Aero-naut A-10

[Gary Binnie]

1 minute ago, Danny Fenton said:

Easier to plane those spars down before you start I would say, but you already know that ?

 

Cheers

Danny

 

Absolutely, it's not much. Also need to check the height at the root, don't want a mismatch there.

 

I've got a special 'spar planing jig' in the shed for planing spruce glider spars. Two bits of right angle aluminium basically!

 

 

 

 

 

[Danny Fenton]

Very clever, I use the mk1 eyeball......

[Gary Binnie]

I only use it for spruce, the grain causes a plane to dig in, it's a pain to sand so I plane it as close as I dare.

 

 

[Gary Binnie]

Corrected the spar thickness problem, the step was 1.3 mm to the centre section spar which could have caused a problem.

 

Glued in the rear fuselage formers, one at a time and checking alignment with each one.

 

Pulling the fuselage sides in at the top required some force, lots of clamps, CA and activator.

 

Had another go at deciphering the instructions last night and discovered that the engine pylons should not have been joined until after the rear upper sheeting is added.  I don't think it will cause a problem, there would be no other way to do it with the fibreglass fuselage.

 

1. Height difference of the centre and tip panel spars, the red hatched area will be sawn off (mating faces of the panels).

 

 

2. Sanding the spars down to size, initially both were taped together.

 

 

3. Gluing in the rear formers.

 

 

4. Engine pylon resting in position, starting to pull the fuselage sides in at the top.

 

 

5. Motor wires exit the hole in the pylon skin and pass forward though the former hole.

 

 

7.  An excerpt from the instructions. To be fair the chap I spoke to at Aero-naut recently apologised for them and said that this kit is not up to their present standards. That may be true but it's still a high quality kit. I feel a bit rotten because I should offer to translate them, I have worked for a German aviation book publisher.

 

 

[Gary Binnie]

Half day today, have to prep daughter's car for MOT.

 

The fuselage is built as far as I want to go for the moment, will build the tailplane, fin and wings next.

 

1. Pulling the nose in, always fun!

 

 

2. Added remaining battery box rails and structure, added side strips that are not on the plan. Almost made a mistake last night by cutting the upper rear longeron to length, another former (42) needed to be added, caught the error just in time. 

 

 

3. Added '22' which is a Liteply cross piece at the tail, it's probably not needed as it's for the rudder bellcrank mount but it does stabilise the structure. A plastic moulding forms the tail cone.

 

 

4. The fuselage as far as I want to go at the moment.

 

 

5. The canopy moulding, I get nervous cutting these things!

 

 

6. It's got to be done!

 

 

[Gary Binnie]

Lunchtime update.

 

Tailplane structure completed, the leading edge is shaped to an aerofoil section. I use a David plane and then a sanding tool that came with a Carl Goldberg Ultimate kit.

 

The elevator is made from right angle trailing edge stock so there is a top and bottom, I scrapped the supplied hardwood joiner by chamfering it on the wrong side, luckily I had some spare spruce which I remember came from B & Q.

 

I will leave joining the elevator halves until the rear fuselage is almost finished in case the gap between them is different to the plan.

 

The optional rudder bellcrank and snake arrangement can be seen on the plan.

 

Fins next.

 

 

 

 

[Gary Binnie]

A pair of fins pretty much completed.

 

There is another option (one of many!) to have the fins removable for transport, I thought about this but prefer to have them fixed, it will save some weight at the tail end.

 

Piccies:

 

1. A kit of parts for the fins.

 

 

2. Another mystery, parts 63 and 64 are die cut, one balsa one Liteply. To be laminated but balsa outside or inside? When it came to it the sandwich wasn't thick enough anyway and I spied a fin cross section on the plan, the Liteply part is the core with balsa either side. In an addendum sheet which mainly covers assembly of the fibreglass fuselage there is a note saying two more 63s needs to be made, which I did using left over wood from the fuselage sides.

 

 

 

3. Fin plan with the cross section, lower right (R-R).

 

 

4. The rudders come pre-shaped and oversize each end, they are either hinged with tape or glued to the fin. The mating faces needed squaring up a bit to glue them on straight.

 

 

5. Taped up like Egyptian mummies! The fins feel quite chunky and heavy, there is scope for some lightening holes and they are constant thickness where I would guess that actual A-10 parts taper towards the top. I believe they can be fitted on either side, done for battle damage repair ease.

 

[Gary Binnie]

A bonus extra post! I wanted to get ahead of the game by joining the centre section wing sheeting together so I can crack on tomorrow.

 

I've photographed the process and will describe it for anyone who hasn't done this before.

 

1. Select the sheets to be joined, ideally all the same thickness and have straight edges, if not they can be trimmed with a steel rule/straight edge and scalpel (mind your fingers!). Place tape across the join, pulling quite hard to close the gap. the sheets will curl up slightly.

