hi guys the past year has been busy and the coming one even more crucial and exciting. so my coaching centre has given us a break of 8 days before the next brain cruncher begins and it so happens that it coincides with my schools holidays.

well it was my mom who asked me why dont you go and fly in these holidays. you see she has always supported me and also while i was busy in studies she had kept my funjet and easyfly dust free all this time.

flying the planes is not going to be possible since i have to prep them up like the funjets servo's need replacing the gears seem to have stripped and the easyfly the motor and prop have to be tended to since i although upgraded the motor but never got the esc ready so no flying but i have some relief for that.

so i decided to accomplish two things in these 4 days  (rest i will be using for studies but will drop in here)

1. (Massive inspiration from VC bhaiya over here) the lcac just persuaded me to build one

2. this a project i had been aiming for a long time but will just do research and get all the help for now since this is a huge project

so now lets get going with the white pearl (i just love pirates of the Caribbean)

well i built it in 6 hours today and it worked. before going into the hibernation mode i had made a custom fighter jet style duct for one of my ducted fans (inspired by rcpowers) i decided that it had to be in this build and used this as the thrusters and used another 70mmfan for the lift power (its a monster  ).

i was studying fluid dynamics while making this up trying to calculate the gauge pressure needed for the perfect cushion did some calc. too but then i took the tried and tested method of making it before i thought how it wiuld work. the availability of the custom duct just sped things a gazillion times.

DESIGN

the base was just a long full depron sheet and that was it.




SKIRT

took apart 4 hypercity extralarge carry bags and hot glue and electric tape did the rest

i made 5 holes underneath it for venting see photograph





POWERPLANT

2*70mm ducted fans

one with custom ducting and the other one well i just made and circular hole and stuck it there with more hot glue












BATTERY

1*11.1v 2200mah 30c lipo for lifter (for test)
1*11.1v 2600mah 30c lipo for lifter final version\

1*11.1v 1500mah 30c lipo for thruster (test this caused a problem as you shall see in the video)
1*11.1v 2200mah 30c lipo for thruster final version




MANEUVERING  

i am working on the flexible turner mod on the custom duct (rcpowers inspiration here again)
more on this tomorrow

enjoy the video and pics (by the way i got a samsung wave 2 so the video and picture qualities are way better than my n72)

i really think that a cylindrical ducting would be better please suggest (VC bhaiya need your help)

well its a hovercraft and it works as one i think i should send it to you vc bhaiya for the detailing and beautification because i think it doesn't look as attractive as the white pearl should be dont you think











subbu

Pickle,

Well done Lad! I have been toying with the idea of using ducted fans, thanks for showing me the way.

White Pearl may look rudimentary, but she works. What I like best is that you have demonstrated to many, that building a basic Hovercraft is easy and that it can be done in 6 hours flat. Most people on the net seem to portray Hovercrafts (and submarines) as extra difficult subjects that need careful and meticulous planning and can be only achieved by Doctorates in Physics.

For better lift, seal all the large holes that you have cut for the air to escape and punch smaller holes all along the periphery of the skirt. This picture will help you understand what I mean.

All the best!

VC

Also, the problem is not with your lift, it is the Thrust. Try removing the outlet shroud from your Thruster Fan and see how she performs.............................

Sir, a cone like structure, with short length, will give more thrust or not? I mean reducing the dia of the EDF by half to a quater inch in dia through a cone like structure...

That is a good idea Anam. However, for an EDF fan, I guess it is better to leave it naked for an experimental model such as this. The Thruster duct is not required here. IMHO, but I could be wrong.

thanks vc bhaiya will get the smaller holes done and when i used these ducts ib my boeing747 i ubderstood that the ducted fans performed better without the ducting but i had it lying with me so gave it a shot things to do tomorrow

mount the edf without the custom ducting
and
redesign the skirt vent i think small circular holes will do the trick as i saw that in a mythbusters episode

Yes... But this could be used in a design where speed is required...  

hi guys vc bhaiya was right without the duct the pearl was like a monster on the run here goes my turning mechanism and the test observations

turning mechanism well probably the most worstly contructed one ever but i wanted to finish it off soon so i built it in a hurry and it worked perfectly on smiooth and polished marble floor but i think it was deteriorating the thrust of the motor so this one's going to be scrapped and a new one and a better one will be made








hover test

well first i tried it on my marble floor and it was superb there just awesome to control

then i went on to the tennis court with harsh concrete floor since it was still in construction and it did not even move an inch and also the inflation of skirt was uneven  i know that the size of the vents was way too large and has to be reduced

on the somewhat less polished marble at the ground floor it worked well until i my turning mechanism i believe started dampening the thrust

anyway looking forward towards suggestions i know that it was the skirt and i have to rebuild or mend the old one

video is being uploaded so kindly wait it will be done in just a while

subbu

Is everything being held down by hot glue?

