Going Batty

[Chris North 3]

I have ummed and arred about whether I should start a post on this forum but finally decided to have a go. This is my first attempt so apologies for any mistakes, mishaps and upsets.

Rather than try to provide a complete, in depth build blog my intent is to post some general ramblings about my experience building Lindsay Todd's "Batty" using the May 2016 RCM&E free plan.

By way of explanation - and setting some level of expectation! - I should perhaps confess up front that this is my first balsa build in over 30 years. Back when milk came in bottles and Christmas meant getting more presents than I gave, I received a free flight glider kit which gave hours of fun, not only building, but also towing around the local field trying to get it to fly in a lazy circle as promised on the box.

Pocket money being what it was, RC was way out of my reach and so modelling fell into the background although my interest in it never dropped off.

About a year ago I decided to get back into the hobby and so invested in a transmitter and simulator. A rather good investment as it turns out since the cost of subsequent crashes in the flesh would have put me back out of the hobby for sure!

My first toe back into the building pond was thanks to the guys at Flitetest since their videos and plans made building flyable planes seem easy. Obtaining foam board was a bit of problem here in Thailand however a couple of weeks elbow deep in depron and packing tape saw a spitfire flying over (and into!) the local patch.

Since then a HK Decathlon and T28 have joined the stable and my flying skills are gradually improving. While foam is fun the desire remained to get back to balsa building and hence here we are.

I decided to build the model from scratch not only to relearn the building skills but also because it was too expensive to get a CNC kit sent over from the UK.

So far I have made a start on the tail feathers and am about half way through the wing construction.

Progress will be slow compared to most on this site because I am limited to only 3 or 4 hours a week due to other commitments and activities but lets see how it goes.

[Chris North 3]

I am not really in favour of cutting up the free plan as I assume that I will need it again some day so instead decided to make a working copy that could be cut up and abused as necessary. I am not aware of any local suppliers that can scan or copy the plan full size and so had to settle for scanning it myself in sections using an A3 scanner. Each section was overlapped on next so that when it could be aligned properly once printed out.

Unfortunately my AutoCAD skills are non-existent (something I must try to fix) and so I simply imported the images into Word and then, after half an hour or so with the crop, copy, paste, rotate and delete tools, I was able to create a series of pages which included a full wing, tail feathers, ribs and all of the fuselage formers. These were then printed out onto A3, aligned and suck together as necessary.

While I am sure there are far more efficient ways of doing this, it did allow me to have a set of plans that I could print as many times as I needed.

If taking this approach do be careful of the scaling effects or your scanner and printer. I found that even when I scanned the plan at 100%, imported into to Word at original size and printed at 100% there was still a slight scaling error meaning that the plan was printed slightly undersize. Once I was a aware of this it was simply a case of printing the page I wanted, checking its scale and then resizing before reprinting. For the wing I used the 6mm main spar to check the scale and found that an adjustment of less than 1% was required. This was then easily accounted for in the printer menu and resulted in a 100% reproduction.

To cut out the ribs and the formers I roughly cut them out of my print and then stuck them directly to the proper sized balsa sheet using pritt-stick. This is a method I have used on my foam planes in the past and gives an easy way to cut out parts without having to transfer lines to the balsa. Unlike water based glue, Pritt-Stick does not bloat the paper ad so they stay at the correct scale. After 10 mins the pieces are dry enough to be cut out with a craft knife without ripping the paper template.

[Chris North 3]

Having cut out the ribs and various formers I thought it best to start the main build with something simple and so taped down the tail plan and broke out a couple of sheets of newly purchased 6mm balsa. Using my print outs I was able to quickly rough out the various components for the tail frame before attempting to get the best joints I could.

Now, many moons ago, I managed to persuade my Dad to help me get into RC gliding and so after a quick trip to the local model shop we both arrived home with a plan and a bundle of balsa each. After a week or so of building it was clear that my eagerness for progress was not as effective as Dad’s eagerness for quality since while his joints were almost air tight, mine were more like a game a jack straws! That glider was unfortunately never finished – I must ask Dad where it is! – but all these years later I still remember how bad my joints were and so this will be something I will try to watch out for during this build.