 

 

2. Add tape along the join.

 

 

3. Add the next panel (if needed).

 

 

4. Flip the sheets over and rest on a block, the joins will open up to form a 'V'.

 

 

5. Apply glue along the line and rub it in with a finger to ensure the 'V' is full (no air bubbles or gaps).

 

 

6. Remove the block and allow the sheets to lay flat on the board. Cover the work area with saved iron on film backing, not much sticks to it.

 

 

7. They will need to be weighted down, lots of glue will ooze out of the joins, use last year's BMFA Vectis card to scrape the excess glue off (lengthwise) and wipe off any remainder with kitchen towel.

 

 

8. Add another layer of film backing. The glue will take longer than usual to dry because air can't get to it but I usually allow several hours or overnight for drying.   

 

 

9. Cover with donated table mats (not Sunday best ones from the house!)

 

 

10. Add weights and leave to dry.

 

 

When dry lightly sand both sides of the panel, the taped side becomes the outside of the skin as there will be no glue on it, the joins should be virtually invisible.

 

If a plan doesn't show it try to arrange the joints to sit over spars, it minimises possible buckling. In the case of the A-10 the instructions say to cut the panels to span before joining, I prefer to cut the panel to size and squareness after joining.

 

   Cheers

 

        Gary

[John Stainforth]

Gary,

Great work and tips. I use the same procedure as you for joining sheets, but (although I am a massive fan of white glue - aliphatic resin in my case), I find CA ideal for this task. I sheets don't buckle at all, and by the time I have lightly sanded the joints, they are almost invisible.

[Gary Binnie]

Cheers, I've got an enormous supply of aliphatic after a model shop sent it by mistake and convinced me to keep it.

 

I have most of the centre section panel done, no problems.

 

1. Lower sheet after joining yesterday.

 

 

2. A kit of centre section parts.

 

 

3. Trimmed the span using the spar and marked a strip at the trailing edge using the rib tails, the strip needed to be chamfered to mate with another chamfer on the upper skin which should give a sharp trailing edge.

 

 

4 and 5. As the model will be hand launched cut outs need to be made in the lower sheeting for moulded finger grips, the instructions say to cut holes but leave the rounded ends till later.

 

 

 

 

6. Just having a look how they fit with the lower wing centre section fairing.

 

 

7. Dry fitting everything.

 

 

 

8. The leading edge of the sheet needs packing up to match the curve of the ribs, the instructions say to use tapered strip that is used later for aileron facings. This curve is sometimes called the 'Phillips entry', mostly in the States. 

 

 

 

9. Added the Liteply reinforcing between the hand grips plus an extra cross brace, I have cracked carbon fuselages with a death grip!

 

 

 

10. End ribs are canted inwards at half the dihedral angle using a supplied jig ('WS' winkle schablone = angle template) , very little glue applied to the spar as the rib will be cut away for a pair of ply dihedral braces.

 

 

11. Hard balsa reinforcements added for the two wing securing bolt holes, made from left over fin leading edge.

 

 

12. False leading edge added.

 

 

12a. A pair of half ribs are added once the finger grip moulding is in place. Next job will be to lift the panel from the board and open the holes up fully.

 

 

 

 

Edited March 5, 2021 by Gary Binnie
Rm an image

[Gary Binnie]

Lunchtime update, I've gone as far as I want to with the centre panel, moving on to the left panel which has been drawn on the plan correctly.

 

1. I cut the plastic mouldings using a combination of a steel ruler, new scalpel blade and a razor saw, the material is quite thin so it was relatively easy, some of the other mouldings are thicker.

 

 

2. Opened up the finger grip holes with a Dremel, set on a very low speed, finishing off with sandpaper wrapped around a glow starter, just happened to be the right radius.

 

 

3. I could now add the half ribs using the plastic parts as guides, pushing them out before the glue could stick them.

 

 

4. Thought it would be a good idea at this stage to pilot drill the wing mounting bolt holes as it's fairly critical that they are in the right position.

 

 

5. Starting to build the left outer panel, I wanted to use the centre panel to check the chord which is pretty much spot on to the plan. I will trim the right panel lower sheeting to the same root angle as a double check of the corrected drawing.

 

 

 

 

[David Ashby - Moderator]

Those mouldings would have put me off a bit but you're making a very neat job of 'em Gary. 

[Gary Binnie]

There is a fair sea of them! There's a small fear factor of slipping and making a mistake, would not be easy to get replacements but not impossible.

 

Had a panic just now, reading the instructions after building the left panel (as you do!) they have mixed up the part numbers of the upper and lower 'D' box sheeting, upper goes back to the spar. lower is thinner in chord. Luckily I've built it according to the plan and what looked right to me, phew!

