Rebirth of a DH2

[ceejay]

Hi all

been suggested by mr moderator that people may be interested in a rebuild thread, this is of my De Haviland DH2 a model seen around the shows as long ago as 2002 in the hands of Ian Redshaw, i came to own this aircraft three years ago and have flown it for the last two seasons, however it came to an abrupt end last August at a large event in germany, on climbout after take off at approx 60ft the engine quit abrubtly, now one thing the DH has never had is a glide, it does a very good impresion of a well trimmed manhole cover when the power stops, the technique when this happens is to shove its nose down about 45 degrees or more is required to gain enough speed to flare out to land, unfortunately this requires more than 60 ft so the abrupt "arrival" caused some damage as it came to a sudden stop (well most of it did the heavier bits carried on for a few inches!!) in a recently plowed field, so for those interested i will post some pictures i have been taking during the procces with descriptions of its rebuild,

chris

[Pete B]

Looking forward to this, Chris - I think I may have read about its untimely arrival elsewhere?

Pete

[David Gilder]

Watching and waiting!

[ceejay]

well you asked for it

first things done was to strip the entire airfame so all the panels were disassembled from their struts and rigging, lots of this on a double bay wing!! and i starte with the fus, as it has booms for the rear its avery small fus but i has to contain everything so everthig out left me with the above. it should have a nice nose on the big space but thet rekitted itself quite well on the rhineland earth

chris

[ceejay]

after a session of regluing and filling and sanding it eventually looked like this

 

now its at this point that the nose job takes a turn.

 

chris

Edited By Steve Hargreaves - Moderator on 28/03/2013 23:44:59

[ceejay]

it was during a conversation with ian that the subject came up that a nice alluminium nose cone might be a better option, so having talked himself into a job, he got to work

tools at the ready alluminium suppliede by me was 1.2 mm thick and before beating started was anneald after much bashing and tapping and magic this started to emerge

and is now at this stage

enough i hear you cry so orf to bed more tomorrow

chris

[Danny Fenton]

Nice one Chris, that Reg Shaw is a clever chappie indeed. I thought maybe when his hair was cut off his powers would vanish. Obviously tis not the case

Cheers

Danny

[Terry Walters]

Chris - really interesting - will watch your re-build with anticipation! Best of luck!

Terry

[MikeS]

Always good to sea a rebuild after a crash, I seem to learn something from everyone. That nose is looking very nice.

Mike

[ceejay]

Hi all

yes the nose is looking ace, its back with me now and waiting for its final fit before being sent off to Ian for the finishing off beating and final finish prior to paint,

here are all the bits that make up the cockpit detail that will be going back in very soon

all that is except the large ply section botton right as this is a bit aged and fuel soaked so a nice new bit will be used!!

fortunately the main damage was confined to the fus section and the lower wings but as this is an over 20 kg aircraft the whole structure is to be uncovered and all joints inspected and repaired where needed, it get a regular inspection on all and everything that is repaired or replaced,

chris

[ceejay]

and so onto the next section of interest, uncovering sections as i go i started with the elevators, start small i thought !! the main reason for this is that over the last few years the elevators have developed warps a result of spending lots of time out in the weather and living in a workshop in between, so the oppurtunity was taken to correct this. so this is the way i set about it, first of all i made a simple MDF jig to hold them.

this will clamp them 1" above the main base and allow them to be clamped for a long time with out being disturbed.

so the elevator was warmed and moistend with steam, being carefull here not to scald me pinkies, you can do this with a kettle but i found a nice little steamer that is used in the house to clean tiles in bathrooms and kitchens !! was the perfect tool as it comes with little adaptoers to aim steam jets where to want it, the whole thing was then clamped into jig and the trailing edge deflected dow by the same amount that it was warped up clamped and left for two days in a cool workshop to dry slowly

then repeat with the other one

chris

[ceejay]

just read some of my posts. hmm my typing is terrible so apologies in advance. as my fat pinkies dont seem able to press individual keys ho hum!!

