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Hobbico Hobbystar 60 rebuild (older version)

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Hobbico Hobbystar 60 rebuild (older version)

Old 02-13-2015, 05:26 PM
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Default Hobbico Hobbystar 60 rebuild (older version)

I have a Hobbystar 60 that I bought used from a club member at the beginning of 2014. I had previously build a GP PT-60 from a kit and, well, I figured I needed a sacrificial plane to endure my learning process.

The Hobbystar had the flat wing, wooden push rods, etc. This plane served me well through the summer. I moved on to pass my pilot test. And I was basically trying to get out each day, weather permitting, until the bitter (cold) end.

I made the mistake, on a great October Sunday, by saying I was a dead stick virgin. (What an idiot). My instructors had dealt with the motor cutting out, so I had seen this multiple times. I think the common expression I hear is you need altitude, speed or an idea.

So that day I got my first dead stick. I was out beyond the tree line avoiding some guys who were doing a first flight on a 3D plane. It was hard to hear my plane but I could tell the engine was fading and I did two things: started bringing it around and tried to get the engine to respond. Soon after the engine cut out. I had a nice line to the field when a tree flew up and into my plane.

The fuse was snapped ahead of the tailfeathers. The right wing side was confetti and the right stab was hit hard.



The reason why I thought to post this was for other beginners who want to rebuild a trainer. I would have just bought a new wing, but the shape (wing profile) changed in the new model and I didn't want to carve up the wing seating area on the fuse. I found just a couple threads for my particular plane.

If this helps someone, great.
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Last edited by BatteryBob; 02-15-2015 at 08:58 PM.
Old 02-14-2015, 09:21 AM
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I started working on the fuse first. With the tailfeathers completely severed, I needed to see if I could create a strong attachment and keep the fuse straight. I wasn't too worried about adding weight to the back since I already had several ounces of lead in the tail.

I made sure to take a picture of any assemblies before I started cutting things up. I needed to remove the stab/fin, but pay attention to the joints that were created in the back of the fuse. There were a lot of similarities to my PT-60, which of course helped.



The pic on the right gave me the relationship between the fin as it rests on the stab, a pretty common fitting method.

Luckily the guys at the field were extremely helpful retrieving pieces however small. At the time, I was thinking that the parts were so busted up that they were worthless. I didn't realize that while the parts may not go back in the plane, each helped me trace a new part. Now I know why some guys keep the left over balsa sheets that the cut parts in a kit came from - future stencils.



Now it became a process of piecing things back together, assessing the strength of the parts and looking for hidden cracks.
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Old 02-15-2015, 01:27 PM
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I brought the two side pieces together by aligning at the tail. I had scraps from the top and bottom that helped me maintain the right V shape at the tail. I was still concerned about twisting or bending of the fuse.



For the remaining missing section, I needed to make a cardboard part to test the fit.



I added a basswood spar to make sure the fuse had extra rigidity and help with alignment while I glued this in place. I used a steel rule to check for straightness and I created a simple jig to keep the fuse straight while everything set.
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Last edited by BatteryBob; 02-15-2015 at 08:57 PM.
Old 02-16-2015, 09:26 PM
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I had several splintered pieces from the bottom. I did a trial fit to see what I had vs. what I didn't have.



I went net to a local art store and picked up a sheet of heavy poster board. I traced the parts I had and used the mirror image on the side where tabs, etc were missing. From there, I cut out the cardboard part and did a trial fit before cutting balsa.



I did did the same for the top



Once again, it was real important to watch for any small twist as this would also affect the alignment between the wing and the rear unit. I filled in some of the glue joints with filler. I had not yet had experience with epoxy/glass fillers.
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Last edited by BatteryBob; 02-17-2015 at 10:35 AM. Reason: typos
Old 02-17-2015, 12:00 PM
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Next, I moved on to the fin and stab. I had the earlier pictures that showed me how they needed to insert back into the fuselage. The fin and rudder were unscathed. The stabilizer was a different story. The tips of the stab and fin had the blue molded plastic pieces attached All were in pretty bad shaped before I bought the plane, so it was one item I had planned to repair in the off season.



