1/10th scale Blackburn Beverley.

[MalcolmDouglasPorter]

Had a busy day, 6mm ply is much more difficult to cut, so these four frames took most of the day to get to this stage. There is still a lot of work to do on them, fettling to the line etc, then cutting the joints.

The remaining three "C" section frames have been mentioned several times and are now cut, you will notice the new kid on the block, frame No. F1. The "E" section will consist of two 1/8 inch ply frames and they are positioned above the two "D" frames, ahead of F1 as part of the rear assembly. A glance at the picture of the drawings (above) will clarify this for you. The "F" (and "G") frames are in essence the rear portion of the fuselage and not really needed yet, but I need to match the rear section to the front, the F1 being the main support for the rear section and is made from the same 6mm ply as the C2,C3 and C4 frames. With the exception of the spine longerons, the remainder of the rear section will be balsa.

The F1 frame is probably the most complicated as it forms the link between the two fuselage assemblies. On the real aircraft, all the strength for the rear boom was gained from the upper fuselage, the cam shell doors were removable for air drop functions. On this model, the doors will be fixed and form part of the structure of the model. This will be part of the F1 frame and attached to the boom. I have a good idea how the two fuselage parts will attach, but will need to assess this once the two assemblies are made and then clamped together to work out the best positions for the attachment lugs.

[MalcolmDouglasPorter]

Another good day!

Most of the fettling and joint cutting has been done, and had another dry run assembly. In the picture you see the assembly from B4 to D2 which in essence is the main structural portion of the fuselage. Virtually the whole of this is where the wing roots are located. When assembled, this portion will be a little over 31 inches, the chord line at this point is about 30 inches. There is another 28 inches of fuselage ahead of this, and about 60 inches behind. These frames weigh in at 5 lb 10 oz total, so I may have to consider cutting some more weight saving holes?

There are a couple of things yet to be finalised regarding the fixing of the undercarriage to the bottom of this assembly, and the rear assembly attachment points. I have done no further work to the F1 frame as yet. I will continue with this one I am sure that the central assembly is in good order. The F1 will need to be matched to the rear end of the central portion, it must be accurate.

I may have to do a little rectification work to the top of these frames. There is a 3 degree rake form C1 to the leading edge of the tail plane, and there seems to be some undulation on the rake line. I will better determine this on actual assembly, and then adjust the rake accordingly. The more observant among you may notice that there is not a good line at the top of these frames. Thankfully this does not affect the structure, so is not a problem.

[ian redshaw]

That all looks nice and neatly cut Malcolm. Can't believe its all going to turn into something so ugly!! Alright, perhaps not ugly, just purposeful. Look forward to your next installment.

Ian.

[MalcolmDouglasPorter]

It took ages to cut these parts for the wing mounting box. They won't need a lot of fettling. Most of you use tubes for this purpose, but I'm sure this will be OK once assembled. These kind of joints are easy to do if you keep the chisels nice and sharp, I use a diamond plate and water stones, they polish up like a mirror. This box is situated between frame No's C2 and C3 as you can see from yet another dry run!

So this model is going to be ugly? Better fit a blond wig and some sunglasses then? LOL

[MalcolmDouglasPorter]

Slow progress today. I actually spent most of the time working out how to attach the undercarriage. These details are not yet on the drawings as I needed to see some actual frames to make these decisions. I am certain that the undercarriage will be secure and strong enough to take a two or three G landing. It may actually be over engineered, but that's OK with me.

In the picture you can see the fruits of all this "thinking". Doesn't look much, but it will make all the difference, as I will now be able to detach the undercarriage from the fuselage for transportation. The main wheel bogeys will be about three feet apart, making it a bulky item if the UC was fixed.

See you at the AGM on Sunday?

[MalcolmDouglasPorter]

I made two bits today, the last (rear) inner wing root spar attached to C6, and the web that fits between C4 and C5 to help support the undercarriage. There is not any stress on this part and is required to keep the undercarriage support strut in its correct position. Any stresses will be transmitted in a downward direction in the centre of the fuselage due to the leverage on the strut. This will be countered by some struts attached from under the support strut to the bottom of the frames in that area. Clear as mud at the moment, but will clarify as the assembly of this central section progresses, but that will be some time yet as there are many other fiddly things still to do. There will be some 1/4 plywood beams attached across the fuselage under the position where the UC support strut slides into its position.

The idea for my design of the undercarriage is the confine the stresses to the central area of the fuselage. Although the real thing has the UC leg attached to the wing at the rear of the inboard engine nacelles. On this model, the UC leg will be in its correct relative position, but will not actually be attached to the wing, but to the support strut mentioned earlier. This strut will sit inside a slot in the wing with a little space to keep it separate from the wing. When assembled, it will appear that the UC is attached to the wing.

