Scale Soaring UK

Max. I suspect that there is quite a bit of variation amongst the full size examples. Here is a pic of the one I based my model on:

Max,
It could be that Cliff Charlesworth positioned his prop height to suit his planned engine installation, rather than keeping to true scale in that area.
Having said that, it’s interesting that the cowl appears to have the cutout in a more scale position.

Hi Trevor

That one has the crank shaft in line with the top of the tear drop.

Hi Peter

No one appears to be addressing my question.

Cheers

Peter Balcombe wrote: ↑28 Oct 2021, 11:18 Max,
It could be that Cliff Charlesworth positioned his prop height to suit his planned engine installation, rather than keeping to true scale in that area.
Having said that, it’s interesting that the cowl appears to have the cutout in a more scale position.

I think Peter addressed the question!

Hi Cliff

The question was/is . . . If the motor is moved above the thrust line, does that cause the model to require up or down elevator to compensate? My research is telling me that it will require down elevator.

That should be an easy fix - place washers under the top stand offs to shim it down.

Cheers

Max,
In olden days it was necessary to add down/side thrust to compensate for thrust lines & torque roll, which tended to complicate the cowling penetrations as the prop shaft/backplate wasn’t square to the cowl penetration/front face.

These days, I suspect that it is much more practical to compensate by mixing elevator with throttle etc. as required & keep the motor installation/cowl penetration straightforward.
Peter

Yep. Thanks, Peter.

I have those mixes on some of my planes.

It was as much an academic enquiry as anything.

Starting in this hobby at 70, I have a lot of catching up to do.

Cheers

Hi Max, I have looked at every image I could find for GVZ.
Firstly, I think the motor thrust line might be correct or very close to it for the standard Falke T61.
Secondly, GVZ has a different cowl shape. The teardrops are a different and are angled down compared to the "standard" cowl. That may change the visuals a bit. Plus there is an optical ilusion in the image you posted.
Thirdly, provided all other factors have already been addressed for balanced flight. Thrust angle would be more important to set correctly (during the application of thrust) and once set moving the engine up or down a bit wouldn't affect much.
Those power pods you see on top of models induce a large pitch down, so they have the thrust line angled up around 5deg or more, they are also mounted nearer the CG longitudinally and have a much larger moment vertically. The small change you might do on your firewall won't have much of an affect, easily countered by elevator trim.


I found a web advert stating GVZ is for sale for $12000. Buy it, convert to R/C and you have a great 100% scale model.

I forgot about the ABS glue question. I've done a lot of experimenting. Best is to melt some of the offcuts in some acetone and make a slurry about the consistency of cream, apply, clamp or tape and let set for a day. However if the ABS pieces are thin, don't apply too much, the solvent might be too aggressive. Some plastic model cements work well, Tamiya make an ABS cement. I don't use epoxy or super glue on ABS as the results have been mostly unreliable.