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Supporting Owners, Builders and Pilots of the Thorp T-18 and its variants.
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Andrew
 Post subject: Plans 491 Build
PostPosted: Fri Aug 26, 2022 8:04 pm 
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I bought plans set 491 and a partially built fuselage and empennage about 22 years ago. I did a fair amount of work on it and got the wings built and then kids, life, a divorce, and job changes all got in the way or progress.
My project is now going to be the subject of Saturday morning work for the EAA 690 Youth builds. I'll be posting photos and updates.

I had a complete O-290 converted GPU and the ex sold or threw away the jugs. OTOH, I have an O-320 dynafocal mount. So I need either an O-320 that can be installed (if it has enough hours left on it) or rebuilt, or I'm going to need some O-290 pieces, like the jugs, pistons, and rods. Either way, we have some mentors that are good with doing engine work.
So if anyone has an engine or parts that they would like to sell or donate (tax deductible), please let me know.

I also have the rod type tail spring and bracket, but now can't find a tailwheel for sale anywhere. Does anyone have one they would like to sell? And thoughts on the 4" vs the 6"? I figure the 6" is probably better for turf runways or paved expansion joints, but I welcome comments based on experience.

As for the "ADs", I believe they have been accounted for. A prior builder did the horz tail, but I drilled out a rivet to confirm the extra tubing in the spar, plus I pulled off one of the tips and probed with a wire to confirm how far it extended. I also confirmed the tip weights have been installed. And the stainless strips in the elevator tabs, and the fuselage doubler. I recall making sure I addressed all the known "ADs" when I first got the project.

The prior owner had the main center wing spar machined and I built the center wing with the Sunderland airfoil. I also rebuilt the outer wings to the same airfoil. Ailerons, flaps, vert fin and rudder are all built, so this will be largely and assembly and systems project.

I have wingtips that I made at Bill Williams house. (Yes, I was the guy who took the molds home with me to finish the wingtips and made sure to get them to Bill's brother before they got entangled in the divorce mess.) So I guess we can see if one of the kids wants to try their hand at fiberglass, but if anyone has some tips they want to sell, please let me know.

Likewise, I have cowling pieces, but if anyone has a complete cowl, I could be open to that.

So while this will be used for our youth education, I'm not getting younger and I'd really like to get it in the air within a year.
I'll be flying only VFR, so if anyone has older avionics they'd like to sell cheap, let me know.

Andrew
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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Sat Aug 27, 2022 8:40 pm 
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First build session went well enough. I had ordered some small sheets of micarta and some delrin plastic, or something close to it.
The delrin was used to make a forward bump stop for the elevator/aileron beam. The micarta was used to make the rudder cable guides.
Why work on that to start? One team of mentor and kids could be cutting out the plastic while another worked with me on the elevator trim.

We also laid out where slots need to be in the sides of the fuselage for the rudder cables. At the end of the day, we temporarily put the vert fin and rudder in place and put a ruler on the line for the cable slots and it extended right to the rudder horns. Success.
Next session, we'll put the guides on the milling machine and mill the slots.

The elevator brackets had been painted but showed hints of corrosion or maybe just grime, but we pulled them out and had the kids wire brush them to bare metal and give them a good coat of zinc chromate. As I started to look at the elevator trim, I pulled the steel control arm out, had the kids wire brush it as well, and we hit it with a coat of self-etching primer and paint. What is hard to see in the photo is painters tape covering where the bearing blocks are. I also didn't like the plain nuts holding the trim system on and didn't like the idea of them vibrating loose. However, when I went to remove the first one, I discovered the prior builder had put the nuts on with either Locktite or glue. Either way, they'll get replaced with proper locking nuts.

The control stop guide was also installed. Having it in place means no binding of the spherical joints if anyone goes full forward with the control sticks (and they will). We have a crew that will be building a large work table, upon which we can put the center wing and outer wings and get all of that assembled and adjusted before it gets mounted to the airplane. As for the wingtips that I made 12 years ago, it looks like they have sustained damage and aren't worth messing with. I'll be looking to buy a set.

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MartyG
 Post subject: Re: Plans 491 Build
PostPosted: Mon Aug 29, 2022 9:09 am 
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Location: Y51 - Viroqua, WI
Kudos to you for getting the project going with your chapter. I'm the president of my local chapter and we are finally getting organized and getting enough momentum that we could possible take on a building project, so I'm interested to see how yours progresses. Good luck and keep us posted!

Also, I have a box of instruments that I'm looking to sell, let me know what you need and maybe we can come up with something.

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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Mon Aug 29, 2022 1:17 pm 
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I had been leading a BD-6 build with a kit donated by the Bede foundation. We got the fuselage and part of the tail built, and then parts kits dried up. We've discussed trying to just buy the remaining kits and finishing it and selling the completed airplane.

With that in limbo, I took a break and the chapter took in a Zenith 601 that had (I think) a nose gear collapse. The mentors and kids have spent the past year getting it repaired and reassembled and it will soon be out the door, thus they were looking for a next project and I figured my T-18 will fit the bill. It's far enough along that it already looks like an airplane, so we won't spend months on making a loose collection of parts. While most of us can see how those parts will become an airplane one day, I like the idea of the kids seeing something more before they lose interest or age out of the program.