I started out by replacing the LE & TE. The tips were made by using one of the plastic tips as a template. I think there was plenty of room for error. The other side that survived looked to be in good shape, however, after a closer look, I found some hairline cracks in a couple of ribs and swapped those out.



I assembled the tailfeathers and after some extra sanding and filling, the surface was ready for covering. I did not have to do any type of repair work forward of the main wing. The FW and LG were strong, but I did take the opportunity to swap out the hardwood LG blocks.




Hopefully as good new. Now on to the wing.
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Old 02-19-2015, 07:34 PM
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The wing was in bad shape. I could tell when I bought the plane that one side was replaced from an earlier crash. The new side was now blown away and I could see the repair approach. I had built a GP PT-60 and figure creating a new side would not be too hard. But I was hoping to get the plane back to the field before snow started flying.

I have a few picks of the remaining wing.



A thick piece of poly was used as the wing joiner. The Hobbistar wing design has a I beam spar where the top and bottom spar pieces are glued up against the sheer web. In the PT-60, it's a T&G design so very similar. I had enough to rough out the rib design. The rib profile has little change to it from root to tip, except to accommodate sheeting, etc.

The more and more I tore into the remaining wing, the more problems I found. I removed the covering from the good side



This was pretty old balsa that had been rocked by a crash. The ribs had already crumbled, and what was left was equally weak.

I gave age up on the idea of using this. I turned to some club members to see if anyone had a extra wing laying around. One of the guys did, but it turned out that the wing saddle area on the fuse was for a straight flat bottom wing. The dimension of the wing had changed slightly in the new version. So it was close, but no.... We had a local swap meet that weekend. I looked all over, but nothing old to match.

I thought I had a brilliant idea to get the wing parts from GP, but that would not be very cost effective. I decided to build a wing from scratch.
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Old 02-24-2015, 07:51 PM
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I found some useful templates from my PT-60 Kit. I was able to cut patterns from the cutaway views on the plans for inboard and outboard ribs. There were also an interior rib pattern that contains the servo pocket that was important.



The other key template was for the ply wing half joiners. I used the flatter dihedral.



I cut each rib by hand. I did not have a set up for cutting several at a time which would have been nice to keep them uniform. But I also checked the ribs against the master template and each other. You'll notice that I needed to create the interlocking slots for the shear web and spars.

The other parts were for the wing tip (no plastic tip), ply leading and trailing wing joint reinforcement parts, and trailing edge plate. I needed to adjust the length of the center trailing edge section to match the wing saddle in the fuse.
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Old 02-25-2015, 05:48 PM
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I used my plans from the PT-60 as a rough guide. I took the rib spacing from the half of the wing I had. I used square stock balsa for the LE & TE. The PT-60 used a solid TE but the Hobbistar has a built up TE, which is what I reproduced.

I used the same ply joining system that you find in the PT-60. Ply is used on the LE and TE. The I-beam section has a sandwich made up of one ply dihedral former, a ply spacer, the wing I-beam, followed by a spacer and the second dihedral former.

Here's section -


I taped off the ribs, added the tips and shaped with a sanding block



After sheeting



One key key step was getting the trailing edge center section plus the ply reinforcement plate to fit the existing fuselage. All that's needed is covering

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Old 02-27-2015, 11:09 PM
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Good job Bob. I have one of these that I use for training new pilots on a buddy box. It's a great trainer no doubt.

Frank
Old 03-02-2015, 08:50 PM
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I agree Frank. I learned on a buddy box with this plane. I finished it up and have it ready for Spring. I plan to use this plane for the first couple of months of flying, to get the rust off, and then it will be time to pass this on to the next pilot in training.

here are some of the finishing shots. This is my second plane with monokote, so I try to experiment to learn better technique. Back when I was a kid, it was all silks pan and dope. So much has changed.

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Old 03-03-2015, 06:50 AM
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Nice covering job Bob

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