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Large Scale Cub Build 50cc Gas

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Large Scale Cub Build 50cc Gas

Old 01-02-2013, 04:13 PM
  #1  
kevstra22
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Default Large Scale Cub Build 50cc Gas

I have been thinking about building another plane for a while now and finally decided on a cub.

I had seen a 8ft cub SPAD build posted on instructables that caught my attention. The guy who built it ran an 18cc gas conversion on it originally and it was way underpowered. He then tried a 25cc that flew the plane pretty good. With that said I would like a plane that flys really good with power to spare!

So I am building this SPAD using his plans but adding my own twist to accommodate a 50cc Powerplant!

This is the link to the original plans

http://www.instructables.com/id/8-Ft...-RC-Piper-Cub/


Old 01-02-2013, 04:28 PM
  #2  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Here are some pics of the fuse.

It's made of 1/4 inch birch plywood which is a little stronger than the 1/4 softwood plywood used in the original plans. I also doubled up the bottom gluing one piece in between the two walls and gluing the second spanning the two walls for extra rigidity and strength. I added a couple of extra braces around the firewall to fully box it in. The firewall was made by laminating three pieces of the 1/4 inch together ending up with 5/8th due to the 1/4 not really being 1/4. The original plan had just two laminated. The extra braces and thicker bottom were drilled to reduce weight as will be the center of the firewall once I mount the motor. I will probably put a 11/2 inch hole through it for fuel lines etc.
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Old 01-02-2013, 04:37 PM
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kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Here is the spar. It's built mostly to plan except I used 5/16th for the bottom cap and 3/8th for the web. After thinking about it I should have used the thinner piece for the web but its glued and done now.

I tested it for strength just out of curiosity and it held 184 pounds with ease as it is. It will be much stronger when in the wing as the coro will act as a top cap and further reinforce the bottom cap.
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Old 01-12-2013, 10:32 AM
  #4  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Update on the build:

I will post some pics of the progress I have made over the last week soon. I have made several changes to the original plans with regard to the tail feathers. I reshaped them and adjusted their dimensions to appear more cub like.

Some things to look forward to seeing on this SPAD build:

1. Fully rounded and tapered Clark-Y airfoil
2. Fully tapered control surfaces on the wing
3. Functional struts. Should add a nice scale look
Old 01-13-2013, 07:13 PM
  #5  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas



I was able to get the fuse mostly built. The tail feathers have been totally resized and shaped from the original plans. The original plans had non scale looking vertical and horizontal stabs. The length and width ratios were rather odd looking so I did my best to scale them out and shape them while adapting them to SPAD design . I also figured out the fuse length is a bit out of scale too. It's about 5 or so inches longer. I think this might actually make it a bit more stable on take off and maybe reduce some adverse yaw.
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Old 01-19-2013, 09:38 AM
  #6  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Build update:

A couple of parts I have ordered finally showed up.

52cc motor from china. I have one of these on my USS and it works great. The one I have just received has a black head but other than that looks identical to the one I bought 3 years ago. I plan to break it in on a 20x10 APC but not sure what I will end up using on the Cub I was thinking a 22x8 but will have to think on that. I would just test a bunch of props but they are not exactly cheap and the ones you don't like end up sitting around.

6 inch inflatable Durbo Tries. I really think these will look good on the Cub especially with the landing gear I plan to build. Using music wire and solder I plan to build a scale like set with springs in place of rubber bungee cords/O-rings.
Old 01-27-2013, 10:18 PM
  #7  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

I was able to get the tail gear built and the mains mostly done. I just have to saw the wood dowels off the tail gear once the glue drys and it will be Complete. The main gear still needs the rod and tube assembly that the bungee cords attach to soldered.

I decided to use rubber rather than springs. The 3/16 music wire on the mains is so stiff I am not sure the bungee assembly will do much of anything. I put 10 pounds in the fuse and dropped it from 12 inches to simulate a landing and it flexed maybe 1/2 an inch. The 6 inch tires take most of the shock, actually incredibly well!

