Ridge Rat 'Twisty' Scratch Build

[bracesport]

SO to cut a long story short I have followed a friend over here from the FT forum as we have been migrating our builds into other forms than foam board - I really liked the work @thenated0g was doing on a retro Ridge Rat build and I wanted in - Mine was going to be a CF braided sleeve over a green foam core for the fuse and 3D printed wings with a monocote skin - simple!

But along the way, I had this idea to make a twisty - to make it work I needed to add another CF tube as the wing mounts as the original ones were not in the right positions for a wing pivot, and invent a rotor mechanism that allowed me to maintain the low mounted wings!

Here is the progress on the twisty conversion to catch you up to speed - I cut off the second wing mount to use the front one as the wing pivot mount - I added a drive pin into the original front wing mount of the wing - I removed foam from the fuse and glassed the internal surfaces to stiffen the void - I trimmed the side holes for the drive pins to access the fuse - Then I dry fitted the wings and rotor mechanism into place - so far so good!

 

[bracesport]

Here is the rotor mechanism in a CAD video and the 3D printed assy in ABS.

 

[Konrad]

How does the printed material perform against say Fiber Reinforced Plastics (FRP)? Just looking at the wing I have some questions about the structure. To me it looks like the printed material is being used as a direct replacement for what traditionally would have been made with wood. As the parent material (wood vs plastic) have different properties I'd expect that the structure would also be vastly different. I'm thinking that a honeycomb core with a thin skin, ether printed or bonded on.

I think I see the use of mandrel wound carbon tubes being used as the load bearing member. Is there a reason this tube doesn't take up more of the airfoil depth? I also see where the wing appears to be printed in section. Is there a constraint with the printer that larger single parts can't be printed. I know nothing about consumer based 3D printers. I'm assuming that they can index accurately and that one can add fixturing, much like we can with subtractive machining of parts (classic mill and lathe work).

I know nothing about 3D printing actual parts, I've only used 3D printed parts as a tool to show proof of concept. Or if actually making a usable component use the 3D printer to make a core for "lost wax" molds.

All the best,
Konrad

 

[thenated0g]

Glad you posted over here, lots of experienced slope flyers in this forum, im sure you will get some good input. Bracesport is one of my slope converts

 

[bracesport]

@Konrad - thankyou so much for the reply - mostly it is yes, yes, yes, to your comments - my printer is limited to 25cm (need a bigger one) and this has been an experiment to see if I could build a traditional wood wing in plastic - the main 7mm CF spar goes 50% through the aerofoil depth, but is supported by 5x1mm CF flats that run the full depth - the wing feels pretty strong, but well, if it fails, and given it is now a twisty, the great thing is that I can replace the wings easily with different designs!

I am fascinated with the idea of the twisty and will use this prototype Ridge Rat as proof of concept for a new project in 2020 - I came across the Jester with its carbon and 3D printed parts and will design something with that intent.

 

[bracesport]

@thenated0g - over the Christmas break, I will contemplate the 3D printed fuse moulds idea that Ramy RC uses - but given the success of the braided CF over the green foam wrapped with cling film I am leaning towards a thin 3D printed core to replace the green foam - in that way, I think I can leverage some mounts and such for the rotor mechanism and gear.

 

[Diceman]

Very cool and well done! That looks awesome! Do have any flight video?

 

[bracesport]

@Diceman - this one is still on the bench!

I am a nube to RC planes and more particularly to gliders and the slope - but I am hooked - here is my Youtube

 

[thenated0g]

Very cool and well done! That looks awesome! Do have any flight video?

I have a build thread for mine over there in flitetest as well. It was kind of rough so didnt share it over here, maybe after maiden

GlassRat - Ridge Rat balsa conversion

Recently i have switched all my build's to fiberglass. Being that i leave the glass to set for a day or 2 i find i have down time when i want to be working on something but cant work on my current project (booby sloper) so i decided to start up another one so i can do stuff while waiting on the...

forum.flitetest.com

 

[bracesport]

Well, today I decided to go with the V tail and cut the horizontal stabiliser in two and shaped the LE tips - should work well - I will also retain the elevators for a bit more flexibility and trimming options.

 

[Wayne]

Sweet - I have a weakness for twisty wings. Even on the waiting list for a Jester. I have more than a few examples in my collection.
I like that you have come up with your own design for the cams. I think on of the simplest I have seen is what CR Aircraft did in the Turbo kits. Worked well too.

What airfoil are you using on the wings?

 

[thenated0g]

Sweet - I have a weakness for twisty wings. Even on the waiting list for a Jester. I have more than a few examples in my collection.
I like that you have come up with your own design for the cams. I think on of the simplest I have seen is what CR Aircraft did in the Turbo kits. Worked well too.

What airfoil are you using on the wings?

man i was just looking at the jester. That is a really nice setup. I think 2020 is the year i get a production moldy

 

[Wayne]

Ahh,you are having too much fun with your building. Keep it up!! I am highly impressed with all of your projects!!

 

[thenated0g]

thanks @Wayne . Really appreciate you guys taking the time to show me the ropes and helping out over the years.

 

[bracesport]

@Wayne - I think both @thenated0g and I are both using the MH32 but with different constructions - my fuse is turning out quite well, and given these twisty wings are plug-ons, if my wing fails I can always build an improved one!

 

[thenated0g]

All my stuff is splooged on, im screwed

 

[bracesport]

Normally I glue everything together which makes it all harder to transport! My hotliner has an easy on/off wing but I need to sort out the electronics so it is a plug and play affair! seems every time I go out to the slope I learn more about making things easier at the slope - mucking around with Rx's and batteries is a real pain in the butt!

 

[bracesport]

If the Ridge Rat twisty turns out OK it will solve the transport issues!

So, I couldn't help myself today, yes I am still on holiday, but with a little bit of quiet time, I have started my 2020 homage to the 'Jester' - mine will be made for fewer dollars, but it will feature more carbon fibre than the Ridge Rat - I will need to pick a few more brains (@thenatedog) on making a composite wing!

 

[bracesport]

Well here we go for 2020 - I have a (Ridge Rat) pitcheron prototype on the bench and it looks exciting, but it got the creative juices flowing to design something sexy - I love the Jester V-tail and the Xica T-tail is pretty nice too - I will use these two as the inspiration for a new carbon fibre braided fuse over a 3D printed former - I hope my friend and flight mentor will build one too - I can make the fuselage formers and we can hopefully get together and make some composite wings!

Some preliminary CAD.

 

[Doc J]

Nice stuff guys!

Doc.