efish

My Feedback: (5)

Hi, I want to cut down an APC prop to about 5.4" becaue the 5.7 is too big and the 5 is too small. (My plane is too slow with the first and a too quick with the second)

Is there a preferred way of doing this? I was just going to measure then cut with a dremel cutoff wheel. Thereafter, will balance the prop by sanding.

Can anybody help with any tips or suggestions? e.g. should I cut the tip off square (easy to replicate) Or try for a scimitar look a like?

Thanks!

efish

My Feedback: (5)

btw, Sorry about the subject line - think I was typing and clicked somewhere else by accident.

buddude8

My Feedback: (10)

for the measuring part i use calipers from the center hole to the tip. before i cut it down i make a template for what i want the tip to look like. draw it on both sides. you want to make sure the tips are almost exactly the same. the dremel wheel works fine but if you try to do to much at one time you will melt the prop. I snip mine down as close as possible before i use the dremel. since you are going for such a small amount just using the dremel should be ok.

efish

My Feedback: (5)

thanks buddude8. will give it a go.

combatpigg

My Feedback: (3)

The most dead on way that I know of is to first pick out a drill bit that is a nice fit in the prop hole, and sink this drill bit into a scrap of wood. If you plan ahead, locate the hole to the exact dimension from the edge of the wood that your prop blade will be [like 2.7 inches in your case] Now, with the drill bits' shank installed in the wood block, push the prop down onto the wood block, and use your favorite cutting tool to do the work, using the edge of the block as a guide.

My experience with cutting down APCs is it doesn't work as well as I would like unless the entire blade gets recontoured to the original shape, instead of having blunt tips. The other props [like COX and MAS] with the paddle blades seem to respond to a simple trimming better than APC.

BMatthews

Fixed your title....

I also found that with the APC's you really need to reshape the tips to restore the performance. A lot of the efficiency of the APC over the regular prop shape is due to the cresent shape. This means cutting the tip down and cutting away some of the outer leading edge and re-shaping the airfoil. Measure and cut carefully using some method or other (CP's is a nice option) and trim away one side to shape the tip. Then mark the new outline with a sharp pencil on a piece of paper and trim the other side to match it. Check often as you work to ensure as close a match as you can. Then profile the airfoil on one side as a master and then do the other side while checking the balance often. Use the removal of the airfoil thickness to perform the balancing.

For myself I think a dremel is overkill. A razor saw or even a fine tooth hacksaw blade used with a light pressure will easily do the job and not burn the resins in the plastic.

Larry Driskill

I use Pigg's method to get the diameter correct. I am with Bruce and use the razor saw on filled props like the APC. For Cox rubber duckys I use side cutters followed by a single edge razor blade.

combatpigg

My Feedback: (3)

For COX rubber props, I just hold the prop against concrete while the engine is running...

Bipe Flyer

You may say that in jest CP, but I've cut down props by putting them in a drill press and using a sanding block. It ensures that both blades are the same length and the tips have the same shape. I've not done it with an APC prop though.

efish

My Feedback: (5)

Hey, thanks for all the info, guys (and for fixing my title too!). I really appreciate it.

I guess I might leave my APC C-2 props intact and try cutting the few MAS props I have instead.

Thanks again.

Toad

I use toe nail clippers. A small scratch is made on the blade via some older calipers I use to measure first for a mark. After the rough circumcision, I fix it up with a fixture I made, sanding sticks and a balancer. Similar process as what CP does cept I prefer the manly use of toe nail clippers lol

efish

My Feedback: (5)

Thanks toad, that sounds like a good tip. I've already cut my test prop but haven't flown it yet; will try the nail clippers on the next one.