Home build: Pro-Jet-X. Delta wing like projeti / gonzales with 16kg turbine

Sorry for English, i cannot write German.... I understand it (kinda) so feel free to respond in German

When i started flying (many years back ) i bought a Robbe projeti after a few years. I really love the plane and stil have it (a bit damaged but still in 1 piece). Since i started flying turbine jets i have always dreamed of having a big projeti with a turbine engine. A few years back i found the gonzales project and found what i was looking for.... almost. I would really love a gfk fuselage and a jet for larger engines. Last year in Model city (http://www.modelcity.info/) i met a member of the gonzales team and i was hooked. When i got home i started my project the next day (June 2015) and now it looks like a plane Still needs a lot of work....

I started with DevFuse to draw the fuselage. I used side and top views from the original projeti.


After cutting the foam layers of the fuselage and wing cores it looked like this:




The gonzales team had issues with the CG because of the short fuselage and the swept-back wings. I am creating a longer fuselage by moving the wings back. The first position was a bit weird end i ended up with a position that looked nice.


The fuselage looks nice and slim but is a lot wider then the projeti. It needs to be 170mm wide to accommodate a large engine. I want a simple P80 to fit but also a larger engine up to 18kg First gfk part was also created




Wings are made from a styrofoam core with 110g glass fiber cloth and 1.5mm balsa. This makes a very strong wing. A bit heavy but remember the 18kg turbine? It needs to be strong It is only a 2m wingspan.... I had a alu tube lying around from a acrobatic plane and used that with newly created gfk tubes. I used the tube as a drill also.


The fuselage is about 120cm long and weights 950g from the mold. A bit heavy but also very strong.








All put together it looks awesome

Hi!

Ich bin die Gonzales ziemlich lange geflogen mit P60 SE.
Bei 1,7m Spw mit P60SE (offen) ist das Schub/Gewichtsverhältnis besser 1:1.
Beim Landen machte sich der Restschub immer etwas störend bemerkbar, vor allem weil unser Platz zu einer Seite leicht abfällt.
Hier hätte ich mir oft etwas wirksameres als die Seitenruderbremsen gewünscht. (Speedbrake?)
Bei 2m Spannweite mit P80 dürfte das gut gehen, bei 160er denke ich wird es ungemütlicher für die Landungen.
Wahrscheinlich musst du die Turbine abstellen.

Übernimmst du die Bugradmechanik vom Gonzales? Die funktioniert tadellos.
Mein Vater hatte an der Gonzales am Hauptfahrwerk eine GFK Verkleidung, das hat sich aber nicht so gut bewährt.
Besser ist es das aus Holz zu fertigen weil es in sich stabiler ist und die Kräfte auf einer größeren Fläche eingeleitet werden.

Ansonsten - tolles Projekt, werde ich weiter verfolgen!

Thanks Martin.

I am building rudders in the fins for speedbrake effect and also for a bit of rudder effect. I had this on another heavy, small and fast jet and worked really well. This turbine does not have that much idle thrust so it should be ok. Shutdown before landing is always an option. I made the wings a bit thicker to have a bit more drag also. The tips are at a 2 degree downward angle to prevent tip stalling.

Nose wheel will be a normal retract with a short leg (i have more then enough room . Main wheels are in the designing stage and will be placed in a 2.5mm plywood box with carbon fiber reinforcement. Carbon fiber will be placed in a U shape in the box to hold the axle. They bolt to the wing with the same bolts as the fins for easy transport. The wing will be reinforced with some plywood to spread the load of the gear. No springs in the main wheels..... should be good with the low landing speed and wing loading.

Estimated dry weight is 8.5kg now. Wing area is about 68 dm2 so 125g/dm wing loading dry. Should glide very well

With a "normal" retract, you will get massive problems during landing, as for take of you need high alpha, means noseleg must be long. But if on landing you have high alpha too, then it will start jumping, so on landing you need very low or better negative alpha. Gonzales landed on the retracted front wheel, which protruded the fuse slightly, this gave negative alpha.

Nice Project. Make molds, I want one.

Toto

Thanks for the info Toto. I have thought exactly the same. I start my original projeti from grass and this works great if it gets enough speed and a slight bump. Only very little is needed. The main gear is a bit behind the cg so it can rotate but it will not be easy with a delta. The gonzales nose gear would be the best option but hard to make for me. The easiest option is to start with the normal gear and land without gear. On grass this would not be an issue and solves the no-brakes question I have another jet with the same weight and no brakes and it lands very slowly but still rolls the entire field....

Maybe a very small start angle is enough and will not cause an issue during the landing. If it jumps slightly on the nose wheel the power will be enough to push it in the air. 16kg turbine on 11.5kg start weight should do it I hope it can land very slowly with an high angle of attack.

I have molds but they are very bad

The wings can be put on the fuselage Time to check the CoG. I had first measured the MAC in stead of the CoG but forgot that and mistake the markings for CoG... that was a shock because without gear and batteries ect. it balances on the markings. CoG is 14cm in front so no problem I need about 1.5kg of weight in the front to balance correctly but not much will need to go in: Retract, full hoppertank, receiver en 3 batteries. Maybe some lead is needed.

As for the gear i go with a idea i had earlier and was suggested by friends also. 1 glider retract in the fuselage and winglets on the wing tips. I should start very easy so the single wheel (100mm) in the front shoudl be enough. The turbine will push the plane onto the wheel and it should lift quickly. A bit of steer is possible bu pushing a winglet on the ground with ailerons. This worked very good in the projeti Tarmac will be an issue but i will fly 99% grass. Carbon wingjets with a small rear wheel are an option for tarmac.

