Rudder torque?

[PondSkimmer]

Hi all!

Building my 1st 21 rigger and i was wondering how much torque is needed from the servo to turn the rudder of a 21? and what is a good brand of servo to use on the ruddder of a 21?

I have been reading this site for quite a while and getting tips and set ups and some GREAT IDEAS!

Thanks everyone

 

[Ron Zaker Jr]

You need around 70 oz of torque for your rudder,if the turn fin is sized properly.Hi-Tec has a nice selection of servos,and are priced fairly.

Ron Jr 8)

 

[PondSkimmer]

Thanks i put a C80 on my 67 rigger but i thought that would be overkill on a 21 and it a bit slow also.

Thanks for the info!

 

[TomMoorehouse]

ive been using the hitec mighty mini's on mine

http://www2.towerhobbies.com/cgi-bin/wti00...p?&I=LXN662&P=7

it is not 70 though..... it might be close at 6 volts

 

[PondSkimmer]

Do you ever have a problem grtting into turns with that servo? what is the length/depth of the rudder that it is turning? I am noty sure yet as to what size i will use on mine but i was thinking of a 4" rudder or is that over kill also for a 21?

 

[Ron Zaker Jr]

PS,

Keep in mind the rudder really only starts the turn,the fin carrys the load thru the turn.I would start at around 2 inches of rudder below the bottom of the rear sponson.Understand I don't know what you are building and what MPH you expect, but that's a good starting point.

Ron Jr

 

[_laxmasta2039]

PondSkimmer,

i know this is off subject but are you the guy who made the PondSkimmer plans for RCBM? [too much of a coincidence to resist asking : ]

Joe

 

[PondSkimmer]

I wish taht i was that guy! I wouldn'r be asking about this 21 (lol)

I am building a 21 that i think was made for electric use? there was no rear sponsons with the kit so i have to make them and explore what else i will have to do. I will post a pic of it some time soon if anyone has a clue as to what type of boat or any info at all that would be GREAT! As for speed i hope to get this boat into the 60's it is a fiberglass hull that has been reinforced with carbon fiber and it is realy light, only time will tell?

 

[PondSkimmer]

Figured that i would get the pix up now incase i didnt have the time tommorow?

If anyone has any ideas please let me know, i have no idea how to set this thing up ??? There are 3 pics but i cant figure out how to post them all in one reply?

 

[PondSkimmer]

pic #2

 

[PondSkimmer]

Pic #3

 

[EatMyShortsRacing]

Hey Pond...

Your front sponsons are upside down!!!

EMS racing

 

[EatMyShortsRacing]

By the way,

How much torque is required for a 90 or twin 90 rigger??

I just got a JR digital servo with metal geartrain (normal size) claiming 150 oz/in (think it is an 8411)

I amused to using 2 4001 or 4011 servos on my rudders. Have never used those big 1/4 scale things...

EMS Racing

 

[ClayGlover]

he's not kidding, hehe, they really are on upside down and backwards... it definitely won't work like that! :-

 

[Ian Inverarity]

Craig,

I have an JR DS8411 in the Hummingbird 90 and the Kingcraft 90, they work great! I dont know if they would be enough for a twin. I bought a metal gear Multiplex digital jumbo servo, the higher speed version, but it is very big and heavy and not really that quick even on 6V.

Eric A has one of those new Hi-Tec digital jumbos in his twin and says it is very good. They are much cheaper than Multiplex too... 8)

I won't use anything but digital now....

Ian.

 

[Don Templeton]

Hello Pond,

Please don't take this personally but that has got to be the funiest picture I have ever seen! Not that I haven't done things like that before, but when I opened up that first picture I completly lost it. Right now I still have tears streaming down my face and can hardly see. The boat looks good but those upside down sponsons crack me up!

Thank's for the picture and the laugh Pond. I've just got to frame that one.

Good luck with the boat,

Don

 

[PondSkimmer]

Glad to see that i could bring some amusement to the crowd. :-[

Now that everyone has had a good laugh does anyone know what boat this is? Like i said i am going from no plans so i am kinda lost i had no idea that the sponsons on a 21 would go past the tub that far so i figured that they had to go the other way

And to Eatmyshorts i am not sure about a twin 90! that has got to be a site to see? i live in NY and the biggest twin that i have seen was a twin 67. I have no idea what is required for a twin 90? I am running a ciruss CS 80 as i mentioned earlyer in my 67 and it works great plenty of power 130in/oz dont know if that is enough for your twin though?

 

[EatMyShortsRacing]

Pond,

Well there are a few twin 90s here down under.. hope to bring one to the IMPBA Nats if I can have it sorted in time. (hurry up and finish mine Magilla.. oops... Dale !!!)

They are not much quicker than single 90s but the accelleration and cornering speed are what sets them apart.

And the sound!!!! hehehehe

EMS Racing

 

[Ian Inverarity]

Hey Craig,

My single 90 was clocked at 124k in the corner on the weekend! ;D Bring on the twins!

Ian.

 

[EatMyShortsRacing]

Ian,

I am going the same way... I have always used JR Gold servos (4xxx series) on just about everything except mixture controls.. Just the twin is going to need serious grunt and geartrain strength to pull it around.

EMS Racing