Balsa bashing

[Brian Seymour]

Sweet! It won't take long to get past where I am, I spend too long pontificating and fussing - actual building time so far is probably closer to minutes than hours.

 

The elevators were built from stuff that I've got kicking around. I traced round the supplied elevators though, the main planks are 1/8" hard balsa glued to a medium hard 1/4" sq. strip (cut from a plank rather than being bought as strip) and the ribs are 1/16" thick hard balsa cut into 1/8" wide strips. The build seems to be blessed (fingers crossed) I used CA for the elevators and managed to stick the components together rather than my usual trick of gluing them to my fingers - an good omen if there was one!

I'll be making the rudder in the same way and take some photo's at the various stages.

Retract-wise, I think that Graham had these:- https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=37225

I'll be giving them a go.

 

Edited By Brian Seymour on 30/01/2016 16:03:51

[Jon H]

Looks great Guy.

I have made massive progress, just look!

A tidy bench, with a twin pulse wing lurking in the background

[Guy Pickett-Jones]

I will be going with this colour scheme - so officially a YAK 3

Once settling on doing the YAK, and with a bit of quick research, once I'd seen the scheme's with the red noses I knew I would have to go with one of the variations!!

There appears to be one with camouflage scheme as well

[Brian Seymour]

I feel like the days of seeing my bench are a long way off so top job.

The colour schemes look ace the red noses are pretty sweet.

I feel as though I have under achieved this weekend, no flying and little more than a tailplane to show for it. I got the rudder made and sanded. I also clad the fin with very light 1/16" sheet so that I could make the rudder thicker so that it would be more rigid, the rudder & fin have come out 10g heavier than the supplied parts - possibly a bit extravagant but it looks good. I also couldn't resist adding the balance tabs to the elevators but haven't gut the recesses in the tailplane yet..

I made rudder slightly differently to the elevators, I made the main sail with the ribs as a sub assembly and glued them to the rudder post. I used aliphatic for gluing the ribs to the sail and epoxy with milled carbon to glue the rudder post on, the weight of the glue came out less than a gram which was just as well considering how much wood I added.

I also got the tail section dry assembled:-

[Jon H]

Guy, that lower paint job with the 2 tone grey looks great. You could do a real nice soft edged airbrushed camo job on it which would look sweet. I might even have a splash of dark grey you could use.

Brian, i love the tail, it looks superb and a big improvement in scale terms over the kit. Clearly the kit was intended for sport scale so its not a fault of the kit, but it shows nicely how a little touch makes a big difference. Also for 10g at the back i would not be worried. even with a fore/aft of cg ratio of 1:5 you are only adding 60g to the total weight of the model, and i think the ratio is more favorable on the yak anyway.

As for progress i am also a bit annoyed i didnt get more done. Tidying up took forever and i was about to get stuck into building the tail when i noticed that the 1/16 sheet i took from my wood stock was really damp from being in the shed over winter so i thought it best to dry it out before i built anything from it. Given how damp my shed is at the moment i may have to hold fire until the weather perks up a touch

[Guy Pickett-Jones]

Quick update of what got done over the weekend

Fuselage in jig during first part of gluing together - it has now been glued to the tail but didn't get a photo.

Taking inspiration from Brian have also made new elevators with ribs.

How much it will help but have glued a thin strip of carbon to the trailing edge. 2 x 0.3mm.

Have also added the balancing tabs - just need to sand the leading edge now.

Will do the same for the Rudder - whether to make in thicker like Brian's I will have to see!

Jon, Will be in touch about paint - thanks for the offer.

[Brian Seymour]

Not a vast amount of progress, I have re-worked to profiles of the fin and rudder but I reckon that I'll see about laying the hinge line at more of a forward sweep than I have got it at the moment. I laid a photo of the fin and rudder over a photo of a scale drawing and reckon that the hinge line is ~10mm further forward at the top and ~6mm back at the bottom.

Here are photos of the re-worked fin and rudder:-

 

Taking inspiration from Guy, I added the balance tabs to the elevators and got one of them hinged. For the hinges I'm using Robart style hinges. It was a bit fiddly drilling the holes in the elevator, they are made from 1/8" thick balsa and the hinges require a 2.5mm dia hole which hasn't left much wall thickness - to be honest what was more surprising was that I didn't burst the holes through the elevator skins. I'll add postage stamp size pieces of glass cloth over the area's that the hinges are in to give them a bit of strength.

In the hope of reducing weight, I started making a built up tailplane but stopped once the weight of the components got close to the weight of the kit supplied solid balsa one.