chris

[ceejay]

well it worked but i dont seem to have taken any pics of them so i will when i get to the covering stage, this thread may flit about a bit as i have progressed a long way since some of the photo,s were taken and the posts may not be in the same sequence i did the actual work but i will cover it all,

next the wings, starting with the upper pair, as these were the furthest from the ground and thus they suffered no impact damage only shock loads, so off with the covering, here is a before, as you can see looks perfectly fine upon covering some joints were loose and ribs cracked and a couple broken these were glued and/or replaced as needed,

not much else to say other than bothe were treated the same, both ailerons removed and stripped just to check and all is well inside them, a note here that may be of interest, i like to be able to dismantle ny aircraft to as few a components as poss without resorting to cutting or anything so crude, so all my flying surfaces are made with hinges that have asingle hinge wire that goes through all hinges, i use the flat white 6 hole type from kavan (other brands are available!) , so when installed the single hinge pin is made to simply pull out with a small pair ofsnipe nose pliers or even your finger, i will get some pics to illustrate later.

next up will be the lower wing panels, this is where it gets serious

chris

[ceejay]

so the covering was carefully removed from the lower panels, i say carefull as of the two panels one was badly damaged and the other was realy badly damaged and the fabric was keeping all the bits together,

so first one the lesser of the two damage wise

as you can see it was clamped down to my bench and all the broken bits removed and the framework cleaned up, so you will seespaces where ribs and shear webs should be, you can see on the left the metal bracket that is the lower boom mount, this was inspected minutely as its slightly vital to the airframe, no damage at all Phew!!,

so new ribs, i dont know how anyone else does it so here is mine you may have a better solution, the DH has ribs that are basically the same from leading edge to rear sparm with three variations from that point on, so i made a template for the main section first from card, then from 1/8th (3mm) ply the edges hardend with cyano and accelerator, then this was screwed to balsa blanks and the blank then carefully sanded down to the ply, with care for a few ribs this is fine,

bit of card used a a vice soft jaw to protect the wood, (cant take the engineer out of the man) file towards the ply will stop the balsa splitting, then spar slots were filed in using a nice new 1/4" (6mm) square file for the 1/4" spars to sit in.

actually i have just noticed the top pic in this post, its a later one and you can see on the right the new ribs and spliced upper spar in place. told you the sequence might flit about a bit, by this simple but steady method all the ribs were made individually to fit, shorter ones cut to fit easily and the longer ones, only 3 in each wing and only one broken in this wing, were made using another template made from card to get the rear section correct. riblets are made from front section of template

so the finished panel just needs rib caps at this point and a final sand with my long stay straight sanding block, alluminium and 2ft (600mm) long gently over all the rib caps to remove the final discrepancies in profile twixt old and new ribs.

chris

[ceejay]

so finally for today,( i,m told i am going out for the afternoon!!)

the lower panel that took the brunt of 22 kgs landing on it, as befor off with its skin,,OH! whats all this fell out

plus a few bits that were broken but still attached,

firstly as before it was clamped onto my bench and jigged back into its correct perrimiter shape. then as befroe all broken bits removed and frame cleaned up, but this time things were realy broken so all the bits that could be re glued into place were this is to keep the shape correct and the will be removed and replaced as i go, otherwise i would have had a leading egde trailing edge and some bits of spar, and i did,nt want that, at this point there will be some saying surely a new wing would have been easier, true but it would have been new not original, the first thing to address was the boom mount point this had taken quite a thump and had craked the spar both sides of it, so it was unbolted and the spar repair went thus, useng a nice new length of 5 mm birch ply cut to replace the shear webs for two rib bays it was clamped in place using a 10" long (250mm) length of high carbon hardend and perfectly flat and unbendable steel( a new10" smooth engineers file) to pull it all straight, whilst this was drying a lot of measurements wer taken from the other panel regarding pos,n of the boom mount, although it will be clamped back into the same place through the same holes with longer bols it should be the same, but i need to know its in the same place. once the glue was dry the bracket was bolted back onto check and to use as a guide for the structure rebuild. so here it is being done allowing you to see the ply brace.

the card templates you see are for the angled rib sections that will go on once the bracket is ready for final assy

here you can see the sections cut and epoxied to the alluminium brackets tha bolt to the same mounting points as the boom socket.

next shows all the socket and rib section bracket assy,s bolted and glued into place, you will also see ribs apearing in spaces and spaces wher they will apear next

i,m not going to repeat the rib make and fit sequence but same followed for the wing tip section to eventually look like this

once all the ribs were fitted and spars spliced, these will be braced with light ply webs in pace of the balsa where splices are, splices also staggered to avoid stress points, again rib caps a few riblets and spar webs to go on but now it looks like this

i now have 4 wing panels that are within 1mm at the vital points the same dimensions, i still have servo mounts to make for the lower wings as i aim to make the new ones easier to get to servo,s for maintenance as they were removed for me!! remember the heavy bits not stopping for a coupe of inches Hitec Hs 700 series here,

i know its been a brief wiz through but i will tie in previous work on components as i get to them for the next stage, but one thing i can show you is the power plant, i have decide at this point there was no sensible reason i could come up with to put the old engine back in, so a brand new Zenoah G62 was married to the Mick Reeves reduction unit, which has had and a complete strip down and rebuild with new bearings and belt, also sports an easy start and a recoil starter spring.