[MalcolmDouglasPorter]

I enjoyed meeting you guys at the AGM yesterday. One gentleman (sorry can't recall your name) asked me why there are so many frames in my model. Well, it is quite a big model and these frames are four inches apart, quite a big enough gap? The integrity of the entire model is focussed on this central section, so I reckon it is better to over engineer this.

Having had another discussion with John Rickett at the AGM regarding the undercarriage, I have been doing some more thinking and may have resolved the potential weakness problem that was worrying me. I will explain this as the build progresses along with photos.

[MalcolmDouglasPorter]

Somewhere amongst those clamps is the wing mounting box. I used all my four inch and six inch clamps. Would have to break out the 8, 10 and 12 inch if I needed more. It really is a true saying, "you can never have enough clamps". Once the clamps come off in the morning, I hope that the box has set up square, if not, I will have to re-make it. To help maintain squareness whilst the glue sets, I have cut a couple of squared plates from some scrap that are inserted in the box (corners removed so they do not stick in place).

I visited Richard Hughes yesterday, and had a couple of hours talking about my project and learned a lot of stuff. The problem I have with the undercarriage is now much reduced. I will explain the changes as I go, nothing that the rest of you have not all ready done of course. Richard will be cutting the wing components for me, and possibly some of the remaining complicated fuselage parts. I have also learned that I need to alter the design of the rear portion of the fuselage to account for the tailplane flexing. This really entails a couple of extra stiffening frames, not too much problem.

[MalcolmDouglasPorter]

I am an unhappy bunny this morning. I removed the clamps and cleaned up as required, got out my small square and some of this box is OK, other bits are rubbish, and it looks more like a corkscrew than a wing mounting box. It is annoying when we take a lot of care in marking and cutting, only to produce a pile of firewood at the end of the day. If there is any one part of this model that needs to be right, it is this box, so it's back to the drawing board, or the work bench, or both?

Rather than trying to glue the whole thing in one go, perhaps I should assemble this item in three operations? When I have remade the parts, I will glue the top and a side, and the bottom and the other side separately, and then glue these two components together when they are set? It was a bit difficult getting round all those clamps, I have to say.

[ian redshaw]

Keep at it Malcolm!! Could you assemble the boxes around the bit that fits inside? Suitably waxed or wrapped for clearance and non adhesion. Are you planning on binding the boxes to prevent them bursting? I normally wrap the outer ends and a couple of places in the middle depending on how long they are. They aren't necessarily damaged in flight, more when assembling and disassembling the model in less than ideal conditions.

Ian.

[MalcolmDouglasPorter]

Hi Ian,

Thanks for your kind comments. Indeed I am going to use some glass cloth and resin etc around the assembled "high load" area, it does make a lot of sense. The added strength for minimal extra weight is always a good idea! There are some resin types that lose weight as they dry out, perhaps I will look at using this stuff?

Anyway, a blow by blow account today, having suffered the disappointment of a cork screw shaped box, I have now produced the replacement blanks and will be very careful to mark and cut with accuracy (again). Perhaps the gluing up will make me a bit nervous, but I will do it as described in my previous post? I may well start the marking out today, and wait till the morning to start cutting. Go to it nice and fresh? I don't care if it takes all day to do the cutting! It also has occurred to me that some of the weight saving holes could be better positioned. Watch this space!

[MalcolmDouglasPorter]

Been busy today cutting the finger joints on the new wing mounting box. I have been a bit more careful with the weight saving holes. I marked the positions of the aerofoil sections and have placed the holes between them as they should be. Probably a good thing that the first one went pear shaped?

This time, as previously mentioned, I have glued just two of the parts and have set it up to dry square! by clamping one part vertically to a piece of wood in the vice, the other part will not fall away too readily. As you can see, an elastic band helps maintain the squareness. I really am learning to be more patient?

[paul needham]

Looking good Malcolm, usually I have a look most nights to see what you've been up to. I'm interested to see this model through the build and in the air, having been onboard the full size a couple of times when it was at the army transport museum at Beverley and also at Fort Paul. The size of the plane really becomes apparant when standing under it. Keep up the good work with the model and also the build thread.

[MalcolmDouglasPorter]

Had a quietish day. I have set up and glued the new wing mounting box and that is busy curing in the garage out of the way. Meanwhile, I have made the mid section main longerons from 6mm ply and decided to have another play having another dry run using the scrapped wing mounting box to see how it all looks. The two longerons you see are the ones I made earlier and will be used in the build. It is possible to make out the wing shape from this picture. The leading edge will be between B4 and C1, and the trailing edge lines up with D2 at the back of this set up. The wing root chord line is 30 inches x five inches at the C of G. The total length of this section of fuselage is 31.1/4 inches.

[Denis Brown]

This project is something to look forward to in the next few years. Thank you for your regular and informative updates. Just the tonic needed to help us through the winter.

[MalcolmDouglasPorter]

Thank you, Paul and Denis, for your kind comments.