I am still pontificating over snakes or push rods for the elevators but reckon that I'll get the turtle deck glued on in the meantime as any clearance needed in the crutch plate can be made from underneath.

 

Edited By Brian Seymour on 03/02/2016 13:51:44

Edited By Brian Seymour on 03/02/2016 14:07:28

[Jon H]

I love the balance tabs, they look great!

I hope to commence this weekend. I was going to work on it this week but have been occupied with the club meeting, a funeral, pc problems and tomorrow an apt with a friend. Friday I am with another friend and then Saturday....all is well

[Brian Seymour]

The balance tabs are cute, I was undecided until I saw Guy's and then it was decision made! I reckon that this the major advantage of a kit, if you fancy making embellishments then you can go for it as much or as little as you like. Of course the down side to making the changes is that the flight performance will inevitably be degraded to some extent but it's completely at the builders discretion. 

On that note, I have decided that my fin and rudder are an abomination and will be making new ones with the hinge line swept forward like the real one (I'm guessing that this will result in a noticeable degradation of flight performance):-

In amongst tracing rudder and fin profiles off of my computer screen I got the turtle deck glued on. I fitted rails to the crutch pate to locate the turtle deck and sanded steps in the foam to finely position the turtle deck on the rails. Once I was happy with my fitting and clamping I mixed up some epoxy, added some micro balloons to bulk it out a bit and got it glued and clamped. It's not perfect but nothing that smear of filler won't sort out.

Rails:-

Steps:-

Clamps:-

Finished:-

Edited By Brian Seymour on 04/02/2016 13:27:54

Edited By Brian Seymour on 04/02/2016 13:44:45

Edited By Brian Seymour on 04/02/2016 13:45:18

[Jon H]

abomination might be a little harsh but i did spot the non scale fin/rudder. Your added weight to the tail might not be desirable but the added directional stability will be no bother!

[Brian Seymour]

It's hard getting the profiles right, the fin and rudder sketched on the plan were traced off a 3-view drawing (off my computer monitor to be fair) but that was different to other pictures and drawing. Looking at the pictures that Guy has posted, the hinge-line sweep is even more pronounced than on my sketched re-vamp. I'll see how it looks dry assembled, there is scope to tickle out a few bits and pieces here and there but I might have to go for a fourth effort.

[Jon H]

remember that the yak 1, 7,9 and 3 all had minor tweaks. Most likely the rudder hinge line was not the same

[Guy Pickett-Jones]

Well have I have glued in the blocks the Tail plane sits on and put in the snakes for the elevator and rudder.

Turtle deck has also now been glued on - in the end I used 5 minute epoxy for this, working from the back and gluing in sections, one side at a time, so I could get the turtle deck to follow the profile of the sides. Worked OK in the end, now just need to do some sanding to blend the tail blocks into the turtle deck.

Picking up on the points of subtle changes. Have printed a few orthographic drawings of the which claim to be YAK 3 and there are subtle differences - main one I picked up on was the different design, position and size of the flaps. Will look into this in more detail once I get to the wings.

In the second photo you will note that the engine has arrived!

Bit of advice here. I was going to mount the engine fully inverted - will be the best fit and as a four stroke I won't have the issue of a large 2 stroke exhaust to worry about. What isn't clear form the instructions with the engine is the best position of the fuel tank. If working from the centre line of the fuel tank should I am to get this inline with the carburettor? As said not had a four stroke before and been a while since I've built a glow engine plane!

Also, the kit come with some down thrust built in but there is no side thrust built in, and as Jon has mentioned, although being a pre production kit nothing is mentioned on the plan so I'm assuming none is needed? Should I add some? and if so how much? or just go with none?

Looking at the weather this weekend it appears to be more suited to building than flying!

Guy

[lightning 759]

hi

built their P40,P47 & spit many years ago non had side thrust that I remember all were great fun to fly ,though 2 had short careers (dumb pilot ) the P40 went on for ever till I sold her after many flights

still fancy their new updated spit

 

andy

Edited By lightning 759 on 06/02/2016 17:24:09

Edited By lightning 759 on 06/02/2016 17:25:27

[Guy Pickett-Jones]

Thanks for the info Andy. I have mounted the engine now with no side thrust. I am using one of the adjustable width engine mounts which have slots for the mounting screws to allow for the adjustment. I have mounted to allow the mount to pushed to the left and then angled to the right if a bit of side thrust is needed.

Guy

[Brian Seymour]

Mate, you aren't hanging around!

