diabolic-mind

hey guys ive posted here a few other times and gotten great info. so i figured what the heck ill try my luck at getting some questions answered.

1- is there a pump that you guys use for the water cooling systems or how does it work?
2- is there a reason why the rudder is next to the prop rather than behind it? and what advantages does it have if any?
3-what is the purpose of the little metal fins on back outter sides of the boat?
4-are all electric boats direct drive, or do some have gearing and if so what is the best gear ratio to use?

i know these questions are probably insignificant to you guys but like i said im new to boats. thanks in advance for any info given

SV27dayton

No problem - these are nice specific questions that are easy to answer. If I am incomplete someone will finsh for me:

1- No pump is used. In FE, if the boat is not moving the motor is not making heat so using speed induced pressure to push water through the cooling system is ideal. This is done 1 of three ways: 1) pickup on bottom of the rudder (adds almost no drag but not always sufficient for systems that are on the edge and require lots of cooling) These are sometimes touchy as their effectivness varies with rudder position (turning) ex SV27 gets lots of water on straight and rt turns, almost none on left turns. 2)Transom mount pickup: usualy more cooling water/bigger inlet but at the cost of more drag. 3)prop wash pickup, (works only on surface drive boat) tube mounted in the roost coming off the prop above the surface of the water. These are really effective/zero drag but hard to get setup exactly and if they get bumped things get hot.

2- rudder location- Most V hull have the rudder to the right when looking at the transom. This optimizes the boat for right turns which is what happens in typical RC oval racing (CW). The rudder does alot of things with deep v's. It provides some lift that helps lay the boat over for the turn. I have an open class cattamaran and the rudder is behind the prop. Many rigger and hydros have an offset rudder and sometimes even the whole dive is off center. I don't know as much about these.

3- those are turn fins. They stablize the boat. My theory is that they help ensure that the boat track straight. This is not necessary on full size boats because the hulls rarely competely exit the water (if you are doing things right these are all the time). The turn fin will help the boat re-enter the water and track true. I added a second turn fin to my SV on the port side and it made it turn left more smoothly. It would hook in sharp, highspeed LH turns, this corrected this (at the cost of drag).

4- Many are direct- which is most reliable. (simple means less stuff to fail). gears fail, universals fail, flex shafts rarely fail. With the selection of props and motors available I see no need for gears. You can buy motors that will turn 10000 RPMs on 21 volts or 30000 on 14.4 volts and anything in between. I don't see a value in gearing. But I've never used it. My favorite gear ratio is 1:1. with gas and nitro it may be different but many of those are 1:1 as well.

NobodyFamous

3. with any boat, to turn you use a turn fin. This simply creates force on the hull pushing to the right or left. (the same deal with any kind of out drive) this force to the left or right needs to be countered in order for the boat to turn. Generally if your hull is wetted (in the water) enough friction is present to allow to boat to turn, rather then the back end just skidding out. But, when you get going rally fast, you begin to "fly" the boat and the only thing in the water is the prop and rudder. This will most defiantly not allow the boat to turn. By adding a turn fin, you provide a point for the hull to pivot on because it is still touching the water. It is important that there is a horizontal distance (rudder is farther back) between the rudder and fin. On a V hull they are often on the outer edge because as the boat turns, it lays down on the one flat side, so you loose the sharp V bottom and transition to a flat bottom. The fin will hold the hull in place because it will also now enter the water.

SV27dayton

I'm told that properly designed cats do not need turn fins. I suppose it's mostly due to the vertical sides of the tunnel behaving like a side of a turn fin. I remember when the brushless blackjack came out it had turn fins on it and a lot of people were concerned that it was a bad sign. Mine turns pretty good w/o fins. Not at top speed but I think that would be asking too much anyway.

diabolic-mind

WOW, that was awesome info guys, thanks!!! one more question, what is the transom? if anyone feels up to making up a list of the basic technical terms that would probably make it less confusing for me when you are refering to specific things, thanks again guys that was awesome info

SV27dayton

Nautical .
a. a flat termination to a stern, above the water line.

It's the back. flat part of the boat, usually reinforced to handle whatever is being twisted back there. Let's see
Tx (transmitter)
Rx (reciever)
Kv (thousand rpm/volt) motor rating
cavitate (what happens when a prop is dragging air under water and boat spins the prop with not result, somewhat equivelant to wheel spin, very preveant in surface drive boats)
wet (boat running with lots of hull sliding on the water)
dry (boat trimed back so that the hull is in the air) faster/less stable
trimed (the art of setting the boat up such that it does what you want it to do)
chinewalk (usually v hulls, in action where they rock back and fourth from side to side at higher speeds) sometimes people say prop walk but I thin that's different
Read Ryan's sticky at the top. It's excelent.

http://www.rcuniverse.com/forum/m_9069147/tm.htm

NobodyFamous

Prop walk is the force of the prop acting like a paddle wheel, walking the boat to the left (back end slides left) with clockwise rotation.

diabolic-mind

awesome guys, thank you. i would have never guessed some of those terms lol. good info to know though, it will be easier to descibe any issue i may come across