Bill Hempel Yak 55

Now that I'm in the correct thread, lets continue our journey with The "Good", The "Bad" & The "Ugly" Part II.

In this installment, I did not get any pictures of the "Good". It wasn't much anyway. It was that I was able to bolt the cowl to the fuselage by removing the velocity stack. I do have some more good news, but I will wait until the end of this post.

Now for the "Bad"




Now, if the "Bad" wasn't bad enough, here's the "Ugly". . . .




It doesn't appear that my Yak is going to get a red head after all. This also means I won't be able to give @Snoopy1 any input regarding how the plane flies with this engine.. . . . . .

With all of this "Bad" & "Ugly" news lately, there is a silver lining to this cloud. While I was talking to my flying buddy last night about the problems I was having installing the engine in the Yak, he tells me "you know, I have the DA-100 that was in my Carden sitting here that you can use in your Yak if you want to". You could have knocked me over with a feather when I heard that. We also had a very informative (for me) discussion about what the function of the "so called" velocity stack on the 3W engines actually was.

In all honesty, I should have bought a DA-100 for my Yak instead of the 3W-110. It would have been the smart thing to do. . . . . .

I don't see what the big deal is, shim the cowl or shim the engine and notch the edge of the firewall for head clearance. A Yak is not suppose to have right thrust but us modelers need it to compensate for our short comings, so somewhere something has to look off.
I have some engine installs that are bad and ugly, yours is just a little off normal but it is designed that way.
And for what it is worth I have had a machine shop take a 1/4" off a prop hub and shaft.

I've seen props an inch or more in front of the cowl. Doesn't bother me.

Why not grind away the area it's touching and reinforce around that?
I don't think the extra prop clearance would be an issue on the Yak cosmetically.

I agree with everyone else. Grind the firewall edge back to clear it all. Glue in some hardwood tristock on the inside of it in that spot. And just let it roll with the prop clearance. Will look fine.

Just cut the fire wall off and shorten it as required. That is the easiest way to solve your problem.

Here is shot of a full scale. Two things to note, one is how far the prop is from the cowl. And second is full scale run radials so there is no thrust angles, makes ours with 2-3° look really bad.

And as a side note, anyone think there ARF has some really narrow legs. LOL!!!

As much as I appreciate everyone's input, I am almost glad it's going to be too hot this weekend to work on my Yak. It will give me more time to think about it and make up my mind. Robert eluded to the one issue that is giving me more and more heartburn, the more I look at it. The heartburn is coming from the amount of offset the prop and spinner will have through the cowl. To me it will look awful and I don't think a smaller shorter spinner will help that much. I know you guys are sitting back and thinking I'm a nut, but I'm just anal. Also for me, moving the firewall back is out of the question, since I have the option of using the same engine that the plane was built to use. Of course, if I didn't have such an AWESOME friend, I wouldn't be able to say what I did. So, I'm going to sit here and ponder my options for a couple of weeks and I may even work on a different plane if it cools off any.

Stay tuned Fellas

HRRC Flyer said:

The heartburn is coming from the amount of offset the prop and spinner will have through the cowl. To me it will look awful and I don't think a smaller shorter spinner will help that much. I know you guys are sitting back and thinking I'm a nut

Click to expand...

Maybe we cannot see what you're seeing. Dummy mount a prop and spinner on there and let us see... You'll figure it out.