[NDW]

Paul... Straight pipe may be fine but what about back preasure for the tank and fuel draw.... Just tap the straight pipe and thread a nipple in.... For back preasure..

D.

[Skidoo55]

Hmm, good point. I guess that I'll continue to set it up with the ugly muffler that is on it now, but I do have a small tuned pipe that I can secure below the fuselage. Obviously not very scale in appearance, but I think it will look nicer than how it looks now. I may try my hand a fabricating a custom muffler, just need to get an aluminum wire feeder for my mig welder, and some aluminum to play with.

[michaely]

Originally Posted by Skidoo55

Hmm, good point. I guess that I'll continue to set it up with the ugly muffler that is on it now, but I do have a small tuned pipe that I can secure below the fuselage. Obviously not very scale in appearance, but I think it will look nicer than how it looks now. I may try my hand a fabricating a custom muffler, just need to get an aluminum wire feeder for my mig welder, and some aluminum to play with.

Paul,

Also Bisson Mufflers - which is located in Ontario and has website - could fabricate a custom muffler that would fit the existing cowl - but obviously pricier that you fabricating one yourself and gaining that skill.

One possible solution for the next time is a channel within the fuselage for a muffler or tuned pipe........ looking at the side view of the plane with the existing muffler, it looks like there is enough length and vertical height to reduce the height firewall box to accommodate the muffler coming straight back into the fuselage and, if the landing gear attachment can be modified, to allow a short channel for the muffler in the bottom of the fuselage, with a exhaust exiting before the leading edge of the wing.

But I wouldn't too concerned about scale appearance..... with the top wing held on with elastic bands, it's a stand off scale model (smiley)

good luck

Michael

[fledermaus]

The design of a muffler (or as the Europeans would say, a silencer) depends on the frequency of sound you are trying to suppress. The reason "2-stroke" mufflers are different from "4-stroke" is that the peak frequency from the 4-stroke is 1/2 that of the 2-stroke. There is a simple program you can download for PC at http://www.mh-aerotools.de/airfoils/ called "Silencer" that lets you determine the approximate attenuation a given design will provide. You can't expect decent results just slapping a muffler from a 4-stroke onto your 2-stroke engine.

[aspeed]

If you go with the tubing, you could maybe insert a plug in the end with about a 6mm hole for back pressure to the tank. If you get the right length it may give a performance boost. If the length is wrong, oh well, it is just like any other stock muffler. My MVVS .15 is kind of slow, but sure looks nice, and converts to rear exhaust too. If you blow into the muffler like a flute, (no kinky jokes please) and listen to the note, it will be similar to the rpm of the motor that will suit it best, or tell you how far off you may be anyway. The F2D mufflers are quite short, 2 to 3" much like a 4 stroke one, and they work fine at high revs at least. 30,000 rpm or so.

[Skidoo55]

Thanks for the idea guys. I'm not too concerned about scale, as mentioned, the elastics kind of give it away, and being that it's so small, it's really about goofing around at this point. I bought two more cowls so that I can fool around with different setups, but I'm leaning towards just mounting a pipe on the bottom, and seeing what happens. Now I have to find some silicon tubing that is the right I.D. and about 4" long. Off to the hobby store!

[technician]

Hey paul, judging from my experience or lack of it ,what you have actually looks pretty promising from a volume point of view for a 15 size. If theres a baffle in the muffler you can always take it out for more power.

Good luck !

[Skidoo55]

Peter, the muffler that is on it looks like a good match for the engine, what bothers me is that I pretty much had to butcher the cowl to get it to fit. I was hoping for something a little cleaner in appearance, but do realize that it is a small plane, and not a show piece. It's the second plane that i have ever built, so I'm disappointed that I couldn't get the nose a little cleaner looking. I'm not going to worry about it too much, it'll look perfect when it's in the air.

[technician]

Well if you don't mind doing some rearranging you can always re mount the engine so the cylinder is 30-45 degrees below horizontal & then the pipe exits the belly .

Since its only your second airplane you built you have to live and learn.

Whoever said this hobby was fun was the guy who sat on the bench everyday . This is work ! ,........but in the end its all worth it .

By rotating the engine so the cylinder is below horizontal you also bring the cylinder closer to centre & a neater appearance in the cowl openings . Also the airplane will be easier to balance with out all that weight on the right side . Since you have a couple of spare cowls you can put them to good use.

[OLD PRAIRIE RED NECK]

That is the biggest ugliest muffler I have ever seen on a little engine! No wonder you are trying to get rid of it!

For all you young pups, I well recall the days when mufflers and tank pressure were unheard of and guess what? Our two stroke engines ran and lasted just fine! Then exhaust baffles that linked to the carb came out to put a bit of back pressure on the engine at low speeds to what? Retain heat and keep the glow plug warm to improve idle! Then mufflers to make them quieter.

Those short stock mufflers that come with the engine do nothing to increase power! In Clarence Lee's engine articles there was always a power gain with open exhaust. True tuned pipes are 4 or 5 times longer to get an effective power increase.

Go ahead and try a 4 stroke muffler. At the very worse it will reduce power from being to restrictive.