Sonic - like VTPR build

[Red]

Because I have airplane ADD, here is another build thread lol. The truth is I like to have multiple projects going at once so I can always work on something if I'm waiting for parts or still working out part of the design etc. I get to pick and choose.

VTPR is a French acronym that loosely translates to "Aerobatics Close to the Ground". Originating in France, most of these aircraft are homebrew types with the zenith being about 100" span. There are/were a few kits offered, one of them being a Sonic. I wanted to build a Sonic for VTPR flying, but after my emails to the mfg to buy a fuselage they stopped replying, so I decided to just roll my own. These planes are typically very light for their size, with large control surfaces. Think of them as somewhat the 3D type of the unpowered world.

This is a Sonic:

This is one of my favorite videos of this type of flying:

VTPR at Lestrevet, 2018 |

really love this style of flying. I have an Ahi, but I'd like something bigger which is why I'm going this route. I was able to get a Mark Allen Falcon 880 fuselage. Not ideal, I'd like more side area, but it will have to do. Airfoils will be what seem to be the accepted SB96 series, 100" span. I plan to sheet the 1 lb. white foam cores with 1/32" balsa, trying to keep the whole build as light as possible. No flaps, just ailerons. I want a Madstab (180 degrees of total travel) as well, so I've designed a pull-pull arrangement with 3D printed root ribs and cams. The ribs weigh 4.5g as shown. I have the core templates laser cut, so that's where I'll start. I'm waiting for a carbon wing tube, and a few other bits to really get going.

 

[Red]

For the Mad Stab, I'm still playing with ideas for actuation and have narrowed my choices down to two basic methods. pulleys/pull-pull & cam/pivot style. Here is an example of each:

Each has its own merits and problems, so still noodling this one out.

 

[Red]

I had my wing and stab cores CNC cut. Since the panels are about 48" long each, they had to be in two pieces and joined in the middle. I have just started laying out the joiner and figuring out the dihedral angles. I will build up a rudder from balsa.

 

[Wayne]

I like it!

How bad is the weight on the Falcon fuselage? As I recall they tended to be heavy.

Have you checked out the SC17 airfoils? Basically a hybrid between the profiles of SB96V and TP42.

SC17, an aerobatic airfoil proposal

It is a great pleasure for me to propose here, in collaboration with François, the coordinates of a pair of airfoils dedicated to aerobatic gliders: SC17 and SC17s. It is not a revolution. As the a…

voltige-planeur-rc.net

and

SC17/17s Flaps

Voir l’article pour en savoir plus.

voltige-planeur-rc.net

I'll be using these on a few projects in the near future.

 

[Red]

I like it!

How bad is the weight on the Falcon fuselage? As I recall they tended to be heavy.

Have you checked out the SC17 airfoils? Basically a hybrid between the profiles of SB96V and TP42.

SC17, an aerobatic airfoil proposal

It is a great pleasure for me to propose here, in collaboration with François, the coordinates of a pair of airfoils dedicated to aerobatic gliders: SC17 and SC17s. It is not a revolution. As the a…

voltige-planeur-rc.net

and

SC17/17s Flaps

Voir l’article pour en savoir plus.

voltige-planeur-rc.net

I'll be using these on a few projects in the near future.

The fuse is a little chunky for sure, but it’s what I have. If I love it, I’d carve a plug more in line with what I want and I can make it lighter.

 

[Hill Hobbit]

Hi Red, I like your plan! I’ve got a Sonic variant using Quabeck sections which is great. It was built by my friend Mark, and is the first in a line of three models he’s built for really close in VTPR style hooning. Mark was one of the Redshift team back in the day. Sonic 1 is 2m span, very efficient and buoyant in low lift, and is a hoot to chuck about like my Ahi.
Sonics 2 and 3 are 2.5 and 2.4m span, one with a carbon fuz, the other with a ply/balsa build that is beautiful.
I’ve found it makes a nice change to relax and enjoy some close in hooning compared to my usual sloping where we pray for decent wind to get mucho ballast in a mouldy and fly ‘em Curare style…
Hope the Madstab comes out ok, and looking forward to this build.
All the best
Jonty

 

[Doc J]

Hi Red, I like your plan! I’ve got a Sonic variant using Quabeck sections which is great. It was built by my friend Mark, and is the first in a line of three models he’s built for really close in VTPR style hooning. Mark was one of the Redshift team back in the day. Sonic 1 is 2m span, very efficient and buoyant in low lift, and is a hoot to chuck about like my Ahi.
Sonics 2 and 3 are 2.5 and 2.4m span, one with a carbon fuz, the other with a ply/balsa build that is beautiful.
I’ve found it makes a nice change to relax and enjoy some close in hooning compared to my usual sloping where we pray for decent wind to get mucho ballast in a mouldy and fly ‘em Curare style…
Hope the Madstab comes out ok, and looking forward to this build.
All the best
Jonty

Passingham rears his shiny head again...Actually Mark is a great home builder/designer.

