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Derek Woodward 'Amelia'

Wing construction confusion.

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Matt Carlton03/10/2020 23:56:06
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131 forum posts
12 photos

Hello all,

This is probably a case of me being stupid but here goes.

The free plan for DW's very charming 'Amelia' appears to have an anomaly at the wing centre section. The plan appears to indicate a centre line to the left of the servo. That centre line measures out for the correct span.

However, it makes no sense for there to be a centre rib and a servo offset to the side as the torque rod horns would straddle the fuselage sides.

My assumption is that the centre section is built as a separate unit, with the dihedral brace and u/c bearers.

It's an easy enough thing to sort out, but I wondered if anyone has built this model and as a long shot, has a photo of the centre section construction.

Many thanks all,

Matt

screenshot_20201003_234952.jpg

Edited By Matt Carlton on 03/10/2020 23:59:21

Edited By Matt Carlton on 04/10/2020 00:00:06

kc04/10/2020 11:55:58
6777 forum posts
174 photos

No. it does not seem to make sense. Could be it used two aileron servos one each side, yet this was not common in the days of expensive ( £ 12 each! ) servos. More likely a draughstmans error not Derecks and should be shown central. The dihedral brace is shown as flat at centre section, but this could also be an error. Not easy to get a separate centre section to fit both wing halves, so maybe make it without a flat bit? Depends on undercarriage though.

The important thing might be avoiding clashes between servos in the fuselage and aileron horns. But otherwise fit servo as any other model - centre with torque rods or two mini servos further out not forgetting to put holes for servo wire tubes at an early stage.

The plan and article is on Outerzone for anyone wishing to study this attractive design.

kc04/10/2020 12:12:08
6777 forum posts
174 photos

Studying the underside photo in the article suggests the ailerons start about an inch out from fuselage sides which means the wing plan is incorrect and has  a rib bay missing

Edited By kc on 04/10/2020 12:14:39

Bob Cotsford04/10/2020 12:15:21
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8845 forum posts
496 photos

Looks to me as though that first R2 should be a CS1, otherwise the width of the centre section on the dihedral brace makes no sense. I'd say that what you are reading as the centre line (through the drawn CS1) is the LH dihedral break. That puts the aileron servo inside the fuselage, but how that works out against the drawn half spans can't be seen from that section of the plan. You say that the CS1 measures up for the half span , it may be the plan has been drawn with one too many rib bays in the left wing. If that's the case either reduce the left wing or extend the right wing to match, that or fit control lines and fly in circles teeth 2

kc04/10/2020 12:54:47
6777 forum posts
174 photos

Bob, only one wing half is on the plan.

Personally I would mark the rib spacing ( including 'wrong' centre section) onto a bit of balsa and transfer the markings straight onto a 4ft piece of plasterboard, add a new centre section and flop the balsa over to mark left hand panel. Then just draw the rib positions on to plasterboard with a Tee square. Then build two separate wing panels. prop them up and build a centre section between them as advised in the instructions written by Dereck Woodward.

Just my way - plenty of other ways including drawing a new wing plan on paper or photocopying the wing tip and adjacent rib bay then sticking it on the end over the tip to get proper length.

Matt Carlton04/10/2020 14:37:35
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131 forum posts
12 photos

Phew.

Glad it wasn't just me.

I think I'll just redraw the wing plan the correct full size for a left panel and a right. Then make up a centre section using CS1 on the inside face with cutouts for the u/c bearers and use R1 as the root rib of the wing panels.

To be honest, it's just as easy to stick a micro servo in each wing. That'll give room to make the wing bolt on instead of bands.

Thanks for the input, I though I was losing the few marbles I have left.

Cheers

A Davidson24/10/2020 21:18:23
14 forum posts

Great model and a pleasure to fly. I built mine in 91 from the RM free plan. Had some head scratching but built the stbd wing as per the plan and the pt wing to the same pattern but reversing R3 and 4 ribs with the first two R2 ribs. The ply bracer also was a worry but I ended up half lapping the ribs and bracer. Naively this weakens the bracer but after 30 ish years of aerobatics and sport flying it has only just failed. I had a total loss of control and planted it nose in from height. The wing broke cleanly between CS1 and R1 on the stbd side with no other damage. Currently replacing the aforementioned bracer and will be ready to fly again when the weather gods stop being pesky.

