In November 1949 Aeromodeller published the original plan for the Lulu; a 50″ span, simply designed contest glider which has no doubt started many aeromodelling careers in it’s history. John Barker the designer was just 22 years old when it was published after have started aeromodelling at the age of 11, he went on to develop a lifelong passion, still contributing to the hobby in his later years.
The design was originally a free flight glider for towline launching but its roomy fuselage and good proportions lend it to conversion to two channel Rc with rudder and elevator control. Its inherent stability and good gliding performance also make it ideal for modellers wanting to try RC as well as more experienced flyers looking for some old time thermal soaring. It also goes well on the slopes as the Ivinghoe Soaring Association have proved with their own club build last year.
Construction is straight forward and would also make a good first build for any ARTF flyers. The original article boasted it could built in just 4 hours which is a little optimistic to say the least but there is nothing that would be to difficult for the novice builder.
There several routes to building the Lulu. Perhaps the easiest is the full laser cut kit which is available to order from Neil Pritchett for £55 plus post and packing. This version has already been converted to RC and has some lightening to the original design as well. Email Neil at RetroPlanesUK@gmail.com with your order.
There is also a short kit available from skyhighrc.co.uk which has laser cut ribs and formers and you add your own strip wood for £18 plus post and packing. It doesn’t come with a plan but the original ff plan can be downloaded from OuterZone, this would need the builder to convert the design to RC themselves though no doubt there will be lots of help and advice on here if you need it
If you are building a Lulu please do send in your build pics to webmaster@oxfordmfc.bmfa.uk and we will feature them here
Aeromodeller ran an excellent article by Jim Wright on the Lulu RC which can be downloaded here by kind permission of Aeromodeller.
LULU BUILD BLOG – Bob Lee
Part 1 – Wing Middle Section
Welcome to what I hope will be a complete build blog for the RC version of the Lulu Lite, built from the kit that I know a number of you have. This is my way of building it and hopefully it will be of use to less experienced builders and a useful guide to those of more experience even if they may wish to deviate in some area’s from my building methods. I’ll try to use lots of pictures and will try to remember to use flash for all of them so they are consistent, but will probably forget from time to time so please excuse those that look a bit different.
I started with the wing and I’ll use the term middle section (as per the instructions) rather than the more normal term centre section for the flat middle part since this middle section has its own centre section!
The instructions say that it’s not necessary to build it over the plan. I disagree !!!! The first job then is to pin the appropriate part of the plan down on the building board and cover it with something to stop the wing sticking to the plan. I use cling film but if you use this then DON’T USE CYNO for any joints that are in contact with the cling film. If you do then you will end up with lumps of dissolved film stuck to all your joints which will take forever to remove. Most of my build used PVA.
The first job is to identify the correct pieces of stripwood from the bundle supplied in the kit and it’s very important that you get this right. It’s also important to note that the LE, spars and TE are all supplied as two pieces that need butt joining together to make the full length. Not an ideal arrangement by a long way but required I guess to get them into a standard sized box. The joints are all reinforced to what looks to be an adequate amount but if you have a stock of suitable wood then you may wish to use that and make these parts from a single piece and not use the halves supplied with the kit. Since I had some 1/8 sq spruce this is what I did for the spars and then left off the reinforcing. The stripwood that you need to identify is :-
Leading edge(LE) – two pieces of ¼ x 3/16 which are 455mm long. These are actually over length and you can cut those to the correct length(plus a few mm which can be trimmed later)
Spars – there are 5 lengths of spruce in the kit. 4 are the same length and are for the spars. The shorter one will be cut to make other parts and you may as well cut a length of this now to make the TE reinforcing joiner. The spars can be left at the length supplied for now.
Trailing edge(TE) – Two pieces of 1/8 x ½ which are 325mm long and can be left at this length for now.
When joining all of these pieces make sure that the ends to be joined are truly square in both directions, when the parts mate there must be no gaps. Also use a straight edge to ensure that the joined parts are straight. I started with the TE, pinning it down against the straight edge with PVA on the mating ends:-
Next I moved on to pin down the bottom spar, in my case this was a single piece as noted earlier. Note the pins on either side(not through!) the spar to keep it straight and the crossed pins to keep it flat to the board:-
The next two parts to add are the TE reinforcing piece(that you cut earlier from the 1/8 sq spruce and the centre web, CW, which fits on top of the spar. Actually I didn’t fit CW at this stage thinking that I wouldn’t need it given that I had a single piece spar but then realised later that is was needed after all so added it later on.
The next part that I added was the bottom sheeting that goes between the spar and the LE(part WSB on one of the laser cut sheets). Align the centre mark on this with the centre of the wing. I then added the LE, two pieces butt joined and kept straight with a straight edge again. Adding WSB first ensures that you get the correct distance between the spar and the LE. Next I added the two ribs, (MR, sheet 5) and had to make a tiny adjustment to the notch for the bottom spar( a fraction of a mm) to get this :-
Note the use of the square to ensure that the ribs are vertical.
Now you can add all the other ribs and webbing(W) pieces, so first glue one of the W pieces on top of the spar at the position nearest the centre rib that you just added and this is best done using cyno for an instant joint but don’t forget my warning about not getting it on the cling film(if that is what you are using). You can then fit the first of the ribs and I had two issues. The first is easy, the slot in the bottom of the ribs isn’t quite big enough to take the spar, you need to make it a tiny bit bigger. While you are doing that you may as well enlarge the top slot as well to take the top slots. Beware, theses slots are only undersized by a very tiny amount!
The second problem is that having fitted that sheeting piece earlier to make sure that the LE to spar distance is correct, the front of the ribs was just a bit two small, they didn’t quite reach the LE(remember, don’t try to use glue to fill gaps!!). The solution was to apply a bit of pressure to the LE to force it onto the rib and then pin it there. The rib can then be glued in place using PVA. Repeat the above process until all the W pieces and ribs are in place except for the last one.
The last rib has to be inclined to allow for the dihedral in the wing tips so the last webbing piece is DW which is angled at one end. I actually had to shorten this by about 1.5mm for two reasons. One was my error, having carefully(I thought) cut the spar to the correct length I now found it was a little short (urghhhh!!!). The other is that the repeat process of W,rib,W,rib,W …..
built up a small error in the position of the last rib. So, carefully check that when the final rib(DR) is leaning against the last webbing(DW) the rib is in the correct place and adjust if not. You can then glue DW in place.
Next find the dihedral braces on the laster cut ply sheet. There are two types, one deep and one narrow and two of each. Remove one of each type.
The deeper brace fits behind the spar and again check for length, the angle on the bottom edge must be at the same position as the outer edge of the last rib(DR) and adjust if needed. Once you are happy then you can glue it in place and clamp it. You can now fit the back half of the final rib(DR) using the ply gauge supplied to ensure that it is at the correct angle as below:-
OK, you can see in that picture how the spar being a bit short left the last rib a little out of position. One wing will be about 1mm shorten than the other, I can live with that.
You can now add the narrow brace behind the LE and again, clamp it, then fit the front half of the last rib, again using the angle gauge (not shown the picture, it wouldn’t stand up on its own):-
The final stage in fitting the dihedral rib is to add the two gussets, the edge that abuts the end rib will need to be chamfered to match the inclination of the rib. It now looks like this :-
Its now time to add the top spar. Having first checked the fit, the way I did this was to apply PVA to the tops of all the webbing pieces(W’s) then put the spar in place, pushing it down firmly. I then whent along the spar with some cyno and put a drop on this into each rib position, again pushing the spar down into place. This is what it looks like with the top spar in place:-
This method of making the main spar with strong upper and lower spars, separated by softer webbing pieces makes for a very strong but light spar and is common engineering practise, it’s the way an I beam works. If you are making the two piece spars you need to add MB(its on the ply sheet), I left this off.
Although it’s a bit later in the instructions I decided to complete the centre section at this time, so started by adding the piece WF on top of the LE:-
I then added the top sheeting WST and the centre ribs, CR, two of which need to be glued together first for each side and then finally the gussets. At this point, the centre section started to make sense :-
You can see that the CR ribs stood a little proud so I had to sand off the tops.
That’s the middle part of the wing finished for now, time to move on to the wing tips which will be the subject of my next blog.
Part 2 – Wing Tips
After building the main section of the wing, you will be pleased to learn that the wing tips are much easier.
