How tight should I tighten the bolt for the prop? I have a torque wrench. Is it necessary? Thanks.

Hold the prop with a rag, then tighten by hand with basic open or closed end wrench. Tighten as much as you can with your hand then enjoy.

cap,

as tight as you can get it




bassman

No, you don't need a torque wrench. But you do want to get it as tight as you can get it. Here's what I recommend. First off, if you have one of those 4-way combo wrenches that will also remove glow plugs get a good grip on it with your right and and throw it as far as you can!!! Seriously, those are no good for tightening a prop. What you do need is a good box end wrench and a glove (a good rag will do as well). Use the glove to hold the prop while you tighten it down, this will keep the prop from cutting your hand. Don't worry about over tightening because the nut and shaft are steel and will be very difficult to damage. Pull the wrench just as tight as you can get it. If get it nice and tight now you won't have to worry about ever throwing a prop. It's been at least 6 years since I've thrown a prop.

Ken

What engine? Do you mean the prop nut? For glow engines, the nut needs to be very tight, and for a four stroke both the nut and jam nut need to very tight. I use a 6" cressent wrench for my wrench, although a box end or an open end wrench of the proper size would be better. Snug down the nut, making sure the spinner screw holes are in alignment, then set the wrench so it is away from one blade, so if you squezed the two together, it will tighten. Watch the new plastic blades as they can be as sharp as a knife. By using one hand to squeze the blade and wrench to gether, you can get a very tight nut, but not so tight to snap off the crank nose. Just keep fliping the wrench over when the wrench and prop blade are nearly together, this gives you a fresh amount of movement. Usually just moving to the next flats is to much of a change for you hand to handle. 1/2 flats, or flipping the wrench works. If you are flying a four stroke with a jam nut, tighten it in the same mannor.

Always watch that your prop is thick enough that the nut and prop washer can fully tighten it before running out of threads on the crank nose. I have found that most of the 4" pitch props have to have a spinner back plate in order to fully tighten them.

Don

I hear this a lot. I use one of those wrenches, and haven't yet lost a prop, but then I REALLY turn hard on the wrench, (See the rest to qualify this statement).
I was told by a guy watching me just this weekend he didnt tighten them that much. Then, I fired my starter to run the engine dry so I could go home and guess what happened?[:@] Prop nut spun off LOL!! Fortunately the engine DIDNT fire up, so it was just the starter torque spinning it off not the motor.

Getting a box wrench into my kit tonight. Im just glad Ive been lucky till now, and that I didnt lose the prop.

I used a rachet and socket and tightened it real good. Thanks, Guys.

I like the explanation that RCKen gave. Let me add to that just a little. Use the small cross wrench on the prop. Tighten it till it hurts your hand. Now you have reached the point where it has to be tightened further. I tighten it 15 to 45 degrees further using a large adjustable wrench. Once you do this a few times you will know how hard to tighten it. This is an area that needs attention on the part of the engine manufacturers. I used the cross wrench for at least 15 years and dealt with the occasional prop that fell off on starting the engine. The prop can also come off in the air and cause a crash. I have not had one problem once I changed to using a large adjustable wrench.

Some of the engines have metric nuts. Be sure to use the correct wrench and not be satisfied with "something that works".

A good sign that the prop nut is tight enough is a melted plastic spinner.
That's why you gotta stop when it floods. So you don't loosen the nut

Why does everyone come in and repeat everything I already said, but with more words? Kinda funny huh?

I would think the OP would feel better when a statement is verified. This is why I personally sometimes echo previous posts. It's one thing if Joe off the street says something, but if Joe and six other members all say the same thing there's a much better chance that the information is good.

Good point, but they could've just said "Yeah, what he said".

yea what he said....

Just remember, if youre using a wood prop they need to be tightened before the days flying. The wood expands with heat and causes the prop to loosen.

I'm guessing 20 ft-lbs of torque on engines up to .40 and 25 ft-lbs thereafter. I use a 6" Crescent or specific size 8" open-ended wrenches to tighten mine.

At the risk of re-iterating what has already been re-iterated, all threaded fasteners have a max torque spec that should be reached but never exceeded. In light of that statement, just get it really tight, most .40-.50s use a 1/4" high strength thread, so yah....about 20 pounds sounds about right.

Are we having an "insecurity" problem?

What about the prop? I was tightening an APC 19x8 on a Saito 220 the other day, and wanted to make it really tight (maybe I have an insecurity issue). All of a sudden, the prop made a noise, as if it had cracked or something. It really freaked me out, and I had to inspect it very closely before I dared to use it. There was no visible damage, so I suppose it was OK, but I'm just wondering if in fact you can damage the prop by tightening it too much.

Now you've hurt my feelings Not really, just think its kinda funny that people would spend all that time typing up the same explanation when a quote and ditto would suffice. Guess I just think differently.