Anyway, a couple of evenings with the scalpel and sanding block saw the tail components cut out and glues together.

Nothing has been sanded to final shape just yet as I have been waiting for the postman to deliver my new perma-grit block from the UK. Also the tail will be trimmed up once I build the fuselage to make sure that it fits properly.

[Chris North 3]

Having completed the main components for the tail it was time to make a start on the wing.

When cutting out the wing spar doublers I noticed that these had a very slight angle indicating some dihedral in the wing however the building instructions in the magazine said to build the wing as a single structure. A quick email to Lindsay confirmed that the wing is indeed intended to be flat and so I will need to make up some new doublers when the time comes.

With that sorted and the full wing plan stuck to the board it was time to start assembly. The first thing to do is to pin down the spruce spar. Unfortunately I have not been able to source 6mm square spruce or indeed any 6mm square hardwood and so a little bit of improvisation and elbow grease was required. Having acquired a strip of hard wood molding of about 6mm thick I proceeded to cut 6mm wide strips as best as I could using a steel ruler and a small saw. While not exactly perfect it was pretty close although I did have to cut from both sides of the molding to ensure I had at least one factory edge on each strip. Thankfully I had planned ahead and cut the spar slots slightly undersize on the ribs and so was able to gently sand these out to ensure a snug fit. I guess in hindsight it may have been easier to try and use 6mm square carbon fiber tubing. Oh well next time!

Assembly of the spars and ribs was very easy thanks to the supports designed into the ribs and so an evening at the bench had all of the spars glued into place.

After leaving this to dry it was time to fit the trailing edges from 6mm sheet. I had a little bit of difficulty here as the instructions say to cut the t.e to the depth of the ribs before gluing into place. From the plan it appears that the t.e. wing sheeting runs over the top of the t.e and hence the t.e. needs to be installed flush with both the top and bottom of each rib. This was fair enough but how to confirm the depth was exact when the depth of the spar was a bit of a guess due to the building tab? Well rather than worrying too much I decided to make the t.e. slightly over sized with the intent that this could then be sanded down as necessary prior to installing the wing sheeting.

The installation of the leading edge and the rest of the spars was fairly straight forward however it is worth noting that the instructions reference the wrong spar numbers compared to the plan although this is fairly obvious and easy to work through.

[Chris North 3]

While pondering my handiwork over a cuppa, I started to think about when was going to be the best time to install the support rails for the aileron servos. Hmmm…something wasn’t quite right but I just couldn’t put my finger on it. After a head scratch and a chocolate hobnob I realized that all of the ribs are solid with no cut-out shown for the servo wires. A quick search on google showed that I needed to install some servo tubes however my rookie error meant that all the ribs were now glued in place and so access was somewhat limited.

Using some scrap balsa I made up a jig that sat across the top rib spars thus allowing me to mark the center location of the cut-out at a fixed distance from the spars on each rib. Due to limited space between the spars I had to drill each hole by hand and then expand them to size using a file. To make the size of the hole consistent I used the inside diameter of a dremel sanding drum as a marker which also meant I could then use the dremel attachment to check the hole for size and roundness.

Here is a picture showing the completed holes in one side of the wing – note that the ribs still have the paper template attached.

To make the tubes I trimmed up some A4 paper and rolled it tightly around a pencil before slipping 3 of the dremel sanding drums over the top. The paper was then allowed to unroll against the inside of the drums at which point I had both hands free to tape the tubes together. By shuffling the drums along the length of the tube I could tape up the full length while maintaining a constant diameter. This method was repeated for the second tube resulting in two identical servo tubes.

