Scratchbuild 84" Depron DH Mosquito

[Shane Sunday]

Hey Roy some great and clear ideas there. These types of builds are of immeasurable value to builders like myself. Many tips and techniques I might never have thought of. So thank you again. I'm horrible at build logs as my building is sporatic at best. Are the gear doors going to be a mechanical deal or the linear servos that can be found on HK website?

I've been staring at a set of plans for a dual 80mm tomcat and have been flip flopping between your build style or more of a tetris hotwire type build. anyhow enough about that. keep up the good work sir. we are watching.

[Electriflier]

Shane,
Thank you for comments - appreciated!
I too am not red-hot on the build log front and often struggle to explain myself clearly. in fact, I find the build log far more difficult than the build itself!!!
Rather than slow the build down to a snail's pace by working on the retract doors (sorry Ian), I'll be leaving the centre fuselage section for a short while now whilst I concentrate on the actual fuselage. Again, if you've followed any of my other builds, I'm a 'cruciform' style fuz' builder in that I construct a 'keel' and attach formers to the keel etc.
It works for me and so, its the 'if it ain't broke' attitiude.
The fuz section from F8 backwards. The protruding caron tube will be cemented into the rear of the blue foam block.
The central keel is cut from 6mm Depron and because I will be building the mid to front section of the fuz' around the blue foam central block, I started the rear section first (F8 backwards). I glued in some 6mm carbon tube into a slot cut from the keel and then, on the underside of the cut, Uhu'd a 30mm wide slip of 6mm depron. This effectively acts as a dam to stop the PU glue that I'll be using for glueing in the carbon, foaming out. A liberal run of PU glue was applied to the cut-out section and the carbon tube inserted, twisting as I inserted to ensure good coverage of the glue. I then UHu'd another slip of 6mm Depron to the top of the carbon tube to seal the PU in! If you ever do this by the way, please note the PU glue takes a lot longer to cure than normal..... hours in fact. All the fuselage ribs were then cut from 6mm Depron and before I removed the paper from each rib, I transferred the relevant alignement marks on the the depron ribs. Before calling it a day, I glued one sides worth of fuselage formers in place and then left the glue to cure overnight.
Today....... loads of cutting out to do.
6mm Depron tailplane ribs, vertical stab ribs.....
A good time to mention yet again just how important it is to keep your knife blade sharp and equally as important, at right angles to your cutting board.
All the ribs that I am cutting will be sliced through the centre to form a 'top and bottom' rib. Both the vertical and horizontal tail plane airfoils are symmetrical so I'm not having to put deeper ribs on the top surface and shallow ribs underneath thankfully. Thankfully because they are sooooo slim towards the tips..... almost slithers!
Anyhow, PU at the ready, set to with what seemed like thousands of pins and went about fixing on the ribs.

I think I might have forgotten to mention, I also strengthened the horizontal tail plane with a 6mm carbon tube again, capping off top and underneath. The vertical tail stab ribs were also applied.
I had a Doc's appointment this afternoon so I just managed to get all the ribs in place before I went. On my return, I couldn't resist hanging the bits together for an early photo-call.
Later this evening I cut and glued in the side fuselage keel parts ( full depth longerons).
And Phil...... - it's a pleasure!
Roy

Edited By Electriflier on 16/09/2015 21:23:53

Edited By Electriflier on 16/09/2015 21:30:58

[Colin Leighfield]

That looks wonderful Roy.

[Andrew Price 2]

Colin. If Carlsberg did understatements!!!

[Colin Leighfield]

You have a point Andrew!

[Philip Rawlinson]

Gordon Bennett, shall I leave the weekend free for the maiden !!!!!

When do you eat and sleep ??

[Shane Sunday]

HAhahahahahaaha. I was looking at the wing and thinking hey!!! he's getting way ahead of himself here. Only until I actually read and look do I realize it's the horizontal stab. That's big. The build log is great don't you worry too much about that. theres a fellow over on another forum, goes by the name Drice, and his thread is insane with the detail not only in the model but in the thread as well. they seem to be part of the hobby now and need almost as much time as the build itself.

