Hi there !

After experiencing the thrills of duted fan aircraft, I'm willing to enter the turbine powered jets lobby...

The hurdle i'm facing right now is : which turbine to choose ?

Indeed, there's a quite large number of manufacturers out there, offering complete turbine kits, but at rather diferent prices.

For example, a basic JetCat is around 3000 $, while a Wren 54 set is around 1500 $.

My questions are :

1) What are the technical diferences between all these available turbines ? They seem quite similar to me ... Is it related to the material quality involved in their biulding or someting else ? Are some of them more reliable than others ? Will some of them last longer, for example the quality of the bearings ?
2) I know 'In factory' Servicing is needed rather often for these engines ; how often ? Is it the same thing for all available turbines ?
3) As a beginner on a reasonnable budget basis (3500 $ max), which engine should I buy first ? Is there any turbine set which is more user friendly than others ?
4) I've searched some information by myself, and it seems to me JetCat should be the beginner's choice, as I'm currently living in France. I do not think servicing is available for any turbine brand in France ... French dealers generally sell Jetcat, AMT, and SimJet. I think sending a turbine for US servicing may be expensive on the long term.
5) Flying a 'Roo' as a first Turbine jet does not interest me (I would prefer flying scale birds). Do you think starting with a Rafale of a F15 may be the right choice for me ?
6) Servo question : i use Graupner / Jr servos : which class should I use for full moving tailerons ? Are digital servos really worth it ? I think analog ones should fit .. Am I wrong ? What about u ?
7) Is it really that easy to home build a turbine, like a Wren, or do we need some turbine related kind of experience ?


Regards.

Hi, I'll try to limit my answers to that which I know

1) As far as I'm concerned (user wise) there is very little technical difference between the turbines available today. They are all marvelous pieces of machinery. This one may have better acceleration while the other might be easier to use. I think that basically they are all very reliable, safe and user friendly.

2) I don't think that they require servicing "often". I've heard that some require servicing after more than 100 hours (and that's a lot).

Barring crash damage the only thing that wears out is the bearings. When I inquired about my Wren someone told me that I should replace the bearings when they sound like a "bag of rusty nails" (his quote).

Servicing is the place that Wren really shines because it's you that does the servicing.

3) I think the choice is purely personal. It all depends on how much money and time you have. I don't know enough to tell you which turbine is more user friendly.

4) Can't help you there

5) Having had my share of wet starts I would really discourage you from using an enclosed engine configuration for your first jet. You WILL have wet starts. On a Roo this would mean some neat flames and a missed heart beat, on a Rafale this would mean a new fuselage.

6) I'm using Digitals on control surfaces. When the airplane costs more than $4000 and flies at speeds above 200mph I really would like to think that my control linkage is as good as it can be. It's not that you can't use analogs, but is the extra $100-$200 really worth it?

7) If you're asking about the kit than the answer is yes, it is that simple. They have done all the difficult steps for you. All yo have to do is bolt the thing together, just like an ARF.

You do not need prior experience (except using a screwdriver of course). Better than that, building the engine by yourself will help you learn a lot about it.

Having said that I must admit to being very fond of the MW54 having built one myself (not from a kit). I guess I might be somewhat impartial but you can search for the opinions of others on this forum. It really is a good engine.

Hope this helps

Great questions, Strykaas.

I am limited in what I can answer here, but I sent you a PM (private message) that attempts to explain some of the technical and customer issues associated with picking a turbine. I hope it helps.

Good luck with your decision!

Hei Strykaas, forstår du dette?
Navnet ditt MÅ være norsk. eh?

Otherwise, go for the Wren. The best for the money!
Jonn

A couple more points you may want to consider...

The pricing may well be different in France than here, but over here I believe that the $1500 wren is the manual start one, not the one with the built-in electric starter which ups the price to something like $2000. Not that there's necessarily anything wrong with the manual start - I'm just suggesting that if you compare apples to oranges, you should at least be aware of the differences

Since you have a limited budget, one thing you may want to consider is the availability of a suitable range of kits for a given turbine size. Hopefuly you will be able to reuse whichever turbine you buy in a multitude of models, and so you may want to ensure that your choice of turbine size does not adversely limit your choice of models to put it in.

Good luck no matter what you buy,

Gordon

Strykaas I thing I can halp you with the kit
What about Aero L39 This is a trainer in real world and in small is user friendly too, its scale
Wren used it as a test bed for their MW44 - ready to fire for £1,450
For L39 look here and good luck
http://www.savex.cz/Savex_en/index_en.html
Oour products - Jet Airplanes - L 39 Albatros

Hi,
have a look @ www.modellturbine.de ....look at the prices!In germnay, many modellers are more than satisfied with these turbines.
I owned my second this year.
jair

Hi,

I'm comparing oranges and apples on purpose : why ?