A really great model. Even as a follow on first low wing a/c after a trainer.
Have fun.

A Davidson24/10/2020 21:22:50
14 forum posts

Ps

The aileron servo was fitted vertically in the centre section within a box section I added. There is loads of clearance for the torque rods and all the other gear in the fuselage. My repaired wing will sport an aileron in each wing now they are smaller than my original house brick Sanwa servo

kc25/10/2020 16:14:59
6777 forum posts
174 photos

Did you mean 'half notching' when you said " half lapping" ?

Low pass Pete25/10/2020 16:44:22
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274 forum posts
144 photos

There are some basic instructions on the Outerzone site. Seems to suggest that you build the 2 wing halves and then do centre section. I would go for two servos and stick with the basic dimensions and wing it. No pun intended.

Have fun.

Peter

A Davidson25/10/2020 19:30:41
14 forum posts

Thanks for the input but I wasn’t asking for instruction. I merely was explaining how great the aircraft is and illustrating the method I have used. After approximately 30 ish years of enjoying this a/c I was also explaining the modification to the aileron set up.

Jonathan M25/10/2020 20:09:15
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870 forum posts
335 photos

Just going back to Matt's original question: I know single servos for both ailerons via torque-rods was the common method at the time the plan was produced, and the weight of an extra (standard?) servo wouldn't have been welcomed in this small light model. However the way the servo is drawn on the plan, lying on its side on part CS1, would preclude it - even if it was mounted at wing centre - from geometrically working two opposite torque rods. My guess therefore is that two servos were originally intended, but close to the centre-line to keep the weight inboard, hence the torque rod solution shown.

Low pass Pete26/10/2020 03:52:45
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274 forum posts
144 photos
Posted by Matt Carlton on 03/10/2020 23:56:06:

Hello all,

This is probably a case of me being stupid but here goes.

The free plan for DW's very charming 'Amelia' appears to have an anomaly at the wing centre section. The plan appears to indicate a centre line to the left of the servo. That centre line measures out for the correct span.

However, it makes no sense for there to be a centre rib and a servo offset to the side as the torque rod horns would straddle the fuselage sides.

My assumption is that the centre section is built as a separate unit, with the dihedral brace and u/c bearers.

It's an easy enough thing to sort out, but I wondered if anyone has built this model and as a long shot, has a photo of the centre section construction.

Many thanks all,

Matt

screenshot_20201003_234952.jpg

Edited By Matt Carlton on 03/10/2020 23:59:21

Edited By Matt Carlton on 04/10/2020 00:00:06

Matt

I have looked at the plan detail on outerzone and think that the plan actually shows the right wing plus the Whole Centre section. If you look at the width of the Fus and the length of the dihedral brace this supports my thoughts. I agree that the plan is probably incorrectly drawn and unfortunately the article in RM Feb 91 is not clear and does not mention 1 or 2 aileron servos. The plan shows CS1, R2, R3 and R4 but does not actually show R1 (except for info on wing rib). Looking at Derecks build I would say that the centre section is flat with no dihedral and that the dihedral starts outboard of the centre section.

Cheers

Peter

Matt Carlton26/10/2020 08:35:34
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131 forum posts
12 photos

Agreed Peter.

What threw me off is that what is drawn as the Centreline of the wing is actually the dihedral break for the left wing panel. If that is the case, then the dihedral brace is drawn correctly, but the top view is wrong, as it extends further into the rib bay than would be the case if the brace shown were used.

So, my plan is to make a centre section using CS1 to support the UC plates, splitting the ribs to fit the brace. Then make two panels using R1 (without the slots for the UC plates) as the root ribs.