Doc.

 

[Red]

Hi Red, I like your plan! I’ve got a Sonic variant using Quabeck sections which is great. It was built by my friend Mark, and is the first in a line of three models he’s built for really close in VTPR style hooning. Mark was one of the Redshift team back in the day. Sonic 1 is 2m span, very efficient and buoyant in low lift, and is a hoot to chuck about like my Ahi.
Sonics 2 and 3 are 2.5 and 2.4m span, one with a carbon fuz, the other with a ply/balsa build that is beautiful.
I’ve found it makes a nice change to relax and enjoy some close in hooning compared to my usual sloping where we pray for decent wind to get mucho ballast in a mouldy and fly ‘em Curare style…
Hope the Madstab comes out ok, and looking forward to this build.
All the best
Jonty

Hey Jonty,

How do you like the Sonic? I would have preferred to go that route had I been able to get one. Do you have any pics you can share?

Cheers
Red

 

[Hill Hobbit]

Red, I don’t have any right now, but I’ll sort that out asap.

 

[Hill Hobbit]

Hey Red, Mark’s full Sonic (the Hedgehog) build thread is on page 11 of Builder’s Workshop on the BARCS website. The title is Pressed Foam Wings.
That’s way better than a few pics from me!
Cheers

 

[Markp]

My full size Sonic built on an Airtech-rc carbon/ kevlar fuselage.
Span is 2,5m, airfoil is HQA 1/9.
White foam cores covered with 0.8m balsa with epoxy glass cloth finish.
Unlike the original it has flaps and ailerons which increase the performance window and most importantly make it easy to land as Crow braking can be deployed.

Mark

 

[Markp]

Sonic 2m and 2.5m fuselages from Airtech

 

[Markp]

My original 2m Sonic that now belongs to Hill Hobbit

 

[Wayne]

Mark,

Great to see you here. Love your builds.

Guessing the Airtech stuff is gone now?? Or are they still around?

 

[Markp]

Airtech are still running. They are based in France. The 2m size model is marketed as the Evolution. They still have the moulds for the full size Sonic but don't advertise it as the moulds are bit worn and don't produce the quality of finish they are happy to sell. That's why mine is Kevlar/Carbon as it doesn't need paint.

Website details https://www.airtech-rc.com/

Mark

 

[Red]

My full size Sonic built on an Airtech-rc carbon/ kevlar fuselage.
Span is 2,5m, airfoil is HQA 1/9.
White foam cores covered with 0.8m balsa with epoxy glass cloth finish.
Unlike the original it has flaps and ailerons which increase the performance window and most importantly make it easy to land as Crow braking can be deployed.

Mark

Mark,

I'm starting to play with control surface sizing. Are you happy with the roll rate at the size depicted? I'm assuming you are mixing flaps with ailerons for roll? I think I'm just doing (large) ailerons, I'm focusing on light weight and want to keep the wing inertias low. I'll use spoilerons for glide path control.

Cheers
Red

 

[Red]

Mark,

Great to see you here. Love your builds.

Guessing the Airtech stuff is gone now?? Or are they still around?

I emailed them to hopefully get a Sonic fuse. OLivier indicated that the mold was tired so quality would suffer, but I was ok with that. I attempted to order 2, then he just stopped replying to emails. The website is still active. https://www.air-rc.com/category/supplier/AIRTECH


Hello,
Thank you for the mail.
We have the mold and we can produce a fuselage.
However, the mold is very old and the quality of the fuselage is.. not
so good and you may be disapointed.

OLivier

 

[Wayne]

I'll see if I can order some stuff from them. It has been a while since ordering anything from France, I hope it is a little smoother than the past.

 

[Red]

I have a 16mm aluminum/glass wing tube and sleeve so I started mocking up the wings. Turns out the tube is really too think, and heavier than I’d like. By the time I get the dihedral I want and with the wing taper, the fit isn’t good. I have a 13mm carbon tube which is much lighter but no socket, so I decided to roll my own.

I covered the tube with flash breaker tape and waxed it. Then I wet out a piece of 1oz S glass. I rolled it around the tube about 3-4 times then wrapped that with flash breaker tape again to compress it. Should give me a nice light socket and I can continue with the wings.

 

[Markp]

Mark,

I'm starting to play with control surface sizing. Are you happy with the roll rate at the size depicted? I'm assuming you are mixing flaps with ailerons for roll? I think I'm just doing (large) ailerons, I'm focusing on light weight and want to keep the wing inertias low. I'll use spoilerons for glide path control.

Cheers
Red

I would go for ailerons at 25% of chord width. Went for slightly smaller flaps/ailerons at 22% on the larger model and despite mixing in the flaps the roll rate definitely suffered.