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BEB's Dawn Flyer Build


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Well in the end I got a fair bit done today.

Here's the bodge to fix the "F4 is too narrow" problem,...

df37.jpg

Basically its just two lengths of 6mm sq glued along side and sanded to profile. I will sort the underneath of them out to "blend them in" later. For now I just want to attach the framework of the upper tail I built yesterday.

Now the thing is, this has to be a straight as we can get it. We don't want the tail on ski-wiff - not only will that look awful, more importantly our model wont fly properly like that! I'd normally resort to the fuselage jig for this. But it occurs to me that, in the spirit of the Mass Build, many folks may not have a fuselage jig. So, is there another way we can attach the tail and be reasonably confident its straight?

Well yes there is, we can go back to the very early day of full size aircraft manufacture - back almost to the period that inspired the model - and do it that way. In the good old early days of aeroplane making, faced with a task like this, they would first have found the flatest bit of floor they could and taken a length of string longer than the intended length of the aircraft. They would then have coated the string with french chalk, stretched it out along the floor very taut and given it a good "twang". The result would be a dead straight chalk line on the floor - this would then become their datum. Well we're going to do the same - only slightly scaled down and with a felt tip pen!

First turn the plan over to get the blank side,...

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Now take a 1m straight edge and draw a line down the middle (doesn't have to be exactly in the middle - just there-abouts),...

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A long straight edge is another very useful building tool, not only for marking out like this but also to assist in making long straight cuts. This line is our datum. We now take the "canoe" and mark the centre point at the front and rear. Actually measure this don't just assume the sheeting meets in the middle etc. Lay the body onto the datum line so that these mid-points lay over the line, like this at the rear,...

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And this at the front,...

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That looks out of alignment but its just the paralax of the camera view. Squinted at from above it is aligned with the datum.

OK that sees the body lined up. We then pack around it to hold it in that position. We can now place the tail in position and by aligning its centre mark with the datum we know its straight! See below,...

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And Bob's yer uncle,...

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Part two to follow!

BEB

Edited By Biggles' Elder Brother - Moderator on 03/01/2014 21:55:36

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A very neat retro-fit that VA! Well done.

Now - on with part two of today's efforts. Having put the top of the tail on the canoe its time for the paddle on the bottom. This can be done with the Mk1 eyeball by positioning it over the top section,...

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We can then insert the stern post and a couple of bracing triangles,...

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(Its no good looking at me like that Teddy - you look as if you've been on the Old Percular again mate!)

Now we add further reinforcement via some ply gussets,...

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Returning to the top of the tail we add the formers and the top stringer,...

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This was done by threading the formers onto the stringer, adjust the spacing and then gluing the whole assembly in place. Much easier than the more customary glue the formers then feed in the stringer.

Finally today I added the rear lattice work - makes the tail nice and stiff - just don't look to closely until I've cleaned it up a bit!,...

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And there we are, here's an overall view of where we are up to,...

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Weather looks rubbish over the weekend - so tomorrow I'll build the fin and tailplane, I can't finalise the back end of the fuselage without them.

BEB

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Hello Dawn Flyer builders,

I'm also building the Dawn Flyer and had the same problem with the differences in width from the body and the tail part. If you measure the width on the plan from former F4 including the wing sadle ( 99 mm) and the width from the body seen from above is 108 mm. In my opinion the fault is caused by the fact the top from the fuselage side is behind the wingseat 7 mm lower then at the leadingedge side from the wingsadle. This is not taken in account when the topview is drawn. I fixed it by making the first two cross members shorter so the tail part matches the width from the fuselage body.

will post some pictures from my build later.

Koen

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Hi there.

Please excuse me for butting in but I am also trying to build the DF as my first ever build and it is not going as well as I was lead to believe it would be.

What I want to do is build it a bit larger ( about 58 inch wingspan) and so I decided to make the only fuz and the wings from the root rib to the ailerons to test my skills and see how it fitted together using the free plan before I scaled it up.

