Hi all! I have just finish a CAT project. There are 2 videos of the first test. My friend record it by hand phone so it is small. Please give me suggestions about my boat to edit it better.
Thanks alot!
i603.photobucket.com/player.sw...nk/02072009.flv
i603.photobucket.com/player.sw...02072009001.flv

That looks like an Insane Gen2 cat... The engine is not revving out as much as it should. The pipe seems too long to me. What prop are you using? Give us a little bit more details on the hull, motor, pipe and prop please.

Thans Marc. The hull made in Vietnam and same the Insane CAT2. RCMK S254 engine. I make the pipe with total 50cm long (may it is too long). I use the Octura X678 for the first test.

Measure from the exhaust port face to the center of the band in the pipe. Follow along the centerline of the header and pipe. Adjust the pipe to be about 32-33 cm at this point. Fine tune from there, you will probably end up going shorter. Cut off excess header inside the pipe past the Orings. Leave no more than 3cm hanging inside.

For props I would suggest contacting Brent at Propworks West here is his profile link, you can send him a private message: www.modelgasboats.com/index.ph...ofile&user=4704

If you must stick with the Octura props you have there, I would try something like a X470 3-blade or possibly a X670/2. Brent's props would be much better though for sure.

How deep are you running the strut?

Good luck.

The X-678 is too large for an RCMK. Try something around a 67mm prop.

i393.photobucket.com/albums/pp...cantho/pipe.jpg
I cut down the pipe whith Lt=43cm (Is Lt=43cm right?) use the Proshop 6717 and Brather 275 for the next test. It run better

The correct pipe length should be around 11-1/2" to 11-7/8", here's a link that will teach you how to measure it, 6717 is a good starting prop for your cat.

www.americanrcboats.com/howto/pipe/steelpipe.htm

The second method mentioned at that link is actually the correct way do it, except that you should measure from the exhaust port face, not the face of the flange. Actually we should measure from piston center but that's more difficult to do accurately so most people measure from exhaust port face. I start with 12.75 - 13.00" (32-33 cm) from exhaust port face to center of band section or center weld if there is no band section. Work your way shorter from there, taking notes of changes in performance.

My pipe have the length from the center point of the
exhaust flange to the highest peak of the belly is 34cm (13-10/25")
it run better but not the best. I will cut down it to 32cm anh test again.
Thanks you for the help. I'm a Vietnamese so my English is not good. soo sorry!

Always leave a little bit of header inside the pipe (about 5-10mm) so that you can pull the pipe back out a bit if you go too short. Otherwise if you cut it too short you will need a new header.