The fuse is suprisingly stiff with the two formers installed. Overall I am quite happy with the way it's turning out so far.
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Old 01-29-2013, 05:55 AM
  #8  
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Default RE: Large Scale Cub Build 50cc Gas

Looking Sharp !!!
Old 01-29-2013, 11:24 PM
  #9  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Thanks Mustangman!

Here is a shot of the two formers. I decided to put two holes one on top and bottom to keep the center in tact so the shape acts like two cross braces, or an x shape.

I have mounted the motor and it feels like the balance/CG is off to a good start, nose heavy where the spar will cross. The aft portion of the wing and the three tail feather servos will add weight in the tail direction. I have room to mount the fuel tank over the CG and the RX battery and receiver can be used to fine tune.
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Old 02-03-2013, 08:58 PM
  #10  
kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

I have made some more progress on this build as well as finalizing my wing design which I will start next week.

I have finished the landing gear except for paint and bungee covers. I used 3/16 brass rod and brass tube that it slides into to create the rod and tube assembly. I used brass flat stock to make the brackets the rods attach to. I tested the suspension using rubber bands and it works perfectly, although I think it will work better with heavy o-rings. Once painted these will look really nice!

I decided I will go with a 106 inch wing made of all 2mil coro with 6 plywood ribs and a second small spar behind the main similar to the way the full sized is built. The cord will be 17 inches as this will make for an exact Clark-y with my spar height. It turns out a 25% super cub wing would be 16.5 inches cord wise so it's pretty close to scale. Another interesting measurement was the final length with the motor and prop mounted. It came to 67 3/4 inches exactly 25%. So as far as SPADs go this will be fairly scale!

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Old 02-06-2013, 09:43 AM
  #11  
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Default RE: Large Scale Cub Build 50cc Gas

That's some really nice detail on the gear. Looks like the whole plane is coming along nicely too.
Old 02-07-2013, 04:42 PM
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Default RE: Large Scale Cub Build 50cc Gas

+1 Keep up the good work. Capt,n ....in Aripeka Florida RV Park!
Old 02-07-2013, 05:18 PM
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kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Thanks Team Monkey and Capt,t!

I have made some more progress just need to take pics. I will post them this weekend.

I have the motor mounted as well started shaping the front end. I am looking for something to make the cowl out of and want it to look like a super cub over the J3.

I plan to start the wing this weekend and now am considering a two piece. I might use some kind of fiberglass or aluminum extendable paint pole for a wing tube. There does not seem to be a lot of information on suggested size, length etc for a given wing so I will just make my best guess
Old 02-10-2013, 06:29 PM
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Default RE: Large Scale Cub Build 50cc Gas

Made some progress on the wing over the weekend. I made some fiberglass sleeves for a fiberglass tube I found. The tube was from a yard tool and was cut to 30.5 inches. It's 1 3/16 OD and seems quite heavy. I might replace it at some point with something lighter, maybe CF. The sleeves were then attached to the spar using fiberglass wraps. The assembly is as sturdy as can be but the tube flexes a lot more than the spar did before it was cut. Once the wing is assembled it will flex a lot less as the end caps will but together.

8 wood ribs and two 4 mil coro ribs were cut out using a Clark Y template that is 16 7/8 cord wise. The second smaller spar that will sit behind the main ended up being a 1/4 inch by 3/4 inch strip of fir. It will finish the trailing edge of the wing and be what the controll surfaces will attach to. The ailerons and flaps will be made from the another peice 3/4 by 1/4 inch fir with a half round glued to it. 2mil coro will be bent in a triangle shape and glued to the fir to complete the fully tapered ailerons and flaps! Once finished I will post pics to show how its done.
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Old 02-10-2013, 09:32 PM
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kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Here are a couple of pics showing the motor mounted with the mostly done landing gear. I still need to make bungee covers and attach fairings. Oh yeah, paint of course!
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Old 02-13-2013, 09:48 PM
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Default RE: Large Scale Cub Build 50cc Gas

