I figured I'd post this here in the beginner's forum since I am a beginner and this appears to be a "beginner type" question. I am flying a Trainer at my local club with an instructor. I have an OS .46 FX engine turning a 10x8 APC prop (see image 1). My instructor suggested that I get an 11x6 or possibly 11x4 prop instead of the 10x8, so I purchased. What a good student.

Now the interesting part. I have a 2" Dubro Spinner. The 10x8 prop fits perfectly, however, the 11" props are too wide to fit into the spinner! When I lay the 10x8 on top of the 11x4 the difference is quite startling. See image 2.

So my questions are:

1) Are there different "widths" of props that I need to be aware of (apparently so)? How does one tell? One prop says 10x8 while the other says 11x4 - nothing else.

2) How does one ensure that the prop they are about to purchase fits the spinner? Do I need to take the spinner with me to the LHS? What about online purchases ... how do I tell?

Am I wearing the dunce cap on this one?

Thanks all!

-MasterAlex

You'll have to trim the spinner to clear the prop. Try to keep the slots as close as possible to the same size.

This is a common problem. You can shave off some material from your spinner on each side so the prop will fit. However, you will want to try and remove the same amount of material from both sides to keep the spinnner balanced properly.

Now that sounds like a pain! [:'(]

Any advise on how to make this not painful? Besides putting back on the 10x8 ...

Is this a job for the Dremel? How do you guys tackle without making the spinner look like garbage.

Thanks!

-MA

Edit for spelling.

I use a dremel with a cut off wheel, but it takes some care and practice to get it right. If any one has a better way of doing this, please post as I am open to suggestions as well.

You can trim it with a pocket knife, exacto knife, dremel, file, sandpaper, etc.

You can dump the spinner and use a "prop hub" or "spinner nut" instead. There are several styles. Here's what Tower stocks; there are probably many others available but this list was easy to pull together.

If the plane does not "need" a spinner I prefer the hubs or nuts.

Dubro
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=DUB

Goldberg
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=GBG

Great Planes
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=GPM

Higley
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=HIG

OS
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=OSM

Tru-Turn
http://www2.towerhobbies.com/cgi-bin...p?&C=QKC&V=TRU


edited for spelling

I use a 12.25 x 3.75 on my UCD .46, and have a 2" Tru-turn aluminum spinner with the wide slot for a
wide prop. I hate widdiling out spinners so I now use the prop hub or if the airplane
needs a spinner I will spend the extra $$ and get a Tru-turn aluminum spinner. They usually offer them in a wide
version for wide props. I think aluminum looks better and they are easier to put on and take off.

In your case since you probably have a trainer I would go with the prop hub by Du-Bro.

Also, when the pitch goes down the prop is going to be "wider" at the base. 11x4 is an 11 in diameter
prop and a 4 pitch. Less pitch equals less speed. Good for a trainer to have less pitch.

the dremil is the easy way to go, it will turn out ok just dont take to much off at once
then when you go to higher dollar planes you can order from tru turn and have them size them for ya[8D]

Thanks to all that have replied so far. I just grabbed the spinner and wanted to see just how much wider I needed to make it. It appears that the spinner simply won't take that wide a prop. See picture.

In order for me to widen the spinner, I'd need to take out the guides that fit into the backplate. Presumably a bad idea.

So for now, I'd like to stay with the spinner concept - personal taste, I guess. So additional questions:

1) Do I purchse a larger diameter Spinner? I currently have a 2" Dubro ( http://www2.towerhobbies.com/cgi-bin...?&I=LXE128&P=7).

2) How big a spinner can I get for a OS .46 FX?

3) Is this something you "just know" with experience? What rules of thumb are there so I can avoid this in the future?

4) Isn't a True Turn (or equivalent) too heavy for a .46? (mentioned here: http://www2.towerhobbies.com/cgi-bin...?&I=LXFBJ5&P=7 ). What is the adapter kit needed for?

Sorry for the newb questions... I really thought I had a decent grasp of this hobby.

Thanks!

-MA

I would think cutting out the guides would not be ideal. My thoughts on the questions:

1. That’s what I’d do since you want to stick with a spinner. If you can find them, SIG nylon spinners are advertised as having “slots for APC props� (whatever that actually means).
2. The spinner size is dictated by the plane rather than the engine. Just go as big as you can without it looking “too big.� I would think 2.75 inches would still look fine on most of the trainer planes I have seen.
3. It’s really just what looks good. On planes with cowls the spinner size is determined by the cowl size
4. Tru-Turn spinners are surprisingly light. The adapter kit has a special nut to accept the retaining bolt for the spinner cone. Your Dubro has multiple screws around the outside to hold the cone on. The aluminum spinners use a single bolt in the tip of the cone and it screws into the adapter nut.

Even though I’ve been on RCU for a few years, I’m still very much a beginner and have lots of questions. I answer as many as I can but I still have more questions than answers. The forums really are a good resource so keep asking questions.

Spinners aren't specific to a particular engine size -- they are primarily a fit to the airframe, then fit to the prop -- the engine really doesn't come into it. For instance, I have a 3" spinner on a 46-size engine with one model & a 2" spinner on a 78 size engine with another model.