I like the meld between extruded polystyrene and depron I have to say I knew where you were going to go I think but having seen it now makes more sense that I thought it would. Make sense?

Cheers

[Simon Chaddock]

Electrifier

That looks very impressive!

Bearing in mind it will be a 10lb plane, the size of the tailplane and that it is a single spar structure will it have adequate torsional rigidity? Depron is pretty flexible - certainly when compared to carbon!

[Electriflier]

Evening,
Makes sense to me Shane........... I think
Simon, you'd be correct to question the torsional aspect of the fuselage. Today has been spent adding additional depron longerons along the rear fuz section at the 2, 4 8 and 10 o'clock positions. Not full depth ones as you'll see when I post the photo's tomorrow. I suppose this is the problem with posting photo's too early in that it might appear that a section of the build is complete because I took the photo. The fuz , centre wing section, horizontal and vertical stab's are nowhere near complete but seeing the component parts together in a photo spurs me on no-end.

As I've mentioned, no photo's tonight as I didn't intend updating the blog this evening. I have spent a few hours this afternoon working on the fuselage rear and measuring and marking-up the foam block in readiness for glueing the tail, wing centre section and nose components tomorrow. So, hopefully, by the end of play tomorrow, I should have a one-piece fuz and wing centre..... til then
Regards

[Electriflier]

As I explained yesterday evening, I had already added additional longerons to the rear fuselage section and as promised, the pics are here:-

Not full depth longerons but being set at angles between the vertical and horizontal fuselage plates, have added a considerable amount of strength to this part of the model.
Note also that I had added the upper and (although you can't see), the lower fuselage formers around the blue foam centre section. Formers 1 & 2 were added to the nose section and then side pieces added to form the usual cruciform structure
Almost an afterthought as I hadn't included this in the drawings was the need to create another battery compartment for the 6V flight pack. I will be adding this to the nose section (depron box) before I skin the main fuselage.
I trimmed the nose side pieces to shape once the PU had set. With the benefit of hindsight, It would probably have been best if I had not added the nose section at this stage as I was no longer able to stand the model on the motor mounts!!

Anyone who has read previous build logs will know I struggle to elaborate on the skinning process, This build is no different!!
After sanding the whole of the upper section of the inner wings, I applied the 3mm depron skin. Uhu Por being the glue of choice being a contact adhesive. No dramas really, the 3mm skin went on without any trouble at all. After applying the 3mm, had to take the odd picture as at last, I see an aeroplane developing.
Oh, again, forgot to mention, I have glued a felt tipped pen cap into the area where the antenna is on the fuselage so that the mast (which will be made from the felt pen body) will be removable for transport.

Anyhow, a few more pictures for anyone who's interested.......

So, for now,....
Roy

Edited By Electriflier on 18/09/2015 20:35:41

[Steve Jones 2]

Amazing as ever...a couple of my 72" Brian Taylor.  Good Luck !!

Edited By Steve Jones 2 on 18/09/2015 21:29:55

[Philip Rawlinson]

Looking like a Mosquito

[Shane Sunday]

Any updates on the mossy? Chomping at the bit here.

[Philip Rawlinson]

NI know Roy is batting on at a pace with the build because I got a sneak preview at the field on Sunday and it is looking awesome.

Meanwhile now the oleos have arrived I said I would have a go at fashioning the undercarriage.

We have gone for the eflite electric screw retracts as on the Texan but obviously the mossie undercarriage is I bit more involved even at the stand back a bit scale we are happy with.

My approach is a lot more of a bull in a china shop approach than Roy's meaning I had knocked up a first attempt to test the idea in an evening. This is just the main part and hopefully a few scale additions will be added later.

In true Macgyver style it all started with a trawl through the scrap alloy skip at work and a couple of alloy bumper brackets from a damaged car yielded a couple of little alloy blocks. This was drilled at both ends to take the 4mm rod the oleos slide onto . To secure these and prevent them turning a 1.5 mm hole was drilled through the block and the 4 mm rod so a piece of piano wire could be inserted in. This was cut 1mm shorter than the width of the alloy block so a couple of taps with a center punch on the alloy block either side meant it could not possibly come out. Hope that makes sense but I have tried to show it on one of the pictures.

