Gliders construction, Race rules, Design, DIY, Pareto, Curiosity

[jmf11]

Hello,

The discussions about the MoM races really interested me. Because they are about fun, race and performance and construction. I'm far, more in Thermal Flying, and don't fly enough... so definitively not a top tier stakeholder on that topic. But I can't help thinking about it.

And as disclaimer, I know that much less people than in the past enjoy building their planes. But I do, because it is the best way to understand how they are done, which is one of the main interest drivers for me. I'm involved in fablabs, and enjoy to see how open source softwares (or free for hobbyists), internet, forums, and new tools empower makes to do incredible things: xflr5, freeCAD (onshape, fusion360), 3D printers, laser cutters, 3D printing molds, free plans for Foam cutters... Whaouhhh. Also, I like sailing catamarans and I have seen how racing can sparkle creativity and improve performances inside the the "box rules" / given set of constraints. I love that ! And also how the rules influences the devices.

I' flying a F3L (Wiki) a class created for beginners, enforcing open design with simple constraints on materials (wood, carbon for boom and spars), and span. This sparkled many designs (some open source), reasonably price kits (was 100-200€), good flying gliders. Good ! Ribs on spar tubes are easy to build. Fuselage also. And solid enough for the usage. This quickly appealed also experiences pilots. The class makes the most of laser cutters and readily available carbon profiles where it matters. They just should allow 3D printing, to see where it would creep

I've read ODR rules (http://nebula.wsimg.com/11cb30bc1a90…&alloworigin=1) and they look very interesting. What would it give updated for today's tools and easily available materials ? That last part changed a lot over the last (50 years (when I started the Hobby with small free flight planes). Much more easy today to find 3D printer filament than good balsa or samba ! But 3D printed material performance is not on par with wood... and requires a lot of creativity and engineering to make the job. Slingshot design seems to be an example for that.

Pareto and diminishing returns: the last performance % are really difficult and costly to gain . I have flown F3K and loved it (but not my knee and had to stop). Moldies are really nice ! Love it ! But price and impact of damages not that much... Where to stop to get 80% of the fun for 20% of the price?

What could this give for MoM races? Which construction options would be interesting to explore for fun, cheap, easy to build and repairs, resistant enough glider ? How new tools can help ? Where not to use those and keep things basic? What matters in the different gliders subparts, and what doesn't that much ?

I'm really interested i hearing about your experience and ideas here for 2026 60" fun slope racer DIY construction:

• tools possible to find in town fablab (3D printer, laser cutter...),
• < 150$ / € (negotiable) as pareto cost part,
• as easy as possible to source building materials / parts,
• 10 evenings constructions (realistic) ?

Don't hesitate to challenge the objectives if you want ! Good design target is often the most important

Best regards,

JMF

 

[jmf11]

On my side, I settled on the idea that the good old hot wire foam cutting and vacuum bagging was still (very) relevant. Low cost, low tech tools. Now some people food sealer vacuum machines for the bagging. XPS foam easily available. Only difficult thing hard to find in my area is the mylar.

Single tapered 30" half wings should be easy to manage. Juste use cheap cloth: glass with a strip of UD carbon if needed (or heavier glass).

Molded fuselage are an issue for me. Wooden or Wood+3D printed should do the job more easily, with laser cut parts.

Elevator and Rudder in balsa or vacuum bagged depron ? Flat to ease construction. Or 3D printed ?

3D printing for all fixture / interface / support / nose.... Also joiner sleeves in the wings ?

 

[Dominic Bayani]

Hello,

I very much interested in composite slope racer. 60" or something the size of the Slingshot.

For Mylar, vacuum bagging composite wings, the normal thickness was 0.014". I have bought polyester film from eplastics. It goes around curves at leading edge and rounded wing tips. Gives and does not buckle.

0.010" X 24" X 48" Clear Polyester Roll at ePlastics

Polyester film is possibly the most versatile and multi-use plastic on the market today. ePlastics stocks quality 0.010 X 24 X 48 Clear Polyester Roll and can special order custom widths up to 60 inches wide. Read more on our website.

www.eplastics.com

A good molded fuselage is hard to buy. Someone would have to splash a mold. It takes me 6 hour to lay one up.

I made tails with balsa core and newer style spread tow. Build in the hinge using kevlar or thin nylon.

I have couple samples of3d printed part.

 

[Doc James Hammond]

You never know...I wonder what would happen if there were an Old Skool/advanced design 60" slope racer under development.

The old "short kit DIY" recipe of glass fuse, veneered foam wings and balsa feathers with a very advanced racing design at an affordable price?

Not moulded bar the fuselage, not printed apart from maybe a couple of accessories for mounting, etc., and maybe not even that.

Glass fuse, veneered foam wings and balsa feathers.

But how many could construct and finish this kind of model? I think there are still a lot of us out there.

As I said, you never know.

Doc.

 

[Wayne]

Totally agree.

For the local area, the guys up at the Slot do offer a 60" class. Think the rules are just the span and the normal safety stuff.