I am enjoying doing this project and using these posts as a record of the progress. You will notice that I am showing the cock ups as well as the good things. I have so far made two massive cock ups and have remade the parts. Some smaller C U’s are easier to bodge or ‘get round’. I have discovered that some ‘gaps’ are OK, whilst others are not OK. I am convinced that as long as about 70 to 80% of the total joint area is sound, then the whole thing will be solid, the other 20 to 30% being taken up with gap filling adhesives. I got these figures, many years ago, from an engineer friend who explained the theory to me, regarding mating surfaces, especially bearings as being the worst possible scenario for an effective function. This and my knowledge of building houses etc seems to hold water. From my own work experience, some of the principles that hold buildings together can be applied to model aircraft.

However, since I first started the drawings, some months ago, and thought through many things, I am now beginning to learn a few more things and am changing what I am doing in certain areas of the model. I have yet to modify the drawings to match the changes already made, and those yet to come. I am confident that the finished thing will be a great success. I will be constantly brain picking as the build progresses.

The basic plan as things are is to get it through all the inspection stages and flight tests before the final detailed stuff (and paint job) is added. No point in producing a Christmas tree that cannot fly?

I will be seeking the help of people to make some of the bits that are beyond my capabilities. I know they are there as members of the LMA!

[MalcolmDouglasPorter]

Been busy today poncing about with bits and pieces, fettling slots to allow their mating piece to fit properly, cutting blanks for the rear fuselage attachment lugs (16 inches long, all will become clear in time). I also cut a few weight saving holes, can't do too much of that at a time coz the cutter gets hot (perhaps it needs sharpening)? I did a little more fettling and cleaning up, lots more of that still to do (internally), and as you can see from the picture, I attached the new wing mounting box to frame No. C3. The other side will glue to C2 when the actual assembly stage happens. C3 and C2 will need to be aligned in conjunction with all the frames, this will actually be easier than trying to line up just the two frames. BTW, the new mounting box is about 98% good, so I'm happy with that!

Just one moment of excitement, the band saw blade snapped. Always happens when you haven't quite finished. I have ordered two new blades.

[MalcolmDouglasPorter]

I am quite happy with yesterdays effort. I removed the clamps and did the clean up this morning, the wing mount box is in its correct position, and lines up nicely with all the others on the 'stack'!

As you can see from the photo, I have also made an aerofoil pattern for the main part of the inner wing. (The outer wing has dihedral and will have the required washout built in). This pattern can be used to reproduce all the aerofoils for this part of the wing. There is a horizontal and vertical datum that you can see. These remain constant except that the vertical datum moves gradually backwards as the size reduces to keep the C of G in the right place along the wing. The shape of the wing is a bit like a French Curve, you just need to work out the length, height and the relative positions of the leading and trailing edges of each aerofoil frame in relation to the datum. The flaps are just two straight lines, so very easy to determine. The difficult part of the flaps are the curves at the front, these reduce as they go further out along the wing, and a bit of trial and error is going to be needed to get this right. I don't have a CAD, and if I did , I wouldn't know how to use it!

This pattern is made from some scrap packaging ply that I got for free at the builders merchants. It is no good for the model itself, but better for patterns than using otherwise good materials. As the band saw is out of action, I had to make this pattern the old fashioned way.

The outer wing portion will have a separate pattern.

Christmas is on the way and all that goes with that, and I need some more materials. These materials will have to wait till it's all over. I did say in an earlier comment that I would be using balsa for the remaining frames, I rather think that 1/8 inch lite ply will be better, and use balsa for the skin as originally planned.

There are a few important things still to do on this mid section before I can even think about assembly, and are mostly related to the undercarriage. I will need to spend a few days at the drawing board to get it all worked out properly. The various conversations I have had about this in the last couple of weeks leaves me in no doubt that this aspect must be absolutely right! It's got something to do with "heavy landings"?

[MalcolmDouglasPorter]

Been busy today but not a lot to show for it. In the picture, four of the six aerofoils needed for the wing root in the central section are marked out. There was a little bit of builders terminology to accompany this at times. These frames will slide sideways on to the spars and mounting box, the No. 3 frames fitting to the outer edges. The No. 1 frame will slide down in the slots you have seen on the 'C' frames as only the top of this will be needed for the wing skin to attach to. As soon as these frames are fitted to their respective mating pieces, I will do another dry run assembly which should look more like it?

I am still waiting for my new band saw blades to arrive, I reckon they should be here tomorrow afternoon?

[MalcolmDouglasPorter]

Started the day checking my measurements, (there were some errors) and then marking out the L1 and R1 frames. The band saw blades turned up as I expected they would, but too late for me to cut the curves. I'll do that tomorrow. As you can see, I have progressed the aerofoils to the next stage. The mating joints for the L3 and R3 frames need to be fettled to the correct size, and then do another dry run assembly. Will it all fit together first time?