Topic: DB Hurricane build

Hello all,
  Thought I would do the build here as I need to get stuck in and give it the commitment it deserves. Bit of bumph for those who don't know. DB Sport and Scale kit, span 88", fully built up, with flaps, retracts and the other 4 functions.
  Being built basically from the kit, modded as and when to include more detail, hidden linkages, hidden switches etc etc.

  First off are the wing panels, built upright on the bench. Packing is used under the trailing edge to jig in the washout. The packing used in the instructions is balsa blocks (3 off), but if I'd have had a full length the right the right thickness, I would have used that as the trailing edge is not suprisingly a little floppy!



 Another point, the wing is built on top of the aileron bottom skin, so this thickness has to be added to the rest of the trailing edge to ensure an unstepped T/E.



  There are anti twist braces between the ribs, very thin in section, but probably work well in the completed, sheeted panel.



More soon, Ian

Time to sheet the outer top skins, but not until the aileron control race is fitted to the bottom skin of the aileron, and packed up to the line of the aileron top skin. Didn't take a pic of this as it was done and covered up by the time I realised I was supposed be to taking pics, (thicko on line build virgin!! - GrahamD and Cliff wouldn't have forgotten!)  First sheet on is the aileron top skin, which lines up the sheet in front of it, then the leading edge sheet and finally the bits in the middle, all done while still on the packing and board. The trailing edge sheet above the flap is left off until the wings are almost finished, to allow access to the aileron hinge and the flap linkages. The kit shows the flap driven from the smaller, inner flap, but I would sooner drive from somewhere nearer to the middle span of flaps, to lessen any blowback. This means driving the outer section, and slaving the smaller, inner section from that.



Once the top sheeting is on the aileron is cut away, along the skin lines and the full length hinge tube is let into the face of the now exposed aileron ribs. The aileron leading edge can be put on next. On the drawing, it shows the aileron bottom leading edge round, but if left square, it can be altered to frieze type sections, much more in keeping with the full size. Doing the means the wing sub spar immediately infront of the aileron needs moving slightly, about 10mm, but we'll see when I get there, so as not to catch the leading edge of the down going aileron. Easier to do than write!



Wingtips are next, made up from balsa block with plywood core. The tips are added now as the outer aileron hinge is embedded into it, in a plastic tube. The hinge itself is a piano wire rod running right through the aileron, secured at either end into the tip and the structure above the flap.



The tips are somewhat oversize, and will be left that way for as long as possible, they make good building rash preventors! On the bottom pic you can see the outer hinge tube end. A fair bit of looking at was done with the tips, as they have to have their inner faces angled so the hinge tube meets the aileron square to the tube in the aileron in rear view, whilst still leaving the plywood core on th chord line of the wing.

When the sheeting is on the panels can be removed, and very light they are too, but I suppose there is fair bit more to go on yet though eh

More soon, Ian.

Now the outer panels are off the board, the ailerons can be hinged, taking care to get the hinge gaps even, and aileron movement the same both sides. The aileron drive cranks are fitted next, they are quite simple to fit and are completely slop free in operation.







The centre section is built up in your hands, then aligned over the plan. The main spar and rear spar continue out into the first bay of the wing panels. The spar tongues have slots in them so the outer panels slide UP into them. There must be a reason why it is done this way, but all I can see are reasons for them to slide DOWN onto the centre section. First is that you don't have to cut slots in the outer top sheeting for the spar to slide through, as the bottom sheeting isn't on yet. Second is that the angle of dihedral on the outer root rib means that the spar tongue cannot be cut perfectly to match the rib it buts up to, without having to force the structure.



The pic below shows the spar tongues, going through to the outer panels. Normally, I would like to see the spars being linked together across the whole span, so the strength runs through the whole wing. On the plan, the spars are not completely physically linked. the tongue is secured at the ends with triangle stock onto the ribs, only the front spar is packed to the other parts of the main spar. This is strong enough, but as piece of mind, and as the opportunity is there for not much wood, weight and effort , I will be linking the outer spars to the inner spars too.



