
once i have got it to fly spot on then i will
have a go at trying to get it to hover ?
i have lot of idears on how to do that .
regards planeking-robin

I think you should have a look at this thread, it may help you. A guy called Pegasus has been working on the project for almost 15 years and has the best model out there so far

http://www.rcuniverse.com/forum/tm.asp?m=102347

Skymaster also have a harrier test bed. They did a bit of hovering a while ago and have the actual model made for forward flight, but i'm not sure if it's flown yet.

hi duncan,
many thanks for the info, i will take a good look
at that, once again many thaks  .
regards planeking

hi tsr, some  more pic's of the engine and ducting
and intakes .
regards planeking-robin

hi tsr , forgot to put the pic's on .
regards planeking-robin

hi all,some pic's of the moulds,
the front one i have cleaned up and removed the resin left behind
from the last time they where used, still a lot of work left to do.
the edges need tidying up and reinforcing then lay-ed on a flat
serfice then reinforced to stop any twist or bow then cut the nose off
then mould lips on the fuz half and the nose half.
when i have done all that i have to do the same to the other mould
planeking-robin

when i have done all that i have to do the same to the other mould
planeking-robin

I'm glad you know what you're doing with it.

My heart sank when you started this thread with "hi all i am new to this and not shore what to do" - I thought you were new to RC flying and had bought this to get you started!

hi yoyo ,thanks for your good  comment's most welcome.
i know it is a lot of work but so are all the the planes i build.
i have a real big plane all so on the go witch is a grumman duck
j2f-6 100" wing span ,look it up and tell me if you like the look
of the plane.
i like to build the large size planes now
regards planeking-robin

hi yoyo ,thanks for your good  comment's most welcome.
i know it is a lot of work but so are all the the planes i build.
i have a real big plane all so on the go witch is a grumman duck
j2f-6 100" wing span ,look it up and tell me if you like the look
of the plane.
i like to build the large size planes now
regards planeking-robin

Well, I only fly gliders, so (a) 100" isn't all that big and (b) the Grumman Duck is a complete non-starter!

I'll keep watching this thread anyway to see what it's like when it flies. Good luck! 

hi yoyo ,ok each to there own 
planeking-robin

hi yoyo ,ok each to there own 
planeking-robin

Don't get me wrong, it's an ambitious project. There's a hell of a lot more plane in a 100" Duck than a 100" F3F flying pencil.





I just don't like the noise of powered planes... 

 hi yoyo, point taken i have flown gliders and when i have flown them
i did enjoy them.
but i have reach the time i my life i need bigger challenges if you know what i mean
robin

hi yoyo, point taken i have flown gliders and when i have flown them
i did enjoy them.
but i have reach the time i my life i need bigger challenges if you know what i mean
robin

Fine by me, my thumbs are still providing me plenty of challenge!

hi yoyo, thank for the chat i have enjoyed it
very nice, keep it coming
regards planeking- robin

I will back up what Erez said about testing the thrust system before committing to any other work.  Ducted fans are extremely fickle about their intake and exhaust ducting and small errors can cause serious reductions in thrust.  The jet engines don't have that problem on the intake ducting, they can be plonked inside an empty fuselage and still work beautifully as long as the exhaust pipe is ok, but d/fs are very picky about having intake ducting that is within fairly tight parameters.  The cross sectional areas, taper rates and changes in direction of flow are important to d/fs.  Since you are using convoluted intake and exhaust ducting, the possibility of getting thrust measured in ounces rather than in pounds is rather high!  If it was me, I would not do any work at all on the fuselage moulds etc at this stage, I would only work on making a thrust test rig and a complete intake to exhaust nozzle assembly to trial the effects of the ducting and any changes.  Start by measuring the thrust of the fan unit alone with no ducting, then run it in the full duct system and see what the drop in thrust is and start work to improve the thrust.  Have a hunt round the web or books or old magazine articles about ducted fan installations as they will have formulae for calculating max and min intake and exhaust cross sections, max rates of taper, whether divergent or convergent ducts are allowed etc, and design your ducting to those rules as they were found out by a lot of experimentation by other people and there is no need for you to a heck of a long time trying to work it all out from scratch again!
Once you have got the best thrust you can get from your twin d/f system, consider if you would be better off using a single d/f system - the better installation may mean thrust is more than half the twin system but without the weight and increased probability of flame out problems.

hi mpx, many thanks for your input and suggestions i value
them highly, a Friend gave the name of a book to get he has
a copy and sent some pages on v.t.o of the harrier models
and a link on where to get it, the book is d/f by david james
do you know of it? any info you can give me will be most
welcome, as i Ame to d/f.
i would love to get in to jet turbines but i know nothing about
them, as i have just paid the mortgage off Early no pair cash
at this time,need to put some Penney's back the bank

, the book is d/f by david james
do you know of it?

Sorry, no.

