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Bristol Blenheim Mk1V


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Ok well I got a bit more done this evening starting with the simple task of glueing some steel tube into the tailwheel support, this passes through top and bottom plates for maximum strength.

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Next was an update to the front with further stringers added, these again 6mm square balsa and soaked to help them bend. I also took the opportunity to get the cockpit floor installed, this is 2mm basla sheet. The glass house structure was also strengthen with the addition of a soaked 6mm by 2mm strip.

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Finally went back to the tail and finished off the location blocks for the tailplane that sit at the front of the ply crutch that extends the full length of the fuselage and controls the incidence. With that done and some simple measurements to ensure the tail was square this was marked onto the surface of the tailplane for future reference. I also added some 6mm basla between the crutch where the tailplane sits for extra gluing area. Had to then sit the tail parts in place. I reckon I can make the rudder about 25% lighter so planning to remake this as it still requies some sheeting to be added.

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More soon. Linds

 

Edited By Lindsay Todd on 15/09/2013 21:43:43

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Well a bit of updating to the plan has been required as things have developed but nothing new there at least I'm getting used to the habbit now of documenting as I go. With that out of the way its been time to make a little more progress starting with the glasshouse at the front. This is made up of ply sections of 3mm thick by 6mm wide strip cut to various profile and butt joined between the formers. I am re drawing this as I go so evetually the plan should have a series of interlocking parts but with the three views all being slightly different so having to work between these and photographs its been the easiest way at this point. Just time consuming, the front has also now been finally shaped to the distinctive angle.

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I have also added the remaining stringers, in part these are structural and in part surface area to secure the sheeting too, as such not all run continuously from nose too tail. Local areas around the wing position have been reinforced with some supporting blocks but we are generally now ready to add some surface sheeting.

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NB the cut away diagram on the bench, an invaluable aid on his project.

Now for the fun of sheeting and to make life a little easier hopefully later on I am starting with the forward cockpit area or more specifically the region between pilot position and navigator bomb aimer. This needs to conform to the profile so I am building this up in sections of 2mm balsa sheet soaked and clamped, then rewetted and glued all to help it conform to the shape without cracking or splitting. From this I can then mark out other areas of the cockpit framing and then carry on sheeting the upper fuselage areas. All good fun I hope.

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More soon Linds.

 

Edited By Lindsay Todd on 18/09/2013 23:47:27

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More sheeting, decided to attack the fuselage side after all. First job was to trim a sheet to length, actually that should start by scarf joining two sheets of 2mm balsa sheet and then triming off about eight inches, position centrally on the central longeron having been first soaked to allow to conform to shape by pinning and clamping and weighting with pegs. I will then trim back to find centre of a suitable lower longeron before gluing in place.

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This is going to take some time! at least the first sheet is on. I should also point out I checked the aluminium wing tube did fit through the fuselage prior to this. Once one side is in place I will cut through to clear the tubes and then sheet the other side.

More soon, run out of pegs for now. Linds

 

Edited By Lindsay Todd on 19/09/2013 21:30:28

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Surprise more sheeting time, now the nose section or at least the region just below the glass house, managed to do this in one piece by pre soaking to bend and peg in place, before glueing down and clamping again with pegs and pins. I do all this with aliphatic as this allows for sanding later without getting the hard ridges between joints that can occur with cyno and epoxy, it just takes a little longer.

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Once dry I will trim back to shape and edges of the glass framing. More soon. Linds

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Sheeting always seems to take ages doesn't it? Eventually you begin to wonder if you'll ever reach the end of it!

I always start enjoying the work then gradually I get a bit less enthusiastic as the job seems to goes on, and on, and on,... The funny thing is, you look at it, and think "nearly finished just a few bits to do". Then three days later you're still sheeting the fuslage!

I think its just that some aspects of this can't be rushed, you have to soak, form, hold, wait, glue, wait, peg or pin and wait,...you just can't speed these steps up.

But having said all that - its well worth it in the end! Looking nice Linds.

BEB

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This is a work of art, Lindsay. I'm far too ham-handed to get anywhere near your standard of workmanship. I don't recall seeing a scale Blenheim IV before this. I seem to recall seeing a Mark 1. I've never seen any attempt at a Mark V (Bisley). That would be another interesting challenge, but I think I'm a way off trying myself!

