Following my disappointment with BMFA/BARCS 100S competition (see Elan 100 build thread), I've decided to put my money where my mouth is and promote the F3-RES class in the UK. I'll put up a thread on any meetings that I organise, but my current plan is to do something, probably at Buckminster, next year.
The first job for me is to build a suitable model, hence the purchase of the Slite V2 and a suitable bungee from Hyperflight
Looking inside the box, I found about 15 metres of laser cut wood! To be fair, about 3 of the sheets are jigs for building the flying surfaces...but either way, that's a lot of wood to have to stick together! The box also included a plan, a pack of accessories, some snakes, some lengths of carbon including a very nicely produced fuselage boom, and a set of instructions in german!
The instruction book includes photos and text of the build, but I found interpretation of what was required a bit of a challenge. There was nothing for it but to get the book translated. So with the help of Google Translator, amongst other things, I have learned that this version of the model includes:
The surface patch is made of 4mm spring steel and now sits in the handlebars.
On the other hand, the useful part of the instruction book has translated well and I'm now in a position to give the model a go.....
The first job was to build the jig for the wing, which I did over the plan - note the dihedral wedges at each end of the jig:
Next off was to laminate the centre and end ribs from ply and balsa. There's a nice hint in the instructions that advises to use the 2mm locking pins to help line up the parts. To help find the bits, each sheet is marked in the top left corner and each part is marked. Both references are in the instructions to the right of the picture showing what you need to create.
With the laminated ribs drying, I turned my attention to separating the ribs from the sheet wood. Unfortunately, the laser cutting was a bit thin on some of them and despite careful cutting with a sharp knife, I broke off a number of the jigging tags - they were glued back in place before continuing with the build.
The instructions recommend fitting the ribs in the jig and then inserting the spar. The fit of the spar on the ribs was tight to say the least, so rather than force the spar through the ribs with the possibility of breaking more tabs, I slotted the ribs onto the spar before slotting the latter into the jig. The file on the cutting mat is required to open out the spar hole in the end ribs to allow setting the rib at an angle for the dihedral joint.
Slotting the ribs into the jig proved to be a bit of a challenge, but here's the result, weighted down with some lengths of mild steel. I've removed the plan from under the jig as it's not required for this part of the build.
There was not much happening today, so I could get on with the build.
I fitted the leading edge earlier, but there's no photo of that. Suffice to say that there was no issue noted.
The first issue quickly appeared, however, and that was how to stick the trailing edge (TE) onto the wing. The instructions call for thick cyano, but a dry fit took me well over a minute to achieve (and I broke two ribs in the process), so the glue would have gone off way before I got the TE into position. I tried removing the jig from the board and turning the assembly over, but the tabs either fell through or came out of the jig putting a nice twist into the wing.
In the end, I fixed the TE at each tip with cyano with the wing flat on the bench. The board was then put into an upright position and clamped, giving me access to the underside of each rib where I could get some cyano into each joint and clamp it as I worked down the wing. The two missing clamps in the pic are the two ribs I broke earlier. these were fixed later.
Note that the TE overhangs the building board to allow the clamps to be fitted.
Back into the horizontal position with weights to keep the tabs touching the base board. (a Merco 61 and a Laser 70, if you're interested)
While that was drying I made up the spoiler and spoiler box
The wing could now be removed from the jig and the riblets fitted. The instructions (somewhat glibly) say, align the riblets with the help of the rib-comb and glue them in place. Easy to say...not so easy to do! Two combs would have made the job a lot easier. Anyway, we got there in the end.
With the riblets done and the spoiler box dry, the latter was fitted to the wing. The clamps are an Aldi special - 10 small and 10 medium clamps for £1 in the gardening section - they double up as plant ties.
The laser cutting tags and some of the laser discolouration was taken down with a home-made sanding block - I use double sided tape to fix the paper to the balsa.
You can see how thin, and therefore vulnerable, the rear end of the ribs are - if you build this model, you really do need to take care.
