well i think the pictures says it all, i think my only two options is to either take the dremel tool and cut an area around the muffler to clear the fuse so the vibration is not so bad from the engine plus the heat on the fuse there. or take engine mount off fill the hole with epoxy or balsa filler and ca then redrill where it will be centered in the area for the muffler to fit. i checked the manual and the template was done right and the holes are where they are suppose to be per the template the manual says a os 91 fx is the highest to go for a two stroke and pictures use a os 61 fx so the muffler clears fine with a 61 fx. but give me some input on what you think thanks mike lansford

Army, I am about to order the same plane using the same engine. Tower suggests a pitts muffler, but I don't think that will work. I do know you are supposed to leave that sleeve in the stock muffler. We may both have to dremel out the opening for the muffler. Is yours rubbing the wall? Second pic is fuzzy.

yes it is rubbing the wall there i thought about sanding it down a little bit and just leaving enough wood to apply epoxy and fuel proof it.it does not need that much sanding i figure an 1/8 of an inch would be good to get the muffler to clear. like i said before i could just leave one of the engine mount holes fill the other three in with epoxy and move the engine where the muffler is off of the fuse it would not take much moving doing that way to just wonder how it would affect the engine thrust and all that. the plane is a good plane easy to assemble, this is the only preoblem i have ran in to take care mike lansford

Mike, provided the centerline of the crankshaft is not moved, I don't think the thrust will be affected if you rotate the engine about the centerline of the propshaft. I just ordered mine, and I will learn from your experience and rotate mine. I really want to use a 4-stroke, but the 2-stroke will have to do for now. Are you going to add any scale details to yours? I'm looking for close-up pics of the full-scale version right now. I also might put Robart struts on it, if finances permit. Very scale looking!

BTW is the head going to protrude thru the cowl?

yes the head will protrude but not much i cut a square right up front on the cowl it gives it good cooling to,that way does not take away from the looks. I put the robart struts on mine give me a minute and i will post them for you. im going to look at rotating the engine a little bit to get it to clear. Im going to work on it tonight and i will post what i did and the results. I also have put a perry pump on mine it was about 30 dollars i think, people said they have had problems with the os 91 fx and air bubbles so i went ahead and got a pump.

i just went and looked at it again i think im going to rotate the engine mount a little bit to get the muffler to clear does no look to throw of the engine being centerline here is the pics of my robart struts i paid 109.00 for them here is some pics of it take care mike lansford

VERY nice struts. Did they require modifications to the wing? Do you know the part number & vendor?
I'd love to see a pic of the front with the cowl on when you finish the engine installation.
Thanks, Mike. Rich.

no mods had to be done it is just a matter of cutting the landing gear wire that was supplied with the arf and then putting the struts over the wire and tighting two set screws for each one took about thirty minutes to do and i liked the way it came out perfect fit. I looked on the website today and it says they are down for updates but the struts you need are for the hangar 9 pt-19 they fit the great planes pt-19 as well just do not get the dyna flite ones i hear they do not work on the great planes arf. i got the part off of robart then had my local hobbyshop order them same price and that way i support the local hobby shop too will post a pic of the finished cowl and engine tonight for you take care mike

Thanks again, Mike. Looking forward to it.

here is the engine after moving it over a little, i still sanded the inside of the fuse then applied thinned epoxy to fuel proof it hope this helps in your upcoming build of this arf, just make sure you put the muffler on and fit it before drilling your mount for the engine but here is what i have after getting the muffler to clear the fuse

here is the cowl you can look here and get an idea of where to cut. I cut this cowl up more after turning the engine for the muffler to clear you can see there is a cut out in front of the carb you dont have to cut that out after i moved the engine a bit i cut it out but it just made it look bad. i have ordered another cowl and i will cut it much smaller and not butcher it as bad. This is my first large plane and im happy with it so far but i hope this pics help you anymore you need just let me know.

