Are there any drawbacks to flying with no spinner? Does it hold the prop in place with its ridges?

You can fly with out a spinner, however if you do, you should have a safety hub instead. Your spinner should not hold the prop in place per say. The ridges are usually just used for the alignment of the spinner and the prop. Good Luck, Dave

You lose 15% of your air flow without it.

Prove that, EZer.

As DavidAgar says, you can fly without a spinner - no problem. If you do, you need a rounded "safety nut" for a couple of reasons. It makes a nice smooth place for the small cone of your electric starter to grab, it protects the end threads of the crankshaft, and it gives a little protection if the plane hits someone.

Dr.1

I am not quite sure what you mean by this.

And yes you can fly without a spinner. I actually prefer a lot of the hubs you can buy shiny aluminim or anodized ones that look really nice and sure beats having to cut out a spinner so that it fits over your props.

Generally if I use spinners its on my nicer planes and I only use aluminum ones. That gets pricey to do on all my planes so I opt for one of the hubs. Here is an example http://www2.towerhobbies.com/cgi-bin...?&I=LXE166&P=7 There are lots of colors and styles to choose from. Just make sure you check the size to make sure it fits the threads of your engine.

i just do not have a 2 blade one right now and i would rather not spend the money if it doesnt affect performance or allow the prop to loosen the nut or something.. what is the purpose of a safety hub? i do not use a starter i use a chicken stick, always. so do i have to have one? or will it decrease airflow or air distribution over the prop.. basically will it decrease performance just to have the bolt sticking out as opposed to a nice smooth cone?

A spinner is not needed for safety but, depending on the airframe, may help with looks and a slight performance gain. Q-500 race planes do not use a spinner but a bullet shaped prop nut.

On our sized model, no. Its way too little to make a difference.

I dumped spinners when the plastic spinner on my trainer failed 7 years ago. I've used Dubro prop nuts ever since. They're easy to install and remove, inexpensive, engage the starter cone well, and never break or spin off like the plastic spinners. On my 4-strokes I use a large hex aluminum lock nut (Higley, I think) behind the prop nut.

I cant really prove the 15 % but it sure did help on my 20cc and my 100 Saito. I was trying to do knife edge loops and they didnt have enough to pull threw. A guy said to put the spinners on and know problem now.

Certain models in AMA sanctioned competitions are required to have a spinner or safety hub. The safety hubs are not required for regular flying.

As long as you use your prop washer, and the nut doesn't "bottom out" on the shaft before the prop is tight, there's no real reason to buy anything. My trainer has just the washer and nuts that came with the engine. My Uproar has a safety hub. I know you do not use a starter, but, it works fine if the rubber insert is turned around so the small hole goes over the prop nut.

An engine that stops suddenly, or back-fires, can throw the prop. Hard enough to stab someone fatally.