All simply because my question is today :

Which turbine should I buy , If my criteria are :
- as cheap as possible
- good overall preformance (not the best needed).
- good reliability
- service parts visibility (viable brand ?)
- I do not care about electric starters (is this an error ?).

As far as I Know, JetCats are not (correct me if I'm wrong) available without electric starter, which is not the case for Wrens.
By the way, if no electric starter is provided, what do you need to start your engine ? Even if it's as expensive as the "included starter" option, it 's a better investment, because "on ground " equipment does not suffer from crashes !

Therefore comparing oranges and apples seems relevant ...

Thanks for your reply, though.

Regards.

Strykaas,

On the electric start, one nice thing is you don't have to have equipment to help cool the turbine, the electric motor will spin up the turbine to help cool it. Those with manual start, you'll have to have a blower or hook it back up to the air tank.

I have not got into turbines yet, just from what I've seen. If it was me, I'd go for an engine with electric start. Just less equipment to drag around.

Michael

Just a few words of advice in my humble opinion. Ive been in this hobby for a while and the one thing Ive always said is YOU GET WHAT YOU PAY FOR!!!!! Ive dealt with a lot of garbage in this hobby. Ive tried to cut corners several times to save money and have always gotten burned. Spend a little more money if you can up front and get better equipment if you can and it will pay off in the long run. I have used only a select few kit manufactuers for years and only certain engines which have been a little more expensive than the rest up front, but they have lasted me for years no hassle no problems. Think twice before going real cheap, you might have to buy your kit and engine twice if you do. Just some words of advice from someone who has made plenty of mistakes.

Pete

This one is rather heart frightening ! ! !

So you advise me not to buy a Wren then ?

If anyone recommends NOT buying a Wren, I would seriously question their motive and affiliation.

I have heard NOTHING bad about Wren and believe you will get plenty of responses from Wren users around the world, or at least, Europe,Canada & US.
JA

Imagine my budget is unlimited (no kids yet),

What is the best overall turbine out there :
- time response
- reliability
- ease of use

There are quite a lot of brands out there. May I consider the following ones as the major and more serious ones ?
JetCat, AMT, SimJet (Do I forget any ?)

These are quite similar in terms of overall performance.

Then, If my criteria is ease of use, I mean, I only want to make it start with one single button press, and never have to come to grips with any trouble, which one should I choose (unlimited budget) ?

Thanks

I am certainly not telling not to buy anything. My only point was do some research on everything before you do and sometimes spending a little more money for a quality product has always worked for me. I stick with what works for me and Ive been successful with the things I feel are best for me. Some people on this forum might say that what im doing isnt the best way but for me it works. Every turbine you have mentioned are quality turbines. Ive seen them all run and run well. But when it comes to a turbine I think you will find them all being very reliable engines. Fortunately there are a lot of good engines on the market. But what I was trying to say, my point again, Dont cut corners or else you will be sorry. Example.....When I build new everything in the aircraft is new. I dont have to worry about a servo or a pushrod or batteries that Ive pulled out of some other beater or maybe even a wreck that gives me firts flight gitters. When a model of mine goes into the air for the first time, there is no question of the integrity of the equipment. thats what has made me successful in the hobby as far as I can tell. But again Im sure the way I do things someone else might think isnt the best way. this is just my humble opinion take it for what its worth.

Pete

The nice thing about the Wren is you can make it as cost effective or expensive as you wish.
If you want air start and no ECU just a fuel speed controller the option is there.
If you want a maual start with ECU, ie turn on the gas and starter motor yourself the option is there.
If you want a fully auto start with all the bells and whistles the option is there.
I have gone from a hand starter wand to a Fadec ECU and mounted starter with a bendix and this is fine for me I have complete control over the engine during start up, but no expensive gas and fuel valves and there is nothing more satisfiying than building it yourself.
just my 2 dhs worth!!!

Lee

but it seems to me the issue of thrust level is completely ignored in this thread (other that what Gordon so diplomatically posted)

There is quite a difference between an 11-12 pound thrust motor and a 19 pound thrust motor. I think a new buyer needs to think quite a bit about the thrust they need before they can make any decision

I can't help but jump in.

I think all turbines today are reliable. Internal parts like bearing and turbine wheel are made from the same material and CNC machines. Thats why the cheapest and the most expensive engine still runs at high RPM with out coming apart.

Engines become more expensive when you introduce the autostart feature. there is no internal part needed to turn a air start engine into autostart. all air start engine can be fitted with auto start ECU when you are ready. So thats the differance in price its not much. So for cheaper and up gradable turbines (I personally preferred) for 12+ thrust engine buy Wren and 21+ buy artestjet engines.

IF you can afford 3K+ price engine like jetcat or amt engines go ahead is for you but remember the cost of servicing these engine is also high.

For airframe the Kangroo is not the best looking jet but it helps alot in learning or the aermachi mb339 never flys either one but watching newly turbine pilots having success in there first flight.