Due to my bull in a china shop approach I didn't take many pictures but if anyone is interested I will take more when I do the proper ones next week.

Just need to get approval from the boss to carry on

[Electriflier]

Evening....
Shane, sorry for the down-time. It's been a busy week for me.

Thanks for the update Phil. They're looking really good mate.

As Phil mentioned, I took the 'work in progress' to the field this weekend so he could have a good look and to discuss further development. Great opportunity to get an idea of scale by placing it next to the Depron Texan. They're both 84" wingspan so not too difficult to imagine what the finished model should look like size-wise.
As mentioned, it's been a busy week on the home front so, to be truthful, have not had a lot of time on the build.
Progress will appear to slow now though due to the necessary fiddly bits like servo installation, snakes etc. I have done a bit on this front though as you can probably see. The 2 high torque metal-geared servos (elevator & rudder) have been installed as far forward as I possibly can within the fuselage. I let-in a ply plate to hold both servos and routed the snakes through the fuz formers so they presented at the correct height and location when finally connected up to the servos. I will be building an access hatch around the servos but before working out how best to do this, needed to be sure that the canopy/cockpit area wouldn't be affected by such a hatch.
Snatching the odd hour here and there, decided that the cockpit area was next on the list. I cut out the acetate canopy that I had purchased from Traplet and set about masking it off so that I could paint in the cockpit framework. I use the 'anti-bleed' Frog tape to ensure that the painted lines would be clean once the tape was removed. Fiddly but worthwhile......
It was difficult to try and work out where the curvature of the fuselage and canopy would meet so I decided to make fuselage formers from Depron to continue the fuselage shape through the canopy area.
I UhU'd these formers into the floor of the cockpit and then skinned over them with 3mm Depron skin.
Much easier then to drop the canopy onto the cylindrical fuselage section, draw around it and then cut away the area that would ultimately become the cockpit.

A lick of black emulsion later, started to look a little more like. Again, as Phil has mentioned, we're not trying to win any prizes for a super scale model so the cockpit area will have some detail and proportionally-sized air crew but that's about as far as it will go...... stand-off..... through squinted eyes!!

For reference only, I have stuck a profile scale-sized chap in the front seat to give me a better idea of internal sizes. He will be replaced by a couple of more life-like ones before the canopy is secured.
Working forward from the servos, cockpit area and I had to address the flight battery pack compartment.

It only needs to house a standard 6v 2100mah NiMH (AA's) so, a small hatched area has been created just forward of the cockpit. I'm sort of working on the fly here and so hope that a couple of rare earth magnets will be sufficient to hold the hatch cover in place. More on this later........

Apologies for the rather rushed update but as Shane pointed out, the silence can be deafening at times

Regards
Roy

[Philip Rawlinson]

Loving the cockpit.

[perttime]

I love seeing the progression!

What thickness will you use for the skins?

I'm contemplating a design from 3-views and have a question that might be dumb - except several authoritative individuals have told me that there are no dumb questions.... When designing from 3-views, you have to account for the thickness of any surface skins, to get the formers right. Correct? Otherwise you end up with a cartoon version (which you might or might not want). Am I on the right track there - or overthinking it?

[Dave Hopkin]

No your right, the thickness of the skins (almost always 3mm Depron) has to be deducted from the former sizings

Roy can manipulate the white depron for skinning, that his skill, I find the grey 3mm far more forgiving for wrapping round curves

[Electriflier]

Perttime,
As Dave mentions, 3mm white Depron for me. White is a little more difficult to shape than the grey stuff as it's a bit harder. I prefer it but there are still areas where I would use grey if I weren't able to coax the white stuff to the desired shape.

As for allowing for the 3mm skin in your drawings. I'd say yes wherever possible but sometimes, when you're working from 3 views at enlarged proportions, the drawing lines can be vague to say the least and so accurately allowing 3mm for skinning is sometimes nigh on impossible.
I'm sure I've built models that are 3-6mm too fat but at the sizes I build at, almost impossible to detect.