Edited March 6, 2021 by Gary Binnie

[Gary Binnie]

Left outer panel progress: Quite similar to the centre panel but the spar has to be packed up with scrap balsa as there are open bays that have rib cap strips.

 

The instructions say to leave the rib noses in the air, add the false leading edge, shape it then add the lower sheeting. I did it the same as the centre section but adjusted the tapered packing strip as there is a very subtle change of section toward the tip, washout but it's not mentioned.

 

1. I'm getting braver with tapering the trailing edges, using a razor plane which speeds up the process, there are six panels to chamfer.

 

 

2. One of the pre-cut lower 'D' box sheets was quite bent and couldn't be straightened, unusual for sheet to warp in this direction. Replaced from my stock.

 

 

3. Watching the glue dry! Upper sheeting front and rear to be added, the ailerons are cut out later and faced with the tapered strip that is packing the leading edge up.

 

 

[john stones 1 - Moderator]

You're working well Gary.

[Gary Binnie]

Nothing else to do! In the last 12 months I've built and/or restored about six models, hopefully I will get to fly them soon.

[Gary Binnie]

Last update for today, another instruction induced panic but I think all is well.

 

I lifted the outer panel from the board and trimmed the false leading edge.

 

On checking the outer panel against the centre section there seemed to be a disagreement in the dihedral. The instructions say to raise Rib 105 (tip rib) 50 mm to set the dihedral. At this angle the mating ribs have a gap but the instructions definitely say to use the 'WS' template on both ribs (thought I might have slipped here).

 

Part 113 is a thin ply dihedral brace, there are four, this matches a fore and aft view of the dihedral break and placed on the spar the ribs close up.

 

I expect that the 50 mm measurement is wrong, I will check the German instructions.

 

All good fun!

 

 

 

 

[Gary Binnie]

Curiosity killed the cat!

 

Checked the German instructions, also says 50 mm under the tip rib.

 

By extending lines on the plan and double checking geometry 50 mm is correct and the dihedral angle is 7°.

 

The jig WS agrees with the plan.

 

Using the jig it's possible that the centre section root rib is leaning in too much, a small angle difference but significant.

 

Various ways to fix, unpicking a rib and resetting is probably easiest.

 

 

[Toni Reynaud]

Glue a dummy ribe to one face and sand to the correct angle. Possibly less hassle thathan ungluing one of the end ribs.

 

 

[Gary Binnie]

Hi Toni, I did consider that but the ribs are very flimsy and once the root rib is cut away from the spar (which it has to be to accommodate the ply dihedral braces) I will pull it to the centre section.

 

I've cheated today and used the centre section and a 50 mm block to set the root rib. It's a mystery but no point dwelling on it. just something to be aware of for future builders (I almost want to build another one!).

 

Today I built the majority of the right panel and checked it matches the left (which it does, yay!), had a tidy up and another inspirational assembly session.

 

There looked to be a problem with prop clearance on the motor nacelles but it should be ok.

 

1.  Dry fit of the right outer panel on the corrected drawing.

 

 

2. When it came to gluing the root rib I propped the panel up at the tip and used the centre section to set the angle...

 

 

3. ...and separated them quickly before any stray glue set.

 

 

4. Both panels back to back for a sanity check.

 

 

5 and 6. Time to throw it together, it's a nice size, not too big, not too small.

 

 

 

7, 8 and 9. It looked to me as if the propellers wouldn't clear the nacelles, it's close but I think it will be alright.

 

 

 

 

 

 

 

[Gary Binnie]

Today was mainly spent on adding the outer panel upper rear sheeting and cutting out the ailerons.

 

Tidied up again and separated built assemblies and parts still to be used from scrap/offcuts by moving them into the kit box halves.

 

Getting quite close to joining the wing panels though I want to do as much work as possible on each panel before that, just more convenient.

 

1. I marked the corners of the aileron cut outs by sticking a pin through, once the upper sheet was on and dry I could push the pin through the second sheet. The ailerons look too big to me, especially in span. They are supposed to extend to the tip rib which would have left no structure and just the tip block for strength, I've moved the outer end of the ailerons inboard by one rib, if it doesn't roll like a Pitts Special then I can only blame myself!!   

 

 

 

2. Upper rear sheet glued on and drying. The wing is not taking the full weight of the batteries, one end is on the building board.

 

 

3. At the trailing edge I used an aluminium bar to spread the load (milled from my glider winch to save weight). The instructions say to use laminating resin but I didn't see the need for that, they were probably thinking it would add strength.

 

 

4. One panel needed some encouragement to fully close up the trailing edge. Tesco's clothes pegs with rubber grips so they don't slip and ping off like wooden pegs do, don't know if they still sell these, had them a while.