Start by pining down and gluing the TE, spar, LE and the tip pieces, note that the spar is now balsa rather than spruce. You will have to cut the two spars from one piece of 1/8 sq, note that the top spar is shorter than the bottom spar so don’t panic when you think the supplied piece of 1/8 sq isn’t long enough:-
At this point it’s worth offering up the correct end of the middle section of the wing and just checking that the LE, spar and TE all line up and adjusting if not. At this stage with a bit of luck the ribs will also all be a nice snug fit as well.
Next glue in the rib nearest to the tip, followed by the tapered piece WT, doing it in this order puts WT in the right place:-
You can then fit the ribs, noting that most of them do not have the webbing piece(W) between them. It’s just one W piece near the end and a DW piece at the end position. You can then finish off by adding the top spar, you can see why this is shorter than the bottom spar now:-
I removed it from the board and trimmed the LE,TE and spars to length and then did a dry fit(no gluing at this stage) with the middle section:-
A couple of things to note here. The first is that 4” support at the end. Please don’t just hunt around for something that’s 4” high, if you take the trouble to make a proper stable support it will make life much easier in the long run. Mine made from quite thick card.
The other point is that the strength of this joint lies in the dihedral braces rather than the end to end butt joints. Obviously make them as good as you can and don’t leave gaping gaps, but if you aren’t careful you can end up chasing your tail, trimming one part that then means you have to trim another was previously OK and then that leads on to trimming another part, etc,etc………. When I do glue these I may well use epoxy which is the one glue that can be used to fill a small gap on a less than perfect joint. But don’t glue these joints yet, there is more work to be done before this.
Having made one wing tip, you then have to build the other and I don’t need to tell you to make it the other way round, so they aren’t both the same !!! Both tips are shown over each other on the plan.
Part 3 – Finishing the wing
OK, having built the basic wing middle section and both tips, ‘all’ that remains to be done is shape the LE and TE, tidy it all up and then join the tips to the middle section. But first, two words of warning !
There are two dihedral braces at each end, a deep centre brace and a narrow LE brace. It’s very easy to break that LE brace. All it takes is for it to hit something as you are moving it around in the workroom, this is course is just what I did:-
There was no way that I could repair this but I figured I could do without it and just rely on the gussets that will be added later, two reasons for think this. The first is that if the brace was that weak then it wasn’t really doing anything anyway and the second is that the original Lulu plan didn’t show a brace here. I just sanded the broken end flush with the end rib and carried on.
The second warning concerns the joints between the ribs and the TE. Other people that I spoke to at the recent club meeting expressed concern that the ribs weren’t notched into the TE and this would have been my preference as well. As it is there is very little glue area on these joints and when I started sanding the TL, these joints started to fail to the point where on one of the wing tips, the TE detached completely. At that point I wasn’t a happy bunny to say the least.
The solution was to add gussets at all of the TE/rib joints:-
So, two things about these gussets, firstly, there are a lot of them! And secondly, as with all gussets the grain has to run along the diagonal, which makes marking them out accurately a real pain. The solution to both of these was to create a simple template using my CAD drawing package:-
This pattern is 36 gussets, each with 10mm sides (I can send the file for this on request). It was now just a matter of printing this, using a glue stick to glue it to a piece of medium 1/16 balsa and start cutting. If you do it straightaway then the paper can easily be peeled off the cut gussets. The result was a pile of gussets, all the same size, and all an accurate right angle. Actually you need more than the 36 so have to do it 1 and a bit times to get the required number. Trust me, it’s worth the effort to do this.
OK, almost ready to start shaping but you need a few things before you begin. The first of these is a decent sanding tool and you can’t beat a Perma-Grit tool, essential in any workshop, wouldn’t be without it :-
Next, I find balsa dust very irritating so always wear a mask when sanding and I also have a vacuum cleaner to hand to keep the whole area dust free. You can’t blow the dust away when checking progress with a mask on!
When sanding the LE and TE you need to be very aware of not damaging any of the ribs. It’s all too easy to just clip a rib and take a chunk out of it or even break it, so be aware of where the edge of the sanding block is at all times. Also remember that it’s very easy to take material off but you can’t put it back again if you take too much off, so take it slowly and keep stopping to check on progress.
I started with the LE and found the ply gauge that is supplied with the kit very helpful indeed, not too much more to say about that. On the TE then my advice is to be careful not to make the edge too thin, it’s easy to get carried away here (been there, done it in the past!). Aim for about 1.5mm and if it ends up at about 1mm that’s fine but no less.
