[Helijet]

And thank you for checking out the thread
Much appreciated.

Just an FYI - I have joined the RC Micro Turbines Group on Facebook which shares builds and info on turbines less than 50N ( thx for the invite Paul ). Some cool projects from around the world. This facet of turbine modeling is really taking off fast ( ha, ha, ) with lots of new offerings coming in 2020.

I will however, continue to post builds and info here on RC Canada for those not on FB

dw

[Helijet]

So...had a few questions about the sizes of EDF jets. Generally I have been working on converting 80 - 90 mm ( diameter of the fan unit ) aircraft which is the sweet spot for power / weight / landing gear configuration. Foam turbine conversions are generally heavier by 3/4 - 1.5 lbs on take off than their edf cousin but once the fuel burns off the aircraft is about the same weight or in fact lighter than an edf version. Flight times and overall increase in thrust values are game changers IF you can accept the cost of turbine admission. No way around it - they are expensive. While you may find a decent second hand P20 or KT 30 for around 1800 - 2000 CDN, expect to pay around $2400 CDN ( taxes and shipping in ) for a current engine. Depending on the manufacturer 25 - 50 hours will require a checkover and possible bearing change. On average a run lasts 10 minutes. You can do the math for the number of flights.
The smaller engines can run on kero or diesel ( oil mixed ) although when the temperature drops below 10 C they tend to run better on kero.

I'll try to list the items needed in the next build ( Freewing Avanti S 80mm ) along with costs for us here in Canada.

[Helijet]

Many jet enthusiasts consider the Sebart Avanti S airframe to be one of the best sport jets ever designed. With a bit of Italian flare, it not only looks good but has excellent flight characteristics. It can be very snappy - quite capable of 3D maneuvers to gentle and graceful FAI flight. Some may not like its pregnant goldfish looks ( right Jeremy ! ) but one cant argue its gentle handling by less experienced pilots. The Freewing Avanti S first came out in 2015 and has become the first line practice/throw around bird of many turbine modeler, in its EDF form.

Inexpensive ( $279 US for ARF plus ) the bird features metal geared servos, electric retracts, a robust trailing link gear, oversize wheels ( good for grass ) and a very visible color scheme / lighting package. Its a full house meaning - you will need a minimum 6 channel radio. I added JP Hobby brakes ( 55mm ) to my converted Avanti as this will be my frequent flyer at our local 600 ft paved club runway. The cost for the brake upgrade is around $90 US but this is not necessary at all if you fly off of grass. I contacted Amir at HAB models in Sweden earlier in the fall to discuss some design work for the Xicoy X45 turbine. After several emails containing measurements and pictures I was sent the complete conversion package. The cost was around $ 150 US which included a set of pretuned turbine rails ( basically drop in fit to where the EDF fan goes ), a single wall pipe with bellmouth, 800cc tank with felt pick up / hardware and an exhaust tube rear alignment ring. Expect the total cost ( less the electronic brakes ) to be around $600 CDN for the airframe. I am going to assume you can source your own lipo battery packs and receiver. The only thing left to add is some aluminum tape which can be sourced at a home hardware store such as Home Depot. I don't use anything special and high temp- automotive manifold tape is overkill. Ok...so lets get on with the build....

First step is to assemble the basic kit. Remove the landing gear and go over every set screw and bolt. Apply medium strength Loctite where needed. I cant emphasize this enough! It will pay huge dividends down the road. Next attach your receiver, power supply and hook up the linkages. Check to make sure everything works. A note - the flap servos on the Freewing Avanti must not be set with timed deployment. For some reason, these particular servos loose power after you deploy them, then try to bring them back up. This is a well known issue and you may want to replace them with a Hitec or like alternative if you want the flaps to go down with timed delay. I have kept the original flap servos and don't use timed delay ( no problem after 75 plus EDF flights ). You will need at least 2 batteries in your aircraft - one for the turbine and a second for the electronics. I'm using a 2200 mah Lipo with voltage regulator set at 5.4 volts for the servos/retracts.
The pipe install took about 15 minutes / aluminum foil application took about 1.5 hours as I wanted a neat clean look.

A word of caution...don't let your wife or significant other, see you do an outstanding job with tape in one hand and scissors in the other. I am now on Christmas wrapping duty for the family.....doah!!!!!

[Helijet]

I bit more work and the turbine is nicely nestled in its location with adequate cooling dimensions. General rule of thumb is to have a minimum of 3/8 " airgap all around the engine and the widest part of the bellmouth.

The placement of the turbine to the bellmouth is very important. Always follow ENGINE manufacturer's instructions - NOT that of the airframe manufacturer. Often supplied exhaust tubes are of a generic variety with questionable instructions. Improper placement can lead to a variety of problems from the turbine overheating, tail area getting hot, lack of thrust, high pitched whistling to worst case scenario...exhaust duct implosion.