The main problem that I am having is how the wings fit to the fuz involving wing bolts etc. as the plans seem quite vague on this point, could I please ask that when you build this section you show exactly how to do this as it would be much appreciated.

Also could anyone explain why when the rear of the fuz is attached to the front part you glue a flat part to the angled fuz sides as I think would have made more sense to sand this part of the main fuz flat to give a flat to flat surface instead of a angle to flat surface.

Thank you

Bill.

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There is another way to make a bend in balsa without steaming. Kerfing is done by making many cuts about halfway through the balsa, filling with epoxy and then clamping in the bent shape until the glue dries. The cuts are on the inside of the curve and allow the wood to move in instead of compressing. This is done on the Peter Miller 58 inch Turbulent and works well. I cut about 8 cuts halfway through about an 1/8 inch apart. This allowed a quite sharp bend in 1/4 sq balsa. Might be worth reinforcing with a ply plate as well.
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Hi Mouse, I am trying to cover each step in reasonable detail - as a number of builders have taken the line "Here's the plan I intend to build a Dawn Flyer." Then a few weeks later we get a handful on build photos then "And here is the finished item"! This is fine as far as it goes - but its not particularly helpful to new builders who I think need to see the "warts and all, blow by blow" version. So, when we get to wing joining I'll be sure to cover it in detail.

Regarding your other question - which was why not sand the bearing surfaces, on which the upper framework of the tail mounts, flat rather than glue to sloping surfaces and then fill the gap. Well as far as I can see no reason at all - in fact it is what I have done! I only noticed the plan inset suggesting the packing pieces afterwards. Obviously you need to take considerable care that if you do flatten these surfaces you do so level - or the tail will be twisted - but you can do it.

Koen - great build, lovely model. But, I hope you don't mind, I have moved our post to the Dawn Flyer chat thread here - as for someone following this build (maybe trying to use it as a guide) it was a bit of a break in the flow. If you have a build record in photos we'd welcome a build thread from you - I'm sure that there are many tips we could pick up.

BEB

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Time for an update - its been a day spent on the tail feathers today; fin, rudder, tailplane and elevators. The basic build procedure for all of these is the same.

Let's begin with the simplest - the fin. First cut lengths of 6mm sq balsa to the required shape envelop over the plan,...

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I say "shape envelop" because, as you can see, I do not trim the pieces to the exact profile - I just make them the maximum length they need to be. To do this part of the build (here and for the other tail components) we use the famous 6mm sq balsa, but we will also need 6mm thick strip of 10mm, 12.5mm, 15mm and 20mm width. This will all be cut from 6mm sheet. Now you can do this by measuring and cutting along a straight-edge. But its much easier to use one of these,...

df52.jpg

A balsa stripper. You adjust the setting of the blade with the wheel at the back which is on a very fine thread - the knife moves 1/32" per rotation of the wheel. So you can set the spacing of the knife to whatever width of strip you want then place the edge of the tool against the edge of the wood, hold firmly, swish and one perfect strip. This is much much cheaper than buying strip.

Once the fin is dry we lift it from the board then sand to shape,...

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Next up the tailplane. When doing this sort of building it best to get the big "datum" pieces in place first, then add all the bracing and fiddly bits. So for the tailplane we start with this box,...

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Then work our way around adding the centre piece then the bracing etc. That gives us this,...

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Then lift that from the board and profile sand, giving us the finished article (well finished barring a very final sanding immediately before covering),...

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Next we do the rudder,...layout the parts starting with the main hinge post,...

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And once again lift it from the board and sand to shape,...

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Just the elevators to do now - they are in part two....

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OK, here's part two.

We begin the elevators with what we might call the leading edge,...

df58.jpg

Then as before we add all the gubbings,...