Since spinner manufacturers can't possibly know what your engine/airframe/prop combo will be, they simply make spinners with arbitrarily-sized holes & expect (quite rightly) that you will do the fit.

There are a couple of rules:

The prop blades shouldn't touch the sides of the spinner, or the rubbing/vibration could make either, or both, the spinner & prop fail.

A spinner shouldn't be larger than ~ 25% of the diameter of the prop blades, or you will start to lose prop efficiency -- eg. a 3" spinner is about as big as you want to put on a 12" prop. That isn't cast in stone, but it is a reasonable max size relationship.

You could just get a Master Air Screw prop and probably not have a fit problem. Some pilots prefer APC and some MAS. Not a significant difference, especially on a trainer.

APC makes different models/shapes of props too. You may have props from 2 different series, hard to tell from the pictures.

I use my dremel & it's very easy. As stated above, just make sure to keep it even on both sides for balance.

The other thing you might want to consider before you dismiss carellh's suggestion of a spinner nut is that during training we tend to eat up alot more props than an experienced rc pilot. With that in mind it is alot quicker & easier to change out a prop with a spinner nut on it than an actual spinner. The spinner nut still carries the same nice appearance as a spinner too. Just something to think about.
Good luck.

Thanks Bruce.

Looks like a visit to the LHS tomorrow with my spinner and props ... I'll check out the MAS props while I'm over there.

-MA

use a dermal tool and the pointed burr tool to cut the prop i also use the drum sander attachment sometimes also.when you go to your field try to find some broken props of the same size and type,we have plenty at my field because of the amount if new flayers we have.i use the broken props as templates,also for paint stirrers,epoxy mixing sticks.

Cut the prop? I was under the impression that altering the prop was a recipe for disaster and fairly unsafe. Again, as a beginner, maybe that's an "urban legend", but that's my "perception" for whatever that's worth...

I know as a beginner I do not feel comfortable altering the prop at all. I understand adding weight (like spray polyurtherene) for balance purposes, but removing prop material is something I will leave to those with more experience than I.

Thanks for the tip Horace315.

-MA

No, you dont want to remove any prop material. These spin and way too high RPM's to
be messing with the structure of a prop. MAS is fine but at higher RPM's they tend to flex,
APC is a better prop all the way around. I have used both and APC also seems to be a
quieter prop. But this is my opinion. Go with the prop nut, like elenasgrumpy said it is
much much easier to change a prop with the prop nut. I wouldnt spend much money on
a Tru-Turn for a trainer.

Speaking of Tru-Turn they are very light, the adapter and the spinner probably weigh just
slightly more or equal to a plastic spinner. On Towers web site they tell you what adapter you
need for your motor.

The prop nut from Du-Bro shaped like a spinner is a good choice, and like somebody else
said still has the shape of spinner for looks. Good Luck.

With the glaring exception of cutting the prop (BAD idea!), all the advice you've gotten here is sound. Some folks will tell you that if you trim a plastic spinner, use it on a four stroke engine, etc., etc., it will blow up, destroy your planes, and in general cause you grief.

Nonsense. While you are correct in assuming that cutting into the locator pins will weaken the spinner and raise the possibility of failure, you CAN do so to a degree without drama. The red spinner pictured is a 2.5" Goldberg cut out for an APC 16x6. I went WAY too far on this one. I was in a hurry and didn't do nearly as neat a job as I did on the blue 3" Goldberg. But both have lasted for a good long time; and these are on big engines. The red one is on an OS 1.08; the blue one on a Laser 150. Both have slight encroachments on two locator pins to fit the wider blades.

I don't use an electric starter, and I don't run the Laser lean; back-firing four strokes will trash a spinner quicker than anything. Some guys think their electric starter needs a "running start" to crank the engine. They spin it up, then jam it against the spinner; and wonder why their gear fails.

Anyway, just get a larger size if you don't want to chance messing about with the locator pins. A 2.5" DuBro or Goldberg should handle an 11" APC prop without having to get into the locator pins.

And I agree with Brother Cranford regarding Master Airscrew props; APC is LEAGUES above these paint stirrers...

See next post for the pix; you cannot post pics in a "Quick Reply" post, which is a constant source of annoyance to me.

Here ya go...

Well, I dunno what's up; the photos didn't seem to load. I'll check back later this evining and re-post if necessary.

Thanks Steve.

I visited the LHS this morning and picked up the MAS props. They do appear to be a bit more "flimsy" than the APC, however they fit in the Dubro spinner - which is what I was looking for...

For what it's worth, I checked out the 2.5" Dubro spinners while I was there and the APC prop didn't fit into that either. [&o]

I figure since this is a trainer and props aren't really all that crutial as compared to other aircraft that I'll fly the MAS and see what they're like. If I want to go back to the APC, I'll pickup a prop hub and have at that. I'm sure this isn't the last visit to the LHS for props ...

Thanks all!

I know. I said you could trim that spinner to fit without having to trim the locator pins...

You're right; its not a big deal on a trainer. But with the model restrained, blip the throttle (rapidly advance/retard) and watch those Master Airscrew prop tips flex back and forth like a willow in the wind...

my mistake i meant to say use an old prop as a template for the spinner.never never cut a prop or hub.