Once the panels are fitted though they fit quite well although it becomes obvious that the outer root rib must be built in at the correct angle from the very start, as there is no real adjustment possible without major surgery. The reason I say this is that in the storybook, it says assemble the three panels, propping up to the correct dihedral, hinting that you have a choice at this stage. Wing join re-enforcement, retract mounts, more sheeting and flaps are next.

Bit more soon, Ian.

  hi idi great build  i have a db hurricane still in its box had about 2 years now! brought the new wing at the hop farm show last year been watching your build with a lot of interest, looks great learning a lot
   thanks cougeruk

Ian, how does this compare in size to your YT Hurricane?  What engine are you intending to use?

You're moving fast. I bet it's flying before my Auster! 

btw did you get my email?

Geoff

Hi Ian.

That hurricane is gonna be cool !
Want to do that one myself as my DB spit is done. The wing construction is almost identical to the spit. Looking forward to se this project evolve.

What´s gonna be under the bonnet ?

Wings gusseted and inner and outer spars are all joined together, turns into a very strong unit. The kit includes a thick glass bandage, to be put on the outside of the two join lines, on top of the sheeting. This would make the wing even stronger but would require a fair amount of the dreaded filler to make smooth for a good finish. What I normally do on areas like this is not to use the thick bandage. Instead I will use skinning cloth, using 2 bandages, on top of one another,  one 40mm wider than the first. Followed by the glass cloth finishing skin, this provides a very strong tapered stress joint of minimal thickness. The bandages won't be put on until the wing is ready for finishing.
The pic below shows the rear spar, with the extra wedge between the inner and outer spars, and the triangle stock gussets. The actual glue / wood surface area on the wing join is very substantial.



The retract mounts are next. These are two beams of beech each side, mounted between three, actually four ribs, the front beam also sits on the front main spar. The rear beam will have a shear webbing up to the sub spar on the centre section too, to box the lot in. The pic below shows the retract bearers in place, just tacked to check the angles in both retracted and extended positions, to make sure they are both identical.



Once this is OK the bearers can be glued and gusseted with all joints filleted with epoxy. Don't mind adding a bit of weight here now, as if they come out later, I'll be adding a considerable amount more trying to get them back in. Make sure now is the best way.
The next pic shows the starboard mount looking in from th top, showing the gussets, fillets and the extra shear web for the rear beam.



This one shows the retract mounts finished, also the completed inner / outer wing spar join.



Move on next to the flap construction, plus time to think of the aileron , flap servo installation and access hatches.

Ian.

Geoff, the wing looks much bigger than the YT one, it's only 18 inches bigger, but it looks like a foot and a half!

I'll send another e-mider to you as it looks like my PC has started censoring what I can and can't do.

Ian again.

Just a bit more. Nearly ready to sheet in some of the underside. First though need to decide where the aileron and flap servos are going to live. More convenient to have them under the same cover, but they need to be aliigned to the linkages they wil be driving. Heres what I thought for them, accessed from underneath.





Also, before the bottom forward most sheet goes on, the landing light aperture needs boxing in. It lines up with a rib on one side, which has front end angled over to match the scale drawing. Another part rib is fitted for the other side of the light, followed by a back. Doing this means that I can now sheet over the and then simply cut up to the ribs, with no arsing about trying to box it afterwards, and no lost strength.



The first sheet is on, note the feint cross at the landing light position, so I can find it first time after the sheeting and leading edges are on. ( My Better Half is a smart arse!!)



A bit I am looking forward to next, the flaps.

Ian.

Right, the flaps. The Hurricane has huge flaps, split into two sections each side. The hinge line of the two sections each side has a difference of (I'm guessing) about 15 degrees in plan and 4/5 degrees in end, dihedral view. As the flaps move down, there either has to be a wedge of flap missing (as on the plan) or as on the full size, this wedge shaped piece of inner flap is hinged and moves out of the way as the flaps come down, but moves back again as the flaps are raised.

I know it's sad, but the wedge has to work!!

Also, as I mentioned earlier, the plan shows the main flap driven by the smaller one, by means of a wire pin, about half chord of the flap. I am driving the main flap, and making a universal type joint to slave the smaller section. The flaps are very thin in section, and need to look right when down as well as up, so the ribs need to show on the inside of them. In the kit, the inner flap is carved from 1/2 sheet, and the outer is built from ribs with sheet top and bottom,ie. no ribs showing
This is because they are thin and the manufacturers know they need to be quite rigid.

I am going to build the flaps from 1/64 ply skins, with balsa ribs, doubled at the hinge end with a 20mm strip of 1/64 ply on top of the ribs, to keep things twist free. They will be skinned on the underneath with litho, bonded with UHU type sticky stuff. Using this lamination technique means the flaps are rigid, but can be tweaked slightly to make them fit at the trailing edge perfectly. The ply skins will be made too short at the trailing edge by 5mm or so, so the litho, when folded round the T/E can be left with a sharp edge. The Hurricane has 7 hinges per side, with a visible notch in the leading edge at each hinge. Robart hinges are perfect for this and the quality Dubro flat hinges supplied will go in the hinge box. Thing is do I try and line up 7 hinges, or fit some dummy ones to make operation, assembly easy.

Thats the plan anyway!

Ian.

Right, after a bit of experimentation, the flaps are progressing well. It all went similar to the above but the link between the two sections was tried a couple of ways until it worked with no slop, un equal movement or damned ugliness!!





The sliding, universal joint was the main stumbling block. It has to bend in the middle, about 15 degrees, and compress by about 10mm as the flaps are lowered, but remain rigid enough so the slave flap doesn't 'flap'! as the flaps are raised. This was the solution.



The joint was made with two lengths of brass tube, soldered onto a bowden cable with about 3mm gap between the two tubes. This makes the universal joint. One end is fixed to the master flap. The other end slides in another tube which is fixed to the slave flap, to allow for the compression of the linkage. This link is installed about a third of the flap chord away from the hinge, sandwiched between the flap skin and the top stiffener. It would be better further away, but it would then foul the wedge door. There is no slop at this position though.

The wedge shaped door was hinged with strips of mylar, let into the outside surface of the flap skin, and will be completely hidden by the litho covering. The wedge is held up level with the wing skin when the flaps are up, but when they are lowered the wedge bends 5 degrees, to miss the main flap as the gap between the two sections closes. The pics explain better than I am in writing.



Ian.

A couple more of the finished, but unskinned flaps. The first shows the horn for actuation, made from one half of a YT Hurricane flap hinge. Very good for this purpose as it has two arms, one either side of the heavy duty 3mm ball link.



the next shows the hinge blocks and a flap (has to be trimmed back at T/e yet to allow for litho



The next two show the wing at this stage. Flaps have been trimmed back, rear skin is on, but the flaps still 'un lithoed'. Also the servo mounts are visible.





Last one for now shows a close up on the wedge shaped door, with it's mylar hinges. A dummy piano hinge will be over the top of this and hide it completely.



Ian.

One side litho plated, didn't do the other one as I was so pleased with the first one, I couldn't stop dribbling on it!!

First two show one finished side.





Next one shows the flaps down, the wedge tucks itself out of the way.



This one shows a close up of the dummy piano hinge and wedge panel.



Finally, this one shows the trailing edge, straight and sharp, due to the folded litho.



I'll make a mess of tuther now!
Ian.

Very nice Ian, are the rivits done with a dressmakers (ponce spl?) wheel

Steve

  Ian, agree with Steve, excellent work on the flaps, did you use contact glue?

  Cliff

Cheers chaps, the rivets are done with a dressmakers wheel, that's had every other tooth removed, to get the pitch very close. Glue used for the litho to ply was UHU contact.

Ian.

VERY impressive ian, lookin great so far.................the flaps are lookin great in Litho, what did we do without dress makers 'star' wheels !................

Srill love the old Hurri............I 'blew up' the BT 70" plan about 3 years ago to 140"..........once I can find a decent engine that'll fit in at 150cc+, it'll go on the 'to build' list..................

Watchin with interest.