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Now, at this point I made a small boo-boo - I decided to make up the triangular ply-balsa-ply sandwich that supports the connecting rod linking the two elevators separately and then glue it in after I had lifted the finished elevators from the board. The problemette we have with this is I now can't taper the inner part of the elevator! Ah well - its not a big problem - let's just call it an "individual feature" of my Dawn Flyer!

So, elevators lifted from the board,...

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And then with the reinforcing ply-balsa-play triangles and sanded to shape,...

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With the aid of a little masking tape we can see what our efforts today have produced - so complete empennage,...

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And even a trial fit on the fuselage,...

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Well, well, well,...it isn't a canoe after all! Not bad for 5 days though I say so myself.

OK, next up - wings!

BEB

 

 

Edited By Biggles' Elder Brother - Moderator on 04/01/2014 21:40:00

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BEB

glad to hear that you are going to do a detailed build, I personally think it's what is needed and hopefully will encourage more people to try and build there own plane.

I know it will give me more confidence to not only build the dawn flyer but also give me a better understanding of how to build generally so I can go on to build some more obscure early aircraft in the future, (maybe even do a blog).

One thing I would like to see with ref to Dawn flyer is to do with where the two wing halves join as on the plan it seems to show a hole underneath what I think are called the root ribs ( the very first R1s) although to me this whole area seems quite vague.

Good luck.

Mouse.

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Nobody seems to have picked up on the point that Mouse made about this being his first ever build and also that he was scaling it up to 58 inch.
Its not just a matter of scaling everything up by the same percentage! It's necessary to adjust the size of all the materials to suit the new size and weight of the model. This is where experience comes in......
So for a first or second or third build stick to the design size. When you have built several planes of the 58 inch size you may be ready to redesign a model to that size.
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I've been on family duties today so not a lot of time on the build today - but I have managed to make a decent start on the wing. We start by pinning the two lower spars in place and the false trailing edge that the aileron will hinge to,...

df64.jpg

Just a couple of pins to hold the spars flat - mainly holding them in place with pins at the side. These spars are only balsa - strong enough for a small model like this but let's put any unnecessary weakening holes in them!

Next we start adding the ribs, these must go in square,...

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I'm reverting back to my favourite aliphatic adhedsive here. Working along the wing we add each rib in turn squaring it up,...

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Next up is the 6mm sq (again!) bracing piece that runs from the wing centre to the first full length rib,..

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And that's it for today sad. Next up will be fitting the leading edge prior to the front sheeting - here it is being "lined-up" for the job - a bit wide that, will need trimming,...

df68.jpg

BEB

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BEB, I am really enjoying the detail of your build thread, along with the dash of humour. I started early December getting a lot of help from Dylan's thread - good to see you posting again, Dylan.

I am just a little ahead of you but have stalled on the build of the cockpit section. So putting in a plea for your continuing detail when you get to this stage. I am particularly having problems with the positioning of F2A, F3 and F5.

Also I would draw attention to a discovery that I and I think VA made that the assembled wing appears to be too wide from leading edge to rear at the wing's centre point, so that it does not drop straight into the wing mount area on the fuselage. F5 still has to be placed against and in front of F5A, making this problem even more acute.

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Hi John,

yeap the idea of the Mass Build is to encourage those new to plan building by the fact that there will be very detailed blogs done by those who have done this before so there are examples to follow. And more than one example - because there is "more than one way to skin a cat" and while two experienced plan builders will build the model broadly the same there will be differences of techniques, order, tools used, adhesives used etc. All of them are valid and you can learn from them all.

Well I was back at work today so things will slow down a little now - tonight I just got the time between coming in and dinner being ready (or "tea" as we call it here t'up north). Anyway some significant progress was made - even if it wasn't a lot.

First I trimmed the width of the 6mm thick piece of sheet I'd selected for the leading edge - I said yesterday it was a bit wide. You want it wider than the front of the ribs plus twice the thickness of the sheeting so that when we sheet the front part of the wing (top and bottom) we'll have something to glue to. A bit wider both sides is good to give us something to sand away - but not too wide so we are producing a small mountain of balsa dust! Here's the item glued in place, its hard against the board at the bottom,...
df69.jpg

The white boxes contain some of my 6s Lipo's, they are pushed up against the leading edge to hold it against the nose of the ribs while the glue (aliphatic) dries.

