Willy Nilles Tiger 250 Build

[speedbirdted]

Merry early Christmas to me, I guess.

I had a Goldberg Tiger a while ago and loved it, so why not get one of these. Hopefully I will have enough time to put this together before semester break ends for me in 2 more weeks. I don't anticipate much of anything crazy here in terms of mods but I think I'm going to at least try to add a steerable nose wheel which shouldn't be too hard to implement. I also forgot to buy wheels so I get to lathe those out of foam too.

I'm also going to try to cover it in Polyspan which is something I've never used before, but from the little bit of experimentation I did with it today I actually quite like it. It has properties of both fabric and tissue type materials, because that's really what it is - basically just polyester tissue.

I decided it would be a good idea to experiment a bit to see what can be done with it so I made like a dozen of these 2x2 inch square test pieces out of 3/16 stick and coated them in a bunch of random adhesives I had lying around in my house, just to see what could be used. I got the best results understandably from coating the base wood with nitrate dope and then going over the polyspan with thinner and more dope to secure it to the wood, but my supply of dope is limited and it's far too smelly for my liking. Same with Balsarite which smells a little better but I also don't have very much of it.

However, I made a very surprising discovery: Titebond works incredibly well, almost like Balsarite. I found if I brushed un-thinned Titebond onto the wood pieces to be covered, and then ironed the polyspan on, it re-activated the adhesive and tacked the polyspan down. From there I could shrink it and then brush more Titebond onto the polyspan where it was adhered with heat, and then seal the rest of the polyspan weave with Titebond thinned 50/50 with water. The straight Titebond applied to where the polyspan was adhered makes it incredibly hard to pull off, and it lets you feather the covering edges together nicely. My concern with this though is it took a lot of coats of thinned Titebond to completely fill the weave of even the tiny test patch I used and I'm concerned that this may add up quickly in terms of airframe weight. I'm curious if something like Polycrilic would do a better job to seal the weave and I'll try it at some point down the line.

I'm also probably going to paint it with latex now that I understand it a bit better. I'm wondering if even sealing the weave fully is even necessary as latex can do this to a small degree on fabric but I don't know how it works with polyspan. Another thing to test...

 

[JetCrafts]

cool
never seen an electric balsa

 

[Merv]

....I brushed un-thinned Titebond onto the wood pieces to be covered, and then ironed the polyspan on, it re-activated the adhesive and tacked the polyspan down.......

Plain old white glue will also reactivate with heat.

 

[Ketchup]

Looking forward to seeing the rest of the build! Are you building the clipped wing version or the full size?

 

[speedbirdted]

Plain old white glue will also reactivate with heat.

Interesting you say that as I tried Elmer's glue (which I think is the same as white glue) and while it did work the adhesion was pretty poor. Titebond is far superior though maybe I wasn't using the right kind of white glue?

Looking forward to seeing the rest of the build! Are you building the clipped wing version or the full size?

Full wing. I did think about clipping a bay off the wing on both sides though, but the thing I liked about my full size Tiger was how good it was at doing aerobatics in slow motion because it has a bunch of wing. This being small it won't do that quite as well and especially not with less wing.

In other words: we have a fuselage. I had to use the non-drilled firewall because I bought a Tee Dee mount and the bolt holes for that weren't included, but it's no big deal. I'm going to be building this with two hatches instead of gluing the one that covers the ESC compartment on. The one for the battery compartment has magnets while the one for the ESC doesn't as it doesn't need to be opened nearly as often (hopefully)

I also fully sheeted the cockpit area as without it the gaps looked a little weird.

I had to get a bit creative concerning the servo mounting in the fuselage. I think the intended servos here are a little smaller, as I tried to use the 4.4g ones and they didn't fit under the cockpit sheeting. So, I had to add a 3/16 inch spacer as well as move them backwards about 1/8 inch which necessitated cutting rearward extensions in the servo holes as well. But - the servos now fit perfectly. I had to drill some additional holes in the plate that holds the nut for the wing bolt to get to the rear screws holding the servos in, as I want to be able to take them back out if I need to...