Phil

Finished the other side of flaps, they even work like the first side



Leading edges are now on, but won't be shaped until the fuselage has materialised from the huge amount of wood that is still in the box 



A few more planks of sheeting are on. The rest of the wing, ie. the root trailing edge and the root leading edge is being left until there is a fus to make it all fit to.



The next job in my build are the tail feathers, as I like to have the rest of the bits around when I build the fuselage, makes visualising the parts fit easier (for me anyway). The instructions show the fuselage next, although they are set out in chapters so building out of their sequence is an easy job. I have done it this way, so that I can see how the wing fairing is going to fit, and alter or shape the parts as they are fitted, saves a lot of retro shaping of bits already fitted to the model.

Listening to comments made on this and other forums regarding this model, very few seem to escape the need for ballast up front, so, taking advice where it was given, every attempt will be made to lighten the structure at the rear end. On the tailplane, the ribs have been drilled out, and the elevator cores will be fretted once the structure is attached.



More Tommorrow Ian.

On to the tailplane then. A fully built up structure with ribs, spars, sheeting and now cap strips. 

The ribs are assembled onto the mainspar. This is from 1/4 sheet with slots half through to locate the ribs. In front view, the finished tailplane is tapered, with the untapered mainspar being pinned to the board and tapered to suit the ribs afterwards, neat. The sub leading edge is added next, this is packed up equally at the ends and the middle to ensure a warp free structure. Once that is done, the upper front spar is fitted in the notches behind the leading edge, one strip over the whole span.



The leading edge and the centre section is sheeted. The rib profile should allow for sheeted areas so the finished profile is smooth from sheeted areas to the open ribs (it will become clear!!). The ribs in my kit were not perfect, so I sanded the whole structure smooth before adding the leading edge and centre section sheeting. This meant putting capping strips on the ribs which were left exposed. This is probably an easier way to get the shape correct and makes for a better finish under the covering anyway, so I think the slightly mis-shaped ribs were a blessing.



The tailplane is then removed from the board, flipped over and the underside completed in the same way. Hinge blocks are added, with an extra block either side of the centre rib, to support the elevator crank. In the kit this is unsupported, but really needs it as the nearest hinge is approx 3 inch away (6 inch unsupported).The leading edges are then added, along with the pre-shaped tip blocks, and associated ribs. It builds into a scale like structure, very strong although I would have liked it a tad lighter as the paranoia has set in about nose weight. Still, if it needs noseweight, noseweight it shall have, but it will pay to be careful. A note here, the wood supplied in the kit has definately (upto now) been well selected for it's purpose, light and soft for some of the blockwork , and quite hard for spars and places that need a bit of strength. Another advantage of the rib cappings is that the hinge spar needs capping too, which means the small hinge shroud on the tailplane is a piece of cake to do, without having to try and glue a very small section of balsa end on, onto the back of the spar. The last pic shows the tailplane before the cappings are added. Also still to be added are the centre hinge blocks.



Elevators will be next, and the whole tailplane can be finished.

Ian.

 

Just typed a bl**dy page of explanations and stuff about the finished tailplane, pressed the post button and the s*dding server was too busy, (so it said) and then proceeded to eat all my words. So I am not putting them on again today.

AND YES I AM 5!!

Mardy Ian.

Bugger, I was looking forward to reading that 

I also got the dreaded server busy message a little while ago, are we that popular 

Steve

your 5 what?

Just typed a bl**dy page of explanations and stuff about the finished tailplane, pressed the post button and the s*dding server was too busy,

just a thought, you may already know this but, if you type up your post in word or notepad, you can save it and just copy and paste to the forum, that way you'll have a copy of your build and you'll not loose all that effort

Nice build too

Steve

Just typed a bl**dy page of explanations and stuff about the finished tailplane, pressed the post button and the s*dding server was too busy, (so it said) and then proceeded to eat all my words. So I am not putting them on again today.

AND YES I AM 5!!

Mardy Ian.

