I am thinking about using a Mac muffler also. What problem do you attribute to the fact that you are using a Mac muffler? I am also planning on a CG mounted tank and a Perry pump on a OS120AX in my VenusII.

maynardrupp,

When I was building my Venus II I read this thread and was looking for idea's on what and how to install the exhaust and have it clean looking. The stock muffler is a little bigger and boxier so I went with the Mac muffler which is smaller in size and the OS 120AX stock extension and modified it somewhat. I had to special order bolts that were long enough and have the correct thread size as the stock OS bolts that come with the extension were a different thread size than the Mac muffler. The Mac muffer is very quite.

Is anybody able to measure the width of the cowl of the Venus II in line with the cylinder head of a 1.20AX?

I have a 1.20AX with a Jett Engineering Turbo Jett in-cowl muffler, which mounts to the engine in the same way as a pitts muffler does, with the engine on it's side.

When mounted, the top of the round shaped muffler is below the top of the exhaust port, and the diameter is 88mm (3 1/2").

I've been wanting to buy a Venus II for a long time and finally have the funds, so i'm just gathering all the required components and would like to be able to use my existing engine/muffler combo.

From the pics in this thread, it looks to me that the 1.20AX exhaust port is within the cowl when mounted horizontally. If the cowl is more than 3 1/2" wide at that point then my muffler will be a good fit.

guys...my venus II was very good with OS120AX...i win intermediate class,from 2007 till 2008...and this year i fly P-09 with this plane,and the power is incridible...venus is my favo plane...no need 2x2 plane...

What type of exhaust is in your plane?
I have a crushed venus that is being fixed, and I am going to install the 120ax instead of the 110fz. I have to decide if I go with a tuned pipe or not, and make the mods now that the plane is on the work shop.
thanks,
Alejandro

Did any of you find that you needed to drill out the holes in the belly pan a little more in order to fit the paper tubes through?

Belly pan was a pain for me, I had to modify holes, etc.

Me too (on two planes).

I don't think the Venus needs a pipe. It has ridiculous amounts of power with the stock 120AX, even with 10% fuel.

I assembled mine about 2 years ago, so I forget the process for installing those paper tubes. However, just for info the paper tubes will wear through eventually, even if you're very careful, from your screwdriver tip touching them when installing the wing bolts. If possible, it is a good idea to toughen them up with something... perhaps thin CA, or wrapping the outside of the tube with fiberglass tape and epoxy.

I am in the process of totally refurbishing and re-covering my Venus II and am almost finished. I will post some photos and description when I'm done. I had hundreds of flights on the plane before, and hope to get that many more in the future!

Thanks. I do not use slotted screws for wing bolts, especially when screwing down in a tube situation as with the Venus. I can never keep the screwdriver stable and it's just a pain. I prefer the DuBro type wing bolts. If the paper tube isn't big enough for a socket head to fit to screw down the bolts, I use an Allen Wrench Driver.

Anyway, it looks like some drilling out of the holes in the belly pan is in order. I always like to get confirmation before I go ahead and perform an irreversible modification on the building table. That said, I NEVER get confirmation before performing an irreversible modification while flying .

Great to hear that. I will leave it stock and try that way, while I break in the engine.

Here are some pics from my Venus II refurbishment project. Totally stripped and recovered with Monokote and Ultracote, and I shortened the nose about an inch and installed a new firewall, which should help with CG. I really didn't like the "shovel" type wingtips, so I lopped them off and used some scrap balsa pieces to stack, hack and sand the new ones. Fuel tank will be on CG, and I am using pushrods for elevator and rudder, keeping everything inside to keep it neat - the external servos on the tail are admittedly ugly, and covering up the holes (and the hole in the tail where I had buried some lead in the tail) was a chore, but worth it. I've got a Perry oscillating pump (VP-20) for the engine, the OS 1.20 FS that was in the plane before.

vacaman i use stock muffler...i set the engine in 60 degre or at 8 o'clock,so the muffler just rightin below of the fuselage...n like gaRCfield said,no need tune pipe man...the power was amazing...

