Second trial today in much calmer conditions. With no forward or reverse thrust, the craft rotates clockwise quite rapidly almost on its own axis . How can I trim it to stop this happening? It makes control very difficult. I have added perspex extensions to the rudders which now work better but still cannot overcome the rotation problem. I dare not go out on open water until I can correct this. Help please!

I would start be double checking that the skirt is one a straight as possible and absolutely no creases that could be letting air leak out at the contact surface.
Craft rotation is something that a lot of folks seem to suffer with for craft that have separate horizontally mounted lift fans. The degree of rotation is dependent on the amount of torque created. You can reduce the torque of the prop by using a thinner and lower pitched prop (e.g. 3" pitch or less), and perhaps using a 6" rather than a cut down 8" as it will be aerodynamically better at the tips.

I have found that both fore/aft and side/side balance is critical to keep my hovercraft from spinning when it is "stationary"

Originally Posted by JeremyBB

Second trial today in much calmer conditions. With no forward or reverse thrust, the craft rotates clockwise quite rapidly almost on its own axis . How can I trim it to stop this happening? It makes control very difficult. I have added perspex extensions to the rudders which now work better but still cannot overcome the rotation problem. I dare not go out on open water until I can correct this. Help please!

Any chance of some pictures on the underside with skift fitted please.

Originally Posted by PITPUP

Any chance of some pictures on the underside with skift fitted please.

Pic as requested. Double sided tape round the perimeter of the platform re-inforced with duct tape.
Hope to see more pics from you and Chris as your builds progress.

Dear Forum, Iīve been looking this post about the SRN6 hovercraft and I have to say that itīs amazing.
Now I have a question for all of you that have built this model and of course have more experience than me.
Where to put the electronics...
How may this afect to the balance.. and other tips you may have to me..

Best Regards
Luciano
From Buenos aires, Argentina.

most peoepl at this scale seem to be making the cabin removeable as the the balance of electronics the reciver and escs wont make much difference its the Batts that effect the balance but you can use this to your advantange when on land you need to trim the model so its level when hovering when on water you need a slight nose up to aid getting over the hump

Ok, thanks a lot...Im posting photos of my project soon...

Best Regards,
Luciano

Originally Posted by JeremyBB

Second trial today in much calmer conditions. With no forward or reverse thrust, the craft rotates clockwise quite rapidly almost on its own axis . How can I trim it to stop this happening? It makes control very difficult. I have added perspex extensions to the rudders which now work better but still cannot overcome the rotation problem. I dare not go out on open water until I can correct this. Help please!

Suspect you may have a torque issue possibly? On the full size craft there are four puffer doors, two forward and two aft, that dump plenum air via door on the top skirt shell. Served two purposes, firstly to provide low speed thrust to control the craft, and to allow you to dump air on the inboard side on a high speed turn. Also I note that your skirt does not have a keel. The full sized craft had a keel bag running form roughly a third from the front to the twin rear bags, and there was also a single bag from port to starboard ahead of the keel bag. The keel bag did drag in the water.

Just a comment, and a nice model by the way

Mike.

Out on the open water for the first time. I have fitted a baffle in the air duct to try and counteract the turning motion when stationery. Seems to work at least to some extent. U-tube video:

SRN6190812 (1 min 25 sec)

Nice work, looking very good.
Mike

Nice work Jeremy, looking real good i must say. I am almost at the fitting out stage now and was wondering if you could remind me of your running set-up.

Lift motor, Thrust motor, ESCs battries used.

By the way, mine is 1/12th scale so im guessing yours may not fit my needs but it would be a good starting point im sure LOL.

Many Thanks.

Hi Pitpup

It's good to hear that your model is coming along. I look forward to seeing more pics of your build.

My lift and thrust motors were
http://www.hobbyking.com/hobbyking/s...dproduct=17588
The lift motor ESC was
http://www.hobbyking.com/hobbyking/s...hless_ESC.html
and the reversible thrust motor ESC was
http://www.hobbyking.com/hobbyking/s..._10_1_12_.html
The lift prop was an 8*4 two blade cut down to 6" and lift was achieved at about half throttle. The thrust prop was a Graupner 4 blade 6*3.
Batteries were Turnigy nano-tech 11.1V 2650 mah Lipos.
It all works pretty well although I could do with less noise and vibration on the thrust set-up. There are pics of the set-up earlier in the thread.

I guess you will have to scale up everything for a 1/12th scale model. A lot will depend on the weight.

Jeremy

Here are a few pics of my progress to date, advice, tip, hints welcome.

Hi Pitpup - It looks pretty good to me . From the size of the lift duct, you must be using an impeller as did the real things. Do you have an idea of the lift thrust you will get in relation to the weight of the craft? Are you building to a specification which someone else has already used or are you working from scratch?

A member of the Model Hovercraft Association in the UK is also building a 1/12th scale SRN6 and I think others have done before. I will let him know what you are doing and he may well have good advice to pass on.