 

[Merv]

...I tried Elmer's glue (which I think is the same as white glue) and while it did work the adhesion was pretty poor. Titebond is far superior.....

Good to know Titebond works better than Elmer’s.

I’ve also use the hit it with a hot iron trick to reactivate contact adhesive.

 

[Tench745]

I'm curious if something like 3M's Fastbond would be good for Polyspan. I know they use it for applying fabric on full scale aircraft. (Same stuff as Stewart Systems' Eko Bond)

 

[speedbirdted]

I'm curious if something like 3M's Fastbond would be good for Polyspan. I know they use it for applying fabric on full scale aircraft. (Same stuff as Stewart Systems' Eko Bond)

Another thing to try. I have a million more ideas for things to try both for adhesion and sealing. I'm even thinking of trying sanding sealer on the fully sheeted areas of this plane to prevent having to cover them, and maybe even on the polyspan too.

Today I sat down to think about how to put a steerable nosewheel in this bird. My initial idea was to print a bracket to put the wire in and another little nosewheel arm, but my printer is far from either operation or existence so that idea was trashed pretty fast. I ended up putting a brass tube in the fuselage secured to the bottom sheeting and a little triangular brace I added to fill the gap in between it and the firewall. I added about 5 degrees of rearward rake to the nose leg. That will make the ground handling a bit more predictable, as I know the steering mechanism isn't going to be 100% play free.

My only concern with this idea is the bottom sheet it's secured to may be a bit weak and end up splintering. Maybe I'll pull it out and replace it with basswood, or add some gussets or something..

The steering arm also had to be custom made. I made it by taking a little hardwood block and drilling some holes in it for the nose leg to go through, and also for a screw filed flat on one end to key into a flat spot on the nose leg. It's the exact same practice used on bigger airplanes and when soaked in thin CA the wood is more than strong enough. The arm itself was made out of a servo horn that I cut and sanded down. I was originally going to make it out of 1/32 plywood but trying to cut a tiny control horn out of it was causing my blood pressure to go into the megapascal range and I gave up...

Next comes the wing as the fuselage has had everything I can do to it for now pretty much done.

 

[speedbirdted]

Wing was put together today. Went mostly smoothly but there were a few fit and finish issues here and there which I'd consider atypical for Willy Nillies kits. Most severely the dihedral brace does not fit correctly between the spars, and is not long enough to butt up against the ribs tightly enough to be secured with thin CA. I got around this problem by cutting out some 1/32 shims and splitting the center ribs in two pieces so the dihedral brace can be secured flush with the top spar and the shims can be glued in below it. I think this will be just as strong.

Also... I think I might have also somehow gotten then wing sheeting from a different kit. There's holes for servo wires in the wing bottom sheeting and I don't exactly see why there's any reason for them to be there as the aileron servo wires will exit from the top of the wing. I just glued them in place and will go over them with filler to make them flush. The sheeting was also a bit on the long side and had to be cut down, which is what makes me think it's from a different kit...

This kit comes standard with a bolt-and-peg wing, which I like, but the peg installation stumped me for a bit. It took me a while to realize there's a weird plywood piece included in the kit that both holds the peg and keys into the front of the wing. When sanded down it actually works pretty well. I cut the sheeting back a little too far and had to fill the gaps with some scrap balsa, but overall I like how it came out.

Did the string trick to get the wing mounted straight and sanded the tail bed slightly to get the tail sitting straight, and everything's framed up. Next steps are to add filler to seams and tab holes in the fuse and wing and other preparations to put the covering on.

I don't think I'll bother with the shear webs. The spars here are pretty hard balsa and none of the other WN planes I've built have had them and they all do just fine...

I really wish I could go into more detail on this but these kits just go together so quickly...

 

[speedbirdted]

Time to make wheels. I considered using foam but I think that the wheels would not hold up well even if I coated them in something so instead I used balsa. I used to use a drill press to do this but the dremel is so much better and that's all I use now really. I think this might also be the first time I've ever managed to make three good wheels without screwing up at least one (well technically I screwed up the first one by sanding it too much but I just made that one the nosewheel since it needs to be smaller anyway) I cut the threads with a screwdriver as the x-acto blade was too narrow.

