Details of the Baby-J

[MPP]

In my kits I try very hard to keep things simple, inexpensive and reliable. If you will bear with me I will explain my thinking on this subject.

I use the ply because it is the best material for THIS APPLICATION. the emphasis is because if I was charging $2K for a kit I would make them from 3mm carbon. However, that is simply overkill for my planes. However, I always put pieces of glass cloth in my kits for incidentals. It would be quite simple to fiberglass the ply with either CA or WPU.

Konrad has suggested I offer two sizes so people could use out-runners or In-runner motors. I totally understand why he has suggested this. In-runners are really sweet, easy to mount, and very smooth most of the time. They are however quite heavy in most cases and very expensive if they are small and light. Even so, if someone wanted to run an in-runner they could easily put the firewall on a bolt, put it in a drill and sand it down to fit the very nose of the fuselage.

This might be a good point to actually give a run down of what my teammate and I are flying in our Baby-J's. Keep in mind we do indeed fly in competitions:
I have run a couple of different Emax motors and none of them were over $20. I just ordered two more of the XA2212. I don't really like how they do their wires but they are overall nice motors.
We both are flying Corona DS843 servos. Wayne can verify I practically buy these in bulk....LOL
We are flying Super S props.
I really like the CN spinners but the Aloft turbo spinners really help airflow through the fuselage.
We are flying 3S 850 packs most of the time and two packs can keep you flying all day.
A simple 20-30A ESC will do the job.

Obviously MKS servos will work and a $300 in-runner could be used but these basic components would allow a person to set up a Baby-J that will fly great. My goal has always been to help more people enjoy this great hobby. That means I design my models so they can be flown with good quality but inexpensive components. This being said I have thrown cheap servos that had major centering issues.

The one in the pic and the video are being flown by a good friend, it is 900g. I am flying a recent build and it is 917g.

 

[2MUCH2DO]

My $0.02, I think that your reasoning is perfect for your application, this seems sort of inline with some past planes are hard to come by, like the Horejsi(sp) Geronimo for instance.

 

[Konrad]

For the record I know nothing of the Baby "J". And I made no recommendation as to any mounting system for the Baby "J". I do know I don't like to mount any motor to plywood. The bolts crush the wood fibers far too easily, even more so on nose impacts. I like front ring mounted outrunners as it aids in keeping the cooling air going the correct way in the thermal path. The use of pressure cowls pays huge benefits in drag reduction. A key concern in my glider designs.

Motor in a can??

Motor in a can, as these are marketed to the glider community I'm posting this power thread under "Gliders". I can’t for the life of me understand why anyone would want to use these! These are just motors supplied with their own mounting cage. The design as I see just adds weight and if not...

forum.alofthobbies.com

I, and I'm sure others, have a lot of Razor and Aveox inrunners that fit great in the narrow nose of gliders. Having as small a frontal area is again a noticeable benefit in glider design. As for power to weight and thermal efficiency I'd take a proper sized inrunner, maybe with gearbox, over the outrunner systems. Now as to practical consideration the outrunner is a more flexible powerplant.

Here I used a geared Hacker outrunner to convert a failed F3-RES to the proposed F5-RESt. Notice the use of a phenolic bulkhead as a stable medium to keep the small screws from pulling through. I'm using the 25mm CN spinner and a custom fitted set of blades to best match the airframe and powerplant. With 50 years experience in the hobby, some as an OEM, I can say that the plywood mounting bulkhead is far from an ideal motor mount. Yes. I've used it and at times still do. But if starting a design from scratch this is not the place I'd look to cut costs.

DJ Aerotech Chrysalis F3-RES to F5-RESt

On the competition circuit the last two years haven't been kind to the DJ Aerotech Chrysalis lite F3-RES. Most of these problems can be traced to a nagging problem with the V tail flutter on the high start. In the USA it is getting difficult to get enough workers to man the lines for a classic...

forum.alofthobbies.com

Now I am using the ubiquitous 1806 in my latest F5K build. Again notice the composite bulkhead. Price point aside there are good reasons for it over the wooden bulkhead

Stika (F5K)

I found a great deal on this DLG based F5K electric assist 1.5 meter glider. (Thanks, Wayne and Aloft)! As it is looking like my conversion of an F3-RES to a F5-RESt is going so well I thought I'd might as well own up to my demographic (Fat Belly) and electrify a smaller 1.5 meter glider...

forum.alofthobbies.com

To be clear I post as a perspective customer what I'd like to see in the market place. These preferences were learned in the school of hard knocks over the last 50 years.