Now we touch upon the area te Mouse was enquiring about - joining the wings. We are not going to actually join them at this point (that would be a bit tricky as I haven't built the second one yet!) but we are going to put the wing bracer in place.

Now I had to look a bit carefully at the plan and the wood at this point. The first two ribs have enlarged slots for the spars - enlarged to take this ply wing joiner. But that's a bit of a "red herring"! What you have to do is cut the ribs leaving a "bracer sized" gap!!! Shock horror!

Once they're cut you can place in the ply bracer. First mark the centre of the bracer (you want half in each wing!) and push one half down flush with the bottom of the lower spar. As this is a bit complex and difficult to explain here's three pictures showing it from different angles,...

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Note that the other end of the brace is slightly lifted off the board, this is due to the very slight dihedral of the wings. The two severed ribs - the leftmost two - are re-glued to the bracer as part of this process. The adhesive I used for this job was slow epoxy (1 hour) as I want a really strong joint - the strength of the wing largely depends on this bracer.

Next, on to the sheeting.

BEB

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Tonight's missive is all about letters. Not just any old letters - capital letters. To be specific, the letters 'I' and 'D'. Confused? Then allow me to explain,....

Let me say at the outset that I have the very highest regard for Lindsay as a designer - he has designed many very successful models, of which the Dawn Flyer is but a single example. But there is something about the design of the Dawn Flyer's wing I'm a tad unsure about. There are no inter-spar webs?

Now I have seen Lyndsay's prototype fly - so I know its perfectly happy without webs. And its true to say that the DF is quite a lightweight, petit, model not designed with 3D'ing or high-G aerobatics in mind. But,...well maybe Lyndsay's model has hardwood spars - mine only has balsa spars. And what's worse I can get a little excited on the controls; I've been known to try snap rolling trainers for example! And webs are easy to fit, add next to no weight and, well better safe than sorry eh?

So what are these "webs" I'm going on about? Well at present we have an upper and a lower front spar. They are held in position by being glued to the ribs. Now while this may look pretty strong in reality it isn't really any stronger than having just one spar - you see the ribs contribute very little to the strength of a wing all they really do is hold the aerofoil shape and space everything out. They are not providing any true meaningful, load bearing, link between the two spars. So the spars are not "working as a team" - they are just two individual spars.

Take a small piece of 1.5mm (1/16" balsa - a soft piece maybe 6x3cm or so. Bend it across its width - in line with the grain. Bends like a piece of wet paper right? No strength at all. Now bend it across its length - at right angles to the grain. Stiffer, yes? But still not that impressive. Now turn it onto its long end and, keeping it dead straight, try to bend it now. Wow! pretty stiff eh? Inter-spar shear webs (to give them their full monicker) exploit this stiffness for extremely low weight.

We glue small rectangles of this 1/16" balsa between the spars in the bays between the ribs - with the grain running vertically. As in the picture below,...

df73.jpg

This is very strong. Now the spars are linked by a stiff vertical plate and work together. What we have made here is an 'I' section beam, with the spars as the top and bottom flanges and the balsa sheet as the web. In a beam under bending the maximum stresses are at the top and the bottom - an 'I'-section has the virtue of putting the maximum material where the maximum stress will occur. Its the shape that gives us the stiffest structure in bending for the minimum weight - hence why 'I'-section beams crop up all over the place.

But while 'I'-sections are very good at supporting bending, they are not so good a resisting torsion - or twisting. But this is where the next step comes in - in part two.

BEB

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OK, part two...