 

 

5. I marked the aileron cut outs, the middle line wasn't necessary.

 

 

6. Cut out the sheet and portions of the ribs that have facing strips, used a straight edge and lots of light cuts with a scalpel then a razor blade.

 

 

7.  Each aileron needs two end ribs, they are shown as internal on the plan (could make them external). I won't face the ailerons yet as I need to fashion control horns and support blocks. 

 

 

 

8. Facing the ailerons with tapered strip is a brilliant idea for top hinging with tape, first time I've seen it. Usually have to sand chamfers which can easily go wrong.

 

 

9. Tapered facing strip added, the clamps look brutal but they have quite weak springs, specially selected from my stash of Rolson quality tools!

 

 

10 Another bonus mystery is this 30 mm measurement on the plan at the wing joint. I can find no mention of it in the instructions. It might be for positioning the landing gear block (not used in the hand launch version) but taking a measurement from the rear face of the spar would be more logical to me. It's not the CG range, that's on the fuselage plan. Dunno!!

 

 

11 and 12. Sorting finished parts, it was getting difficult to find things in the box.

 

 

 

 

 

[Gary Binnie]

Have solved the mystery of the dimension on the plan, it is an area of lower centre section sheet to be cut out to be able to clamp the two ply dihedral braces to the spar.

 

The instructions intend the panels to be completely sheeted before joining, all the upper D box sheet is still off to allow servo cable to be threaded through in my build.

 

Can't be too many mysteries left now?!!

 

 

[Gary Binnie]

Leisurely day today, joined the wing panels together.

 

1. Glued the ply dihedral braces in to the centre section, they're fairly thin as they have to bend slightly, the outer spar is swept back.

 

 

2. Gluing the left outer panel.

 

 

3. Adding the rear centre section sheeting, I pre-joined these a couple of days ago.

 

 

 

 

 

 

 

[Gary Binnie]

Bit of a blustery day as Winnie the Pooh would say!

 

Today's progress was work on the wing fixings and closing the centre section.

 

1. Taped some scrap sheet on to check the wing seat fit.

 

 

2. Looking at the leading edge from the front I could see that the ribs and false leading edge needed more sanding, there is no surplus material on the shaped leading edge so it has to be right.

 

 

3. A good way of holding the fuselage to work on wing fitting is clamping it by the firewall or nose former to the bench if the structure is strong enough.

 

 

4. With the wing sitting where it should be the dowel holes that I pre-drilled were slightly low, this lead to some head scratching and a swift re-design.

 

 

5. Wing seat fit is quite good.

 

 

6. At the trailing edge I placed two drills through the pilot holes.

 

 

7. The dowels have been sharpened to points for marking purposes, not shown is a ply plate that I've made to take the back of the dowels. The balsa strip is a spacer to simulate the leading edge shaped stock. Luckily this area is covered by a plastic fairing.

 

 

8. Added the servo cables.

 

 

9. Adding the forward centre section sheet.

 

 

10.  Pegs used close up at the front, load spreading strips used top and bottom.

 

 

Tomorrow I will be finishing the wing fixings, adding the outer panel D box upper sheeting and possibly the rib cap strips.

[Gary Binnie]

Late lunch/mid-afternoon/tea break update:

 

Have applied the upper D box sheeting now, second side drying. The second sheet was reluctant to bend to the airfoil shape but the pegs persuaded it, the sheet wood in this kit is variable, some of it is quarter grain/rib stock and on the hard side (which is also a heavier grade). I know these panels are original because they are roughly pre-cut to shape.

 

On lifting the wing from the board I chuckled as I could clearly see the servo cable as the lower D box sheet is only half chord. I could have completed the outer panels before joining them to the centre section. It does allow more glue to be applied from inside if needed. I'm more used to seeing fully sheeted D box structure.

 

While glue was drying (I give it at least an hour) I fitted brass M4 inserts for the wing attachment nylon bolts. The instructions say to harden the holes with CA then cut a thread, not really a fan of that idea, it might work but probably not for long.

 

1. Trimmed the right upper sheet slightly oversize before gluing, for a design with rib capping strips I like to position the rear edge at the mid line of the spar, this gives the strips a ledge and prevents them from rolling off the rib edge one way or the other, the plan has the sheet aligned with the rear face of the spar.

 

 

2. More peg and battery therapy, chairs positioned to protect from dogs and Mrs B.

 

 

3 and 4. Opening the wing bolt holes and fitting brass inserts. I drilled to 4 mm then use a round file to progressively open the holes to just under 6 mm, I find drills have a habit of digging in and tearing (or worse!) at larger sizes in ply. The inserts have an external thread so they can be wound in using a steel bolt (instead of pushing in with a G clamp as you would with 'T' nuts) then a drop of CA or epoxy to secure.

 

 

 

5. Underside view of the D box, I will be able to pull excess cable through.