I think a single rudder will work better. Rather than deflecting all the thruct for turning , deflect about 75% and 25% fwd thrust. This will make the turning smoother and not "sudden".

well other than the edf's and servos there is nothing that has been hotglued the control rudders i used mechanix tools set to get them there.

well too much hot glue is not my concern since my beast has enough power to hower about twice as big hovercraft (according to my gauge pressure calculations and the bleed of air from vents although the vents would have to be made smaller for dispersion)

the twin rudders was something i was not satisfied but when it worked on the marble i thought it might do the job on the harsher surfaces too.

the pearl glides smoothly and zooms by when i mocked it up without the turning mechanism and now that i have scrapped it it still zooms by.

i think you are right and i guess i will use my direct connect method to connect the single rudder directly to the futaba s3001 and try it out and

yes this rudder system was wasting too much of the thrust and i found that the vent air bleed was extrememly high if you notice in the video i (still uploading) you will see the hind part is a bit bowed down.

i guess the video will make stuff clearer

subbu

here is the video




subbu

Noticeable improvement!

Make the holes smaller and spread them out. Also I noticed that the rear left seemed to be dragging. Am I right? In that case a weight placed at the front right corner may help a bit in trimming it.

yes vc bhaiya
i guess the skirts redesign with smaller and more dispersed holes will do the trick

do you have any ideas for the turning mechanism

thanks for the help

subbu

You are using 2 small servos for the two rudders. Why don't you try using a single rudder? or else use two rudders with a linkage driven by a standard 40 gram servo.

well vc bhaiya i have used 2 standard futaba servos on the 2 rudders you can see it in one of the pictures

anyway i will go in for the single rudder system now

subbu

got some onboard footage as well here it is




subbu

Sir, I have seen many videos of RC hovercrafts... they drift a lot... Obviously they will due to less friction... So is there any mechanism or technique which can reduce this drift...

i guess that question was for vc bhaiya (since he is the only one worthy of sir in hovercrafts)

but anyways the drift can be minimized by selecting an appropriate skirt ones which make the craft subject to more friction hence it comes into play and the craft does not drift

well i have also noticed in my case that while you turn if you reduce you lift motor speed it does not overturn or drift and once the turn is done you can power up the lift motor again.

you can also use a gyro to sense your turn command and tell a servo to shift the position of some defined mass to counter the inertial drift

subbu

The question was for both, anyways. Then the gyro will have to be put in the YAW orientation to counteract the drift... Moreover the Gyro should be in standard mode, i guess...

yes the gyro must be positioned for yaw and standard mode only since head lock may put it into a constant drift too



subbu

We (MM/VC) have not used a Gyro in any of the models that we have built. Even in real life, Hovercrafts are notorious for drifting while taking turns on land. If two lifter motors are used, one can use contra rotating props to counter the torque and the resulting drift. The other option would be to use a variable direction thrust ducter. We wanted to do that for the LCAC but ran out of time.

i too thought of using the variable direction thrust ducter and it would have helped me in turning as well as drift control.

the counter rotating props on two lift motors i don't think it would be as effective

1. if on a y cable set up the torques that they create will get cancelled and the drift would continue.
by further analysis in this mode the positioning of the motor would also play a crucial part and can achieve unidirectional drift cancelling

it might work here

2 if we mix them onto the throttle and the aileron channel and put in a gyro on the aileron channel (gyro in yaw positioning and normal mode) we can cancel this drift by adjusting it such that when it turns the prop rotating in the direction opposite to drift speeds up. this will help too.

but i still dont think that variable direction thrusting can be beaten in any form but it needs time too if you can add it vent gates in here the gyro can direct airflow to counter drift here precisely

subbu

Hi Subbu,

I like the RC Hover craft you have built, I am very much interested in building similar one, Can you please share the electronics used on this RC Craft with Circuit diagram. As I am new to RC I am not sure what are the components to be used. I wanted to know how did you control the lift and propeling for the craft. Both motors are controlled seperately or only one line taken to control both the motors. Kinldy help me my kids are very curious to see this built one.