We are now going to add the front sheeting. In his article Lindsay describes this sheeting as going over the leading edge - fine, but I'm not going to do it that way! Instead I am going to butt the sheeting up to the over-width leading edge. Why? Well I find Lyndsay's method works fine for me if I'm going on to add a further true leading edge piece stuck on the front. But in this case we are not. I then find it tricky to get a nice leading edge profile withput sanding away unacceptable amounts of the sheeting doing it the way Lyndsay recommends. It obviously works well for him and others - but not for me.

Now one of the beauties of plan building is your freedom to adapt the design in order to implement your own prejudices! So, my model, my wood and my responsibility - I'm going to butt the sheeting up - rather than overlap it.

I start by cutting a length of 1/16" (3mm) sheet of just over the required length than will span from the inside edge of the leading edge to well across, but not beyond, the top spar. Then I put a very slight bevel on one of the long sides, butt it up against the leading edge and just "tack" it in three places with a single spot of CA each. Check its right up against the LE, if not it will pull off at this stage and you can try again. When happy that it is right up there, run a thread of thin CA right along the join between this sheet and the LE while holding wing vertical. Holding it vertical means that gravity helps in running the CA along the joint and then it will "wick" in.

OK we now have the sheet stuck by the front edge and jutting up. I now do something a bit unconventional, I pick up the wing, hold it in my hands and stick the sheeting to the ribs whilst holding it in place with my fingers - rib by rib. Finally I run a length of CA along the back of the sheet to be sure its well stuck down to the spar. For sheeting to do its job - which is not just covering, its to add rigidity - it must be stuck down at all points, all ribs, right along the LE and right along the spar.

Here's the result of doing that,...

df74.jpg

And to show its completely stuck down all the way, here's the view from the underneath,...

df75.jpg

As you can see, no gaps.

Right well we now have to do the front sheeting on the underneath of the wing. We start exactly as before, butt up the sheet, tack in three places, check its hard up against the LE then run in the CA. Like before we now have a sheet stuck down at the front. But we can't do the trick we used for the top sheet now - because as we close this sheet we can't get at the inside to apply the CA. This calls for a change of tactics.

We can gently lift the back edge of this sheet,...

df76.jpg

So, switching glues to aliphatic, we take a McDonald's coffee stirrer (the kids are under standing orders to get me a dozen whenever they go in there!) we sand the end of this stirrer to a fine flat blade. We then use this to feed glue onto all of the ribs, going in under the back of the sheet, right up to the CA joint at the front, then we smear glue over the spar and close the sheet, pinning it to the spar all along its length,...

df77.jpg

Now in the Dawn Flyer's Clubhouse earlier today kc was advising against the use of these glass-headed pins. Normally I would totally agree - for general use they are dangerous. But, in this particular case they are just the ticket. The sheeting is very soft - the spar is not much harder - these pins push in here very easily. Inserted at an angle and pushed in right up to the hilt, which is what I want to hold the sheet down, they have the virtue of being very fine - so they only made a very small hole. But if this spar had been hardwood there is no way I would have used them.

OK, its just as important that this sheet is fully in contact with the underlying ribs - so re-enter the 6s batteries,..

df78.jpg

Above I said that sheeting is not just covering, its there to impart strength. So let's look briefly at what this sheeting is doing. We said in part one that the webs gave us an 'I'-section beam that was good on bending but less good in twisting. Well the 'I' has now become a 'D' with the upright of the 'D' being formed by our old 'I' and the sheeting and the LE forming the curved part. This is called a "D-box girder" and its solves our twisting problem. This structure is not only good in bending (due to its 'I'-section part) its also good in twisting, or torsion (due to its D section). The best of both worlds. Its a very efficient, strong, section and its extensively used in model and full size aircraft (one of Mitchell's strokes of genius was that Spitfire's wing was thin, but also very strong because its front half was basically 5 D-box sections each one nesttling inside the other like Russian dolls!)