The turtle dog looks ace, much neater gluing job than I did.

Scale or not, for the current 5mins I'm happy with the fin and rudder. The prep for hinging the tail feathers is done as well as the holes for the elevator snake and the tubes for rudder closed loop wires. In a few more swipes of sand paper the back end will be ready for covering.

The skim of filler down the turtle deck was a breeze, although I did it in 2 hits, one to fill the gap under the turtle deck and a 2nd skim to blend the deck to fuselage sides just nicely.

The battery hatch has been cut from the top deck and the mating face have been glassed to toughen them up.

No tricky to bits to report and nice day building has resulted in some progress.

[Jon H]

Looking great guys. Alas my plan to get stuck in has been thwarted by a hefty bout of man flu. I must have slept 5 hours yesterday as I was just broken and figured that balsa dust would not help my condition.

As for fuel tank, the CL of the tank should be in line with the CL of the carb +0 -15mm. With the ASP this should be really easy. Did you go for the 52 or the 61 in the end?

[Guy Pickett-Jones]

Well got a fair bit done in between the Rugby!

Engine is mounted, fuel tank in and the Rudder, Elevator & Throttle servos are in.

The fuel tank is in and the throttle cable has also been installed. Built up an internal box with a 'foam liner' for the fuel tank and have used a SLEC 9 oz tank that I already had. Area has been fuel proofed and there is a balsa plate that will cover the fuel tank, which will then have the balsa blocks glued above it which ultimately will be shaped to form the front of the fuselage. Picture is just to show what's going on inside!

Throttle cable actually worked well and went together nicely after several plans. Interesting point is the throttle linkage on the engine is pretty much dead centre at the back of the engine. With the fuel tank pretty much straight behind the engine a straight run with a cable past the fuel tank wasn't possible. Again with the engine inverted this may have added to the issues. Anyway with a bit of thinking the end result is in the last picture which seems to work fine.

[Former Member]

[This posting has been removed]

[Brian Seymour]

Good job done, especially in-between rugby matches.

I got less done today than yesterday, I got distracted with family visits. The top deck is glued on, having left it on the radiator over night to speed up the curing of the epoxy on the glass cloth, it had yawned open so needed to be clamped as the glue cured. I used litho plate to shim a bit of clearance for the the battery hatch - it all came out just right!

I couldn't resist making a start on the wings. There were no liberation slots cut for the ailerons so I traced the split line off the plan and made a template which could be flipped over to ensure that both wings were cut the same. I was pretty chuffed with how neatly the ailerons came out.

I also could resist dry assembling the bits I had to hand for a sneak preview of the finished model.

With the recreational follies done and dusted the prep was done for the aileron and flap servo boxes. The hot paper-clip trick worked a treat - thanks for the tip fellow builders. My first efforts were pitiful and needed a bit of tidying with sandpaper but by the time I got onto the third and fourth boxes it was child's play. I'll get them glued in once the servo extension are in.

[Guy Pickett-Jones]

Thanks for the advice Percy - just done a quick search and see what you mean about the dubro linkage. Will see how mine works out but will certainly keep this in mind. Will certainly be putting Loctite on the grub screws.

What servos are you using in the wings Brian? Need to get some for mine.

[Brian Seymour]

The servos that I'm using are Turnigy 9018 servos, folk seem to recommend avoiding them. I haven't had any in-flight problems with them and use them on the VQ Hurricane 60 (also electric and weighing in at 9.5lbs) but the rudder servo broke when I dropped the fuselage after tripping over my pet cat - not all of the gears are metal.

If I don't have any more car expenses over the next few weeks then I'll see about replacing the Turnigys with Savox SH0256 servos, they are plastic geared but, according to the spec sheet, they have 4.5kg of torque.

Edited By Brian Seymour on 08/02/2016 09:18:06

[Jon H]

From a torque point of view little servos are fine but i find they cannot handle the abuse they get on a bigger model. That said, i fly only IC and its possible the additional vibration makes them unhappy.

That said, a bigger servo like a futaba 148 or hitec 311 will have much tougher gears due to its larger size. For me personally i wouldnt use something smaller in physical size than a hitec 225 on a ic model, unless the gears were metal

[Guy Pickett-Jones]

Thanks for the info on the servos Brian,

Have gone with my original plan and will be using the Hitec 225's. Again like Jon mentions mine being IC just feel I need something bigger!!!

Guy

[Brian Seymour]

Good choice, I'm happy to use the 9018 servos but am troubled about recommending them and would have been gutted if you had used them and wrecked the model from one of them failing.