.....and the lower ply centre-sheeting was glued and clamped in place. The instructions say use cyano, but I'm allergic to the stuff and prefer aliphatic, which is what I used in this case. Aldi clamps again.
While that was drying, I laminated parts F37 and F38, making sure to create a handed pair, to make up the doublers around the wing mount screw hole.
For some light relief away from the wing, I started on the fuselage sides - the instructions remind that a handed pair should be made. A nice touch is that if the parts are stuck down with all the numbers showing in the same orientation, then a handed pair will result.
By now, the fuselage bottom sheeting was dry, so the front top sheet was applied and the screw-hole doublers fitted. The hole has not yet been drilled.
With a bit of time to fill in and space available on the building board, the two middle wing jigs were laid down. Again, if all the part numbers can be seen in the correct orientation, a handed pair will result.
Wing middle section rear sheeting is now fitted. I had to cut about an inch off the back to fit it to the wing - the instructions do mention that the parts should be 'adjusted' - I take that to mean cut-to-fit.
...and finally for today, the fuselage former R11 has been laminated from two similar ply parts.
Following on from the last post, the wing retaining nut was epoxied into it's laminated ply plate and left to dry:
The fuselage sides could then be mated. The instructions say fit the formers on one side first, but such was the accuracy of the laser cutting, it was possible to assemble the fuselage free-hand in one go. I stress that I made constant checks as to the 'squareness' but it all fitted together very nicely with no apparent errors.
The underside was then added:
Here's a nice touch from the designers. They've added a blank servo tray to the laser cut sheet so you can cut your own holes to suit your own servos.
Next job was to make up the hatch. To ensure a good fit, the parts were joined using a straight edge:
The whole was then laminated and stuck to the ply rails - you'll find the assembly under the clamps if you look hard enough...
With the hatch completed (and the retaining magnets epoxied in place) the remaining upper surface sheeting could be added. The nose block has also been fitted in the following photo:
This lead to a quick trial fit of the centre-section, which went together well - so far so good!
There's no more pics of the fuselage construction, I'm afraid. Suffice to say that the rear fuselage boom was epoxied in place, the snakes dry fitted with foam 'rammed' up the back end to support them - see plan 'Schaumstoff' is German for foam) - and the fuselage to boom fairings were fitted. The whole was then sanded ready for covering.
The spars were cut off flush using a jewellers saw with a very fine blade. The root ribs were then tidied with a fine sanding block.
The jigs for the tailplane and wing tips were assembled. As before, if all the part numbers can be seen on the parts, then two 'handed' wing jigs will be produced.
Each rib has a ply doubler fitted to its trailing edge. The instructions say fit the doublers after the wing has been built, but I decided to do it pre-build on the middle wing section pieces. It wasn't a good idea as I forgot about the small allowance for the trailing edge and fitted them too far back. It meant opening up the notch in the ply trailing edge a little, so there were no real issues.
As with the wing centre-section, I fitted the ribs to the spar before adding the assembly to the jig. The spar holes in the root ribs were opened out slightly to cater for the root rib angle.
After building the centre-section, I noticed that the TE had a slight wave in it. On closer inspection, it appeared that the TE parts were slightly too long. It looks like they've been 'cut to plan' and the slight inward tilt of the root ribs has not been taken into account. You can see the difference between the notch for the rib and the root rib in the below pic.
The notch was increased in size accordingly and the TE added to the wing.
With the wings still in the jig, the LE was added with scrap balsa holding it in place until the glue dried.
After removal from the jig, the riblets were added using the comb as a guide. I used the plan for the centre-section, but I had better luck lining up the riblets with the markings on a cutting matt.
The wing tips were made up in a similar way...but this time, I didn't add the TE doublers.
The three extreme ribs on the tip panels had to be cut down a little and notched with a round file for the LE. The latter was fixed at the tip first, and when dry, pulled on to the rest of the wing ribs.
The wing tips are permanently joined to the mid-sections. The resulting outboard wing assembly is then joined to the centre-section by steel dowels running into a brass tube inside the hollow spar with a steel pin close to the trailing edge to maintain the incidence. The steel pins and brass tubes are set into boxes made from ply. The gaps are filled with balsa and epoxy and the whole sanded to circular cross section to fit inside the spars. The end plates on the ply boxes set the dihedral angle, but the whole is accurately laid out, so the execution should be simple ....
I had two issues.
The first was that the box end plates were small and complex, but the laser cutting was heavy, so the end plates broke up as I removed them from the carrier sheet:
Luckily, the bits that were left were enough to set the correct angle on the steel rod, albeit with some of the end plate missing
Here's another view of the first one, including a view of the second with broken bits.
The brass boxes went together a lot easier as they were correspondingly bigger
And finally, a view of the assembled boxes with balsa and epoxy fill.
The second issue was getting the 'right' angle for the boxes in the spars. The outboard wing spars are swept back when compared to the centre-section spars. If the boxes are fitted 'square', then there is a gap at the TE
Therefore, the boxes have to be twisted slightly to get the rod and tube to mate at the right angle for the spar join.
This will then give a flush joint between the wings.
The following pic shows an exaggerated twist in the ply box so that you can see what needs to be done. It took a lot of fiddling to get the angle right
With all that sorted, the boxes were epoxied into the wings and the wings clamped using s suitable spacer (to prevent the wings sticking together!)
Finally, the outboard sections were removed and the tips glued and clamped using the glass dihedral brace inside the spars.
...and the TE doublers were fitted to the remainder of the wing - it wasn't as fiddly a job as I'd first suspected.
Tailplane, elevator, fin and rudder:
In general, the laser cutting in the kit was good...but there were three exceptions. We've already seen that some main wing ribs were not fully cut and the ply boxes in the spars were cut too heavily. On the tailplane, several of the ribs were not cut cleanly and required some very careful cutting with a sharp (new blade) modelling knife:
The taiplane was made up in a jig as per the wing. It proved impossible to fit the ribs tnto the jig after fitting them to the spar, so the spar was fitted after putting the ribs in the jig. Apart from the above, there were no issues
With the tailplane off the jig, the LE was laid down on the board and held with scrap balsa. Note that there is a clear plastic sheet between the board and the LE and one of the TP ribs has broken
Such is the accuracy of the laser cutting, the fin, rudder and elevators could be laid down on the board without using the plan - except to check positioning of the parts. With all part numbers in view, the parts are correctly orientated.
with the empennage built, a quick trial fit was too good to miss:
I've used Oralight covering for the model, translucent on the flying surfaces and solid colour on the fuselage. I have to say that it was easy to use, it produced a good finish and was well worth the expense.
I've picked up two tips recently:
1. Vacuum the model before covering to remove all the dust and stray bits. A see-through reservoir on the hoover is a good idea for this one as is emptying the 'bag' both before and after the exercise!
2. Use two small pieces of masking or similar tape to separate the backing from the film - I've been covering with film for some 40 years now and I so wish that I'd been passed this tip when I first started!
The covering job progressed pretty quickly, so there's not many pics, I'm afraid.
I covered the centresection in one piece as it had a straight leading edge. The rest of the wing had to be covered both sides separately as both the LE and TE are curved.
The spoiler was hinged with film, as per instructions. The sequence was as follows: fill in the spoiler box with film, cutting a strip abut 6mm proud of the box at the front. Cover the inside of the spoiler. Lay the spoiler on the wing and stick the strip of film to the inside leading edge of the spoiler. fold the spoiler back into the wing, then cover the wing itself. Cut the film on the side and rear edges of the spoiler and a nicely front hinged spoiler results.
Moving on to the empennage, the lower surface of the tailplane and elevator were covered first.
A strip of film was then ironed onto the edge of the elevator and tailplane as shown - note that the elevator is folded back over the tailplane to do this.
The tailplane is then turned over and the whole covered in one piece. A top hinged elevator results.