It did take me a long time to do this sanding but its worthwhile taking it slowly and carefully.
Having done the LE and TE then the wing tips need the edges rounding and generally fairing into the LE and TE. You may also want to give the ribs a gentle sanding to get rid of the black edges that result from the laser cutting and then give the wings a final light sanding all over to finish, that’s easier now than later. So these are the wing panels ready for joining (see if you can spot the missing TE gusset!) :-
At long last, you can finally join the wing tips, one at a time. I showed a picture of this earlier when it was just a dry test fit and stressed the importance of making a 4 inch high support rather than pile of books:-
The picture below shows two things. The fist is just how small and cluttered my workspace is(needs a bit of a tidy up) and also that the building board doesn’t have to be the full 51 inches of the wing, as long as a substantial part of the middle section and one tip are on the board, the rest can hang over one end :-
The final part of the job is to add the large gussets in the kit to the wing tips at the dihedral joint. Now it’s time to be very careful when moving the wing around. Unless you have a large workspace it’s easy to damage the wing by hitting things as you move it around.
The plan does show a 1/32 ply reinforcing piece (TER) on the trailing edge. This is to stop the wing bands damaging it. I’ll added this later, after covering.
OK, on to the tail feathers next ………….
Part 4 – Tail feathers
You will no doubt be pleased to know that having built the wing, the fin and tailplane are very much easier, just one thing to be aware of which I’ll come too shortly.
I started with the tailplane and first built the outline, i.e. the LE, TE and tip pieces, thinking that this would have put the LE & TE just the right distance apart for the ‘ribs’ to fit nicely between them. Wrong! The ‘ribs’ were just a tad too short, not much, just a fraction of a mm but we all know that glue shouldn’t be used to fill gaps. The other issue is that the ‘rib’s (which are actually just 1/8 square strip) are very brittle. Don’t ask me why, but I never like stripwood that has been laser cut from a sheet. The answer was to cut some 1/8 square from a sheet of 9lb/cu ft balsa or use some medium 1/8 square if you have some to hand. Since I was now going to have to cut all the rib’s to length, I did the same as Alan Trinder (see his article in the latest Meadow Flyer) and used diagonal ribs. I don’t know how much they really contribute to rigidity but they certainly look better:-
There are two fins, upper and lower, built separately and these are very easy, just outline pieces and gussets:-
Note that the upper and lower fins will later be joined by an 1/8 sq spruce sternpost, but not yet, that’s for after they have been glued to the fuselage.
Once the fins and tailplane are dry they can be removed from the building board, sanded flat and the leading edges rounded off, but not the trailing edges !!!!!.
OK, all the flying surfaces out of the way for now, time to move on to the interesting bit, the fuselage.
Part 5 – The Fuselage
OK, finally the interesting bit, the fuselage.
Each fuselage side is in two pieces with a zig-zag joint between them. I couldn’t make any sense of the instructions about turning the rear sides over because of the zig-zag’s being different on each side, so ignored this and just carried on, both sides are the same to the point where they are both marked as ‘inside’ so one of the ‘inside’ markings will end up on the outside !
Rather than just rely on the zig-zags to accurately get the front and rear fuselage sides aligned, I glued them together pinned down to the Clingfilm protected plan, one side at a time. It’s very important that the front and back are accurately aligned and that both sides are exactly the same. When pinning down to the plan, you will see that the rear side pieces are actually a little longer that the plan shows, ignore that! Sorry, I forgot to take a picture at this stage.
For the next stage I did deviate a little from the steps in the instructions. First find F1,F2 & F3, they are all on the ply sheet. Now, mark one of the fuselage sides L and the other R, both of these markings being on the inside of course. Mark F1 and F3 with Top and Front(or bottom and back whichever takes you fancy) and mark F2 with Top. This ensures that every time you test fit the assembly, it’s always the same:-
Now you can take F3 and chamfer the sides to match the plan view on the plan(the instructions say side view, ignore that). You don’t need to chafer F2 so ignore that instruction as well. Ignore F1 at this stage.