Just a small update.
I work full time so I really only have the weekends to get any real building done however I do sometimes get an hour or two in the evenings to get small things done.
I made a pair of bungee covers out of a black reusable shopping bag and a couple strips of Velcro. In the pic you can see how to sew them and how they attach with zip ties and Velcro. They cost next to nothing and are easy to make! They also look nicer then I expected they would.
This weekend I will get some better pictures in full light
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Old 02-16-2013, 04:05 PM
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Default RE: Large Scale Cub Build 50cc Gas

Everything's looking good!
Old 02-16-2013, 04:07 PM
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Default RE: Large Scale Cub Build 50cc Gas

Nice! Loving this build! Gonna re-visit my corocub build now!
Old 02-21-2013, 05:51 PM
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Default RE: Large Scale Cub Build 50cc Gas

Looking good. I built an 8' span delta outa coro with a 50 cc on the nose that flies good. This cub should fly nice. I just finished this 12' 1/3 scale cub outa blue foam:


http://www.youtube.com/watch?v=2Es6S...e_gdata_player
Old 02-21-2013, 09:16 PM
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kevstra22
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Default RE: Large Scale Cub Build 50cc Gas

Nice Foamy Disarray! I have a couple of questions for ya:

Did you do a two piece wing, and What is the all out weight?


My cub is coming along. My wing is almost done! I just have to pull the corro over the top and glue it down. Oh yeah and finish the flaps and ailerons. They are partly done and I think they will finish up real nice. This wing has taken a lot if time, I have close to 16 hours on it. A lot if time planning and waiting for glueo dry.

I am shooting for between 17 and 18 pounds flying weight. As it stands the fuse with motor is at 10 pounds and the wing is a 5.5 pounds. Believe it or not the 6inch tires add more than a pound, But I think it's worth it. My wing tube turned out to be 8.5 oz! This is my first two piece, but something tells me 8.5 is heavy


Old 02-22-2013, 02:16 AM
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Default RE: Large Scale Cub Build 50cc Gas

Yes, I did a two piece wing. I used 1" square aluminum tubing for the spar. The weight is about 17lbs. It is a real floater.

I find building with coro gets heavy, fast. I built a 16' Telemaster out of coro that wound up weighing 55lbs! And that was dry. Big problem I had was balance. The tail is so heavy I had to add 6lbs to the nose.
Old 02-22-2013, 10:09 AM
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Default RE: Large Scale Cub Build 50cc Gas

Disarray,

Do you have any pictures of the Telemaster? A 55 pound SPAD would be a site to see!
Old 02-24-2013, 08:48 PM
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Default RE: Large Scale Cub Build 50cc Gas

The wing is nearly complete.....Yes still nearly complete. This thing has taken way more time than I expected. I like the way it is coming along so far for the most part. The only thing I would like to have had turn out better would be the leading edge. It's got some imperfections in it. Slight ridges, which I will try to smooth out, formed while stretching the corro over the frame. I anticipated this but hoped my preparation would smooth the edge completely. I think with a little heat and some finesse I might be able to reduce the appearance. The top and bottom are glass smooth and its nice and ridged. It will finish out at just under 6 pounds which I think might keep me on my weight goal of matching a balsa 1/4 scale!
I still have to cut out the rounded tips and the aileron and flap slots.
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Old 03-17-2013, 05:41 PM
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Default RE: Large Scale Cub Build 50cc Gas

I have not been able to get as much done on the plane as I would have liked over the past couple of weeks but I have made some progress. I finished the ailerons and flaps and they came out pretty nice! The wings finished weight looks like its close to 6 and 1/2 pounds, not bad for a SPAD wing close to 9 feet long!
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Old 03-18-2013, 10:38 AM
  #25  
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Default RE: Large Scale Cub Build 50cc Gas

It's looking really nice Kev.  I usually get some kind of waves here and there whenever I build with 2mm.  I don't know if it's so thin that it gasses off when you put various glues on it, whether it's the heat in the field, or what.  Kind of an annoyance, but to use that over-used cliche, it is what it is, I guess.  Looking forward to seeing this thing put together and some flight video!

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