superflyboy1988

im looking for a tack i can use in my boats

thanks a lot

Ron Olson

My Feedback: (1)

Do you mean a tachometer?
The next question is what's it going into. Nitro? Electric? Gas? Steam? Sail?

boatnut

Ron,  What would you need a tack in a sailboat for?



Having this much fun must be illegal

Ron Olson

My Feedback: (1)

The last one was a joke? See the smilie? Sailboats do tack with the wind though.
There are various tach's for whatever powerplant that you're using. Some use a magnet pickup mounted on the flywheel and gas engines use a wire that's an inductive pickup that's wrapped around the plug wire.

superflyboy1988

sorry for that yes i mean a tachometer and it is for my nitro boats

advanced builder

We use
www.radarguns.com
$80 get you a gun Busnell

superflyboy1988

im looking for a tack so i know what the rpm my motor is runnning at

boatnut

Ron, sorry about the oversight.
How do you check RPMs on a boat motor {nitro}?
I need to do this to help pick out the correct prop.
I know you can GPS, for speed , is this the only way to get
correct , prop/ RPM?


            Having this much fun must be illegal

siberianhusky

RPM isn't very important in choosing a prop, as posted earlier either a radar gun or gps will give you what you want to know, which is speed. You might find a prop that turns whatever rpm you may be after but it doesn't work on the boat.
My last boat I set up was far faster on a 40 mm 3 blade prop even though it is turning fewer rpms. The added lift allows the hull to run a little looser, less drag = more speed even though I am turning fewer rpms.
Either the boat goes faster or slower with a new prop about it!

superflyboy1988

ok but i dont need one for a prop im using it to set up a 2 motor boat i want both motor at the same rpms

Ron Olson

My Feedback: (1)

Somebody makes a tach for nitro burners that uses a magnetic pickup that sticks on the flywheel. I'm bangin' my head trying to remember who makes it.

siberianhusky

http://handtach.com/

expensive though.

http://cgi.ebay.com/ebaymotors/HQRP-...ht_3674wt_1196

cheap. Quality?

http://cgi.ebay.com/GT-professional-...item3cb12a1086

From a rc shop there
didn't realize you wanted to synch a couple of motors, that changes everything
LOL heathkit made a handheld tach kit for years!
Seem to be a number of possible candidates.
Cheers

superflyboy1988

I like this one


http://cgi.ebay.com/GT-professional-...item3cb12a1086

but do you know if it is any good

siberianhusky

Nope! Just kinda knew what to search for, those were the first 3 that turned up, I know nothing about any of them, thought they might at least give you an idea.

Hydro Junkie

I'm surprised nobody has mentioned Eagle Tree yet.

superflyboy1988

thanks for that

what is eagle tree

siberianhusky

A data logging system.
http://www.eagletreesystems.com/Boat/boat.html
basically the same info spektrum telemetry gives you, rx voltage, temp, rpm, have never used mine (Skektrum telemetry) in a nitro boat, can't see the point. A full data logging system would be cool for an electric, they can log amperage, voltage, rpm, esc and motor temp. All useful for setting up electrics that tend to blow up if anything is wrong!
You need a real hand held tach for synching a pair of engines.

Ron Olson

My Feedback: (1)

That's the one that I was thinking of!

superflyboy1988

what one

Ron Olson

My Feedback: (1)

The Eagle Tree.

boatnut

To a certain extent, you can synch by sound.
If you have ever flown in a twin you can tell when it"s
engines are running together, or at different RPM,
by the type of sound. I don't know if this by prop
or exhaust. May not work on boat exhaust. 
How do they get the twin gas boats to pull together?


              Having this much fun must be illegal

superflyboy1988

ya i would not know where to start with im a little to green to be able to do that lol but maybe one day

siberianhusky

If you have ever tuned a guitar it works on the same principle, when the engines are synched together they will have a nice smooth sound, when they are running different rpm you can hear a kind of warbeling, very hard to explain but things will not be resonating together, kind if like a wa wa wa wa wa wa, the closer to each other the rpms are the slower you will hear that sound, when they are together that sound will disappear, you will be able to tell as they get closer as the warbeling will get slower and slower as the resonant harmonic frequencies come closer together.
Sorry the explination sucks, I just don't know how to explain what your listening for.
If you have ever heard two chainsaws operating at the same time you have heard the sounds I am talking about. Very distinctive but hard to explain!
After doing it a couple of times with a tach you will understand what I'm trying to get across.
You just got me thinking, how do people synch twin RCMKs? I use matched vacuum gauges on my bikes and have a uni-synch for cars, just wondering how people are setting synching the carbs on those?