Now Fit F3 and F2 together and test fit them to each fuselage side in turn. The edges of F2 should lie along the fuselage sides, if they don’t then the chamfer on F3 is not enough and needs to be adjusted. Now you can glue F2 and F3 together as per the plan instructions and you can see the importance of marking Top, Front etc:-
Now find F5 and F6. After a test fit, glue them to one fuselage side with some engineers squares to make sure they are vertical and leave to dry:-
Next position the other fuselage side over F5 and F6 and glue in place taking great care that the two sides and aligned with each other(check with a square). The drill vice is probably overkill, but add some weight at this stage:-
Now add the doublers HD and HDV taking care with the alignment, as per the instructions. A few clothes pegs help here:-
And the next job is nice and easy – gluing in the two F2A pieces, one each side, you will find them on the ply sheet:-
Now we come to the part that I always hate, bringing the front together. While doing this, be aware that the back ends of the fuselage are very vulnerable at this stage and are easily broken when moving the fuselage around. Alan Trinder broke his and I can understand why. When the back end is joined later, it will be much stronger.
The instructions talk about doing this with F1, F2/F3 and F4 inserted. I spent a long while trying to dry fit all of these together in one stage and decided that its best done in separate stages. So I started with F4 :-
You will need some sort of clamp to hold the sides together while this dries. The clamp that I used is a toolmakers clamp that I made in school 60 years ago and still use from time to time. I don’t suppose that kids nowadays are allowed to use things like lathes and milling machines. We learnt how to setup a Myford lathe to make the long screw threads, proper engineering … but I digress !
Next insert the F2/F3 assembly and bring the front together with a suitable clamp:-
The clamp that I used is pretty powerful and I really should have added pieces of balsa on either side to stop it marking the fuselage sides – bit late now, I have to live with the marks.
Adding F1 is a bit fiddly and you will have to chamfer the sides with a file but doing it now rather than earlier makes it clear what needs to be chamfered and by how much. I used a less powerful clamp this time:-
Time to bring the back end together, to do this you will have to sand a chamfer on the insides such that the back end is only 1/8 inch thick to match the sternpost that will be added later, this takes a bit of time to get right. Clamp the ends together without gluing and very carefully check that the fuselage is straight with the joined ends in the centre, if not then adjust until it is. Once happy you can glue this joint.
Now identify F7,8,9 @10 :-
Notice that on F7, since the grain is vertical, I added a strip on 1/8 sq balsa top and bottom. Alan Trinder had a problem with formers breaking. This will prevent that. Actually, looking at the picture I should have done the same to F8.
First I added F9, you may have to file the slots in the fuselage sides so that the tabs fit, this applies to the other formers as well. Once F9 was in, I added F10 which I had to adjust a bit as well. And finally I added F8 and F7.
The instructions say to add the wing dowels at this stage, that’s not a good idea, it makes the covering difficult, leave these until its been covered. In fact, don’t glue the dowels in place at all unless you have to, it’s easier should you ever have to re-cover the model.
F7 has a length of 1/8 x 3/8 balsa glued to the top of it, this gives a ‘landing’ to the top sheet covering to be added later.
Next the top and bottoms of all the formers can be sanded flush with the fuselage sides and the sides themselves can be sanded flat.
It’s starting to look like a fuselage now :-
OK, ready for the top & bottom sheeting. The first job is the ply parts BS2 & BS2a which have to be glued together, these are the parts that the towhook is going to be attached to:-
While that was drying I got on with the rest of the sheeting, but first a few points. The first is that I would normally expect the grain to be running across the width of the model not along its length as per the kit. One obvious reason for kitting it this way is that its fewer parts but for the front of the model at least you might want to ignore the kit parts and sheet it with the grain running across the width. But for the back end I figured it was better to stay with the kit since the back end will be stronger with the grain lengthways given all the cut-outs in the sides.
The next point is that it is very unlikely that your model will have turned out to be exactly the shape intended so the top and bottom sheeting parts won’t be a perfect fit, there will either be a small piece of overhang or underhand. The overhang is no problem, just sand it off after gluing. The underhang is hopefully small enough to ignore but if you are a perfectionist you might want to fix it by gluing some scrap wood into the underhang then sanding off. That will all make sense when you try to fit the parts!!
And lastly, up to this point almost all of my gluing was with PVA but I switched to cyno for the sheeting for speed. Attach one end first (making sure it’s all aligned), then cyno the rest in place in stages along the length.