Back in 1988 I helped someone who was trying to make d/f Harrier hover, but he could not get nearly enough thrust.  That was using the best engine and fan of the time and a very very light airframe.  Even if he had managed the last ounce of thrust to hover, he would have had no pressure to apply to puffer jets to control it.  A number of people have tried d/f Harriers for 30 years now and I am not aware that anyone has achieved free hovering.  So it may be possible but it is clearly going to be jolly difficult and afaik, no-one has solved it yet.  Jet engines with their huge thrust are the best way forward but introduce a whole new set of problems about containing the heat.

A Harrier restricted to conventional flight and with no thrust vectoring will work well.  Then you have to ask why bother having thrust from both front and rear nozzles?  A two engine version as you propose may simply introduce a highly increased probability of catastrophic failure.  For example, the ducting is likely to reduce thrust of each engine considerably, such that failure of any one engine might mean that there is insufficient thrust from the other to keep flying, not too bad if it happens at height and you get an extended glide down to a controlled landing but if it happens just after take off at low height over that ploughed field next to the runway......   Yes a single engine failure at the same time would also be catastrophic but having two engines means the event is twice as likely to happen as with a single engine.  If on the other hand each fan alone is enough to allow at least a shallow climb after take off and get around a circuit to land, you have to ask why fit the hassle and weight of the second fan?  Just removing the second engine, fan and ducting weight would improve the thrust:weight ratio and change the shallow climb to a better climb.
Having a single fan as far forward as possible will allow for exhaust ducting to the rear nozzles at a much more shallow angle than the 90 degree of a scale installation and that should reduce the thrust losses.  You won't have the weight of the second engine, fan, fuel, and ducting, thus further improving the thrust:weight ratio and improving the general handling and lowering take off and landing speeds.
Thus, in my opinion, effort is better directed at maximising the installation of one engine and fan using only the rear nozzles and restricted to conventional flight, since two engines will double the likelihood of failure and the weight will not be helpful to other handling qualities.

hi mpx ,many thanks that helps me a lot.
from what you say it would be better with the one fan.
and the 2 rear thrust nozzle's i see the logic.
would you have any thrust coming out of tail of the fuz ?
i am not very good with word's and computter's so it
takes me longer to type out what i would like say,
as i Ame 58 it takes a bit longer for the brain box to
get started.
i have a os 91 with a dinamax fan unit so i can replace
the one that is in the plane,what do you think ?
planeking-robin

would you have any thrust coming out of tail of the fuz ?

You could not have all of it, as the diameter at the tail would not be enough.  You could split the exhaust 3 ways and take one of them all the way down the model and out of the tail boom.  On the one hand that is good because it is straight, and curves tend to consume thrust.  However it is a much longer tube than those to the rear nozzles, and drag along the tube consumes thrust so the thrust lost is related to the length.  Also it would be a small diameter tube since much of the flow is going to the rear nozzles, and since drag is related to circumference (drag only operates on the tube wall) and thrust is related to area of the circle, a smaller diameter tube increases the ratio of circumference to area and hence drag to thrust which is not a good idea.  Imagine a tube so narrow that a flow of only one molecule of air wide can pass down it, every molecule creates drag because every molecule is touching the tube wall, whereas in a wide tube only the molecules at the very edge touching the tube are creating drag and all the others are not.
You would have to determine by experiment whether a third tube all the way down the fuz would make any improvement or reduction in thrust.

hi mpx , as soon as i have a pair of sides made i will make a test bed
and try it , also i intend to make the side thrust able to rotate to adjust
in flight , may help to make it fly better what do you think ?
as for v.t.o , i know this is probable imposable but i did think the electrics
from a quad copter to keep it level ?
planeking-robin

There was a guy named Mike Koskela who spent many years trying to get a DF Harrier to work, I think he built about 12 different prototypes in total; he had some success but had problems with minimal thrust, overheating & blown engines etc, not sure what happened to him?
Can only find limited info on the web:


http://www.edmfc.org.uk/gtba1.htm

Paul.

as for v.t.o , i know this is probable imposable but i did think the electrics
from a quad copter to keep it level ?

I don't know much about ic engines, ducted fans and stuff but I do know electronic systems.

I think you'd need something very special to manage a hover - a quad copter setup would handle the balancing ok, but you'd need at least four jets to balance it on which can be adjusted very quickly and precisely both up and down.

I guess it could be done with baffles if you have more than enough power available, but the ducted fans themselves wouldn't be able to spin up and down anywhere near fast enough.

Also, even with the latest high power motors quad copters are built very light and can't carry a huge payload. Your big engine(s), fuel tanks etc make it pretty unlikely, much as I'd like to see one do even a VSTOL takeoff!

If it was me id concentrate on making it fly well normally rather than compromise to try and make it hover.

Of course now you have the moulds you could always try and make a superlight one that could *only* hover...?

Of course now you have the moulds you could always try and make a superlight one that could *only* hover...?

Harriercopter