All the best,
Konrad

Edit: Add link to cooling path discussion of outrunner and pressure cowls.

 

[purview]

@MPP with wiring you can save a lot of useless weight. I also like the one day two packs flight solution, it sounds that this bird must be thermal well. Sounds of a good project, keep it well and look forward to flights with weather that is not so perfect for flying - that seperates the energy counts... A bird is simply a bird ???

 

[MPP]

Konrad: you made the comment in the thread where I was asking about someone to cut them for me. I simply mentioned you because I agree with you and your comment prompted me to start a thread sharing how we design. Your comments are spot on and quite valid. We try very hard to build a great model at a fair price and if the MMT needs to be from G-10 or carbon to last then that is what we will do. I did not intend to upset or offend you.

Can you share some information about that tiny in-runner you mentioned.

The frontal area is quite nice as she uses a 30mm spinner. I am not familiar with the in-runner you mentioned. Like you, I do like in-runners, they make wiring much simpler and their small OD makes them easy to fit. On the Baby-J a light motor works out nicely, something around 50g normally balances quite well with the suggested gear.

Purview: I do indeed keep wire runs as straight as possible. Eventually we may offer a wiring harness. We are making some pretty neat plugs for our personal planes which I will share soon.

 

[Konrad]

I'm not at all offended or upset. I'm sorry if I come off that way. I do have strong "opinions" and I try to give arguments in support of those opinions. But they are only my opinions and made from my perspective as the customer. As an OEM you have different constraints placed on you.

The Razor and Aveox are long out of production inrunners from the golden era of the inrunner (2000 ish) long before the onslaught of the outrunner. I do have most of the data sheets but as these are obsolete as in out of production they are of little value .

All the best,

Konrad

 

[Wayne]

Personally I rather like the weight and price of outrunners. For me the math is pretty easy, I can buy a spare battery that will offer 100% more electrons to play with compared to the tiny % in efficiency that a carefully spec'd inrunner may save me but will cost me a lot more money and weight. Yeah, I'm cheap and like outrunners for this reason.

Now I will add that the trend of using a mini quad motor in a glider is not ideal due to the layout of the motor. Luckily Dualsky came out with some nice motors with the shafts in the correct direction for gliders that are tiny and powerful. I do wish they had a little better price, but they do make very nice motors!

22EG Series

Small motors for small spaces.

alofthobbies.com

 

[MPP]

That little razor motor looks like it would be awesome in a light 2M or even a lightly built 3M. There are some very nice tiny in-runners available these days but some of them are in the $300 range. That just seems like a lot of $$$ for a motor to fly a 2m or 3m sailplane.

I am glad I did not upset you. I much prefer being a positive input to someone's day.

I just picked up a large foam order and resin is due today or tomorrow so I need to get back in the shop.

Personally I rather like the weight and price of outrunners. For me the math is pretty easy, I can buy a spare battery that will offer 100% more electrons to play with compared to the tiny % in efficiency that a carefully spec'd inrunner may save me but will cost me a lot more money and weight. Yeah, I'm cheap and like outrunners for this reason.

Now I will add that the trend of using a mini quad motor in a glider is not ideal due to the layout of the motor. Luckily Dualsky came out with some nice motors with the shafts in the correct direction for gliders that are tiny and powerful. I do wish they had a little better price, but they do make very nice motors!

22EG Series

Small motors for small spaces.

alofthobbies.com

Those are really nice, I will have to try one of those in a 3M

 

[Konrad]

Actually that Razor 350 is too small and/or the gearbox isn't deep enough at only 4.4:1. Today many of the ultra small geared inrunners are failing pulling up the F5J ships, even with 6.7 plus gear ratios. Now there was the Razor 2500 that might pull a very light F5J.

That EG22 series has me thinking I want to take a hammer to the firewall of the Stika and put it where it belongs as a nose ring bulkhead.

 

[MPP]

With that motor and others that are available the nose mounted MMT makes a lot of sense for the Baby-J.

 

[Wayne]

That EG22 series has me thinking I want to take a hammer to the firewall of the Stika and put it where it belongs as a nose ring bulkhead.

Yeah, hear you.. My Stika is basically like yours.. Not a big fan how the spinner goes onto that layout.