The best "sound system" is a 4-stroke engine.

I have used fuel tubing on my saitos in the past run out the bottom of the cowl to keep the inside of the cowl clean what is the purpose of the brass tubing and by the way it looks very nice.

Here is some info (Was begun as a gas build but changed midway to an electric plane):

http://www.rcuniverse.com/forum/kit-...cub-build.html

And a photo of the motor installation:

http://www.rcuniverse.com/forum/atta...mentid=2132454

Guys running a black friday sale over at my site
For plans, bungee covers, and instruments use code brother to save 10%
For LED's, wire, and more use code black friday to save 15%

I have a set of Cub Man's L-4 Plans waiting for a future build. They are really nice and worth the purchase!

SunDevilPilot

Hello all i need some help i bought a Great Planes 60 Cub from a fellow club member minus the engine. He had an O.S. twin but i will be using a Saito 100. As you can see in the picture he had the firewall mounted recessed to compensate for the O.S. If i mount mine as is the prop washer will not clear the cowl. I plan to add some aircraft ply for a spacer but my question is do i put the engine mount directly in the center of the firewall or how do i determine where exactly to mount the engine mount? I am use to ARF planes with pre drilled locations.

Download the assembly manual from the Great Planes website then check the instructions. You may find your answer there.

Find mounting instruction for the O.S. twin & calculate the center-lines.

Mount the cowl, then use a straight edge from center of the prop opening square to the firewall on all four sides, and that should give you the center line. Also "Find mounting instruction for the O.S. twin & calculate the center-lines." as mentioned above and compare the two. It will take some measuring to get the firewall position translated to outside the fuse so you can do this, but it will work. The horizontal is the easy part, getting the thrust line is what will be difficult as it is not a direct line to the fuse, the firewall has the thrust built in so it needs to be squared to that and not the fuse. I've done it on two ARF that I used larger than called for engines and had to compensate for the longer engine by adjusting the thrust lines on the firewall.

Are you sure that the firewall was moved back? My friend has a GP ARF Cub and it also has the firewall moved back. He runs an OS 70 on it.

The center of the motor shaft will not be in the center of the firewall due to most firewalls are at an angle for proper thrust

And that is why the line needs to be square to the firewall and not the fuse. A good flexible metal ruler comes in real handy for this. Measure the distance from the edge of the fuse to the face of the firewall and transfer that to the outside of the fuse. Do that all around the firewall, then make a second mark that is past the cowl so you can mount the cowl, and extend the firewall line all around. Now place the end of the ruler on the firewall mark so it is lined up, and slide the ruler until it centers on the opening in the cowl and that would be your center thrust line. If done right, you will see that it is no where near the center of the fuse. Remove the cowl, then line the ruler back up to the firewall transfer line, and mark that you just made, then mark the edge of the fuse where the ruler sits, and that's your transfer point. When you put the ruler flat against the firewall, it should line up perfectly with the marks you made. Now when you add filler plywood to extend the motor forward, no matter how thick it is, the alignment will be correct. If there is any down thrust in the firewall, it will also show up in this method.

First I would mount the cowl on the fuse and measure the distance from the front to the present firewall.

Does the firewall have any offset in it or is it straight and square.

Download the instruction manual and see what they recommend.

If the firewall has the correct offset simply make up your ply spacers and motor mount until when you measure the distance from the thrust face of the drive washer with the engine mounted and sitting on the ply spacers there will be clearance on the front of the cowl.

Rig a bracket that will hold the fuselage vertical with the nose facing up when the bracket is clamped to the bench clearing the tail of course.

Tack glue the motor/motor mount to the ply spacers and sit on the firewall (no exhaust pipe at this time. Mount the cowl and center the crankshaft in the cowl. You may have to adjust the openings in the cowl to clear the engine. Adjust the thickness of the spacers to get the proper clearance and offsets. When exactly where you want it remove the cowl and apply 30 min epoxy to the back of the ply spacer and sit back on the firewall. Mount the cowl, center the engine and allow to cure. Mark/drill holes through motor mount, spacer and firewall for permanent mounting of engine. If necessary clear cowl to accommodate exhaust.

Thrust line should be identical to what it was when the twin was installed.

Dennis

Thanks for all the replies there is right thrust built in for sure i measured it and also the guy that built this plane is really good. Most of his planes are 100" plus and he builds them in two sections usually split right behind the cockpit area. The first plane i saw of his was a giant T-28 and i watched him assemble it and i was amazed. I asked him what the reason was for having the fuse built in 2 sections and he told me he lived in Singapore for 17 years and there most of the housing and cars are small and everyone there builds their giant planes in sections. As for the Cub he built it normally. As far as the firewall being recessed i just assumed because it was set back almost an inch from the front of the fuse and i am not use to seeing that on planes. He gave me his split cowl from the O.S. twin he had on it so i can use that as a guide and he also gave me a new cowl from fiberglass specialties.

A lot of response ........didn't read them all so maybe some redundancy here.........

Adjust the firewall extension for engine length at cowl opening for prop washer clearance.........secure fuse with nose pointed vertical.....................with engine bolted to engine mount, set on firewall, screw cowl in place, center prop washer in center of opening, gently remove cowl, draw around motor mount so you don't loose your place....................simple and effective! Who cares about technicalities? Don't over think it! Just remember the fifty-fifty rule.............fifty feet at fifty miles per hour...........nobody can see it!
bird........
Long time guys. Good to hear from yall.

Before you commit to anything permanent, you could try to spot-glue a set of cheap scrap spacers (pine??) in place with hot-glue until you get things where you want them. Once the spacers are right (watch the line-up of glue holes, pushrod exits, fuel lines, etc. too) you could pop things off and glue a permanent lash-up in its place.

Just my $.02

Which is why using the existing mount hole for the O.S. engine should allow one to establish the proper center-lines. The additional spacers for the Saito won't shift the engine that far to the starboard side to matter. If the Saito mount pattern is drilled on the existing firewall & spacer, and the spacer is positioned using those hole it will establish the proper position.

All this is assuming that the original engine mounting was correct.

What O.S. twin was used?. Is the O.S twin an FT-120? If so it should be easy to find the mount specifications.

The hardest part of doing it this way, is keeping it on its tail without breaking anything. :)

I cut and drill 2x4's for the gear wire to fit in and fasten them to the table or , if more height is needed a step ladder.
I did this method once with a picnic table to run an engine in the airframe and forgot to fasten the tail. The fuse almost went nose around the table but luckily my hand caught it, unfortunately I grabbed aluminum sheeting a sliced the mess out of my hand.

I used this method on an old third scale BUSA cub........i used a step ladder and rigged a cross piece of lumber to suspend it by it's landing gear. I actually had to climb it to do it! Now, it ought to work for you.
bird

I want to share this picture with the brotherhood.
It is of me taking measurements of the Super Cub I am building and the owner standing next to me.
Looks like I am giving him a ticket.

Happy Holidays.
Danhttp://www.rcuniverse.com/forum/atta...mentid=2135518

Bad boy-bad boy, whatcha gonna do, Dan the man has a ticket for you!!!!
It surely does!!!

Lol!

He was using a O.S 160 TWIN.

Ready to simplify? You coulda had it done by now!
bird

By the time you got the wood, cut it and made the thing work, I would have had the measurements done and the engine mounted! LOL :) Then again, I have a 4' x 6' work bench that sits the plane chest high, making it easy to work on.