That'll teach you to type long posts 'on line' - NOT!   Try typing in 'Word' or something then copy/paste into your Forum reply.  It's a lot safer    I bet you threw your dummy out of the pram as well   

Anyway, you shouldn't have skived off on Friday to go flying 

Geoff

Why bother typing it in word or notepad, just type as usual but remember to right click and copy before submitting

  Ian  well impressed   nice build mate   keep it up
i look forward to its finish and first flight

Shane

Right, try again!

Elevators are built on a sheet centre core with half ribs and half leading edges. There is a balsa block at each end of the elevators, outer one for the balance, inner one to strengthen the crank fixing and smoothly curve the inner end of the elevator. Since I have strengthened the crank mount with a liteply sandwich, like the hinges and the inner end of the elevator on the full size isn't smoothly curved, I didn't fit these blocks, but did fit smaller triangle fillets, which would only show through the covering where appropriate.  



Because I have moved the hinge line backwards by 10mm, the hinges do not fasten to the leading edge any more, but pass through it, I have to make pockets in the centre core for them to fit into. These were the first job, drawn onto the core and cut out accurately. Doing it now saves a lot of messing later when they are to be glued, as they will line up when they meet the end of the pockets. Each pocket was made with a triangle of lite ply, top and bottom of each hinge (and the ele crank)



The full size has one hinge each side, just inside of the balance, and another either side of the elevator crank at the centre. In the kit, there are two hinges per side, with a wire joiner and crank joining the two halves. The plans show the hingeline on the leading edge, but the full size has the hinges set back from the leading edge, so this is what the model will get. At the scale hinge point, there is a notch out of the elevator to clear the hinge. The non scale hinge isn't notched, just hollowed enough to let the hinge move freely, so, when the elevators are covered, the middle 'model' hinge will not be seen. The crank wire is also set on the hinge line in all axis, so that two nylon horns can be made to provide a rock solid mount right across the elevator. The pic shows it more clearly than I have explained, and I explained it even better the first time I wrote it !



The next pic shows the complete, but still to be final sanded tailplane with the elevators lightened slightly. There is little scope for lightening here really, it's just a token gesture to make me feel like I am trying!! Suppose I could remove more core, but would it make that much difference? What do you reckon?



Ian. apologies for the concise (re. sparse) version, but it's not the same second time round!

Nice piece of work Ian...........I know what ya mean about the lightening at the back, Dad has gone nuts fretting out the stab/elevs on his BT Hurri.............sure it'll pay off in the end though.

Keep up the good work..............Phil

The fin is the next to appear out of the box. Fully built up with ribs, sub leading edge and hinge post, micro ply leading edge sheeting, and a 2 lamination final leading edge. It is built onto the hinge post, which is pinned to the board. Then the sub l/e is fitted.



Make sure the ribs are square to the board, as this will determine the fit angle to the fuselage and tailplane.



After this, the ply sheeting is fitted, followed by the laminated l/e. This required pre bending to fit with no hassle. Dampen it, then tape to a slightly tighter curved former till it is dry. Then fit. It builds very quickly, but care must be taken to keep the leading edge straight as the front edge is quite flexible until the sheeting and l/e is on.



The base of the fin to tailplane joint is made with a thin shaped balsa block, which needs final shaping to match the tailplane section in all axis. The block is quite accurately cut to section, but as the tailplane is tapered in front view, the fin block must be hollowed slightly to match this. I drew 3 lines under the block, 2 at the edges and one down the centreline. When the block is sanded, if the outer lines are still there when the sanding is finished, the outer fit won't be changed, simple.



I now have most of the bits needed to mount to the fus, I just need that minor item!

This has lots of opportunity for lightening, especially the formers, so we'll see what other bits I can leave off to save weight.

Ian.

On with the fuselage. Bits of balsa sticks and sheet, like a vintage build.

The front end of the sides are built from balsa strip, with pre cut balsa sheet for the wing seat. I made both front sides first, easier to get them exactly the same when they are only 2 feet long! As the first was made, every cut was duplicated so I had exact copies for the second. The second was built pinned over the first.



The main longerons are then fitted to the front sides, after they were pinned onto the board. This is where I met a snag. There wasn't enough longeron material in the kit, as the diagonals are made from the same. As with the front sides, all cuts for the uprights were duplicated and numbered, to keep things the same on both sides.