Thanks Oky.
Now that my venus is being fixed I could make a mod to accept the muffler without the extension.
But the pipe setup is a good option if the plane is caming out nose heavy with the 120ax.
The only problem is the pipe and header cost. The es pipe and header are expensive, around 180 USD. But I like to overpower my planes, if there is no to much weight penalty.
Anyway, i will break-in the engine and decide.

NICE JOB CMOULDER.

You can mount the engine closer to the firewall to help with the balance. There is room.

Indeed, achieving the desired CG with this plane with a heavier engine like my OS 1.20 FS is very difficult without adding weight to the tail. Previously, even with 3 servos in the tail I had to add 3 ounces of lead to the tail to get it to balance properly.

During my refurb, I knew it would take some serious changes to get it to balance because I planned to put the servos inside the fuse and use pushrods, making it even more difficult to balance.

What I did was; 1) shorten the nose of the model by 1 inch; 2) not use the 120mm flex pipe extension, which more than offset the addition of the Perry VP- 20 pump; 3) used a GF plastic engine mount and put the engine as close to the firewall as possible; 4) use a much lighter spinner; 5) put the fuel tank on CG, which was in fact the primary objective; 6) install the Rx battery waaaay back in the fuse, which was done by mounting the battery on a ply tray and gluing in behind the second former back from the wing saddle.

With all this, I got the CG to 6-3/4", just where I like it. With the fuel tank on CG it flies in the "sweet spot" all the time.

BTW, I painted the cowl and now have it installed, and some yellow trim on the wings, etc. No pics of that yet.

Instead of the paper tubes in the wing bolt holes, I used some rocket body cardboard tube. I used large enough tube to accomodate socket head screws. I had to enlarge the holes but it is much better this way.

JVB, good idea to "upgrade" those wing bolt tubes from the git-go.

What I ended up doing was to make some little balsa sheet "dams" in the belly pan on either side of the tubes, then fill those with epoxy with a lot of microballoons. Anything is better than the stock tubes![]

I guys, I have a Venus II NIB sitting on my work bench with an OS 120AX due in a couple of days. Has anyone used the Slimline Q series Pitts muffler or a Jett TURBO-JETT In-Cowl muffler with the Venus/120AX combo?

Thanks,

Dean

I plan on using a Mac muffler and mounting the engine at about 135 degrees to line the muffler up with the bottom center of the cowl. There is a comment somewhere on this thread about that install. There are pictures of it also. You do need to keep the weight in the nose down and the Mac muffler helps with that problem.

Dusey52,

I have a Turbo-Jett that fits the OS 1.20 and i am picking up my venus on Thursday night. I'll then be able to tell you if the Turbo-Jett will fit within the cowl or how much cutting will be required.

My Turbo-Jett muffler is a hair under 3 1/2" in diameter. I know the Slimline pitts and others are over 4" wide and pretty sure they'll stick out the side of the cowl.

When i tested the 1.20AX with the Turbo-Jett i recorded 9,100rpm with a Xoar 17x6 on the first (and very rich) run. I'm sure with the favoured 16x8 it will be a killer.

I'm not using a 1.20AX in my Venus. I sold my engine with the plane it was in, but i did keep the muffler and I'll be using it with a Webra .91 in my Venus, mainly because i have the .91 already.

I had my first full day with a broken-in engine, a pump, and a 16x8 prop. I think I'm going to go back to the 15x10. I found that I needed half throttle just for cruising speed and wanted full throttle for verticals. I believe with a higher pitch prop I can work the throttle in a lower range and save some fuel.

Of course there was a bit of wind...

CustomPC - that would be great. Thanks!

So what have people added for tail weight and lateral balance weight? I've got 2.5 or 2.75 oz on the tail and .75oz on the left wing tip, although that might be a little more than I need.

Dusey52,

I've just returned home from the LHS with my new Venus under my arm.

As promised i've checked the fit of the Turbo-Jett and i'm glad to report that it fits completely within the cowl.

I'll have to wait until i can check the location of the engine exhaust port relative to the cowl as that will determine if the muffler will fit without any cowl cutting, but so far it looks like a great fit.

I think the worst case scenario would be needing to mount the engine slighly off 90 degrees, say about 100(ish), but i'll look at that when i get to that part of the assembly.

I'm working towards a maiden date of 13th May.