My recent flying trip to QLD. with 3 models ended up brilliant coming back with six. Just started on the first one I have intention to fly mainly off the beach sand, due to the fragility of its landing gear. Decided on few modification as with all my builds to make it last.

Yak 130? Such a great flying jet! You'll love it! Who is the manufacturer of this one? 70 or 90mm?


QUOTE=jofro;36076613]My recent flying trip to QLD. with 3 models ended up brilliant coming back with six. Just started on the first one I have intention to fly mainly off the beach sand, due to the fragility of its landing gear. Decided on few modification as with all my builds to make it last.[/QUOTE]

Mate, every jet is great when correctly set up. I got a wonderful fleet of them and each is somewhat different, making it always a challenge. This one is 90 mm version fitted with the stock 6S set up but it will take me bit of more testing to decide what power unit I fit in. After the static test I'm not sure if I stick with it or go for latest Stumax (pic), Jet Fan or few other combos on hand. I do few more tests in one of my 4 kilo foamy test bed prototype to make the final decision to upgrade to 8 or 10S.

Grey was never my favored colour, these days very fashionable especially painting external walls of new houses, reason being it is the cheapest to produce. Touch of colour to make it little livelier at least to my liking.

After checking the Air brake action there was so much slop I had to rip it out to look at it closer, it's a bit of a joke, more for an ornamental than practical serving purpose. Probably the last thing needed to fly this model anyway.
After elevator assembly epoxied to the fuselage I'm not quite happy with the design, I believe it could snap off very easily under the load while it is holding only on little bit of foam at the extreme rear part of the fuse. For the piece of mind I'm going to reinforce it with some ply wood fins well in- bedded to the foam.

Hi Jofro. Nice purchase mate. If I recall right, Ready2Fly state the air brake should not be used in flight and those who have find it causes a sudden loss of altitude.
I also find that the use of epoxy to fix a major component of an EPO model a little unsettling, the slightest knock will cause it to come apart as epoxy does not work with EPO. PU, CA and good old Gorilla are my weapons of choice. I use a few strategic drops of CA to hold everything tight whilst the PU (UHU POR) or Gorilla cures. But your an old hand here and know all this , I'm just chewing the fat.

The air brake is a good place to put some electrics and free up the lipo bay, especially if going 10S

Hi Jofro,

good idea with the trailing edge - nice!

I also customiced the hump and lowered the canopy on mine
Thake a look: https://www.rcgroups.com/forums/show...postcount=2931

Also a fin from the HK Cobra would look fast on the Yak

Have fun,
George

Hi Guys, TX for tips, regarding Epoxy/EPO, I know what you meant but after a thorough preparation it works fine, from my experience. (Lot of pointer holes on both surfaces, some sanding and clean up with disolvent)
GS, nice colouring, yes the rudder looks bit out of proportions, somewhat different, that is why I chosen this model. Back to more work on it, Cheers.

After another static test pull run using the stock 6S set up I'm not happy so I ripped it all out and fitted the latest "Stumax" rotor to the stock shroud, using the stock motor which looks identical to the HET, I was going to use, with only slightly smaller intake cooling motor holes. I also fitted sink head to the rear part of the motor to get the maximum air over it. Changed and reprogram new ESC to 8S. It will be interesting to see the static pull test difference, anything over 3 kilos I'll be happy with.

Well, I'm getting closer, just fitted the third power unit inside the model to check the static thrust in this rather inefficient ducting design. The stock shroud/motor with the new Stumax rotor was much better with 3+ kg thrust but there is slightly too much of a tip blade clearance creating some loses in power so genuine SM 90 mm unit was fitted to see what difference it makes. It required some surgery to accommodate this power unit with slightly bigger bell intake and longer shroud. More soldering to minimize the length of power leads and ready for hopefully the final test. This power unit gives me over 4 kilo of thrust on 8S so the truth will come how efficient is the twin outlet in this model.

Today I have learned about the inefficience of the duct in this model by running another power unit I have such a great success in different model. So back to more surgery with the sharp knife to improve the front intakes, scale by scale.

After bit of surgery to my air intakes I got a great news with considerable improvement to the performance. I did 12 separate static tests today with the use of two different 8S power units, running 3 different type of lipos and with the use of stock and new reduced thrust tubes from 55 to 51 mm. With the stock 55 mm outlets and the new air intakes my static thrust improved from 3kg to 3.45kg while using the stock shroud/motor and new lighter loaded 89mm SM rotor with rather large blade tip clearance which will improve after the new shroud will be avail next month. My next test will be going back to the original stock 6S, set up to see what difference I got after the new air intake mod.

New air intakes giving me one pound of extra static thrust. It should translate nicely in flight.

After all the 8S tests I pulled everything out and going back to the original stock 6S to check if there is any improvement after the intake mods. The only change is the new fitted 120 Amp, ESC being re-programmed back to 6S.

GOPR1246 (1 min 4 sec)

- check of the air brake and the landing gear.

Hi Jo,
interesting way to mod ...

I also reworked the duct. But only the innerside to get about 30% more air to the fan. Take a look: https://www.rcgroups.com/forums/show...postcount=2729

Maybe it could also work on your bird

Regards, George