Moving on to the fin, the fin TE and rudder LE were chamfered as shown (the tailplane was chamfered similarly, but no pics, I'm afraid):
The instructions show the fin and rudder hinged before fitting. Unfortunately this is not possible as the fin slots into the fuselage, so it must be fitted before adding the rudder. The pic shows one side of the fin and rudder covered and a 10mm strip of film fitted to the rudder.
The rudder was then offered to the fin at about 90 degrees deflection and the strip ironed on to the fin LE. The other side of the fin/rudder was then covered in one piece producing a film hinged unit.
Another trial assembly gives us a completed model....radio and controls next!
Radio and controls
I've spent the last two days fitting the radio gear, getting the controls to work and sorting the weight and balance. It's not one of my favourite jobs and on this machine it really lived up to it's name. The fuselage is thin and not very deep., so working in it with my fat fingers was a real challenge.
First off, I procured some of the batteries and servos advertised with the model in the assumption that they would be suitable... the rudder and elevator servos were, but there was no way that the battery was going to fit in the nose and the spoiler servo proved to be too thick - see later for the solution to that one.
The only way I could fit the kit into the model was to put the battery behind the servos and the receiver in front, which is not ideal. The solution would need a lot of wire through the servo bay with little room to stow it. Every change of plan required the servos to be removed, the wire laid down, and the servos replaced. The only solution appeared to be to move the servos back but I was concerned about the damage removing the servo tray would do to the balsa fuselage. In the end, luck won out in that on the fifth removal of the servos, the servo tray broke cleanly out of the model. I could now make a plan. The following shows the intended layout with the design layout above:
The servo tray needed some slight modification to clear one of the ply uprights and I glued in some 1.5mm balsa sheets (12mm high) to make the job of levelling the tray easier and to give it something to stick to. I made the side plates a little deeper than required to give a bit more clearance for the cables underneath the servos. There would only be one running the full length for the battery, but there was also the two servo leads.
The result follows:
While fitting out the model earlier, I noted that the central location of the snake holes in the former at the front of the wing bay lead the snakes to cover the area where I was going to put the receiver and also caused the two control rods to interfere with each other. I drilled out two new holes nearer the side of the fuselage.
Here's the final layout with the battery in front and the control rods laying nicely at the side of the fuselage.
A word now on the control rods. I found that they broke easily when bending, in some cases they even broke on the first bend. No problem, I thought, as I have a large stock of 1/32" wire in the workshop. Unfortunately, my stock is UK procured, so it's only 36" long. The model requires 1 metre long control rods so my replacements, as with those supplied with the model after my bending attempts, were too short. Moving the servos back partially solved the problem, but I did have to extend the rudder control slightly by adding a threaded adaptor and quick link.
Now for the spoiler. In contrast to the rudder and elevator, this job proved to be remarkably straightforward.
The servo is mounted using servo tape, so the first job was to cut off the servo mounting lugs as they fouled the servo box in the model.
Next was to bend the actuating arm from 'spare' control rod (I'm not sure where this would come from as most of it was required to join the servos to the empennage!).
I cut a servo arm to the size shown on the plan, zero'd the servo and fitted the arm in line with the servo axis. Then, using a servo tester, I set the servo to full out spoiler and connected the arm to the spoiler and servo. The servo was then fixed to F4 with servo tape. The spoiler worked fine, but wouldn't close. A quick inspection showed that the servo was sitting proud of the wing. F4 was then removed and the spoiler closed.
The initial deflection wasn't enough, so I experimented with actuating arm position on the spoiler and servo arm orientation with respect to the servo. In the end, I used the rear hole on the spoiler, a servo arm as per the plan and the servo arm aligned with the axis of the servo when the servo was at neutral. It took about three removals of the servo, but I used the same tape each time. I renewed the tape once I'd got it sorted.
As you can see from the next photo, the removal of F4 has left only the centre rib of the wing to stick the servo to. It'll do for first test flights, but I'll need to fill in the gaps at the side before I compete with the model.
So, she's now ready for test, but with poor weather forecast this week, I'm not holding my breath .... so maybe I will go do a bit more to the Fury!