Dry weight estimate is now 10kg.... Still not much for 96 dm2 wing area

The wings are aligned and fit perfectly to the slope in the fuselage. I have glued 5mm plywood with glassfiber finish on the inside to spread the load of the bolt. Bolts are 5mm wing nut bolts from the hornbach


I have created a mount for the retract. I will add reinforcements to the bottom to support it when it will be glued in. I need te get the retract unit first..... Support cannot be higher because of the large 3.5L tank that slides out through the front.


In the rear a wheel would make a nice fit. This would make asphalt starts possible with carbon tips to the wings to keep it level. The wheel fits great in the rear and does not look weird. The ME163 has a skid in the rear the same way...

good to see someone doing a scratch build
hey, you`re not so far away from me .....

where do you fly your jets ???

Scratch building turbine jets is fun. I like to do thing my way and rarely use the way described in the manual. When i buy something second hand i change what i can to make it my own. This plane has always been a dream of me and the build goes very smoothly so far.... Only the molds were a lot of work and and always didn't make it.

I fly jets mostly at ACF (near Appingedam) but also in Stitswerd (15 min above Groningen). You are always welcome to visit and fly Our field has just been mowed and the first jet flights of this year have been made last weekend and this weekend.

I made some winglets. These keep the wings off the ground during start and landing. Not pretty and i will make others later....


I installed the fuel system and tested the engine. Runs great after rebuild and i can use the fusulage as a powerful leafblower


I finished the wings with servo rods and fin mounting. Tubes for servo wires are also installed but the servo extensions are put in after covering. It balances very nicely around the CoG with minimal lead. I did some measurements:

Wings with fins, servos and pushrods: 1440g, together 2880g
Fuselage with engine, tank system, receiver, batteries ect: 4450g
Wingtube: 300g

To be installed:
Retract: +/- 300g
Fuel in hopper: 200g
Lead in the nose: +/- 100g
Some wires and bolts: 100g

Total now 8330g Not to bad. I have to add 2 square meter of oracover and primer / paint. Very nice weight Engine is limited to 116k which is about 10kg. Should be nice for the maiden....

Wings have been sanded and are ready to be covered. These need to be protected now so i have made some covers for them. Normally i melt silver plated bubblewrap together but this time i wanted to make them stronger / nicer. I sewed them together with a black edge and they are quite strong now. Looks nice also


TODO:
- Cover wings (waits for prowing / oracover 2e choice )
- Put in the retract (waits for retract....)
- Put in the tail wheel
- Solder extensions in the wings (waits for covered wings)
- Mount servos and make final adjustments (waits for covered wings)
- Place satellite receivers in the fuselage

Not much to do for now......

The tailwheel is mounted. It just fits but that is enough.




I created a heatshield to protect the foam wheel. It is a sheet of 0.8mm plywood with ALU tape.

Main wheel has arrived. First impression is fine. Feels strong and the weight is good.


Fits great in the frame


I like the angle on the ground. The tip rests on the floor now but when the plane is level it is about 5-6cm above the ground.


But all went bad..... The retract touched the fuselage when testing and i heared gears grinding. I opened up the gearbox to check....


The gears aren't aligned correctly. I corrected this and was happy for a while until the second issue appeared. I tested the gear through a servo tester. That worked great. Then i tested the gear in the plane with the receiver. Still it worked great. Then i plugged in a servo...... When the servo moved the gear went crazy and started moving...... beyond the endpoints. The gears were destroyed. The endpoint are electronically limited but the electronics isn't that good. After more testing i found out that a bec filters the noise and there gear works reliable..... except it does not move anymore Luckily i have a second gear that doen's have that problem with interference but it gets a bec also. 5V is enough for the gear and i want to run the servo's on 2s lipo so a bec is a good idea anyway. I noticed HK sells gearboxes also that look identical. Must be the same No i have to find out what the gearing is......

The gear is tested by a professional wheel spinner

Hello Tadango,

I had also retracts from HK for my EF (12kg). My retract looked nearly the same like yours. I got the first retract set and one of the three retractas didn´t work at all. So I made a return and got a new one.
This worked at first. I tested ist tree times in my Garage. The result: one was broken and didn´t say anything any more. (I am happy that it was just a test whithout flying my EF)
I have heard of several problems with this retract and no one managed to get it working savely.
So I got my money back from HK in Bonuspoints...
I ordered an SLR Retract from Lindinger.at That works great and is not too expensive.

Sorry for my english but i hope it will help you.

Best regards Roland

Thanks Roland. The SLS looks the same same as Electron and they are great. If the plane flies (and lands ) i will surely upgrade. I have not found a short leg that will fit so we have to make it ourselfs. I want everything cheap now because it might not fly....

The gear housing itself looks great and strong. The pivot point even has ball bearings.

It was the same idea i had too, to make it cheaper. So my EF ist a self construction in wood. But if the cheap retract has a problem, it may cause a serios accident.



Gruß Roland

The difference is that you have 3 and they need to work the same while i have 1 and land without it Since it is not a critical element it will be cheap until the plane has proven itself. It would be a waist of money to put premium parts in a big flaming ball of fire All parts are used or cheap. Engine has been modified and has a damaged turbine wheel, tanks are reused from a crashed plane, servos are used to (except the rudder servos). Receiver is worth the most to me

It works More details later but it flies perfect. Quite fast which made the landing a bit fast (had the motor in idle for a while ) Power is awesome and it tracks really nice. At lower speeds it is less stable but why fly slow . About 9kg now. The plane is dismantled now for cleaning (muddy field, now in the fuselage...) and painting. Can't wait till it has the final coloring

congratulations!!!!

Thanks