Auburn02

My Feedback: (1)

I was talking via PM about this with setxws6, figured I'd put it out on the forum. In assembling my S/A F-20, I've come to the engine installation. I had planned to use the YS .45 with pipe, but because that engine is so massive, it looks like I'm going to end up with about a 1/4" gap between the cowl and the spinner. I just can't have that. I'm sure I could work the cowl a bit and lengthen it, but my other option is to use a Webra .50. I'd rather have something like Jett 50, but it's just not in the budget. Plus I have a Webra in another plane that I can borrow for now, and when I eventually get a second engine both planes are already outfitted for it.

My question is what kind of power difference do you think I'll see? I'll probably just use the standard muffler for now, but it wouldn't take long until a Nelson pipe found its way onto the Webra (or actually a Jett pipe, if there is one to fit the application). I just don't want to lose a noticeable amount of speed.

What do y'all think? I think I'll be alright going this route, but just needed a second opinion or two. Thanks.

bob27s

My Feedback: (19)

install the Webra .50. Its a real good engine. Will respond well to the tuned exhaust later.

What was the deal with the YS45? I seem to recall that its cylinder center to drive washer spacing was the same as an OS46 and Jett 46 ?

Auburn02

My Feedback: (1)

Well I may have to pull the Webra out of my other plane to look at it, because I think the logic in my head got messed up somewhere along the line. For the S/A F-20, the prop washer/spinner backplate should be spaced 3 3/8" forward of the firewall. With the YS, the absolute closest that can get is 3 3/4", which would leave a pretty significant gap between the cowl and the spinner. This morning I was looking at Webra's website and saw that from backplate to prop was about 3.4", so I figured I'd be alright. THEN, I realized I wasn't taking into account the engine mount itself.

In short, I've left myself confused and need to just get home and look at it.

But even if the Webra or an OS isn't any shorter, I don't know why they would kit this plane with such a short cowl if every average 45 engine is going to be oversized for it.

All that being said I think I've convinced myself to go Webra on this one, though I may still have a 1/4" gap behind the spinner. [:@]

combatpigg

My Feedback: (3)

Why not take a hole saw to the firewall, and then work in a sub firewall that allows the entire motor mount to be recessed?

bob27s

My Feedback: (19)

Perhaps use a backplate mount ?

Razor-RCU

My Feedback: (50)

The Webra is a great engine for this type of airplane--- Not as strong as a pipes YS-45 but it'll be no slouch either-

Recessed firewall is too much work for me, what do you think? I don't care as much about the gap as I do about performance-

Sell both and get a Jett-50 [X(]

Auburn02

My Feedback: (1)

Yeah, I'm not resorting to recessing the firewall on this thing...too much time and effort for an ARF. If it looks like it's going to be a noticable gap I'll probably end up lengthening the cowl mounting blocks to slide the cowl forward and build up the fuse sides to meet up with the back of the cowl and just recover that section. Much easier.

I'm guessing the Magnum they want you to use in this plane is shorter than the others. Oh well.

Thanks guys.

Auburn02

My Feedback: (1)

Yeah, the Webra is the same lenght as the YS. YS is a bulkier engine, I just figured it had to be longer. Either way I've got the Webra mounted and the spinner should be arriving today, so I'll balance the cowl mounting so as to not have a huge gap either between the cowl and fuse or the cowl and spinner. Shouldn't be a big deal. [sm=thumbup.gif]

setxws6

Cobra99, how long is your YS and Webra? Measure them from the backplate to the tip of the prop shaft, and tell me. I figured that most .46 sized engines were about the same.

Auburn02

My Feedback: (1)

I'll measure them when I get home today, if I remember. I haven't mounted the cowl yet, but it's going to be "off" at either the front or the back of it...kinda irritating, reckon I'll deal with it though. I think if I had used a standard plastic spinner it would close up the gap a bit because they have somewhat of an offset on the spinner backplate, whereas the aluminum spinner backplate is perfect flat, but then what's the fun in having this plane without the long nose aluminum spinner?

impactiq

My Feedback: (57)

How about extending the cowl right behind the spinner? A scrap piece of balsa glued to the front of the cowl. Sand to shape, width needed to make up the difference. Add a hole for the engine's front housing to come through. Seal with with epoxy.... finish it off with paint.

Auburn02

My Feedback: (1)

impact, that's probably the easiest idea yet. I might give it a go.

setx, the YS and Webra are both right at about 3.5" from the furthest point back (backplate bolt heads) to the spinner backplate. Including the threads on the crankshaft, it's about 4.5". I ended up (so far) with about 1/8" between the cowl and the fuse sides, and 1/8"-3/16" between the cowl and the back of the spinner.

I also ended up with a pretty nose heavy plane. The CG right now is about 1/2-3/4" forward of where it should be. I already have the battery and receiver just behind the wing (just in front of the servo tray) and don't really see where/how I could move the battery back any further. I've never had to add weight to a plane before, but it looks like I may end up having to stick a couple ounces in the tail cone section.

setxws6

That's weird? Because I just measured my TT Pro .46, and it came out to those same measurements. I didn't have any problems with the cowl not being long enough. Hummm....

As far as the CG, mine was off the same as yours. what I didn't was get some stick on weights, that were in 1/4 ounce increments. I think I added about 1-1/2 ounce to the tail cone section. And then to hide it, I cut out a piece of balsa wood the same shape as the tell section and drilled 2 holes and made a cover out of it.

Auburn02

My Feedback: (1)

Here's a picture of my mounted cowl and spinner. The engine is as far back on the mount as possible. It's really not enough to worry about, but eventually I'll probably make a filler to add onto the cowl like impact suggested.



By the way no, I'm not going to fly it with that wooden prop. I just put it on there to mount the spinner and to break in the engine on the ground (11x6).

rmenke

My Feedback: (13)

Webra VS YS:

Gotta go with Razor. Buy the Jett pipe now or you will go to sleep flying that thing. Think the same pipe will also fit OS and some others, so not a total fixed thing. Have flown T-34s with club racing with stock Webra 50. May take a little prop above the OS, but nothing to talk about. My fastest t-34 engine so far has been the Thunder Tiger 46. Have had only 3 races on it so far, so dont know how it will hold up. Overall best bet is the Jett 50 like the man says. They take some abuse and keep on screaming!