My First Peanut Scale Build: BD-4 by Bill Hannan

[Prosper]

. . .but in what part of the flight envelope does it need 'that' much tailplane/elevator movement?

Hi Nigel, that deflection looks much like (from memory) the up-travel of a Piper 'stabilator' as on Cherokee or Seneca etc. I just looked online - the PA28 has 18° up, but only 2deg down. The BD-4 looks as if it might have a shorter tail moment than the PA28, too.

Neat build, Markus, I'm following.

Stephen.

[OZPAF]

That's a very pretty aeroplane but in what part of the flight envelope does it need 'that' much tailplane/elevator movement?

All flying stabilators could not  be expected to be as powerful as those with elevators - due to the camber changing capabilities of the elevator combined with the change in AOA.

Thus all flying stabs need larger angular displacement. However they do have the advantage of  easy adjustments to the decalage.

John

[Nigel_M]

Thanks Stephen, John, that's directly contrary to my expectations of an all-flying tailplane. Based on large model gliders and the, I guess fairly old jet I crawled all over at university in the 1970's and '80's, a Hunter, the range of movement on those was minimal that I remember, although that may have been only the trim tab come to think of it. I had previously assumed the all-moving surface would be far more powerful across all types, so thanks for the update.
Digression ends 

[g_kandylakis]

Hopefully we will return to the BD4 of Markus now...

As a help to that or perhaps a reason for more discussion... might explain the need for so much up elevator

[Spiros]

              

I have lowered it, no worries.....        

[MockwingF]

Thanks, George, for sharing the video. Great model, Spiros! I hope to continue building tomorrow. Any tips are always appreciated.

[MockwingF]

Here's my latest building progress update.

The nose has now been sanded to shape, and the adjustable fixture is finished.

In parallel, I tried to make a silicone mold from my resin-printed pilot figure in order to create a lightweight PU foam version. Unfortunately, that attempt was not successful. So I'll have to print a new set of figures and make another try at molding them. This time, I plan to dust the resin figure with talcum powder before making the mold, which should hopefully improve the result.

The next major step will be continuing with the fuselage. The side panels are already prepared and waiting. I have only limited experience with box fuselages, so I have a healthy respect for this next stage of the build.

Looking forward to making some more progress soon!

Markus

[RolandD6]

... I plan to dust the resin figure with talcum powder before making the mold, which should hopefully improve the result.
...

I suggest you try petroleum jelly thinned with white spirit but try it first on a scrap 3D print to ensure the print is not damaged. I used petroleum jelly a lot in past years but my patterns were not 3D prints. They were made from aluminium, steel or acetal plastic.

Wash the parting agent off the 3D print before painting.

It is/was possible to purchase a paintable! Silicon based parting agent in an aerosol can. I have some but never used it because the method described above worked for me and is safer for my lungs.

Paul

[nickhawk]

George Spyros since I watched the model flying last November in Nijmegen I decided to build one myself after I finish the projects I already started....You two have one each already so I cannot stay out of the game myself.. 

[MockwingF]

The next attempt to make a mold from my resin-printed pilot was successful.

I reworked the figures once more, filling and minimizing recesses and cavities that had caused problems before. In addition, I coated the resin masters with a mixture of talcum powder and isopropyl alcohol, let it dry, blew off the excess, and then gently brushed the surface.

My first casting trial was done with 2-part PU foam. The mixing ratio still needs some adjustment, as the result is a bit too brittle. However, the level of detail is very good and all the fine features were reproduced nicely.

Tomorrow I will make another casting attempt and see if I can improve the foam mixture.

Markus

[MockwingF]

In parallel, I built my own small vacuum-forming box. It is not particularly pretty, but it works well enough.

My first tests were done with 0.50 mm PS sheet, but it was too thick and did not capture the contours well enough. Today I switched to 0.27 mm PP sheet, and the results are much better.

Tomorrow I will continue testing and will also try white 0.27 mm PP sheet. Based on my previous experience, the white material is usually a little heavier than the gray version, but it should be easier to paint. Since the wheel fairings need to be white anyway, that could be an advantage. The white sheet is also slightly softer, as it is made from post-consumer recycled material.

PP is not exactly a lightweight material, though. The four wheel fairing parts will probably end up at around 500 mg in total, so I will have to see if that is acceptable for the model. For now, I am very pleased with the quality of the formed parts.

Markus

[Stunthenk]

Hopefully we will return to the BD4 of Markus now...

As a help to that or perhaps a reason for more discussion... might explain the need for so much up elevator

A nice thing of this video is the exited voices of kids who are seeing this sort of flying for the first time. When the model hit the ceiling beam one said Ow! But another said No, its built to stand this!

[Spiros]

......true.......          

[g_kandylakis]

A nice thing of this video is the exited voices of kids who are seeing this sort of flying for the first time.

Henk, everyone was seeing this sort of flying for the first time, not just the kids.
Pete's spontaneous "bloody hell" says it all 

George

[MockwingF]

Hi everyone,
Small update on my progress!
The vacuum-formed wheel pants out of polypropylene film worked out really well. Each half comes in at around 65 mg.
The pilot figures made from 2-component polyurethane foam also turned out great. They are already primed in white and still need to be trimmed to final size. I estimate they will weigh around 250 mg fully painted.
I do have a question regarding the landing gear on the BD-4. I've attached the pictures showing how Bill Hannan suggests building it in his plans. Does this specific construction really make sense, and how is it precisely intended to work?
Spiros, George, did you implement this design on your models, or did you go with a different approach? I'd also love to hear from anyone else who has built this model—how did you solve this?
Thanks a lot in advance!
By the way, I've also started putting together the box fuselage using the two side pieces.
Markus