We'll leave that to dry now, we finish it by just planing away the over-width of the LE and shaping it. But that will come later, next up is the trailing e

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Hi BEB, medium balsa spars on both prototypes and no webbing required and despite my most aggressive flying we have yet to have a failure and you had better believe the abuse the first two have had. I almost got a Lomcevac out of mine - nearly. Too stable, need to move the CG back a bit. I think you can sleep assured that the wing is strong enough. Still the beauty from plan building is that if you prefer to do your own thing you can, and that's exactly as it should be. I am really looking forward to seeing all these Dawn Flyers together. Linds

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I'm sure you're right Linds - but you know me - belt, braces and a spare bit of string!

Looks like I'll have to snap roll it for VA now just to prove the point!

BTW - I forgot to mention something above - and forgot to photograph it too. Its something relevant to Mouse's enquiry above. Before gluing on the second front skin I added a balsa block to the side of the front of the inner-most rib. I will do the same on the other wing - and try to remember to show it there. This block is to give me something to drill into when fitting the wing dowel.

BEB

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Glass head pins - I don't see where the danger is - I use only those pins, which are standard sewing equipment on the continent. The plastic head pins available here are a danger, as the head comes easily off which could lead to scratches or penetration of a blunt pin into the finger (how do I know...)

By the way - glass head pins are available in some main street model shops - for instance Als Hobbies in MK.

MK, glass head pin department

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Well there are glass headed pins and there are other glass headed pins!
Until you puncture your thumb it's difficult to tell one from t'other!
So to be safe I advise against them. But T headed pins are so much better they can be twisted out easier and they can be dropped in acetone to remove old glue.

Anyway back to D box construction. I completly agree with BEB that that's the best way to build. The question here is should all the newcomers adopt BEB's construction or stick to the plan? I would say web the spars and form a D box just like BEB. Although BEB's construction is as yet unproven on this model it's known to produce good wings on thousands of designs. And a bit tougher which will be handy for newer flyers.

Edited By kc on 08/01/2014 11:51:21

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Too late for me...

As a large part of the wing is sheeted I suppose it should be enough for every days mechanical performance. Of couse - if you use the biggest engine which will fit in and goo for snap rolls problems may be the result. If I would go aerobatic with this model I would rather go for a longer and/or stronger wing joiner, as this would transfer the load over a wider area of the wing.

The finished wing is pretty stiff, I am sure the original design allows loops and rolls without problems. dawn 6.jpg

VA

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I am with Linds on this one, my wings built as per plan have survived a number of very heavy landings to the point that they are now on their second fus. If you sheet the centre section after joining the wings it can be done using a single sheet, this will add massive strength at the high load points around the wing roots. Once out past the first few ribs it doesn't need the extra strength/weight of the webs.

I do prefer bebs leading edge though.

Andrew

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I'm sure Lyndsay's method is fine - unless you go totally bonkers! But the full D-box, as I've done it, does give more strength for very little weight.

I did it I suppose for three reasons:

1. As I said above I like "belt and braces" especially when there is no real weigh penality.

2. The Mass Build focuses on building specific models - but the real point is to get people started on building from plans/traditional kits and to pass on as much knowledge and skill as we can along the way. This bit of the build gave me an opportunity to show a different way of dealing with the leading edge and how to incorporate shear webs. As a bit of "added value" I think it was worth it.

3. Part of the point is to show that building from plans is a sort of partnership between you and the designer. The designer's part of the deal is to provide you with enough information to build a viable model. Your part of the deal is to consider what he says as a "suggestion" about how you might build the model! Every builder I know who works from plans will modify the design to suit themselves. The more experienced they are the more drastic some of those modifications can become! Its a big part of the fun and pleasure that by the time you've finished the model really is uniquely "yours". So little mods here illustrate that process.

So, to a new builder reading this I would say the following: between this, Lyndsay's article and the other blogs you have seen things done slightly different ways, now enjoy yourself and make your own decisions. Webs or no webs? LE overlapping or butted up? It really is your choice - this isn't an ARTF, you get a say! Enjoy. smile

BEB

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