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Your very kind Colin, like most things it's about breaking it down into simple stages, the whole project is quite daunting so at this stage I don't look, or at least try not to look too far ahead and just work on the next logical step. Yes at times I get a bit pedantic but don't we all. I have also found over the years to keep asking questions and get perspective from others even if you don't take it , it does force you to think things through. I have a feeling Brian Taylor actually did a Blenhiem Mk1 some years ago but I don't think it was ever released as a plan. There was also a large Bisley built in the states that was around for a while so I can't claim to be the first, maybe for a Mk1V but thats not important nor the reason for the project. Its an aircaft my father had some fond memories of and has always been a favorite so that is good enough for me, if others like it then its a bonus. Fingers crossed after all this she fly's. Linds

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"Britain First" ? A start to a potted history of the Bristol Blenheim. As with many aeronautical endeavours it was the Daily Mail, and indeed its owner in 1934 Lord Rothermere that set a target for British Aviation Industry to build a high speed passenger or light commercial aircraft for six passengers and two crew. Rothermere's target was very clear, he wanted to reclaim the title of britain having the fastest civilian aircraft in Europe. Back in 1933 the Bristol Aircraft Company had been working on a design known as Type 135 and adapted this to become the Type 142 for Lord Rothermere and it was this aircraft that was aproved and named 'Britain First'. The design first flew on 12th April 1935 and demonstrated a top speed 50mph faster than the current front line fighters. The Air Ministry whom had not been initial fans of the concept promptly did an about turn and quickly sent out Specification B.28/35 for a prototype Light Bomber.

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Britain First in clight circa 1935.

 

So back to the model, much sheeting has occured resulting in three quarters of one side of the fuz completed, bit of filler on the seems and quick sand.

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Time for a potentially difficult bit now. with the sheeting in place of course the main wing spar tube holes have been lost so these now need to be opened up. I was a bit worried about how to achieve this easily however came up with a cunning plan. By luck I think i had a hole saw that matched the diameter of the phenolic tube, so with a little tape I was able to fix the hole saw to the phenolic tube and use the existing holes to align and spin the tube cutting through the holes. perfect result. yes

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Next job it trim the tailplane clearance in the sheeting, then its time to revisit the cockpit and then more sheeting.

More soon. Linds

Edited By Lindsay Todd on 21/09/2013 18:46:17

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My peg fetish continues, yes now its time to sheet the other side of the fuselage. I trim the sheet so that it spans half way across an appropriate longeron by pinning the sheet, measuring, marking and cutting the sheet carefully. The sheet is then soaked in warm water and then clamped back into position on the fuselage. The extra pegs load up the sheet to allow it to bend slowly and as it dries drops down onto the frame. I find this technique is a little like increasing the tension on clamps over a period of time a little like steaming planks on a ships timber hull. Every twenty minutes or so I re moisten the timber and add a few more pegs till the timber sits or conforms to the shape I need.

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Hopefully I will also get to the cockpit areas again over the weekend to complete the frames.

More soon. Linds

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I had a little time later this afternoon so was able to get a little more work done arong the cockpit area.

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As you can see the pegs have been removed and the sheeting trimmed to shape around the nose area so time to add some of the struts and cross bracing to the pilot cockpit area. This has been laid up in 3mm verticles in medium basla and then braced with 6mm square.The upper frame is in 3mm ply and the central frame also from 3mm ply. As this is the prototype all the parts are butt joined and will have small fillets, the final version on the plan will be interlocking hopefully to simplify construction but at least the left side is the same as the right side here.

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The centre strut is actually a building aid from the point of the upper frame down as this will be removed later to be replaced with a triangular brace but to simplify construction at this point it holds the form together whilst I work out the final angles. the next job is to create the shape from the lower edge of the upper cockpit front windows to the area that is sheeted just forward, there are quite a few angles here and the timber will have to be worked to shape again - more pegs and soaked balsa I feel!

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Access into the cockpit area is still pretty good at the moment but I need to start thinking about getting the internal area painted and some minor details in before too long. Note the slight revision to the former that forms the cockpit dashboard facia backplate, this took some working out. More soon. Linds

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