question for Frank

[laxmasta2039]

frank,

im asking u this b/c u seem like a pretty experienced r/c boater.
i'm building my third boat, but first racing one. it's jay turner's xs cat. i've got two trinity p2k2 motors, with connecters, and all the works [so i definitely want to use them]. i have everything except batteries. the esc i have is an Electronize 43vr. is this speed control sufficient? the batteries i am planning to get are two 1500 mah packs. r theses the right choice? also, if i use the hard shaft systems i have, the props will be at a vey slanted angle in order to completely submerge. however, i cannot find flex shafts and struts together anywhere. do u know a place, or anyone selling two flex drive systems? please help me out. my email is mmlennarz@earthlink.net

[FrankW]

Jay Turner designs excelent boats and the XS cat is an excelent choice.

I found the specs for that speed control from the Electronize webpage:

10 amp. continuous load rating.

45 amp. short term stall rating. (continuous MOSFET rating)*

That amp range might be okay for a low speed scale boat. But for a racing boat, that control won't last much more than half a second. Racing boats commonly pull a continuous 50 amps, and many times they pull more. A better choice would be a speed control from www.rc-hydros.com

The batteries you chose will work for sport running, no problem. But you will experiance high heat and short run-times. For a little more money, I would suggest you purchase Sanyo CP2400's from www.batterystore.com You will have to assemble them yourself, but that shouldn't be too hard and will reduce the resistance in the battery pack. I use Deans Probar 2.0 to connect my cells.

With the XS cat, you do not want the prop to be completely submerged in the water then the boat is on "plane" (riding on the last few inches of the sponsons). Your should have the hub of the prop(s) equal to, or slightly higher than the bottom of the sponsons. The boat is designed with a "surface piercing" propeller design, which allows the prop to spin at a higher RPM, and thus push the boat to a higher speed.

As for running hardware, your best bet would be flex shaft. You can get flex shaft and prop shafts from Octura and Prather. Prather has pre-soldered flexshaft/propshaft combinations. For struts and rudders for your boat, Fuller's hardware would be perfect. Check out http://www.dpileisuresports.com/prod-det.asp?prodid=63

Now, even though you want to use those two car motors, I would have to advise agienst it. Car motors do not work well in boats. They will work, but not well. I would recommend a Graupner Speed 700 motor (Turbo 8.4V BB). You can get one here: http://www.hobby-lobby.com/speed700.htm Any Speed 700 motor would work though. The motor can handle more power, can turn a larger prop (more speed) and won't melt down as easily. Also, with a single Speed 700, you only need half of the running hardware, which means less weight and higher speeds.

-Frank

[laxmasta2039]

thanks a mill, Frank.
you cleared up alot for me.

[laxmasta2039]

since the prop does not need to completely submerge, the angle of the straight shafts would not have to be so extreme. would it be O.K to use a straight shaft then?

[FrankW]

I wouldn't use a strait shaft in that boat. Becuase with a strait-shaft, some of the direction of the thrust will be pointed downward, which is not a good thing for catamerans. Your best bet would be to get a flex shaft where the thrust can be completely rearward, or a little upward, to lift the front of the boat, which keeps the front of the boat out of the water (and increases speed).

-Frank

[laxmasta2039]

alright. thanks for your opinion.