The dremel sanding drums in action

Again due to the space restrictions between the center ribs, I couldn’t quite install the tubes in one go without bending or crushing them. A couple of crushed servo tubes and a bruised egos later I worked around the problem by cutting each tube in half and then making a joiner tube to slip snugly over the outside. Each tube section could then be treaded into place and installed into the joiner tube which was sized to fit between two ribs. Once everything was dry fitted a run around with super glue soon saw everything held firmly in place.

A couple of pictures of one of the completed servo tubes.

[Chris North 3]

With the servo tubes complete it was time to turn my attention to sheeting the wing. Again I found a slight discrepancy between the magazine instructions and the information on the plan – or maybe I just misunderstood it; more on that latter!

The instructions say to go ahead and shape the leading and training edges to match the profile of the ribs ready for sheeting which implies that the sheeting would then be installed over the top of the leading and training edges. While this is certainly the case for the outer sections of the trailing edge, the plan shows the sheeting stopping at the back of the leading edge which would require the l.e to be sanded after the sheeting is on.

Rather than worry too much, I decided to start with the leading edge sheeting and to follow the plan, with the intent of butting the sheeting up to the leading edge and then sanding it to shape afterwards. Apart from making more sense (I had no idea how I was going to make the upper and lower sheeting bend over the leading edge and join in a neat seam!) it would also be easier since I had cut my leading and training edges slightly over size.

Since the wing is not a uniform chord it was pretty obvious that I wasn’t going to be able apply the leading edge sheeting in one go without creating a major disaster. Not having sheeted a wing before I wasn’t sure how many sections would be acceptable but I assumed it didn’t matter as long as the joints were tight, fully glued and positioned over the ribs. Just to be sure, I double checked Lindsay’s build blog which showed that his wing had been skinned in two or three sections – not including the repair of the apparent thumb hole!

Since the grain of the sheeting had to run along the span of the wing, Sod’s Law dictated that my sheeting wasn’t wide enough which meant that the first order of the day was to create some suitable sheeting. Uncle Google suggested that the best method was to simply tape the joint, open it up, apply the glue, close the joint, wipe away the excess, apply weight and leave to dry.

Given that the center section between the two W1 ribs is going to be hidden out of sight inside the fuselage I considered this a good place to start! Following Uncle G’s simple instructions it wasn’t long before a section of sheet was duly widened, trimmed to size, fitted up and glued in place. Although the plan calls for a hole in the top sheeting for the rudder and elevator servos, I left the sheet complete at this stage with the intent of cutting out this hole once the top sheeting is finished.

I didn’t take any photos of the joining of the center section sheeting but here are a few photos showing the process for one of the outer panels.

Butt the two sheets together ensuring a tight fit and then together ensuring the joint remains tight

Flip it over, open the joint and glue

Close the joint and remove excess glue

Weight and wait...

[Chris North 3]

With the center panel complete it seemed sensible to continue sheeting out towards the wing tips so that only one sheet to sheet butt joint needed to be worried about at a time. This meant the next logical section to be sheeted was between ribs W1 and W4 so that the chord change at W4 could be tackled in two sections. However, when offering up a length of sheeting to the leading edge to mark the required width, it became apparent that I had a problem on my hands.

Because of the wing’s shape there are 2 sections of leading edge between wing ribs W1 and W2. According to the plan the sheeting comes over the top of the inner section of leading edge and then butts up to the back of the outer leading edge. A picture paints a thousand words so see below the plan detail and the as-built center section of wing.

Unfortunately (although I didn’t realise it at the time) I had misread the plan and so had butted the center sheeting up to the back of the inner leading edge between W1 and W1 instead of sanding it down to meet the ribs and running the sheeting over the top. I guess that’s what the instructions meant when they said sand the leading edge ready for sheeting!

Anyway the upshot was that between ribs W1 and W2 I had to somehow get the sheeting to pass from behind, to over the top of, the inner leading edge. Since it was late and I was out of hobnobs, I decided this was a decision for later and so set about sheeting the wing from W4 to W8 instead.