I will paint them but I coated them with polyester resin beforehand to make them a bit more durable.

Test mounted - they seem good, and I think the angle the plane sits on the ground is fine.

Also started playing with the covering a bit. The more I play around with this polyspan stuff the more I like it. I figured a good place to start was the wingtips since they are often among the most tedious areas to cover on a wing. The polyspan works great. It shrinks much more than either tissue or plastic films. I didn't expect this either but you can actually use a heat gun on it, at a very low temperature setting and if you be very careful not to get any section too hot - you can over-shrink it, and that usually results in the weave pulling apart perpendicular to the grain. My experimental technique of applying Titebond to the bare airframe and then brushing more over to secure it seems to work well.

I also really like how the seams can be feathered very well with 600 grit paper. It's nearly invisible even with the weave not yet sealed.

 

[speedbirdted]

For the most part the covering is done. I didn't cover the top and bottom sheeting as those are solid and don't need it, as are the hatches. Instead I just went over those with sanding sealer. I think I'll do the same to the ailerons since they're also solid but I'm concerned this may warp them some so some jigging might be needed. Tail isn't glued on either - the bit where it sits had a slight glue overrun that I forgot to get rid of so it sat a little crooked here.

I took that pic before getting around to feathering any of the edges together but I just did that later. I think from here I'll spray some Polycrilic to seal the weave and then maybe some primer to show what areas might need a little more work. I'll definitely put together some more test pieces to see what works best here.

I also need to think of a color scheme...

 

[Bo123]

I also need to think of a color scheme...

Mainly Blue with Yellow Trim.

 

[speedbirdted]

Mainly Blue with Yellow Trim.

That route's been gone down for me already I was thinking something orange or red mainly with white accents. I've also got the luxury of any color I want so I could also try something with more colors. I had some four and five color schemes thought up but once I tried them out in Photoshop they all looked terrible so I'll have to think more on that front...

 

[Mr.Grinch]

I think I’d have to go this route for the color scheme. Maybe I’ll have to get one for myself and do just that.

 

[Bricks]

Another option for sealing the balsa before covering and quicker is spray the wood with clear Lacquer or hair spray same thing. Light sand to knock down the balsa fibers that stand up and cover.

 

[speedbirdted]

Another option for sealing the balsa before covering and quicker is spray the wood with clear Lacquer or hair spray same thing. Light sand to knock down the balsa fibers that stand up and cover.

The bare balsa is not going to be covered. I'm just going to paint it. That's why I used the sanding sealer as I figured it would work pretty well to get a smooth finish. Will lacquer also help with that?

 

[Timmy]

Balsa builds look so rewarding.

 

[Ligbaer]

Balsa builds look so rewarding.

agreed

 

[Bricks]

The bare balsa is not going to be covered. I'm just going to paint it. That's why I used the sanding sealer as I figured it would work pretty well to get a smooth finish. Will lacquer also help with that?

Lacquer is very thin it really will not fill the balsa but it is so light when dry it`s like you put nothing on at all. You maybe could use it as a filler but would take so many coats there are better options, but hard to beat the lightness of it when dry under covering.

 

[speedbirdted]

I started spraying Polycrilic today. The nice thing about it is it sprays really well. You only have to thin it with distilled water at about a 10:1 ratio and then it sprays just fine.

This is after two light coats on everything. Polyspan when dry sands awfully as do most fabrics; when you put Polycrilic on it, a lot of fuzzies pop up but they can be sanded off. I think I will wait to feather all covering edges until I get more polycrilic sprayed on. I need to sand everything first.

One thing I did not anticipate about this Polyspan stuff is just how rough it is. You need a lot of filler to seal the weave up; just look at how rough the surface of the wing is right now.

Don't be surprised if this build slows down a hell of a lot in the near future as school has started up for me again...