Here you can see the placement of the turbine exhaust is predetermined by tabs on the CNC mounts as supplied by HAB / Sweden. Henke has done all the testing already to determine how far in the turbine exhaust nozzle needs to go with no thrust loss. On the other end, you can see how the tube is recessed slightly from the fuse. This facilitates pulling air around the outside of the tube to further assist in cooling. The inside aluminum foil lining of the fuse redirects heat away from the foam when the engine is running but more importantly, to prevent latent heat from effecting the foam structure.

The final pic shows the front end all buttoned up. 2- 2200 mah 7.4 volt packs / regulator, receiver, pump, turbine HUB. It needed 3.5 oz of lead in the nose cone to attain CG. I am using a weighted felt pick up in the 800 cc tank and going direct to the pump. No UAT or secondary tank in this build. Dry weight came out to 2500 grams. The EDF version weighs 2650 grams with a 6S 5000mah battery. So a bit heavier on take off with full fuel but about the same weight or less on landing.

[Helijet]

A word or two... on electric gear / brakes.

Around 2012 I started using electric gear in my big birds. Down and Locked in the US was a source for my Robart and CARF gear conversions. The CARF Tutor that I built in 2011 has never had a gear failure since converting over. Electric gear is now becoming the norm with Robart / Electron etc offering a variety of drop in fits.

Electric brakes have also been around a while. One of issues with electric brakes has been the tendency to be either on or off with little proportional control. Lately, companies such as Xicoy are offering very capable, electronic control units that offer ABS and nosewheel gyro controllability. This allows for virtually stress free take offs and landings no matter what the wind direction is. I have had very good success on my little aircraft with the JP Hobbies line of wheels and brakes. The sets are very well machined and the brakes are very effective. Actually...too effective. Many modelers are thinking the supplied control unit is the issue. It actually works as its supposed to. Here is a little secret....
It is the competing magnets in the HUB that have to be removed if you want any proportional type of control. The included pics sh portional braking control. If you or your flying buddies have had issues in the past with JP brakes - try this little modification. Its secret squirrel stuff that will make you the talk of the club...lol

OK...enough of that ….its time to maiden the Freewing 80 mm Avanti S!

[stegl]

Interesting to know about the magnets , Dean.
After doing some reading on electric brakes , have found that the controller is not much more than a small DC motor speed controller (ESC) that controls the amount of current to the electro-magnet braking coil. All that is needed is one that controls a few amps as the brakes really don’t take much and should be very proportional.

Have a question on the JP brakes ;is the black portion with the wiring made of plastic or anodized metal ? Thanks.

[Helijet]

The drum is metal....with what I assume would be the coil and magnets embedded in resin.
dw

[Helijet]

Maiden Day

KMAS field 1400 ft msl
Temp : 6C
Winds : light and variable

Engine set to 30N of thrust. Initiating start happens quickly ( <60 seconds ) and quick check of the fuse ensures no heating issues. Aircraft does not roll on pavement at idle. The X45 has amazingly low residual thrust compared to other brands. Full throttle test and she's ready to go. Settings per the manual with the exception of roll which many pilots have agreed is too rapid a rate.
( mine is at 15mm ).

With smooth application of power, the take of roll is straight with a brisk build up of speed ( no take off flap ). A slight tug on elevator and she lifts off with a very solid climb out. Bringing the throttle back to about 50%, it quickly becomes evident that 30N is too much. She accelerates quite quickly at more than 75% power. Keeping throttle at about 50 - 70%, rolls, loops, climbs are very controllable and predicable as the EDF version. CG appears correct. I think 25N would be plenty with this bird.
After 5:30 minutes of flight, I drop the flaps to full and fly around the pattern a couple of time in dirty configuration. She remains solid and controllable throughout the pattern. No gyro is needed on this airframe. Downwind - base - final with gentle throttle reduction to idle. Just beyond the threshold, a bit of a flare, hold and she settles in quite nicely. Taxi back, shut down and auto cool kicks in. I do aid the turbine with a portable leaf blower until my telemetry shows less than 100C ( 15 sec. ). After removing the canopy, about 8 oz of fuel remains. I think with the turbine set to 25N, a 7:30 - 8 minute flight of mixed throttle on 800cc is reasonable.

Overall, I am very pleased with this airframe / engine combination. It is simple in design, easy to work on, exhibits excellent flight behavior and IMO would be a very good first turbine sport jet.

See if you can spot something odd on the maiden take off. Had my hand slapped by some students on that one....oops

[Daren71]

Nice report Dean. I have the Avanti, and love it. 5:30 minutes of jet flying time is a very nice bonus. Gens Ace 5000's give me 3:30

Thanks again. Great post.

Daren

[Helijet]

Thank you Daren!

A teaser.....hmmmmm

https://youtu.be/4GGBBUuROPI

My X45 may have found another temporary home...