Sheeting W4 to W8 was straight forward and a slight overhang was left at each of the W8 ribs such that the top and bottom sheeting could be sanded flush with the ribs later, prior to attaching balsa block wing tips.

Still not realizing that I had read the plan wrong(!) I was once again left scratching my head to understand how Lindsay had managed to fit his wing sheeting at rib W2. It was clear that only a session with the sanding block and hobby knife was going to fix it but I wasn’t quite ready to attempt this so instead I elected to sheet between W4 & W2.

With the easy sections finished there was nothing left to do but try to figure out how to solve the problem with the double leading edge.

Obviously the inner leading edge had to be profiled to allow the sheeting to cross over it. The neatest solution seemed to be to sand/file a step to allow the sheeting to fit over the top. This step was positioned to align with the path of the outer leading edge in order to get as neat a finish as possible. The following phots show the outcome. Not quite what the designer envisaged but it seems to work.

[Chris North 3]

So the question should probably be answered as to when I realized I had read the plan wrong? Well about half an hour ago as I typed up this blog and copied the extract from the plan! Oh well, it is supposed to be a learning experience right?

So that is me up to date.

The plan for this weekend is to turn the wing over and attempt to repeat the front and center sheeting on the underside. I could copy my mistake in order to make the wing symmetrical but where is the learning in that? Instead I shall attempt to follow the plan correctly.

Once the front sheeting is complete I shall attempt the trailing edge sheeting – after I have read the plans again…

Hopefully there will be an update on Monday.

[Chris North 3]

This weekend was family time and so Batty did not get any attention until Sunday afternoon – still I did say I was slow.

With last week’s sheeting and plan reading lessons learnt, I decided to take a slightly different approach with the underside leading edge sheeting. I again decided to start with the center section but, since the lower face of the wing has a different sheeting pattern to the top, it seemed sensible to sheet between the two W2 ribs all in one go.

First order of the day was to sand down the leading edge running between the two W1 ribs to allow the sheeting to run over the top. This was achieved using a combination of my new perma-grit block and a small file. I have to say I am very impressed with the perma-grit sanding block although I am still getting used to how much material even the fine side removes.

It is a little bit tricky to see in the photos but the leading edge was sanded to the shape of the ribs all the way between W1 and W1 while the joining leading edges were left proud for the sheeting to butt up against.

With the leading edge prepared, the sanding block was unleashed on the trailing edge which, within only a few strokes, was also profiled to match the ribs.

Using the same tape and glue method as before, a section of sheeting was produced wide enough to run between the two W2 ribs and long enough to cover the full depth of the wing. Starting at the trailing edge and working forward, the section of sheeting was marked up against the ribs and gradually cut & sanded to shape. Once I was happy, the trailing edge was lined up and taped into position. With the sheeting folded back, wood glue was applied to all of the contact points, the sheeting folded back into position and pinned & weighted down.

Once set, the sheeting panels between W2 & W4 were parked, up, trimmed and installed in a similar manner.

It looks like tonight is full already so not sure if there will be any progress but all that remains of the leading edge sheeting is to install the final panel between ribs W4 to W8.

[Glyn44]

Hi Chris,

I like your dogged determination, well done and I hope you are enjoying the build. Interesting model to have a go at. I picked up a good tip from these forums during one of my builds, and I see you have the same difficulty i was.suffering. That is suitable weights!

One answer is to use freezer bags, or similar, filled with either wet, or dry, sand. The amount of sand/water is easily adjusted to give enough weight for purpose. Also they do not make any indents, or damage to soft balsa.

Anyway just my suggestion, I'll continue to follow this post with interest, best wishes for for a successful build. Enjoy.

Regards, Glyn.

[Chris North 3]

Hi Glyn,

Thanks for the feedback and encouragement. I guess Batty is a bit of a strange choice to get back into building but I am really enjoying it and learning lots. Hopefully I will end up with something a bit different - though hopefully not too different from what Lindsay intended!