Managed a couple of hours on the cockpit area today. I have printed out some Mossie' instrument panels onto plain paper and glued them in and around the cockpit. That was after giving the whole interior a wash of green/black paint. I've dropped in a now discontinued pre-painted Eflite 2nd war pilot and will have to ask Phil to paint up another one to accompany him on his missions.
Just to give the cockpit interior a 'lived-in' weathered appearance, I went around some of the painted depron edges with my silver pen giving the effect of worn paint. Once the co-pilot is ready, I could quite readily seal up the cockpit by glueing on the canopy
Rather than just leave it there today I also skinned the fuselage top panels to the front of the canopy in 3mm white (where the battery hatch is).
So,. not a lot today but there's no rush.

[Philip Rawlinson]

Well after a cracking afternoons flying and hearing from Roy the progress on the cockpit I was keen to crack on with the undercarriage. As on my previous post I had put together a rough version to see if my ideas would work which I showed Roy at the field. He was happy with the results so it was just a case of a little more accurate cutting,drilling and bodging 2 neater ones. The previous post explained the process so I will just post a series of pictures which starts with the large lump of Ali which housed the block I used to the finished articles which have ended up weighing less than 150 grammes per leg. The only addition from the last write up is that I added a couple of tubular axle spacers either side of the wheel to prevent the tyre catching the oleos.

Hope that makes

Happy flying

Edited By Philip Rawlinson on 27/09/2015 20:55:48

[Electriflier]

I can almost hear the theme tune.......

Sort of a private joke but just so you know, Phil tends to be known as our club's MacGyver in that whenever we need some gadget or other making..........he's the man!!!
Not having had too much time on the build over the past few days so progress has stalled somewhat, I have started to work on the tail-end of the model so that fuselage skinning can be considered soon in the scheme of things.
The horizontal tail stab was made from 6mm Depron with 6mm Depron ribs top and bottom. Along the line of the elevator, I channeled in some carbon tube to add longtitudal strength. I removed the elevator section of the taiplane and decided it best if the elevator plate itself be made from 3/16" balsa. Once cored-out, would be almost as light as the Depron but with the strength and rigidity that the elevator required. Also, as with most other of my builds, the trailing edge of the tailplane and the leading edge of the elevator would again be from balsa to allow me to use the mylar cyano hinges.

The leading edge of the elevator is from triangular balsa stock and the trailing edge of the horizontal tailplane is from 3/16" balsa sheet glued together to give me the correct thickness at the hinge point.
I continued glueing the tail-end of the Depron ribs onto the balsa elevator and then cut the slots for the hinges.
The Elevator on the Mossie' is in two parts. I'm making this one initially as a one -piece elevator and then will cut apart later in the fuselage construction. I made a torque rod from 12 swg piano wire and channelled it into a groove cut along the edge of the balsa triangular stock on the L/E of the elevator. I'm trying to conceal the controls of the elevator/rudder and so have used a 'tiller arm' type of control which, by use of a grub screw, is the perfect fit onto the 12 swg wire. This control horn will ulimately be concealed inside the fuselage, as will the rudder/tailwheel control horn(using the same type of horn on rudder).
Once I had set the elevator torque rod into the groove along the LE of the elevator, I reinforced the Depron area around where the torque rod goes into the foam by epoxying some 1/16" ply plates on either side of the elevator.
In an attempt to further reduce the AUW of the tail assembly, I cored out the Depron tailplane and the balsa elevator before applying the 3mm depron skin to the elevator. (I'll post the pictures of the skinned elevator tomorrow hopefully)
For now,,,,,,,,,,,,,,,,,
Regards

Roy

[cymaz]

Here is a little something to get the build mojo going

[Electriflier]

Cymaz, many thanks for the link. I have seen it before but just had to watch it again! The mojo isn't lacking though, it's just that personal/home stuff has had to take precedence over the past week or so. I'll be back on the case soon I hope.

Cheers,

Roy

[Philip Rawlinson]

Looking good Mr Hunter. Hope to see you at the shop Saturday.

All the best Macgyver

[Philip Rawlinson]

Looking good Mr Hunter. Hope to see you at the shop Saturday.

All the best Macgyver