Okay here's the deal. I used the measurements & drilled the firewall of the Dragon Lady ARF that I am putting together, for the stock engine mount that comes with it. I guess they are some kind of carbon fiber, or nylon, or some kind of black plastic, not really sure exactly what they are made of. Anyway I got it all set up per the instructions, then scored a good deal on a new Saito 100. I then found the cliff-note in the instructions: you may want to use an after-market aluminum engine mount if using a bigger 4- stroke engine. I got to looking @ the Saito on the stock mount & decided they are right. So I got a better aluminum engine mount for that size engine. Of course now the holes in firewall are wrong, just enough that the holes would actually intersect each other a little bit, not wide enough to clear the existing holes but just a little wider so that they would be partially into the holes I allready drilled. I decided to fill the holes with dowel. I re-drilled the holes just a little bigger to match a piece of hardwood dowel I have. I left the dowels about an eighth of an inch too long, so I would have some sticking out to run a good bead of thick CA around after first glueing the inside of the holes with thick CA. It has set up very well so far. My plan is to let them cure completely before using the Dremel to cut off the ends & sand it back flush to the firewall. Then I will start all over with the new measurements & re-drill the holes. So what do you think, is this gonna hold ok? If not I could add a piece of hardwood ply that came with the model for use with a smaller .60 size engine. I'm trying to get around doing that because I lined it all up that way to have a look & then I have to slide the engine so far back into the mount that the back of the mount rides right up against a carburater bolt. So I would rather not add the new piece of wood unless I absolutely have to. Please let me know if you think this fix with the dowels will work. Thanks in advance for your opinions.

I think you've done exactly what you should have to correct the problem. I wouldn't have done anything any different.

Hi,

Is it possible to rotate the engine slightly? So long as the thrust line doesn't change it doesn't matter to the aircraft if the motor is vertical, inverted, on its' side or any where in between. Rotating just enough so the old holes don't come into play with the new mounting bolt holes is one option. Often with a four stroke to get the muffler to exit the bottom of the cowl the head is roughly at 7 o'clock when viewed head on.

Or have you already cut the cowl?

Good Luck,

Colin

No I haven't cut the cowl yet, or glued the blindnuts in place, thank God! I thought about it & turn it off to the side a little like you suggested, but the pipe does end up in a bad spot. There are also two plywood triangle shaped pieces running vertical on each side of the firewall that make turning it at a different angle a problem. Currently the engine will be sitting sideways with the pipe coming out about dead center at the bottom. I was thinking if the dowels will allow me to re-drill it & install the blindnuts with out popping the dowels back out when I drill, then I would be home free, but I just don't know how strong it will be even if I do get away with it. [&:]

I did the same thing on a recent plane... twice! [:@] Except I used epoxy to glue in the dowels to make sure they were fuel proof. Still holding fine after about a year.[8D]

ho2zoo, That good news to hear, I will be re-epoxying the whole firewall again after I'm done. I just wasn't sure if it was gonna hold or not, sounds like I'll be ok. Thanks for the good news, I'll be re-drilling the holes tomorrow after the CA has had a full 24 hrs to cure. Thanks again!

Your fix will work well. You shouldn't need any more reinforcing. Yes, the engine can be rotated to any position you desire as long as the thrust line doesn't change.

Dr.1

Dr1, Thank you. Yes I'm aware of the fact that the plane, & the engine don't care what angle the engine is sitting at. It's just that this particular model doesn't have a completely smooth flat firewall. It has those two vertical pieces of triangle stock on each side about a half inch in from the side preventing the engine mount from rotating at 360 degreees. You get sideways, upright, or inverted. At most any other angle than those three, the engine mount hits those rails. They are actually two pieces of hardwood ply coming out through the firewall with triangle stock glued up against both sides of them. I don't want to mess with the structural integrity of the plane so I'll be leaving those two pieces in tact. I don't do the photoshop thing like MinnFlyer, or I could draw ya a picture.

Thanks guys, I'll get er squared away today.

That sounds like bracing for the firewall. There should be similar pieces behind it. too. If the interference isn't too much, you can probably take out enough to rotate the engine mount to the desired position.

Dr.1

I thought about that Dr1, and yes you are right they do actually come back inside the fuse about 6 inches to form part of the fuel tank compartment. In this application though the instructions suggested postion of straight sideways is the position I want the engine in as well. It will require the least amount of cutting to the cowl, as well as positioning my exhaust right at the bottom center of the fuse where there is allready a built in exhaust escape area. Hard to explain, but I'll try. There is a cut away about an inch wide & an inch deep at the bottom of the firewall that angles back about an inch or so as well, that with the cowl on & the pipe right there in front it, makes a perfect little exhaust port between firewall & cowl, and that's right where my pipe lands with the engine mounted sideways. So as long as my fix will hold & it sounds like it will, there is no need for me to do any cutting or removing on those braces. I looked at the engine setting in every possible position & decided that the original position was the only way to go. That's when I decided to try this fix. I was just wanting to see if anyone else had done the same thing in the past, & with what kind of results. Since ho2zoo has tried it with success, I'm sure it will be fine. I will cut the ends back & sand them flush to the firewall today, then re do it it all with the epoxy & drill the new holes tomorrow after the epoxy has cured. I have plenty to do to keep me busy while the epoxy cures, like routing the smoke system. Other than that, the plane is just about air-ready. All the control surfaces are in & dual rates are set, adjusted & sub-trimmed on my new JR radio Just need to finish the smoke system & the remounting of the engine, cut the cowl, balance her, & she'll be ready to go. Thanks for all your good input.

It's fixed, & it came out looking good, Thanks for the input, I appreciated it.