Ivan's DH 86 Express by Mike Roach - Page 2 - RC Groups
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Jun 10, 2018, 08:27 AM
Gorilla glue rocks
Spit100's Avatar
Geez, the tapered wings are seductive, yet scary. Any plans to adjust to reduce possible tip stalls?

Jon
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Jun 10, 2018, 11:36 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Hi Jon, the tips are washed out and the ailerons trailing edges are reflexed and there will be 3/2 up to down on the ailerons. Also the section changes to flat bottomed for the last three ribs. Ivan's seems to have no problems in that area.
Last edited by Sopwith Mike; Jun 10, 2018 at 04:21 PM. Reason: Forgot the change in wing section
Jun 10, 2018, 04:19 PM
Slip the surly bonds...
Sopwith Mike's Avatar
I should have mentioned that I built the tail last week...slipped my mind...

The tailplane has a different shape from the plan version, easily seen on the photos of the real thing, and the rudder has a different profile at its base, where there is a shroud at the sternpost of the fuselage that houses the tailwheel mechanism.

I use a slightly different building technique from Ivan in that the outlines are laminations of five strips of 1/16th balsa x 6mm wide (yeah, I know). It's easy to make and very good for planing and sanding because everything goes with the grain. It's also just a strong as strip or segmented sheet. One side of the main spars is pinned down and the finished laminated outline blocked up by the correct amount (decreasing from root to tip), then rib blanks are glued in place, to be planed and sanded to profile after the assembly is removed from the board. You can see how the fin and rudder have been nearly finished, while the tailplane has yet to be started.
Jun 14, 2018, 04:28 AM
Slip the surly bonds...
Sopwith Mike's Avatar
I've been working on the upper wing and it's gone reasonably well, with only a few compromises needing the application of sanding bock, padding and improvisation to fix.

It's raining outside, so the pictures are from inside the shed. It is suddenly a BIG model. What was I thinking of?

One major error was not to build the upper and lower spars at the same time. Getting the sweepback and dihedral about right was a matter of fine judgement (ie a bit of luck) but it would have been so much easier to build the lower spar using the upper as a pattern. Now I've got to use skill.
Jun 15, 2018, 07:28 AM
Summit Model Aeronautics
Steve85's Avatar
Mike,

Looking good. Laminating tail outlines is one of my favourite techniques. And regarding your spar building epiphany, I'm glad to see I'm not the only builder who wishes hindsight could be a bit more proactive...

Steve
Jun 21, 2018, 12:39 PM
Slip the surly bonds...
Sopwith Mike's Avatar
The lower wing is structurally at 75% so a good opportunity to pose the model and marvel at the ambition, skill and foresight of the designer. Thanks Ivan!

Each wingtip is formed round a 6mm depron blank from four strips of 1.5 x 6mm laminated with aliphatic resin from J Perkins. This is a fast-setting version of the glue and I can't speak highly enough of it, except it's not terribly tasty. Balsa cement was delicious.
Jun 21, 2018, 02:31 PM
Registered User
thnilsen's Avatar
Beautiful craftsmanship. I personally think the D86 (and DH89) is one of the few pre WW2 planes that actually looks good.
Jun 21, 2018, 10:37 PM
Ken Stuhr

Hiya Mike


This is looking very good! But there is still time to mess up...............

You're coming back over next year aren't you? I hope to have a very tasty surprise to show then!!

Bets

Ken
Jun 22, 2018, 02:19 PM
Parkcityflier
parkcityskier's Avatar
My experience with building bigger airplanes is that as you get further into the build they somehow always seem to get bigger than what I thought they might be. Should be obvious, I guess, but when it's hard to move around in my shop the point becomes clear.

Love to see you over here again, Mike. For me, May might be a bit doubtful but August for sure

Jim
Jun 28, 2018, 02:28 PM
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Sopwith Mike's Avatar
Hi Ken and Jim, outline approval from both this side and Canada for August 2019. I can taste the Thai food and Jim's coffee already!

Isn't it always that the more reasearch you do, the more complex the subject becomes? I knew about the fairing over the tail end a couple of weeks ago: it must house the tailplane incidence and fin alignment controls and the elevator "up" control wires. I suppose I might have included the latter as a scale detail had I known about it earlier, but instead I have disregarded Ivan's instruction "don't overbuild the tail feathers" and added the housing from scrap 1/16th and a few bits of 1/8th square.

Searching for a better contemporary photo of the shape of the fairing, I came across this beauty of ZK-AEF "Kotuku". But are these external strakes along the fuselage? A single one at the rear and two up front. I thought "they don't appear on any other aircraft, and certainly not on Dorado", but hey, look more closely at Draco and Dorado and there IS some sort of external stiffener at the nose. But only one, and not at the rear end...

Ah well. It's a sport scale model.
Last edited by Sopwith Mike; Jun 29, 2018 at 05:57 AM.
Jun 28, 2018, 07:37 PM
Power Upward
GeorgeG97322's Avatar
Mike,

Do I understand correctly that the Express was a good flying airplane as long as the CG remained within the correct, shall we say range. I got the idea that if anything shifted and CG changed it tended to be catastrophic in nature.

George
Jun 29, 2018, 05:56 AM
Slip the surly bonds...
Sopwith Mike's Avatar
Hi George, I thought that the mods by DH referred only to the strengthening if the fin/ fuselage and the addition of the "Zulu shields" on the tailplane to improve directional stability. The scandal was that these mods were not communicated to the user who had the most accidents, the Australian and New Zealand operators. But I'm no expert.
Jun 29, 2018, 08:10 AM
Parkcityflier
parkcityskier's Avatar
Mike, that sounds great for next year. I hope that it all works out. I should have my 1/4 scale Fokker DVII in the air by then, and the DO-24 is always a question until I get a good maiden.

Jim
Jun 30, 2018, 03:19 AM
Registered User
Those strakes look too small to be anything aerodynamic - could they be batten strips associated with covering and subject to change with fabric renewal?
Jun 30, 2018, 04:50 AM
Slip the surly bonds...
Sopwith Mike's Avatar
I think that is very likely: as you say, reinforcement not aerodynamic. Perhaps not modelling material ...


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