 

[Doc James Hammond]

My ideas for Rules for MoM racing:

60" class:

1. Must be 60" span or under.
2. Must comply with FAI wing loading rules. (75g/Dm2)
3. *Must be safe to fly. (Radio check plus no visible defects, loose or broken parts, cracks or anything that could cause in-flight failure)

*Models that fail the safety check may be re-inspected and flown if the violation has been repaired to the CD's satisfaction.

Open class:

1. Must be 60" span or over - no span limit.
2. Must comply with FAI wing loading rules. (75g/Dm2)
3. *Must be safe to fly. (Radio check plus no visible defects, loose or broken parts, cracks or anything that could cause in-flight failure)

*Models that fail the safety check may be re-inspected and flown if the violation has been repaired to the CD's satisfaction.

Disqualification: Dangerous flying of any type: One warning by the CD followed by the disqualification of the offender if the offence is repeated.

In case of any dispute: The CD's (contest director's) decision is final.

Personally, I don't think there should be any ban on model type or shape as long as it flies and is not dangerous.

That's it.

Did I forget anything?

Cheers,

Doc.

 

[jmf11]

For me, it would s good when design is open and at the same time some rules tame the arm race and the cost of models.

It is an hobby. It should be a first of all game about skills, intelligence, knowledge... not something that can be paid with only money.

Still people can have the Ultim/No limit class. Which is good for science and techno (think America's cup). But not what I would run after.

 

[jmf11]

Doc,

For the short kit,do you believe that molded fuselage is a must? If yes, what are the main drivers: aero? Structure? Aesthetic? Other?

 

[Doc James Hammond]

For me, it would s good when design is open and at the same time some rules tame the arm race and the cost of models.

It is an hobby. It should be a first of all game about skills, intelligence, knowledge... not something that can be paid with only money.

Still people can have the Ultim/No limit class. Which is good for science and techno (think America's cup). But not what I would run after.

Hey JM = remember thats its the pilot that wins the race, not the model. Trust me, there is little difference between a moulded (expensive )model, a printed model and an old skool glass/foam hybrid in terms of speed and manoeuvrability. I promise you that no amount of money spent on a model will guarantee a podium place, or even, in most cases, any advantage. Its just a different way of making models, thats all.

Doc

 

[Doc James Hammond]

Doc,

For the short kit,do you believe that molded fuselage is a must? If yes, what are the main drivers: aero? Structure? Aesthetic? Other?

Of course, not a must, but it does give speed and ease of construction, and easy to replace JM.

Doc

 

[Dominic Bayani]

 

[Dominic Bayani]

Here a good example of a One Design Racer. I think it conforms to the ODR rules. It was given to me. I started work on it. Vacuum bagged the balsa wood to the white foam cores. I should finish it and see if I like it. I mean enough to inspire creating a molded fuse. I think I can make a carbon wing that would take less labor, reasonably priced, and tolerant to minor mishaps.

 

[Doc James Hammond]

Should go well.

But personally, I hope it does not go to the ODR rules.

Why have ODR? You, gents, have Slingshot races for that. Should be ADR - Any Design Racer.

Doc

 

[Dominic Bayani]

I am very excited to see all building and flying and the recent gatherings. Slope soaring in the Bay area getting some momentum. I like being a part of it. I am a builder, so you will see me push fabricating old school construction and home built molded models, My Craft. Hope my input not derailing the MOM effort.

I did maiden my Slingshot yesterday, the 3D printed mini racer. Good day at Coyote Hills. The other guys make the Slingshot look fast. My 2 flights went good. First one it was out of trim and had excessive amount of roll control. Scary. I dialed back the roll and went to 30% expo. Second flight was much better. Flew better than expected. Actually really fast!!

 

[Wayne]

Dom - Make sure you check out the settings from the other race thread. CG is about 55mm and very little elevator throw or you will tip stall her. Ailerons to whatever you find comfortable. She responds well to a tiny bit of snap flap (camber) in the turns. About 1mm of snap flap. Make sure she is trimmed not to climb at all. Let that nose down a bit and that wing will start working and building speed and momentum. Most people new to her tend to fly outside the best lift, and keep the nose too high. She will be a real pig in this form. As she speeds up she locks into a very stable flight pattern and rewards the pilot nicely. That is one of the things I like about this plane, she pretty much forces you to fly her well.

Once setup, I think all of the Sling Shots fly at the same speed and respond the same. Even with considerable damage she still seems to fly well. In the races it really comes down to the pilots skills to keep her on the best path and fly constantly in the turns.

 

[Doc James Hammond]

Hi Guys - since this thread refers to race rules, would it be a good idea to finally designate these Slingshot races as:

PRINTED MODEL (ONLY) RACES?

Or:

"Printed Model MoM" Class?

Why?

This really needs to be designated as a printed model ONLY class before confusion sets in from non-printed models.

As I had mentioned previously, technically, someone could turn up with a 60" moulded model with a much larger wing area, up to 450g extra ballast capability and be lighter than a Slingshot/per sq/in when unballasted. I doubt if they'd be very welcome, though. And rightly so.

This is a great class and started very well, with fantastic participation and promotion from Ollie and Aloft as designers and producers. It has a great chance of even more participation next year. But...If it's a racing class (The ONLY racing class), then let's say so.

Cheers,

Doc.