So, here is BS1 added and you can see what I mean by underhang :-
And with BS2 assembly and BS3 added (there is no BS4, ignore that in the instructions):-
And the first of the top sheeting parts:-
When all of the sheeting is complete then gussetts ate added to the BS2 assembly, sorry, picture is out of focus !
And then the 1/8 sq rails for the wing seating:-
The next thing that I tackled was the towhook and there ae two things that you need to know:-
1)I HATE wire bending
2)I’m rubbish at it
Given the above this is what I did, you can probably do a better job. I also have to say that it’s a very complicated way of making an adjustable towhook. Best study the drawing on the plan until it all makes sense.
There is a length of 22SWG wire in the kit, I started by marking the centre and bending it back on itself:-
The next bends that I made are shown below, to the dimensions shown on the plan:-
Next I turned the ends out but as you can see, I couldn’t get them to lie in the same plan(i.e. flat on the board). Every time I gripped the two parallel centre pieces and twisted, they just slipped over each other
The solution was to bind the centre pieces together with fuse wire and then solder them together, in the picture below they are bound but not yet soldered.
Now it was possible to get it to lie flat.
Now you have to bend those two ends back on themselves with a 2mm gap between them, I don’t know how this is possible, I couldn’t do it, this is what I ended up with :-
You can see that the gap which takes the screws is wider than 2mm. So, talking of screws, I couldn’t find them in my kit, maybe I lost them. I ended up buying some 2mm wood screws from Model Fixings(great range of products), the screws that I ordered are pan headed and the head is 4mm in diameter, they shouldn’t fall through my wider than 2mm gaps so should be OK(I hope).
I might have another go at the towhook some time or ask Andy Crisp how to make a simpler one!
The next job that I tackled is the nose block, there are 5 pieces that have to be glued together, the centre one being ply. Make sure they are all the same way around!!! I then glued the block to the fuselage and this time used some fast setting epoxy, firstly because I couldn’t clamp it in place and secondly because the fit to the fuselage wasn’t perfect and epoxy is good at filling gaps. Again, make sure it’s the right way around, check it against the plan!!!!
Time for the Perma-Grit tool again and a few minutes very satisfying work should produce a nice result:-
Actually the nose is one drawback of the Lulu, really it’s a bit of a menace with that pointed front end.
The hatch was next and I have to say that’s it’s pretty clever in the way that it fix’s. Start by trial fitting the top part. You may have to trim it to length to get it to fit. I then glued the ply bottom part in place, aligning the front edges:-
You now need to put a curve into the hatch to match the curve of the top of the fuselage. The rounded edge of a kitchen worktop is ideal, just gently roll it back and forth over the edge, then trial fit it with the overhanding back edge slipped into place. One you are happy with that then you can add the front CF peg, using epoxy, be sure to get it in the centre !
To get the front peg to fit, I had to ease out the hole in the former with a 2mm drill, it then fitted well. To get the back end in place you do have to bend the hatch quiet a lot and it’s a bit scary the first time, expecting it to snap at any minute but it seems OK. I had to trim the back end by other mm or so to get a snug fit which you can see in the picture of the noseblock a few pictures back.
Almost done!!!! Before moving on I did quick alignment check, this is in the instruction but later on. I put the wing dowels in place, banded the wing on lightly and offered up the tailplane, with a bit of luck, when viewed front the back, the wing and the tailplane should be parallel. Mine were (just luck) if they aren’t then you need to pack the tailplane seat on one side to get them parallel. You can now sit back and admire your work to date :-
The next stage will be the RC fit, I just ordered the bits I need for that.
Part 6 – Radio fit – Part 1
OK, the basic model is finished time to think about the radio kit and get the servo’s installed. The rest of the radio install is best left until it’s been covered but you need to get the kit together now.
The choice of radio kit is going to be very personal and determined by what transmitter you use of course, also what you may have to hand and personal preference. I’ll talk about what I am using, hopefully there will be some useful advice.
Battery. The options here are to use either a 4.8V NiMH battery or a 2S LiPo which will be 8.4V at full charge, falling to maybe 7.00V as a safe minimum voltage. I opted for the 2S Lipo. Although the receiver that I am using can handle the 8.4V, the servo’s are only rated for 6V so I used a BEC to produce a regulated 5V, more on this later.
