Ridge Runt Evo

[Wayne]

I have been wanting to make a modern Ridge Runt for a while.

Why a Ridge Runt, they are a fun classic, and I used to work for Hobby Shack back in the day. I have always found them pleasing to the eye and they are a simple plane to build. Seems like enough good reasons for me.

So, I have been debating some options.
A basic all EPP model?
A deluxe all wood kit with modern features?
A deluxe wood with foam cores?

This decision I have been waffling on. There is good argument for all 3 versions. I'm starting to lean towards the last 2. A nice all wood kit, but we will also sell an option foam core wing. This might be the best solution. The wood wing will probably be an AG35-38 airfoil for nice lift and fun, and the foam core will probably be something like an RG-15.

Here is my starting point for the wood wing. Similar looking to the original, but will be built similar to the AH-100. It will be a 2 piece wing and probably a single bolt to attach it. This should be sleeker than the original wing. Basically the same dimensions. Or should I stick with the simple one piece wing with rubber bands? It is only a 50" span if we go for the stock size.

Speaking of span, should we shrink it down? Maybe a 40" span?

My goal is to have these ready in time for folks to get them and build them for the Sunset Camp N Fly event in 6 months. I started on a wood wing design last night:

Spar is much stronger than the original design, but still an easy build. The center of the wing will get the 3D printed core treatment.

 

[thenated0g]

i like the foam wing / wood fuse kits.

 

[Wayne]

You think an RG-15 would be a good choice? I'm open to suggestions.

 

[thenated0g]

My go to for tail planes is usually the mh32, but a quick google search found this comparison between the two and they are basically the same so yeah RG-15

 

[jakem]

Im game for whatever you guys decide! Sounds fun

 

[rcsoar4fun]

There is a company remaking the standard wood version now, so I would go a little different. I love the idea of a little one.

The originals flew great, particularly because they could be built in an afternoon and were $18 a kit. That equates to about $150 in today's money, so you should be fine.

No one ever went wrong with the RG15, but not sure how it would do built from wood? S3021 or 3014 would probably be perfect.

 

[Wayne]

RG-15 would be the foam core airfoil. Thinking AG35 to the AG38 for the wood wing. (It is a flat bottom with entry, makes for easy building.) I've used the AG stuff a few times now and it is a good performer and works well on a building board.

 

[thenated0g]

When i designed up the mh32 on wood i had to use the building tabs on the bottom to keep it "flat". than after the wing was built i cut all those off and sanded it down.

 

[Wayne]

Yeah, I try to avoid those with the wood. I've found this AG is pretty similar to the MH, might give up a bit of thermal.

Have it roughed in.

I'm not in love with the stock fuselage, especially the nose. I don't want to be band sawing nose blocks all day. So might CAD it up and slice it into many pieces. (painful) or just supply a block of balsa (with instructions to remove the parts that are not a glider nose.) Something will come to me. For now pretty happy with the rough work. Detail work takes all of the time.

 

[Wayne]

I like overly complex assemblies to make building easier. Here is the center section for the wood wing. It sets the dihedral and houses the attach points.

I hate to admit how much trouble this thing gave me to design.. I'll probably change it, but good enough to build a test wing.

 

[Wayne]

For the foam wing I am thinking of the HN-1038. I was originally thinking of the RG-15, and when I compared the 2, I think the HN wings out. We have the wood wing for the light lift, and the HN for fun.

 

[Wayne]

Little update - Working on the fuselage. I had some input to keep it basically the same bulky shape, and I also had feedback to fix the weak tail and increase the fuse length a bit to air tracking. Some even wanted a little longer nose to aid CG. After much playing around and consideration I've come up with a new shape that I'm pretty happy with. Here is the basic design over the original plans.

It is a little longer in length, a little shorter in height. I greatly reduced the curve at the trailing edge of the wing (reduced drag?) and did a little pressure recover curve at the bottom of the rear boom because I like that look. The biggest change is the vertical now has more sweep to get the elevator further back. You can also spot how much cleaner the new airfoil is.

I had been debating putting the elevator servo in the rear, and I may still, but for now, I have mocked up around an 850mah Life battery and an Orbit Eras servo (shown in green). Current thought is the elevator servo will be inverted so the servo arm is at the bottom, and a very nice MPJet pushrod will be used to drive the elevator. With the tightness of the MPJet and the now reduced curvature of the pushrod, I think we will be fine. I am very shy of adding tail weight to this model. Lengthening the nose to make CG really is not a good option with a short tail model IMHO. (Looking at this now, I think I'll shorten the nose to be closer to stock length.

This image shows the basic cut lines for the canopy.

The nose cone is attached at a 2 degree angle for anyone that wants to make it an electric.

 

[Doc J]

For the foam wing I am thinking of the HN-1038. I was originally thinking of the RG-15, and when I compared the 2, I think the HN wings out. We have the wood wing for the light lift, and the HN for fun.
View attachment 21193

Good choice: HN1038 was the same foil that I used on the "Genesis". I'm not sure what it is now, but it worked well on the original little 60" model. Fast, good ballast carrying, and nice inverted performance.

Doc.

 

[Wayne]

Ok - Little update. Ran into some CAD issues last night, really stopped me in my tracks. Figured it out eventually. OK, here is where it's at:

The tail is a work in progress, but will have 2 square carbon tubes buried in the vertical with a little magic sauce to tie it all together. This should take care of the strength concerns. Shoot, just remembered I did not leave space for the pushrod.. Uggh...

 

[Mucksmear]

Wayne, what software you using for CAD? Just curious as my old PC is reaching end of life and my application versions are no longer supported by current OS

 

[Wayne]

It is Shapr3D. I don't think they make it for a PC, but good news, it runs well on a semi-modern Ipad, and you probably have one of those collecting dust? I use it on my Mac. I like it a fair amount for these sorts of projects. It is not the end all be all, but should do most of what a hobbyist wants and then some, but it does come with a monthly charge.
This is my first attempts to build a fuselage in 3D.

 

[Wayne]

As I started to make room for the elevator pushrod, I came up with some curves I rather like for the Vertical stab, you all OK with it?

 

[jure]

how about a bell crank at the bottom of the tail to drive the elevator horn,
splitting the push-rod in two in order to avoid the long curved snake and its inherent friction ?

 

[Wayne]

The MP Jet Bowdens are really nice, but will do a little testing to see if friction is an issue at all. Bell cranks have their own design challenges.

 

[Wayne]

Here is what I have come up with thus far for the tail. Trying to make it strong but light. Red is 3D printed parts, black is carbon square tubes and white is the bowden.

Getting cold - I'm calling it a night.. maybe..