Your suggestion about the sand bags is a great one and not something I had thought about. I have found that the tins can be a bit hit and miss, especially when weighing down the sheeting onto the ribs, as they have a lip and so the weight is only around the edge allowing the sheeting to pop up under the can. As you say, they also mark the soft sheeting. The wheel balancing weights are a good option and quite flexible but you seem to need a lot of them to get any decent weight.

I was having a bit of trouble finding a ready supply of sand in the house last night so it was back in the pantry for other ideas. See below my trial use of a local Thai alternative!

Chris

[Chris North 3]

Not a lot of progress last night however 2 new lessons learnt - so only just a short update today.

First job for the night was to take off all of the weights and pins from the center section sheeting. I was pleased with the way this turned out although I did note that at one of the edges the sheeting had popped-up where I was using as can of beans as a weight. This however was quickly fixed with a gentle push and a couple of drops of Cyano – remembering to keep my fingers clear of the glue!.

So the first lesson is that tins of beans can be a good weight but they do have a rim at both ends which means the weight is applied in a circle and not evenly over the whole of the bottom of tin – therefore while it may look as if the tin is holding everything down, you can’t be certain what’s happening underneath.

This was very timely actually as Glyn had just posted a comment about weights and the use of sand in zip-lok bags so, before attempting the next sections of sheeting, it was off to the kitchen to hunt down a suitable sand alternative.

Tonight’s second lesson was that 1.5mm balsa sheet is quite delicate! While I know this seems obvious I had become a bit complacent when handling the sheeting and butting it up against the leading edge to get a good joint. A little bit too much enthusiasm pushing it against the leading edge resulted in my newly trimmed sheet snapping along its width. Luckily this was quite a clean break along the grain and so the tape and glue were back out and this was quickly fixed up. By the time the left wing panel had been glued and weighted this sheeting was set and ready for installation.

So there we have it, all of the leading edge sheeting is now installed and once dry I can turn my attention to the training edge sheeting.

[Chris North 3]

Well it’s been a few days since I last posted an update since there were other fun things to do this week, including flying, and so Batty slipped down the priority list. Anyway, I did manage to grab a couple of half hour slots on Sunday so here is the update.

With the leading edge wing sheeting complete I took the sanding block to the training edges and gave then a nice profile to match the ribs and then set about applying the trailing edge sheeting. I started with the bottom surface first, trimmed the sheeting to fit and then using a combination of pins and masking tape made sure everything was held securely in place to dry.

The outer section of trailing edge sheeting is straightforward however the plan is a little unclear (to me at least) as to whether sheeting is applied to the centre section of the trailing edge or not. See below.

It seems like it should be sheeted otherwise there would be a step between the centre and outer sections of sheeting which will be a problem during covering. To avoid this I went ahead an added some extra sheeting so everything was nice and even.

Once dry I removed the pins and tape, flipped the wing over and installed the trailing edge sheeting to the top side. Here of course is where my previous mistake came back to say hello!

As you may remember, when installing the top centre sheeting I had run it so it was level with the top of the trailing edge, not run it over it. This meant that with the trailing edge sheeting installed on top of the leading edge I now have a step in the centre!

I have left this at the moment and will come back to see if I need to install an in-fill later but hopefully this will not be needed and can be covered by the fuselage. We will see!!

Here is a photo of the upper surface trailing edge sheeting. If you zoom in you can see the step at the centre of the wing.

[Chris North 3]

Not a lot of progress since the last update. There are a couple of ongoing problems but the wing is certainly starting to take shape.

Today’s activities were all straight forward and so I doubt I am teaching anybody anything here however I will continue to explain the details as this blog is keeping me amused, if no one else.

I have to say that one of the interesting things I have found with this blog is that writing about activities performed and the problems encountered makes you think logically about what you have done and actually helps to solve the problems. If you are having an issue with a build, try writing down the steps you performed and the issue you found as if someone else is going to read it. You may find that things suddenly become a lot clearer!