These are the batteries that I had to hand, 2S, 180mAH. These fit very nicely in the front of the model and are small enough to pass through the front bulkhead with no trouble.
My batteries were bought a while back, what looks like the same battery but branded as Eflite was available but showing a zero stock in most places. I can however see a very similar battery from some other sources. If you use this type of battery be aware that it only has a balance lead, with a non-standard connector. I guess that Efilte had a dedicated charger that charged through the balance lead, fine for low currents but not compatible with most chargers. The solution is a lead from Micron RC that you can see in the picture. In effect it’s a Y lead, one branch goes to a standard balance connector and the other to a pair of 4mm banana plugs, this allows me to charge with a standard charger, turned down to its lowest charge rate.
My transmitter is an old Spektum DX6i so I opted for a Lemon receiver, the LM0080N, this is tiny and weights a mere 2.3g but does have a downside in that it doesn’t have any connectors, I had to fit these myself. To do this you need to be confident about soldering on a tiny PCB, or get someone use to do it for you.
Servo’s – the plan calls for 9g servo’s. you could probably get away with lighter but would probably just end up adding nose weight, so stay with 9g. The size is VERY important. The body length (excluding the lugs) can’t be longer that 24mm and the body width can’t be more than 12mm or else they just won’t fit.
And finally, since I am using a 2S LiPo I need a BEC to provide a regulated 5V, this goes between the battery and the receiver. The one I used I bought from Micron RC and it can supply 1A. I fitted a lead to this from the battery connector and from it to a standard servo plug so it can be plugged into the receiver. Here is my RC kit :-
Having got all the kit together, best to connect it all up, bind it to your transmitter and check that it all works, easier to sort out issues now rather than when it’s in the model:-
Time to fit the servo’s into the model. My servo’s were about 23.8mm long and wouldn’t fit by about a mm or so. This involved removing some material from the front edge of F4, which of course is buried deep inside the fuselage. The saving grace is that F4 is liteply rather than ‘proper’ ply so a bit can be shaved off with a scalpel without too much trouble and tidied up with a small file. Check the servo’s(without the arms fitted) now fit and drill for the fixed screws. In order to do this I used a 0.5mm drill in a pin vice. Screw the servo’s into place to check all is OK
The servo arms will need to be shortened, a lot !!!! Shortened to the point that there is only one hole remaining. The instructions do say to use the innermost hole on the servo, so this should be OK. Before I shortened the arm, I first drilled out the inner hole to 1/16 inch, since I intend to copy Alan Trinder and use pushrods and the. This is an alternative to the thread connection that is given in the plan and instructions and seems to me to be much easier to setup. I’ll still keep the torsion springs on the control surfaces so the ‘pushrods’ are actually ‘pullrods’ since they are always in tension and can indeed be very thin.
If you do this route and also use the Dubro micro pushrod system you will find this has some very nice servo arm connectors that make centering the control surfaces very easy. If you use these, be aware that the hole in the arm needs to be 1/16 inch(or 1.6mm), if you only have a metric drillset a standard 1.5mm drill is too small.
You can now fit the servo arms but be sure to centre the servo’s first(a servo tester is useful here). . Note that one servo is reversed to aid the arm clearance.
I then checked the arm clearance my connecting up the receiver etc :
And now you can see that there is clearance between the arms with the transmitter stick pushed into one corner, but only just!!!
That’s it for now, the next stage is covering followed by the final assembly and part 2 of the RC fit.
Lacing Up Control Surfaces – Roger Mathews
During the Lulu build using a single pull, with sprung control surface, I found I needed to pass a pull control line through a rather small hole in the servo arm.
I fly fish and tie my own flies; and during this process there is a requirement to pass the tying thread through a winding bobbin.To achieve this there is a small tool called a bobbin threader. I have one and it can be used to thread the servo arm, woohoo!
- What we want to achieve is the control line passed through the servo arm hole so we can tie it off.
- Here’s the threading tool, all it really is, is a very fine wire in brass handle, folded into a loop
- Pass the threader loop through the selected servo arm hole, then pass the control line throught the wire loop , with plenty of spare.
- Nextpull threader back with the control line and hey presto the servo has been threaded
Members Models
Alan Trinder’s Lulu flew straight off the building board with little trim changes needed
Roger Mathews Lulu covered in film