So - what is the cost per hour's run time, of bearing replacement in a Jetcat P120, and what is it in a comparably sized Artesjet ?

That's not a rhetorical question BTW - I actually don't know what Jetcat's service prices are since I have not yet had to have any done on either of my engines. Guess I should ask.

You bring up a good point though. It would be nice to have an accurate indication of the total cost of ownership of each engine brand and size. e.g. a table that shows the frequency and cost of predictable service items (such as bearings) for each engine, as well as the cost of other common work - post crash inspection & cleaning, replacing a thermocouple, ECU, starter motor etc.

Of course, for items like periodic service, the service intervals differ, so the cost should not only be worked out as cost per unit run time, but should also include average shipping charges - that way if brand A costs $100 to replace bearings after on average 10 hours, and brand B costs $200 to replace bearings after on average 20 hours, brand B is actually cheaper because there is only one set of shipping & insurance charges vs A's two.

I do know that my P120 is working out cheaper than my RAM 500 so far - the RAM cost me about $400 after only 58 flights, when the starter motor died. Before I switched brands I asked Bob Wilcox what the price for a new starter motor on a 120 was, and I believe he said it was $52 - quite a bit of difference !! Still, there are probably other items that are more expensive, so a "total cost of ownership" comparisson would be really cool to see. I'm too lazy to do the research, but maybe someone else is willing (as well as unbiased)...

Gordon

I am also trying to decide what my first turbine project will be and have learned a lot from this thread.... Thanks.
Question: If the turbine is exposed on top (like on the Kangaroo), does it still have to be cooled (by a start motor or a portable blower) at the end of the flight ? ?
Thanks. Bob

A friend of mine damage is starter assemble on his p120 after a minor crash . The only damage was the starting cover. It cost him
$800.00 for the repairs. Rebalance compressor and some more stuff. I think there hourly rate is 75$.

The problem i have with jetcat or amt is any problem with there engine they will not sell you any internal parts. So you are committed to what ever there cost are for repairs.

With the wren are the artesjet engine you can send your engine for repairs are you can buy all 'are any internal parts balance or no balance turbine or compressor wheel bearing and so on.

So for cheaper guys like me doing my own repairs fully overhaul
my engine two years ago fly every other day and still going strong no problem

BTW the ram starting motor and jetcat starting motor are the same (SPEED300) Motors. Some of these motor burn out quicly while some work for years.

I don't think its critical to cool down a top mount engine than a enclose engine. When the engine stop in a enclose airframe the heat rise and the model get very hot and cause paint damage but weather enclose or not its still a good practice to cool it down after your flight.

one thing that was not mentioned is that the $1595 Wren comes with a hand starter and if I am not mistaken an air system is not a required accessory with the wren. Also for about a $100 more you can have a semi auto start system where the starter motor is mounted to the turbine, but the battery for it is only connected whenever the engine is started, thus saving on board weight and $.

I've been doing a lot of research lately myself, and from what I can tell if you are looking at a 12lb turbine wren appears to be the best and no one on RCU has anything bad to say about it. Also the Artes Jets Bee looks to be pretty promising 1.4 lbs + accessories, and 4 oz per minute at full throttle seems to be really impressive also, it comes completely built with autostart for about $2200 US .

For me, sericing my own engine was a BIG part of getting a Wren 54 (and also building my own KJ66). Why pay someone $60 to $75 US per hour, to change a few bearings? You can dissassemble the engine, replace the bearings and reassemble in a few hours, and save yourself (a) a few hundred dollars and (b) having to pack up your engine and ship it somewhere.

It is definitely NOT for everyone, though, you better have at least a bit of mechanical ability. I know a few guys I dont think can tighten a prop nut the right way, to then I would say buy a preassembled engine.

But if you are interested in the internals and seriously think you can service it, go for it, you will save big $$ in the end.

For instance, if you consider how many guys burn out starter motors and have paid big bucks to get them serviced (not just parts but its the labour rate that gets you, just like fixing your car/truck) you can easily do it yourself and save $$.

Thats Just my way of looking at it.

AJC

Mugen, yes thats right. I have started my Wren 54 many times simply by using an air compressor blow gun pointed at the compressor wheel.

Then again, untill I built the electric starter for my KJ66, I had numerous starts on it the same way, using 90 PSI air directed at the compressor wheel.

AJC

Hello All:

I'm building my first turbine powered jet also, after pondering the same questions being asked here, Price VS power, reliabliy, and my own expereince( or lack of). I looked at a lot of Mfg's, and choose a Jetcat P-70(yes, I'm still waiting), What was the final factor? The guys that have turbines here local, have expereince with Jetcat's, and not wanting to reinvent the wheel, thats what I went with.
I know time will tell if I made a good choice or not, but after adding all the cost with getting a full auto Wren ,the cost gets close, and Jetcat has a good reputation.
Good luck!
Kevin