Scale World Models 1/3 Super Cub Project

[witchfingers]

I don't think the 8.75 wheels will hold up on a 1/3rd scale. There is a weight limit for each size wheel they make. The 8.75 are for 1/4 scale.

 

[Bartman]

I don't think the 8.75 wheels will hold up on a 1/3rd scale. There is a weight limit for each size wheel they make. The 8.75 are for 1/4 scale.

i asked the guys at PR Bushwheels about this. they didn't say go for it but they didn't say don't. so far we're good although running low on pressure makes the tires pretty unpredictable so having enough pressure in the tires is important.

also, i'm swapping out my homemade frankengear for a pair of well used Robart 1/3 scale Cub gear. my gear is ok but i used mild steel for the axles instead of ordering the right material (4130 chromoly steel) and the axles are bending under the load. i can't really heat treat mild steel so i'll just put the Robart gear on. they're pretty fugly so if i have time i'll sandblast them and give them a quick rattle can coat of paint.

@Pancake i hear ya! it actually does a pretty nice knife edge pass! we're talking about fielding it in the Basic category (unless I can pull off a Sportsman sequence with it) sometime before the end of the year.

 

[Bartman]

I'm sticking a fork in this one, we're done!

Can't say it enough, thank you to @pawnshopmike for his support and to Airborne-Models.com (US Distributor for The World Models).

Thanks to @Decal Dennis for doing such an awesome job on the graphics!

Thank you @Pistolera for helping out with the test flights!

 

[Bartman]

Details of the tow hitch I made for the plane. In planning the hitch I was trying to come up with a way to reinforce the fuselage so the tow hitch could be mounted without pulling the fuselage sides apart. After thinking about it for a while it occurred to me that the landing gear blocks were already reinforced and a very strong spot in the fuselage! The plan then became how to mount a tow point across the front and rear landing gear blocks in order to take advantage of those hard points that were already there.

Before committing to the location for the hitch on the plane I did a lot of research and found the most success came when people mounted it behind the CG on the bottom of the plane. The Aero-Tow community puts their sailplane tow hitches on the top of their planes, also behind the CG but since the banner will hang down below the plane, the tow hitch was better on the bottom. I got lucky and it all worked out, the banner is securely attached, it hangs just right below the plane, and we've been able to release the banner with a flip of the switch of the transmitter. Needless to say, I was very relieved after that first flight with a banner (but Earle (wisely) still wouldn't let me loop it!).

I found some aluminum channel in with my stash of aluminum cutoffs and scraps and figured out a way to make it work. After cutting it to length I made a cutout for the servo (the old way!)

Next came the tow hitch point itself which was machined out of 3/8 aluminum bar stock

With it mounted to the aluminum channel you can see how it will work

I had a little trouble getting the servo arm to swing through a large enough distance to open the hitch for when it's time to drop the banner so I had to try a bunch of different control horns and eventually ended up with a big hole at the back of the aluminum channel stock. It works the way it is now but if I were making another one I'd mount the servo higher up above where you see it so the control rod could be longer and supported in at least one additional spot. The bolts you see sticking out of either side are for a rubber band that helps constrain the actuator pin so it can't pop off of the control arm. Rev 2 would be a lot more elegant and reliable but so far Rev 1 is doing just fine!

After test fitting the assembly in the plane it was time to cut the bottom of the fuselage open and get it to sit properly so it could be through bolted to the landing gear blocks. Measure, cut a little, measure again, cut a little more, etc., etc., etc.

I needed to shim the whole thing up about an eighth of an inch to get it to sit correctly across the landing gear blocks and once it was as close as it was going to be I drilled holes and bolted it in!

 

[pawnshopmike]

Very nicely done @Bartman . You made us all proud! Great build thread. I've learned a lot following along with this project.

 

[Bartman]

Thanks Mike!

 

[BalsaDust]

Really like the way you did the tow release.

 

[Pistolera]

It worked well too! These pics are the first time I saw the beefiness of its mount....I think Bart could yank a small table into the air!!! H'mmm....flying lawnmowers, so why not a towable table

 

[Bartman]

thanks guys.

i actually also used some 1/2" aluminum angle to reinforce the joint between the rear landing gear block and the plywood fuselage side. i just wanted more than a glue joint there where the majority of the pull is happening from the banner,

 

[witchfingers]

I love these guys!