Micro servos in their sides will go in bay 1 of each panel to keep the tips light.

Having no servo in the centre section will give a space to put a 6 pin connector like a mini jst to make rigging easier. I'd also go for a bolted wing rather than bands.

Thanks again

Matt

Low pass Pete26/10/2020 16:26:09
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274 forum posts
144 photos
Posted by Matt Carlton on 26/10/2020 08:35:34:

Agreed Peter.

What threw me off is that what is drawn as the Centreline of the wing is actually the dihedral break for the left wing panel. If that is the case, then the dihedral brace is drawn correctly, but the top view is wrong, as it extends further into the rib bay than would be the case if the brace shown were used.

So, my plan is to make a centre section using CS1 to support the UC plates, splitting the ribs to fit the brace. Then make two panels using R1 (without the slots for the UC plates) as the root ribs.

Micro servos in their sides will go in bay 1 of each panel to keep the tips light.

Having no servo in the centre section will give a space to put a 6 pin connector like a mini jst to make rigging easier. I'd also go for a bolted wing rather than bands.

Thanks again

Matt

Looks like a good plan Matt.

What you could do also is fit three CS1s in the centre section. Left, Right and an additional one in the absolute centre of the wing. That would give additional strength for the UC plates. A while back I built an old Dereck Woodward design, Holi. (Short for Holiday Special). He originally designed the model as a one piece affair but I decided to make the wing removable also having 2 servos for the ailerons. Much better than torque rods.

Low pass Pete26/10/2020 16:28:10
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274 forum posts
144 photos

What power are you using by the way. Electric or a small four stroke as per the original?

See that you are in the North Norfolk area.  We love going to that area with our Caravan.

Edited By Low pass Pete on 26/10/2020 16:31:42

Matt Carlton26/10/2020 17:15:30
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131 forum posts
12 photos

Pete,

An additional rib seems sensible, as well as giving a means of mounting a dowel. I'll probably do that.

I was going to go electric but there's an OS20 FP in the cupboard. DW suggests a 'low power 20' so I think that'll do fine. I may need to do some holes in the tailplane or make it built up to compensate for the lighter engine. We'll see.

Yep, whereabouts do you tend to go in this neck of the woods?

Low pass Pete26/10/2020 18:46:04
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274 forum posts
144 photos

Hi Matt

Will be interesting if you do use the 20FP as I have one that I inherited from a friend. You will need to watch the weight however. Do you intend to do a blog on your build? It can be fun and useful for others. I have joined in on 3 of the RCM&E Mass builds to-date.

We usually head for the Cromer/ Sheringham area as we like to go to the coast. There is a good Caravan Club site at West Runton and also at Cromer which we like. It is only a couple of hours drive from home so is ideal.

Keep safe and happy building. I'm currently renovating an old kit build Acrowot. Seems more work than a new build however.

Best Regards and Keep safe

Peter

kc26/10/2020 19:03:31
6777 forum posts
174 photos

I like the way Peter Miller fixes wing dowels on some designs - a 1/4 balsa wing rib with a slot for dowel plus a ply rib either side of the slot. The dowel then contacts both ply ribs. Ribs are actually just the front 'half' and have a 'tongue' that goes between the spars.

Matt Carlton26/10/2020 19:42:12
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131 forum posts
12 photos

Pete - I'm not sure if I'd do a build log, depends on when I get round to building. Working away a lot at the moment so heaven knows. Weight wise, I think it'll be fine. I would estimate about 0.4hp for a tired 20, so 300W maybe. Radio gear is likely to be a good bit lighter, the engine will be lighter, I think 2.5lbs should be doable with care.

AUW of the original was 2.75lbs, so 110W/lb.

I'm not looking for huge performance, if it'll trundle around looking nice on a summer day and throw the odd loop or roll, that'll be perfect.

KC - that's exactly how I was going to fit the dowel. Normally use a 3/16 rib though and file a flat onto the sides of the dowel for slightly firmer grip. No need for anything too beefy here, 'Amelia' is a good 50% fresh air.

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