Anyway, cosmic insights over; back to amusing myself…..

With all of the sheeting installed and dry I decided it would be best to install the aileron servo mounting plates before putting on the rib capping strips. If I did it the other way around then I can almost guarantee that I would be putting some of the capping strips on twice!

With the mounting plates in place and weighted down to dry, I turned my attention to the ailerons and centre trailing edge.

First up was to simply pin some baking paper over the plan and to trace the outline of the components. A ruler was used where necessary with all of the curves traced freehand. A little wavy here and there but this will be sorted out during cutting and sanding.

Once complete, the tracings were transferred to suitable pieces of 6mm and 2mm balsa sheet and pins used to transfer the outline to the balsa. A quick whip around with the hobby knife and I had the centre trailing edge and one aileron blank cut out. For the second aileron I traced around the first rather than using the baking sheet tracing, just to make sure that my free-hand curves were fully replicated. Here are a couple of photos showing the process.

I am still a bit confused about the differences in thickness of various sections of the wing at the training edge. The first issue is the centre section. As per the plan and the instructions, this is cut from 6mm sheet and needs to be attached to the wing trailing edge before being shaped down to a final thickness of around 2mm. The problem here is that my training edge is 6mm + 1.5mm for the top and bottom sheeting = 9mm. This means that there is a 1.5mm step top and bottom, between the wing and the training edge. The wing cross section in the plan (see below) seems to show that the training edge is intended to be 9mm so not sure what I am going to do here. I will double check the magazine instructions but I think the best approach will simply be to laminate some 1.5mm sheeting top and bottom and then sand as per the plan.

The second issue is the thickness of the ailerons. The plan only shows the size of the leading edge (6mm square) but does not show dimensions of the rest of the aileron structure. The magazine instructions state that the 6mm stock leading edge is attached to a 2mm core which then has 3mm riblets added top and bottom. This means that the main body of the aileron will be 8mm thick (2mm + 6mm of riblets) while the leading edge is only 6mm. This just doesn’t add up!

I decided that the core and riblet details were correct and so decided to press on and make these so that they could be offered up to the wing to double check the thickness required. The other reason for taking this approach was that to follow the instructions and attach l.e. to the 2mm core first, would mean chocking the core to ensure it was centralized on the l.e. Way too complicated for me. So I took the easy route and started to attach the riblets to the core first. Once these are dry I will then offer this assembly to the l.e which will ensure it is centralized.

Here are a couple of photos of the progress of the first aileron. Hopefully the rest of the riblets can be glued tonight and I can start on the rib capping while I wait for the ailerons to dry.

[Bob Cotsford]

Could the aileron LE dimension be for the width, with the thickness to match the rear of the wing? IE 9mm * 6mm with the 2mm aileron T'd at the midpoint of the 9mm side? Have you tried a PM to Lindsay asking for clarification?

[Chris North 3]

Hi Bob - No I have not messaged Lindsay so maybe I should try that. For the aileron, my plan was to do as you suggest and cut a 9mm x 6mm strip for the l.e which would allow me to get everything even. I can't do that for the centre section t.e. as I only have 6mm sheet. I think laminating this to get 9mm should do the trick though - especially as most of it is hidden in the fuselage - although that should not be an excuse for not doing it right!

[Lindsay Todd]

You got it Bob, I cut the leading edge of the aileron from 6mm thick sheet to match the aileron cutout in the wing then glue the 2mm plan on centre line, then ribs either side, but either way will work fine I'm sure. Linds

[Chris North 3]

Thanks to Bob and Lindsay for the suggestion and clarification of the way forward with the ailerons. The plan will be to cut some 6mm sheet to size and then to glue on the prefabricated core and riblet assemblies which will hopefully make centering them a little easier. I am definitely learning that there is no right or wrong way to build from a plan – only easier or harder ones!