Maybe see if you can find a partial project or an aircraft that needs restoration is my 2-cents worth.
We also had an engine guy, so we had some kids rebuild an old Continental, and then they ran it on a test stand that was built as part of welding instruction and practice. It's amazing how many kids haven't really seen an engine, much less the inner workings of one. My own son was far from enthusiastic about being dragged out to the education hangar with me, but he'd get very involved in the engine work and be engaged with that for a few hours.

I can say that just off the top of my head, we have a couple of kids that went into military aviation, one who got his A&P and is now with an airline, and a number that have gone to college for aerospace and aviation-related degrees. So a fair amount of success IMHO.

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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Fri Sep 16, 2022 10:00 pm 
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Two of the kids worked with a former student who is now one of our mentors on machining the grooves in the micarta strips for the rudder cable slot, plus two pieces that will be used where the rudder cables go through the aft bulkhead. One set of guides is pictured, waiting for attach holes.

Another student worked with me to pull the top of the turtledeck off. We had to drill out two rivets where the canopy track had been riveted into place, which attached it to the top of the bulkhead that is the back of the cargo bay. We prepared the elevator trim mechanism to be reinstalled, then I realized that I had not procured replacement screws and lock nuts for the trim mechanism and really need to get those fasteners installed before we put the trim pivot arms back into place. (The mechanism had been installed with flat nuts and some sort of glue. Not acceptable). There was a lot of inspection of the fuselage to see just what the prior builder did and did not do and to see if we can begin driving rivets into the clecoed holes.

I also started thinking about the main spar closeout on the bottom of the fuselage. The brakes pedals are on a floor pan that will screw into the bottom of the fuselage via a host of nutplates. But what about the gap under the fuselage where the spar goes? (And it may be in the plans, I just haven't gone back out to the truck to go through them.)

Another question for the gang: just how much difference is there in takeoff and climb performance between the O-290 and an O-320? We have a possible O-290 at the hangar and another one that I know about. So I have an O-320 engine mount but no engine, or use the O-290 and fab an engine mount. I don't know that I'll be doing enough cross country work to worry about a few knots of top end if I go with the O-290, but I can see wanting to fly in and out of turf strips here and there, which makes me wonder about the O-320. I welcome any feedback.

And if the photos load, you can see that my fuselage has a battery box located just aft of the luggage bay. Is this a typical location? If so, do you guys access through the luggage compartment? I don't recall seeing an access door in the side of the fuselage of the Thorps I've seen.

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Ryan Allen
 Post subject: Re: Plans 491 Build
PostPosted: Sat Sep 17, 2022 7:54 am 
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my battery box is in that location for W&B considerations. I crawl into the fuselage when its time to install a new battery.


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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Sat Sep 17, 2022 10:00 pm 
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Good to know. Thank you


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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Wed Oct 26, 2022 8:47 am 
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Been making slow progress. It has been a combination of trying to figure out if there was a good reason for the prior builder to leave holes cleco-ed instead of riveted, and making forward progress. Plus teaching the kids how to do stuff while trying to get work done. At this point, we have the passenger seat attachments done (and as a bonus, had the kids standing inside the fuselage instead of me....), micarta cable guides for the rudder cables, and the elevator trim stuff lubed and reinstalled correctly. Doesn't sound like much, but trying to teach kids slows things down. We did some riveting practice, but we are nowhere close to me feeling comfortable with them riveting on the airplane.
I bought some parts home to work on them, and started with cutting out a baggage area opening on the top of the aft deck. I used a combination of hole saw, snips, and tile knife and was pleased with the results.

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fytrplt
 Post subject: Re: Plans 491 Build
PostPosted: Wed Oct 26, 2022 3:52 pm 
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Don't forget to "triangulate" the seatback area. With the cutout, it will not stand up to people using it to get in and out of the airplane.

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James Grahn
 Post subject: Re: Plans 491 Build
PostPosted: Wed Oct 26, 2022 6:11 pm 
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That must have a flange on it for strength!
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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Thu Oct 27, 2022 6:36 pm 
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Oh yeah, I'll definitely reinforce the opening. (Did quite a few years of structures design in my prior careers).

I have some parts where I want to go ahead and put some paint on them. Any suggestions for a good paint or paint brand?


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Andrew
 Post subject: Re: Plans 491 Build
PostPosted: Sun Nov 20, 2022 10:28 am 
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Back at the hangar with the youth build yesterday, making some progress. Got the vertical fin fitted up and hung the rudder. The prior builder had wallowed out the upper two bolt holes for the vert fin until he could get the bolts to go through (cue me cursing loudly in my head), so I had to do some rework for clean round holes. I just didn't like the idea of the upper holes allowing side-to-side movement...
And fitting up the rudder told us that the left side fuselage skin needs to be trimmed just a bit for clearance.

We also managed to get the pilot's seat brackets aligned, drilled, and ready for installation. It doesn't sound like much, but progress can be slow with the kids. In a parallel effort, there is a crew building the big metal workbench that was in a past issue of either Kitplanes or Sport Aviation. Once it is complete, we'll have a surface for getting the wings, wingtips, and such completed.

We have an O-290 (a D, I think. Need to confirm) that we boroscoped yesterday. It looks good inside, so thinking we have a powerplant. Anyone happen to have an O-290 engine mount they would like to sell?

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