Im in the process of putting together a Yak 54 33% from SD, which engine will fit this cowl 10 1/4" without cutting the crap out of it?

thanks guys

ZDZ super 80, DA-85 or 3W 85. All 3 will rock this plane.

Ok but size wise to avoid cutting to mch out of the cowl.

One thing you have to look at to is the right thrust, If you have a engine that will fit the cowl, With the offset for right thrust you will still have the plug cap out on one side.

Most all the 100 class engine are 11 1/2" cap to cap, Some with the smaller plugs are around 11"

Milton

yeah baby!

You should really also be asking about the muffler. Here are shots of a DA 85 and the standard JTEC Pitts:

Wind, the cuts in your cowl are perfect, is that a lot of messuring? any advice?

Thanks adamiani.

To be honest, it took about 30 iterations of trial and error fittings. I didn't have ANY pictures to go on (cause most of the SD Yak build posts were for older engines not the DA 85). The trial fits could have been worse on a different kit. The rear seat for the cowl is a perfect fit, and the trim scheme on my plane made it easy to line up to see where it "should" seat every time so I always knew how close I was getting with each trial fit.

I used a dremel tool with a small robart carbide bit and some 20 grit sandpaper mounted to a popsicle stick and small dowels. AFter I got to the point where the cowl would seat, I used small strips of 80 grit paper and fished them into problem areas and pressed on the cowl while pulling the paper against the muffler. Ironically, I think the greatest aid for the process was my adjustable astronomy observing chair. It is padded and very comfortable and adjusts so one may sit anywhere from 1 foot off the floor to about 3 feet above the floor. This allowed me to put the plane on the table, and sit so the cowl bottom was at eye level the whole time. I couldn't imagine this iterative process if I had to constantly stand to bend over or manipulate the fuselage to see the fitting process. For most folks without such a chair, I recommend supporting the plane so you can see it well where you are seated comfortably, however you can.

I first mounted the engine without the plug or muffler, and got the square cutout done, then mounted the muffler which stayed on the whole time after that. Because of the thrust offset, the center cowl seam which is barely visible will NOT align in the center of the motor! Only the fins stick through, but I think one should leave generous clearance for those as there isn't any other exit except the scoop.

After mounting the muffler I worked on the small cuts needed in the front of the scoop to clear the pipes for the muffler. Because of the right thrust, these are NOT symmetrical. Then I progressed to the cheek corner and spent the most time on that with many trial fits until I was happy with the clearance.

If you use a JTEC muffler, yours should look just like mine if you were patient. A friend made larger cuts and his still looks good too cause they're only visible when you look from the bottom, really.

I was delighted to see that because this is a glass cowl, I only actually needed a 1/16 to 1/8" gap to clear the muffler it does not melt even when close! I have had the muffler come loose and flown around until I noticed this (muffler riding on one bolt and trapped in the cowl) but it never melted anything and still looks like that picture.

Is the DA 85 a thigt fit inside the cowl, have you seen any 33% with this engine an canisters? thks