Purbeck 1/3rd Scale DG800 Build Thread

[Simon WS]

Tailplane servo tray trimmed in carbon for extra strength.



Cut a series of lite ply parts for lamination and gluing to underside of tailplane mounting



There was a bit of a mismatch between where the tailplane ends and the mounting/cut-out for the elevator movement, so I sandwiched a couple of layers of carbon with the ply laminations to extend the mount.



Ugly series of credit card guides and pegs!



Still it turned out OK after curing



And even better after rough trimming and filling with a bit of epoxy and microballoons

[terry white]

Hi Rob, I couldn't agree more.Its what a build thread is all about, and Simon does it so well. He shows us the problems he encounters and how he gets over them.
I also know modellers who have embarked on projects that they would not have even contemplated without the encouragement from Simon's build threads over the years. Ter.

[Andrew Ray]

Hi Simon, loving the build and the solutions you are coming up with, everything gets filed away in the old grey matter and usually is lost forever but just occasionally the information is found and put to good use, so inspirational.

And I just love to see these large sailplanes taking shape. I want one!

[roo Hawkins]

looking good si when do you expect to finish will it be this year??? . it is important that we post are builds as it is helpful to us all to learn . I am planing to build a 7 meter ash 31 later in the year so it was good to go over my dg 800 thread to see how I did it . we can learn a lot from are posts how to do and not to do . so keep up this great build. ROO

[Simon WS]

Thanks to everyone for your nice comments. I hope to finish it by late summer Roo but don't want to tempt fate! We've just had another family snafu which has delayed things a bit but hopefully I can get back on things soon.

Si

[Simon WS]

Managed to do a little (twice!) in between life getting in the way.

Decided the next step was to measure the longitudinal dihedral by cutting foam parts for the wings and tailplane to measure their relative angles of attack. As it stands I had 6 degrees so I obviously wanted to reduce that to about 1.5 degrees which means most of that work I did on the tailplane mount will have to be re-done. Originally I decided to take a bit of the 4.5 degrees reduction out of the wing mounting, so I set the incidence pins for that but then (schoolboy error) realised that the plane would fly with a constant tail down attitude, so I did them again to gain the right attitude. It does mean I will have to change the tail mount a lot!..


The way I set the various incidences is to use a digital inclinometer.



I set one wing at the angle I want and then paint a blob of colour on the end of the incidence pin and push it through to mark the wing root. Drill a hole and hey presto put the brass tube receiver on the end and glue it in (unless you change your mind and have to do it again (see above!).



Then I do the same thing for the other wing but drill the hole oversize so that when both wings are on I can stuff a load of thickened epoxy into the hole and set the second wing to the same inclination as the other.



Next job is to cut the wing and fuselage root profiles and fill in the gap!

Simon

[GeeW]

Simon
You may have this information
already?

It also looks like (to my eyes) that the tailplane should be further forward. The l/e of the tailplane is (at 1:1) 101 mm forwards of the top of the fins l/e

Regards

Gordon

[Elliot Howells]

Hi Simon,

not wishing to teach Granny to suck eggs, but I changed my tailplane incidence by packing it up with washers and smoothing p38 in - worked a treat and dries rock hard - almost a 5 minute fix too....

Ell.

[Simon WS]

Yes thanks Ell, that's my normal way of doing it too - however, there's rather a lot of change so I will probably take a bit off the back too.

Gordon - it looks that way to my eyes too so I need to look at the viability of moving the tailplane (I estimated where I set it from a very small 3 view from the manufacturer on the LET model site where it looks less). I guess at this scale it should stick out about 30mm and it's certainly not that - more like 10mm. It will be rather a pain to change so I'll have to think about it!...
However, I think the net 2.5 degrees horizontal inclination shown on the 1:1 document is too much for the sort of model I want - good rolling capability and inverted performance so 1.5 degrees is the max I would use.

Thanks for the feedback!

Simon

[GeeW]

Simon
Another option for you is that some DG800's have a larger rudder fitted, the larger rudder is wider in chord (1:1) by an extra 33 mm...all the 3 views I have seen including those in the full size manuals show the original rudder. The wider rudder was made available as an optional upgrade and many have had it retro-fitted.
Please see appended image for a few more possibly helpful dimensions!
Regards

Gordon