Mike, before you cut that second cowl, I wonder if we can find a muffler that will allow us to mount the engine inverted @ 6 o'clock and not have to cut the cowl at all? I am going to start looking. Thanks for those pics. I'll post my search results.

Here is a link to Bisson's inverted pitts muffler for $39
http://www.bissonmufflers.com/en/muf...ing_id=1019600

Think this will work?

that looks like a good muffler but the way the cowl is,if the engine is mounted inverted you would only have to cut out the inserts in front of the cowl for cooling and just a little for the muffler. the cowl is so narrow up front and the distance required from the firewall puts the engine way up front i will look into also keep me posted on your findings and i will do the same take care mike

Mike, can you measure the width of the cowl at the centerline of the engine head? I'm trying to figure out how much clearance is available. Thanks, Rich.

rich, you have 5 and 1/2 inchs from one side to the other of the cowl on the inside where the head of the engine is i would like to find out the width of that muffler i think that would work with the engine mounted inverted do you know when it will be available for purchase take care mike, also i checked robarts web page and they are still down i will look later on today to see if i can find the exact part number for you

Mike, I e-mailed them with the question. Here is a link to Slimline. http://www.slimlineproducts.com/onli...rted_pitts.htm
They also have an inverted pitts muffler, for more money. I e-mailed them with the same question.

Hey, here's another one, with the dimension. Part no. BCMIOS91 , http://www.justengines.unseen.org/silsbcmdims.htm. It's 25mm deep. When I get home, I'll measure the distance from the centerline of the engine head to the face of the exhaust flange. This may work! I'll look for a U.S. distributor. Check back later. Rich

Can anyone send me some general dimensions for that cowl ?

From the pictures, it looks like the turbo-jett muffler might fit very well. Side mount the engine 90deg.... let the cylinder head sick out the one side. The muffler would likely be totally enclosed in the cowl.

For the OS 61 or 91fx the turbo 10cc version will work great. Its about 3" in diameter and stands off about 2" total from the exhaust flange (excluding the exhaust tube.

This is an image of a turbojett installed in the front of my VQ-P-51. That is a jett 46 installed with a 40 size turbo. Fits 99% inside of the cowl. I opened the chin "inlet" to allow some muffler cooling. Cylinder head sticks out the side.

It looks like the PT cowl is fairly large. take a look at the jett web site for the actual dimensions.

Bob

bob i will get that for you in the morning, you just want the width and height around where the muffler would be. and i will give you lemgth overall and height overall. I thought it was a good size cowl too but the engine having to be mounted so far forward it really gets small the way it is designed but i will post the measurements for you soon take care mike

Have you tried to remove the spacer in the stock muffler? that my give you the clearance you need ....JW

JW from what i understand the spacer cannot be removed.

I measure 15/16" from the centerline of the head to the face of the muffler mounting flange on the side of the head. This gives us 1-13/16" of clearance. I'm still looking for a U.S. distributor for BCM.

Jim @ Bisson said the dimension we're looking for is 1-1/4". This will work! I have e-mailed Brison & Tower (distributors) for availability and price. Will keep you posted.

Yes it can be removed ....The only thing you will need to do is pick up shorter screw to bolt it back together....Looking at you pic's ....removing the spacer will give you all the room you will need....JW

bob here are the specs from towers website on the cowl Length: 254 mm 10 inches
Width: 168.3 mm 6.625 inches
Height: 254 mm 10 inches. I posted the width where the engine head is on the cowl you have about 5 1/2 inches to play with there hope this helps you take care mike

I have been told by O.S. support that you cannot remove the sleeve from the muffler, as it may overheat engine.

Jim @ Bisson said the inverted pitts muffler is in stock, and we can order it directly from him. My PT-19 arrived today, and I will decide on the muffler this weekend. I'll post my findings, if any.

rich, I was told the same thing about the engine overheating if you remove the spacer. I hope your arf is complete mine was. Let me know what you do about the muffler i may go that route too. You just need to get the struts now post some pics and lets see what you got during your building process take care mike