AGR,

The Pitts style muffler works well on my Evolution 46.

There's a picture a couple pages back in this thread with that very answer. I don't know if engine performance is decreased any. If you are going to spend money on a new exhaust that isn't a MACs tuned pipe for you Tower 75, you can consider the Davis muffler as well. Though a clunky strap on, I have run them on several different planes and they do quite well on top of not robbing power. The big reason for that is that it isn't just an expansion chamber, it has an inner pipe that the exhaust after expanding in the main area, has to flow through further reducing any unspent fuel noise.

For the MACS header and pipe though you'll need a 2890, 2891 or 2892 header and an 1160 or 1060 and 1260 pipe. Course the exhaust is still pointing the wrong way. You could even run one of them Double quite marine pipes that they sale over there, if'n you want to add 250 more dollars to your exhausting solution.

Or, buy one of them vibrating pumps and leave the stinkin muffler off. At least you'll know where it is, with your eyes closed!

Think I'll try the silicon thing first. If your silicone keeps coming off, drill and screw the exhaust pipe with a small machine screw. Then put the silicone on over that. If you have someone that can tig weld a ridge on it that'll give you something to hold onto it as well. Shouldn't cost much at the local machine shop.

EDIT Hey looky there, there's that picture I was talkin about.

I think my latest solution will work, I put the new exhaust deflector on with Loctite Extreme Repair, it is a clear silicone product good up to 400 degrees F. I also put aircraft safety wire in addition to the Loctite and zip ties!

That'll do it, long as you held your tounge in the upper left side of your mouth while you did it. Otherwise that sucker is coming right off.

Upper right corner is no good.

Hey laugh if you want but this sucker moves out....in hindsight it was kind of funny when it shucked the deflector it went through the prop. Myself and the guy watching went "Uh what was that" but the plane did not disentegrate so I landed.

AGR,
I just your writeup and the video. I see that you have the exhaust deflector pointing up. I should have suggested that running the Tower .75 a while back. I run my stock muffler pointing up and to the side. I haven't had the problem your having with your .75. In fact, I was having the opposite problem and went down to 5% fuel to keep the engine cooler. My setup is a little different with the tanks reveresed and I added a hopper tank which helps.

As far as balancing concerns, I've got all 4 servos in the rear and the 2 oz. hopper tank. I used 2 hydrimax 4 cell packs, 1600mah in the tip of the nose Y harnessed together. No Lead Weight added. Balances perfect. With this setup and the extra 2oz of fuel, you can fly for a while.

Mine originally pointed up and to the side and still had exhibited the richness problem, I went to straight up on the deflector because at that angle I only get exhaust on a portion of the horizontal stab instead of the wing and the boom and the horizontal stab.

So far I have had no heat problems, not to say that you don't but I always set my engines up slightly rich and test them in vertical attitude before I fly them.

How old is your .75? what prop are you running?

Hey AGR413

I read your review and pretty much followed your build, (same servos,engine,etc.) but seeing how you had the back pressure, too rich problem with your muffler, I ordered the Pitts muffler for mine. Just finished putting it together last night.
Will maybe maiden it tomorrow.

CrashPro,

Fantastic, thanks, I hope it helped you out. Thanks for posting the picture that's pitts does not look bad on there. I just could not imagine the scale until you posted the picture.

Make sure you have a dual rate setup and are able to go to high rate elevator if you need to. I ran out of elevator on my maiden and was so glad I had set up the high rates.

A word on the stock landing gear and and landing. I have had no problems until I let an "expert" pilot friend fly my Bobcat. It was handling so nice he was puttering around really slow and tried to land it, you can't do that with this plane it will bounce and bend the landing gear. I have always set up for a nice glide and bled it out the the very end increasing up elevator all the way. If you land this plane smooth the stock gear are fine but if you ever bounce it get ready they will bend. Oh and the plastic hubs on the wheels will shatter. lol

PS Good job on the build..I think your build is cleaner than mine.

PSS I hope you like speed. [X(]

I just got an email back from the guys at Performance Specialties about the use of an exhaust deflector to avoid the pressure problem from the exhaust facing forward. They suggested using a copper "U" pipe fitting. I don't know if this would work or how you would attach it...but it is something to look into.

Tomorrows weather forecast....2 mph wind out of the NW,...high of 76....oh yeah.....its gonna fly tomorrow. I'll be at the field at the crack of dawn.

Buddy of mine has a Balsa USA Enforcer with an OS 1.08 strapped to it's tail. He installed a copper "U" pipe fitting into the wing and has it exiting on the bottom of the delta wing, facing aft. It's a slick setup and your post just jarred my memory of it. It's the 3/8" copper fitting and it matches up to his exhaust hose nicely. He may have used 2-90 degree elbows and soldered a short leg in between to clear the thickness of the airfoil, I'm not sure.

Anyway you look at it, it's way kewl.

Almost forgot...recv'd my Hitech MG125 thin aileron servo today. It's **tiny**! 42oz torque from such a small servo...drops into the framework of the Bobcat stabilizer with lotza room to spare. The output arm is rather short-ish but at the speeds this thing is supposed to achieve, slight deflection should be all that's required...Afterall, this ain't no 3-D machine :-)


Pardon the crude drawing but you get the idea, I'm sure, lol

PM

hi guys.
I am building my Bobcat and doing some mods to it also. I will post some pictures. As for the exhaust I have the blue silicone tubing coming from the exhaust port and going through the left side of the fuselage and exiting out the bottom of the plane. It is a pretty neat set up. Its only about 3.5 inches long and will not effect the performance at all. I would do it now but I gotta watch Ohio kick some butt.
Rich O.

GO BUCS!

hi, i am from Mexico city, i have a new bobcat 50, i want to make you some questions, its ok?

hi, i am from Mexico, i also have problem with my canopy, i make a copy with Dental hard rock, and i will make a copy with a thermal vacum machine, this kind of machines are soo pupular, you can look for this in you town, or if you want i can send you one.

Here are some pictures of my modifications. You can see how exhaust exits out the bottom. I haven't put anything on the exhaust yet to make sure it won't come off. Also in pictures I have put 1/4-20 blind nuts in wings and then use thumb screws to tighten up to fuselage.
Works great. You can see I also put some Goldberg snaps on bottoms of wing and fuselage to hold the back ends together. I am still doing other things and will post some more pictures when I get there.
Rich O.

more pictures.

The Buckeyes scored 14 points in the First Half. So they did kick some butt right?

Boy did they, they kick there own butt to the losers locker room. How pathetic they looked. I think to much hype over the last
52 day lay off. Maybe if the game was played before the Bowl games things might have been a little different. Florida sure looked
good. They have some great players.
Rich O.

The sports radio talk show hosts were SO geeked on how OSU was going to romp all over the gators...I had to look at the game after logging out here which was abot 3 min into the 2nd. Saw about 5 minuts and turned the channel.

I think there were about 25 "bowl" games. I may have seen about 25 minutes of those games.

I don't care for U of M because of the major traffic jams they cause on saturdays. I have to change my route to the flying field.

Well I am off to get mine this week

Dennis

www.densplanes.co.uk

Maiden flight this morning......3 flights....several touch and goes. Had one crappy landing,..came in a little too hot,...got a couple bounces,....bent one of the mains a little. Other than that, no problems,...I love it already, gonna have fun with this one.

Nice pics, congrats on the flights. Did the engine reach top RPM? Any issues with the Pitts muffler?

Has anyone tried to install mechnical retracts on the Bobcat?