toodle pip for now

chris

[ceejay]

just found a "before pic for the wing tip,

chris

[Charles Smitheman]

Thanks for posting, just up my street this sort of thing. I find repairing always goes very quickly compared to new builds. Have never attempted anything so big though! Good luck with the project.

Love the alum nose.

Charles

[ceejay]

Hi charles

i find if you look at a repair as the balsa bashers artf then you cant go wrong,

chris

[Chris Bott - Moderator]

Great stuff Chris, very interesting indeed. There's not much to those wings structure wise is there? Does that mean that the rigging wires have to be functional just like the full size?

[ceejay]

Absolutely correct chris, it is a complet 1/3 scale replica in that it needs all the wires the full size had to keep it together and DH2 shaped, it dissmantles enough to go into my estate car with all the kit and two people so is quite good and with practice i can rig it in 20 to 30 mins on my own.

here,s a link to one of my favorite videos of it, flown at a real WW1 aerodrome

http://www.youtube.com/watch?v=xTsgNSfgLY0

see here

https://vimeo.com/33684457

Dawn Patrol are huge supporters of this venture

chris

[Terry Walters]

Ceejay - just watched the vid - what a lttile gem this is.

If you're reading this then have a look at this vid it will make you happy!

Terry

[Kevin Fairgrieve]

This is how she looked in better times.

[ceejay]

hi terry, is the link missing from your post or is it me cant find it.

hi kevin great photo,s and just what i need to keep me going, been in workshop today for about 4 hrs and at the end i cant see what i have done, i have done loads its just fiddly things that soak up time, desperately trying to get all the wood bits on the wings finished this weekend so that i can get it assembled and rigged to check it all fits together then its onto the re fit and recover stage so things willchange visually pretty quick.

at this point i will go back a bit to the fuselage work that was done prior to its going for its new nose,

this pic shows the fus looking back from the front you can see the plywood sides, then the firewall with its four holes for engine mount the cutout top leftis for the carb trumpet and beyond that is the former that the extension shaft housing is bolted to, thats the four big washers you can see, this is a 9" (225mm) long alluminium tube rather like a long top hatm the rim bolts to the former we see and at the other end is a bearing the shaft runs in. here,s the shaft right hand flange is bolted to the flywheel left is prop driver,

a quick shot of the shaft/motor combo, not bolted together here,

chris

[Chris Bott - Moderator]

She really was, and will again, be a beauty Chris, keep up the great work.

She's already graced the airfield at Greenacres on more than one occasion I believe.

[ceejay]

so the fus

one issue with the DH is the lack of space in the fus in there there is the motor assy above, exhaust all servo,s for elevator , rudder throtle and choke two RX,a and two batteries and a full working cockpit so one problem that had to be managed was cooling, as the only area for the air to go in was through the cockpit hence the pilot was only ever a head on a bracket, so as well as saving a little weight i also thought that removing any surplus wood could be removed from the fus sides, this is made easier by the fact that the fabric on the fus is laced on as per the real ones were, so unlacing it allows acces to wood, so careful measurements were made and no wood remove any where near mounting points for cabanes or joints, i dremmeled out large spaces,this willhopefull yust give more space for hot air to move about and cool

fabric folded back over willcover the sides,

this final one shows the new structure that now joins the front of the fus together, this forms the front of the cockpit floor and will be the lower location for the new nose, set into the reccess will be the front part of the removeable floor panel to give access to the twin RX,s and batteries that willlive in the nose section,

it will all make more sense as it gest fitted out,

and just to confirm my statement re random bits of info popping up here,s one i found of the last lower wing (the bad one) cleaned up and ready for rea assembly this is the boom mounting area,

not a lot left in there!! but crucially there were two of the four strut mounts unbroken and this allowed me to use them and the root rib and wing joiner tubes as datums for the measurements to refit the two missing strut mounts and the boom socket.

will be caught up soon and hopefull will post as i go from then on in some sort of sensible sequence

chris