As for today, not a lot of activity today to report really but more importantly no issues either! The first job was to carry on applying the riblets to the aileron cores. With the first aileron dry it was removed from the tracing and the second core attached in its place. Riblets were stripped from 3mm sheet and attached using the tracing as a guide. The first aileron core was simply flipped over and riblets applied so that they aligned with the already installed riblets. After a couple of hours drying time the second aileron was also flipped and its second set of riblets applied in the same way.

With the aileron cores pinned and chillaxing I decided to make a start on the wing rib capping. This is not something I have done before and so I started on the underside of the wing again although everything was pretty straight forward. The main thing is to cut the strips slightly over length and then to sand to fit making sure there is full contact at both the leading and trailing edge. Watch out if using the perma-grit sander as even the fine side can take off a lot of balsa! Luckily I only had to remake one capping strip although I have only completed ¼ of the wing so far.

I tried a couple of different methods to hold the caps in place but found that weights were too fiddly and tape didn’t seem to hold them down tight enough. Eventually I decided just to pin them in place since the wing will get a fill and sand spar treatment once complete which will hide the holes.

[Chris North 3]

Again not a lot of progress over the past few days as the bits I am doing are a little fiddly and each stage needs the glue to dry overnight. Still, here is a quick update of what I have been up to since last time….

Firstly I have been continuing work on the rib caps. To make sure these are all a nice tight fit I have been working on a ¼ of the wing at a time. As of now the last section is pinned and waiting to dry.

Meanwhile, I have continued work on the ailerons. Riblets were applied to each core and while these were drying I set about cutting some leading edges. As suggested previously, I measured the maximum thickness of the wing’s sheeted trailing edge (9mm) and then cut a suitable strip from 6mm sheet. With the riblets trimmed just over length the leading edge of the aileron cores were given a once over with the sanding block to make sure they were square before being glued to the leading edges. Since both the leading edge and the cores were the same thickness, this made centralizing them very easy. Rather than pinning, some trusty masking tape was used to ensure everything was held tight and square.

With the ailerons sorted, a couple of wing tip blocks were made up by laminating some 20mm wide strips of 6mm sheet. Once dry these will be roughly shaped before being applied to the wing.

Hopefully this should be most of the main components of the wing now complete. The next step will be to cut back the sheeting overhangs etc. so that I can apply the wing tips and add the centre trailing edge section before giving the whole wing a sand and final shaping.

The ailerons then need to have the riblets trimmed at the trailing edges before being sanded to shape.

Hopefully this can be done in the next day or two and then I can make a start on the fuselage.

One thing I have not finalized yet is how or when to hinge the ailerons. I am thinking that the best approach is to mark up and cut the hinge points while the leading edge of the ailerons are still square thus making centralising them much easier. With these cut, the hinges can then be easily installed and glued later on once the wing is covered.

I have not got the hinges yet so any hints and tips about the best type or size and when to install them would be welcome.

[Bob Cotsford]

For any form of pinned hinge such as Kavan leaf or Robart pin hinges I find it's best to cut/drill the locations while everything is nice and square, but for this size model I'd normally use furry CA hinges which just require a slit cutting - that will be lost during covering so I use a hinge slotting guide during final assembly.

[Chris North 3]

Thanks for the feedback Bob, I am struggling to find the CA hinges at the local model shops but I did pick up some intermediate sized pin hinges so I can use these if need be. I am sure the hinges are here in Bangkok somewhere but trying to explain in Thai can be an experience. I have found someone that sells the slotting tools so that looks like good option.

[Chris North 3]

Last night I thought I has better spend some time repairing my Durafly Trojan T28 that did not take very kindly to a downwind landing with zero throttle where a wing tip stall resulted in a nose first landing. This is my only plane at the moment and so a little love and attention was required to get it ready for the next flying session. Apart from some cowling damage and a broken prop it also suffered a cracked and dislodged nose wheel housing and so a little disassembly and TLC was required.

