CEF speed contest Design Discussions (2014)

I like the unusual shape - it seems appropriate.

I do hope that it won't be too heavy.

Theo Kleynhans wrote:Hi Guys

I figured what I wanted to do with the nose on my Nemesis. I used an aerosol can.
This is where I am now:



Theo

WOW! It looks like a jet!

Hmmm... That gives me an idea. A Dynojet is technically a reed valve engine, isn't it???

Mike Mulligan wrote:

WOW! It looks like a jet!

Hmmm... That gives me an idea. A Dynojet is technically a reed valve engine, isn't it???

I had to double check.  The rules specify a cox .049/.051 reed engine.



Phil

pkrankow wrote:

I had to double check.  The rules specify a cox .049/.051 reed engine.



Phil

Drat!! Foiled again!

ian1954 wrote:I like the unusual shape - it seems appropriate.

I do hope that it won't be too heavy.

Yes it does look like it is fitting Ian.
I unfortunately do not have a digital scale that can weigh these light parts. But it actually feels really light.

Theo

Here's a little motivation for someone's racer:
http://www.ebay.com/itm/Rare-Valentines-Cox-Space-Hopper-049-cu-in-Glow-Model-Engine-NIB-/371110141732?pt=Radio_Control_Parts_Accessories&hash=item5667e35f24

Test flew the staggerwing today. It flew exactly as I wanted, visibly arced into the circle. It almost came in on launch but the lines tightened when it got some speed.
I'm not going to give up any numbers but let's just say I am VERY pleased with the results!

Jim

I am very glad that it is flying great Jim. Sounds like we are in trouble.

I have a question: with these planes so loose on takeoff, will it not be extremely difficult to hand launch? I think previously you mentioned you also tested your previous plane without wheels. How are you getting a decent takeoff?

Theo

the launch can involve a significant amount of out yaw, that along with whipping and back peddling can overcome loose lines fairly well.

Have a clear field, and good shoes for nimble feet!

Phil

pkrankow wrote:the launch can involve a significant amount of out yaw, that along with whipping and back peddling can overcome loose lines fairly well.

Have a clear field, and good shoes for nimble feet!

Phil

What Phil said! Exactly!

Theo, if your looking for a decent takeoff use a lot of tip weight until you get used to it. If you traditionally use 1/4 oz., make it 1 oz. . My tip weight is externally applied so that I can add or subtract. If your plane is using a single gear wire, splay the wire over so that it automatically places the outboard tip on the ground. Ken

Theo,
This is my launch today. You'll notice I step back and pull the lines back to my ear to keep the lines tight.


Jim

Thank you for the video Jim. I see what you guys mean.

I am a bit afraid of this launching. I tried a .15 racer a while back and could not get it to take off. Everytime it came into me on launch.

This is going to be the hardest thing for me.

Thanks to all you guys for the help.

Need to get building on my Nemesis again this weekend.

Theo

Hi Kim. Thanks for the tip on the tip weight. I will most definately try that. I was also thinking of moving the leadouts back a bit, for a start. That should also make the nose want to go out, I think.

Thanks also to you Phil. I see from Jims video you have to pull a lot.

Theo

JPvelo wrote:Theo,
This is my launch today. You'll notice I step back and pull the lines back to my ear to keep the lines tight.


Jim

Aw, you teaser! Not even one lap!

Theo,
You are putting a lot of work into that nemesis, it should be a beautiful plane. Maybe you could quick build a practice plane of similar dimensions. Just a real simple similar span and chord, same stab size and distance from wing. Sand it, spray it with black rustoleum , and practice takeoff a before you risk the nemesis.

Jim

Thanks Jim. I hope it will end up to be decent enough. I am trying to do a nice job.

That is a great idea. I will need to try and do that. It should be quick to build a basic one. Then I can practice without a worry.

Theo

Theo Kleynhans wrote:Thank you for the video Jim. I see what you guys mean.

I am a bit afraid of this launching. I tried a .15 racer a while back and could not get it to take off. Everytime it came into me on launch.

This is going to be the hardest thing for me.

Thanks to all you guys for the help.

Need to get building on my Nemesis again this weekend.

Theo

Theo, since the first forum speed contest.. I discovered a few helpful tips that might ease your mind with launching these particular models. Being that the engines are limited to Cox "reed-valve" induction.. gives you the advantage of running your engine ("backwards") in a clock-wise rotation, while using a left-hand propeller. This has "two" advantages.. The first; is the torque-roll induced by the engine/prop pulls the model "outward" (assuming a counter-clockwise flight-circle) and away from the pilot. This creates instant line tension. The "second" advantage is requiring "much less" (if any at all..) outboard wing tip-weight.

You see.. most if not "all" model engines (other than the Cox reed-valve type) use a "rotary-valve" intake/induction design that runs "counter-clockwise".. and requires a right-hand propeller to be used... so that's what most of us are used to dealing with.. and thus; most props are right-hand props because of this. Here's another scenario.. If you "build" a speed model to fly in a "clock-wise" circle.. (bell-crank/lead-outs on the opposite side) while using the conventional rotation/right-hand propeller.. it will produce the same results. It all depends on if you're comfortable turning to the right.. instead of the left.

Build to keep lines tight. Use out thrust, and rudder offset. If you plan for it the rudder can be adjustable (on the ground) either with a linkage or a piece of soft metal. The out thrust can be adjusted with washers behind the motor. This means that as you trim out the model and gain skill you can gain performance.

Phil

Thank you for the information Roddie and Phil. I really appreciate all the help from everyone. I have learned a whle bunch on the forum. I am glad I got involved here.

The Nemesis is assembled. I did the hinge last night. I used the tubing and Piano wire like Mike, it felt really nice before installing it, but now installed it is a bit stiff. I will have to see how I can get it to move more easy.

Here she is:

WOW! I went away for a few days and everyone got very busy! Looking good!

The "Space Duster " is coming along nicely: