Thunder Tiger Trainer – Repair, Refurbish and Conversion to Electric Power

[CheapSunglasses]

I examined the horizontal stabilizer and the damage is worse than I thought. I discovered that the elevator is cracked in half. I was hoping that I could leave the horizontal stab trailing edge, elevator and hinges intact but it looks like I’ll be replacing them. The existing control surfaces appear to have small pin type hinges. I was thinking about using Dubro nylon hinges in the new elevator…if so, should I use the small or standard size?...or should I just go with CA hinges in the new elevator?

Remnants of horizontal stabilizer showing existing pin hinge.

 

[Joker 53150]

eBay auctions have ended. I paid the craigslist seller $30 for the plane and I made $20 for selling the parts on eBay. I didn't cover the cost of the plane but I do feel better about not throwing parts away that others will use.

That still turns a good deal into a great deal, and also gives somebody else a chance to use the parts you don't want.

 

[Joker 53150]

I examined the horizontal stabilizer and the damage is worse than I thought. I discovered that the elevator is cracked in half. I was hoping that I could leave the horizontal stab trailing edge, elevator and hinges intact but it looks like I’ll be replacing them. The existing control surfaces appear to have small pin type hinges. I was thinking about using Dubro nylon hinges in the new elevator…if so, should I use the small or standard size?...or should I just go with CA hinges in the new elevator?

Remnants of horizontal stabilizer showing existing pin hinge.
View attachment 86900

I don't know how big that stabilizer is, but it doesn't look huge. You can probably use just about anything you like - nylon, pin, or CA. Personally, I don't like the CA hinges except on the very thin surfaces, as they have more resistance to movement which creates more work for the servo. On the thin surfaces I use them simply because they are very thin and don't split the wood.

If you're only fixing one side I'd try and match what is currently there, for no other reason than it would just match left to right. You absolutely CAN mix & match hinges from side to side - the way it looks just bugs me so I don't do it.

 

[CheapSunglasses]

I purchased a box of various new and used RC airplane parts (servos, esc’s, electric motors and electric props) from a gentleman who is getting out of the hobby for health reasons. From that box of parts, I plan to use a new 45mm x 50mm 600kv generic motor and APC 12x8E props on this project. I did some preliminary input into eCalc and these components should work with a 60A ESC and a 5S LiPo for this plane. The box also contained a used Spektrum AR400 receiver which I plan on using in this plane with my Spektrum DX5e transmitter.

Acquired components

 

[CheapSunglasses]

From what I can tell this plane once had a plastic cowl that was screwed to the fuselage. I did an internet search and could not find a replacement cowl available so I’ll just have to live without one. The box of parts that I acquired also contained a mount for the electric motor. Since I won’t have a cowl, I think I can just screw the motor directly to the firewall and not use this mount…unless the motor needs to be extended forward for CG or some other aerodynamic purpose.

Mount that came with electric motor. Do I need to install this?

 

[Joker 53150]

I assume the existing firewall is plywood, as it handled the forces created by a nitro engine. If it can handle nitro it can easily handle electric. The motor could be mounted directly to the firewall or you could make a box to push it farther forward, which might be good for your CG. I've done the conversion a few times and normally just build a 5-sided ply box to get the prop as far forward with the electric motor as it was with the previous nitro. So far so good!

 

[roversgonemad]

I think you'll want it forward for CG purposes. I'd probably use that mount if your motor will fit the mount.

 

[CheapSunglasses]

I have no experience with balsa scratch building so I’m pondering how to repair the horizontal stabilizer. I don’t think that I can recreate a replacement balsa stick horizontal stabilizer from scratch that would be strong enough. So, I’m considering sheeting both sides of the horizontal stabilizer. If I use sheeting I think I can rebuild the missing side to be straight and strong enough. The sheeting would add weight but I don’t know if it would be enough additional weight to be a problem. I’m open for advice and suggestions on how I should repair.

Top of horizontal stabilizer with broken pieces and covering removed.

 

[Joker 53150]

I'd try and rebuild it as it was. If you can remove it first the work is easier. Sheeting could work but adds weight. Maybe splice in a little CF if needed for strength.

 

[CheapSunglasses]

I'd try and rebuild it as it was. If you can remove it first the work is easier. Sheeting could work but adds weight. Maybe splice in a little CF if needed for strength.

Yea, I'm not sure what is going to happen with the area between the fuselage and the vertical stabilizer if I start trying to remove it. I don't know if I can remove the existing piece clean enough so that I get a good fit and bond when I install a new piece of wood.

If I sheet the bottom of both sides it would add approximately 1 oz. If I do top and bottom of both sides it would add 2 oz. Is that too much weight? Doesn't seem like much in the grand scheme of things but I guess it is the location of the additional weight that matters.

 

[Joker 53150]

Correct, you're addding weight in the worst area for most planes since it will take much more than that to even it out.

 

[CheapSunglasses]

Life got busy and it has been a couple of weeks since I’ve posted anything but I’ve been occasionally working on the plane when I have time to spare. The firewall was separating from the bottom of the fuselage so I reinforced it by applying Titebond and clamping it down until dry. The nose gear was rusty and the steering arm was broken in two pieces so I decided to install a new Dubro nose gear assembly. The existing setup had the nose gear control rod exiting from the bottom of the fuselage. I’m changing it so that the control rod will now exit thru the firewall to work with the new Dubro nose gear. I installed a new 3” Dubro Super Lite wheel on the nose gear to match the wheels on the main landing gear. The ElectriFly motor mount I mentioned in a previous post will not work. It does not match the existing bolt hole pattern in the firewall or the hole pattern of the new motor. I attempted to mount the motor directly to the firewall but discovered that the new nose gear is now an obstruction. I decided to use 1” aluminum spacers to mount the motor off the firewall. The spacers keep the motor from interfering with the new nose gear and puts the prop close to the original location. I didn’t think the firewall had a thrust angle but I can see it now that the motor is installed. I put a band of white electrical tape around the fuselage at the firewall to hold down the peeling covering and hide the holes where the cowl was screwed down. I hope that this plane flies well because it is not pretty with a missing cowl.

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