With the housing glued back into place I just had time to check out the growing pile of components. The wing is getting close with the wing tips blocks now attached and ready for sanding. I still need to attaché the centre section of trailing edge but seem to be procrastinating on this for some reason. I think it is because I still need to laminate it to get it up to the correct thickness only to then sand most of it off again to get the correct tapered profile.

I realised I was getting older last night as after looking through the completed components I wasn't happy with the rudder and so set about making a completely new one! This would never have happened when I was younger - perhaps I am turning into my Dad after all!

Anyway here are the wingtips - I could have trimmed them down a bit before attaching them but I think it is going to be better to shape them in-situ.

[Chris North 3]

Blimey, balsa dust gets everywhere doesn’t it!

Over the weekend we had an impromptu visit to Ho Chi Minh City so again the workshop (read spare bedroom!) time has been a bit limited. Arranging a visit to the Seagull model factory did briefly cross my mind before realizing that this could lead to having to use more than just the desk in the spare bedroom!

Sanding and shaping has been the main activity this week. First up were the wingtips which were roughed down to shape using a small hand plane before being sanded to match the profile of the wing sheeting.

First lesson this week: it’s very easy to sand the wing sheeting when trying to sand the wing tip!

On previous sanding jobs around the house I have always used the pre-made foam type sanding blocks that you can from any DIY shop. These are very fine and ideal for finishing but are not much use for removing larger quantities of wood hence the reason I bought the perma-grit block and flat sanding file. These things are monsters and I am still getting used to the fact that only a few strokes are needed. Unfortunately my first attempt at sanding back the wing tip resulted in a localized reduction in sheeting thickness! Luckily this was not all the way through and so some light weight filler was applied to fill the gap.

Taking things a bit more slowly, I sanded down the second wing tip and the leading edges along the entire wing, both top and bottom. With these finished I then rounded over the top and bottom edges of the wing tips. Finally, the sheeting and rib caps were given a light sand to even things out where the separate sheets join.

Second Lesson this week: Joining wing sheeting to the leading edge needs more care!

In sanding down the leading edges I found a couple of spots where the wing sheeting weren’t as secure as I thought. See below.

To fix these I applied glue to the two surfaces and then pushed the sheeting back down into position before applying weights to hold it in place while it dried. The plan is look over the wing and to apply filler to any remaining pin holes and gaps before giving the wing a final sand so these areas will be sanded back then.

Last activity for the night was to apply the centre section of the trailing edge. As discussed previously, I eventually decided to face the 6mm core with 1.5mm sheeting top and bottom and this will then be sanded down to final shape once the glue has dried.

I know I am slow but the wing seems to be taking forever so to make sure I am still on track I couldn’t resist a quick trial fit of one of the ailerons. It looks like I need a little sanding to make sure everything is square with the centre trailing edge and the wing tip but it actually looks pretty close to the pictures in the magazine and on Lindsay’s thread so I must be heading in the right direction.

I still have to sand the ailerons to shape but I am getting close to starting the fuselage so in preparation for that I have printed out a couple of photocopies to use rather than building over the plan. Having remembered my previous lesson, these copies were actually printed at 100% scale first time!

[Bob Cotsford]

A tip for sanding down to the level of another part - use masking tape to protect bits that you don't want to damage. For example, cover wing sheeting adjacent to the area to be sanded when shaping leading edges and tip blocks. A couple of layers will do the job, when the permagrit starts to cut the masking tape it's time to swap to a finer abrasive.

I know it's a bit late now but try it the next time you get the permagrit out.

Edited By Bob Cotsford on 21/09/2016 10:01:09

[Chris North 3]

Thanks for the tip Bob - it makes perfect sense once someone points it out . There is a new Spacewalker kit sitting on the shelf which will hopefully benefit from my Batty lessons. The biggest problem is stopping myself from making a start on it and then having two kits on the go at the same time!. Batty is definitely getting my building skills back up to scratch.