I nearly carried on and used other stock for the diagonals, but two longerons left were, I felt too soft for the job, so work was halted. I live too for from a shop just to nip out for longerons!

Attention turned to the tailwheel, which will be needed quite soon in the fuselage construction.
In the kit the tailwheel is a simple fixed piece of piano wire, which needs to bent to shape, then sewn to the former. I like to taxi planes about the place so it at least needs to steer. The way I make steerable tailwheels is simple enough, but with only the addition of a spring or two, the thing can be turned into a sprung, steerable jobbie which has to help the longevity of an airframe, bouncing over grass etc. It is basically a piano wire spindle with a crank s/soldered in the middle. The springs are from the spring box, 3 used, 2 softer ones, and a harder one to take any really hard bumps. At the bottom end is a very short piece of thick walled copper tube, cross drilled with the U shaped wire that holds the wheel s/soldered into it. At the end of the U, at the axle end, is another copper tube s/soldered between the ends.



This tube, when cooled has the middle piece cut out, the two ends the line up perfectly. The middle piece is kept for putting through the wheel, sleeved with brass tube so the wheel cannot rub or bind on the side frame. Apologies for the picture quality, my camera is having a sulk being carted to and fro, warm to cold etc. On the full size, the join between the spindle and the U is made from a casting so I have tried to dummy this on the model.
 The pic below shows, very badly, the soldered unit. At the bottom end of the spindle, above the copper tube, is a thin walled ali tube which is only there to look like the polished oleo leg on the full size. On the U, there can be seen two bits of fuel tubing. These act as a stop for the resin when it is put onto the soldered joint. Resin was put on, and the unit rotated until the resin has stopped trying to run off. It is rotated so it keeps the resin in the area required and up to the fuel tube stops and up to the ali tube. In a couple more minutes, the resin can be smoothed if it isn't already, and the fuel tube removed to leave a sharp edge to the 'casting'.



The next pic shows the nearly finished tailwheel assembly, ready to go into the fus when I get to the emporium. Ignore the lovely wheel, (need one of those too!) The whole unit is only about 5% heavier than the standard fixed, boring one, so would probably be equal as the standard one still would require epoxying to the former. Worth it in my book.



Got plenty of wood, but none that would do, or be stripped down the do the job B*gger!

Ian.

Another pic or two. Work may be slightly halted soon as the Prototype YT Spitfire Mk14 is coming this week. What a shame!





Ian.

OY REDSHAW!!! whats with the swastika---must be story there   anyone else seen it?     build so far is your usual Carp,  keep kicking that weight out   jonesy didnt, nearly 4 lb lead at the front!!   still flew superb though!         spit?? wot spit

Well spotted Alan, apparently it is a WWII Luftwaffe Navigators Square, so there!

Ian.

 This is the scheme chosen, 303 Sqn, Northolt, September 1940. Flown by Flt Lt J A Kent.



Ian.

  Ian,
           I"ve got a great side profile/colour plate of that plane, and pics+info of the pilot...want me to scan them for you?.......he was killed in action later in the battle....but acheveied "ace" status in  V6665....taken from the same book as I got the scheme for mine.....

    Cliff

Cliff, that'd be great, too much info, or duplicated info can never be a bad thing, so fire away my man!! :ww

Your Hurricane looks the biz by the way, cannot wait to hear about the test flights

Cheers, Ian.

  Ian, 
               I"m working today, but will get it done for you when I get home tonight,
   Cliff 

   Ian...here"s the plate of Kent"s aircraft.....actually, I made a mitsake...think he survived the War and wrote a book called "one of the few"...


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....and the man himself...in the centre...
                     .Ian...go to my profile and drop me an e-mail....have both full-size plate, pics, and text info in a zipped folder for you....


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Cheers to Cliff and GrahamD for images, much appreciated.

Haven't done much recently as the YT Mitchell has to be done for the box label, and I aint going to squeeze and rush.

Ian.

My God, took me ages to find this again!!!

More soon.

Ian.