I am a nubie to gas engines and have a DLE 30 on which I have mounted a glass filled Master Airscrew propellor. I have been told by an experienced club member that plastic prop not good on a gas engine as it could transfer shock load to the crankshaft in the event of a rough landing that could be damaging. While I respect the advise of the member who gave me this information I am curious to hear of other views on this subject.

The problem arises not so much as to gasoline itself but because of the mass of the engine involved.

Many people go to wood when the prop size gets to 18".

Others do not trust the integrity of the non wood props in the larger sizes.

If you look around, you will find that the choices in glass filled props sharply diminishes above the 16" size

Here's something similar.
http://www.rcuniverse.com/forum/m_10...m.htm#10408900

Use these.
http://www.zingerpropeller.com/

Dan.

However, some of the better props are made from carbon fiber, which should also be classified as a plastic propeller since it's laminated with specialized epoxies.

Hard plastic props do transfer more of a shock/impact load to the airframe during a propeller strike. One has to decide if they can land with the precision required to avoid prop strikes. If a person is unsure of that ability they should use wood propellers that transfer less of a shock load to an airframe during a prop strike.

Hub drilling raises other factors when plastic propellers are used. One must be absolutely certain that any plastic prop that will be drilled for a multi bolt installation has propeller hub integrity sufficient to handle the additional outer mounting holes. Some brands of plastic propellers will not safely tolerate this modification and have been noted to shed propeller blades after drilling new mounting holes. Always consult with the manufacturer when in doubt.

just go with a single bolt prop adaptor

correct but also if they are unable toland with the precision necessary to avoid prop strikes maybe they not ready for the larger planes and engines just yet...?

Better yet, the engine should come with a single bolt system from the factory. There is no reason a 30cc engine needs a multi bolt prop mount. I don't think it needs a 10mm prop shaft either. Make the shaft the same size as the larger glow engines. Who can help DLE see the light?

No arguement from me on that score. The reason most people stay with low budget (cheap) plastic props that don't perform well is because they break a lot of props during "landings". If they are in that group the really aren't ready for a gas engine yet, Most glow engines will handle frequent prop strikes better because they don't have bearing similar to gassers. Small needle bearings take a beating over the course of a lot of prop strikes and eventually fail. Cranks bend and need replaced or straightened.

A gas engine will not make a bad flyer better. Only practice and skill does that.

Better still, who can make users understand their engines? A smaller diameter output shaft will handle far less abuse that the average small gas engine flyer will subject it to. See the post above about landings. Fact, the average small gas engine user is short on skill and experience, breaking stuff all the time because of it. Then you have people that still want to be flying glow engines and therefore believe a gasser should be more like a glow engine.

Besides, who really wants to have a smaller shaft?

I buy gas engines only if they have/can be converted to single bolt. That said, I really enjoy the APC "W" series props - and have broken my fair share of them screwing off flying "sport" style. I have only bent one engine part. That was on a Quadra 42, and the engine wasn't really damaged. The prop bolt bent.

The thought of not graduating to gas until you can land without breaking props is crazy. Don't believe anything like that for even a second...
Actually, I find the idea of even suggesting that condescending....
99.9% of us will break a prop on occasion.

But some break a prop at the end of almost every flight!, and those people seek out the cheapest props they can find because of it. In doing so, and failing to learn how to land, they sacrifice a lot of propeller performance. It's a fact of life that's been there since we started aero modeling. We've both seen it. I break a prop once in a great while too, but one a year would be a high count.

Fact is that all props are not created equal, especially plastic ones. The M/S plastic props are well known for shedding blades if they have been multi hole drilled. Don't do it and save yourself and others the possible (probable?) injury. APC stopped making large diameter props because some of their larger props tossed a few blades after being drilled. Maybe they know something the users don't?

Wood props, drilled correctly, do fine. Especially the better props. Carbon props, because of the weave orientation, accept hub drilling without issue when done correctly. But even carbon props are not invincible. You have to inspect them periodically for delamination since they experience flex cycles. Everything carbon fiber that experiences flex and vibration cycles has a limited life span, but they vary depending on the application.

Single bolt or multi bolt? Depends on the person. The engines come as they do and if someone is fixed on using a single bolt they may have to make some adjustments to the engine to accomodate their desire. Is one better than the other? It's a good question and one I'm not prepared to debate.

I have seen some warbird guys go through several props a day. DOnt care how good you are at landing try a landing ME 109 or similar. Glad I dont have warbird fever.

I have seen these props shed blades even when they were NOT multi hole drilled. Especially on 4 stroke engines .... which I suppose is out of the scope for this discussion. It seems to be how strong the power pulses from combusion are that causes the problems. The pulses seem to excite a resonance along the length of the prop blade that can cause distruction. Simple solution ... don't use them!

I had a GP Pitts a long time ago that at 15.5 lbs could cost one a lot of money in props. The lessons in CG location were expensive!

Breaking a prop on landing is one thing but having a blade come off in flight is quite another! It becomes quite the spectator sport. With the heavy plastic props, the remaining blade shakes the crap out of the plane and complete distruction is often the result. If you are lucky, the engine leaves the plane early on and the remainder of the airframe just sort of wollers to the ground in a sort of extremely tail heavy glide. Sorta like an unpowered harrier to the ground!

The APC props that are no longer made are the 3 piece ones....2 replaceable blades in an aluminum center piece...We raced our G62 T6s with these for a few years....The blades were clamped between the front a back parts of the hub..If the prop bolt was not tight the blaces could come out....Never saw one come apart at any of the races....The one piece APC USRA G62 race prop is responsible for speeds of up to 130 mph at 9000 in the air...Never saw one of those break either.....Not sure of the size and pitch, it's 19 x 16 (I think)...
ALL Zenoah engines use a single prop bolt...No problems at over 11,000 rpm on a racing GT 80 using a carbon prop.....19 x 18...

The problem I've had in the past, many many years ago was my wooded prop if the hit a tuff of bluegrass or what ever they'd break, so I always ran plastic.
But that was on zenoah's, quadras an sachs.
Yes I had a few prop strikes but those engines could take it.
I don't know about the DLE's though, I've heard of bending cranks and all that.

Yup, me too! Grass fields, especially the one I fly from, are not very wood prop friendly. I have a couple of gallons through a SYSSA, and even more through a 26cc RCGF and Quadra42, and at least 6-8 broken APC's between them. Maybe more(?). Just the one bent prop bolt to show for "plastic" prop damage. I flew MA for a while (love the scale appearance!), but started running into difficulty balancing them, especially the 18" and larger ones. Tried APC, and didn't have the balancing problem. Very good durability, and I think, performance.

APC and M/A props toss a blade easily when encountering an obstruction. Not so with carbon fiber. Before they let go they transfer A LOT of energy to a firewall.

The larger APC props act much the same as the C/F props but not quite as bad. Ralph, even APC recommends against multi bolt drilling their larger props. I have hundreds of APC props around here and all of them drilled, but it's not recommended.

This is a problem with any large engine running any large prop thats not wood. Wood props are brittle in the rotation diecrtion which if they strike is good thing.
Plastic is too tough.
Even Carbon is really only for very experienced and wealthy pilots

I'll stick to wood for now.

But this all revolves (pun intended) around proper landing. If you can land its not really an issue.

Lots of concerns here. For me, I just don't want to hand start a nylon prop. The wood don't feel good if it kicks, but I have all my fingers.

david

Just one more reason for single bolt prop hubs
You can make a really short engine by cutting the threads off the end of the crank a drilling and tapping for a 3/8-24 grade 8 prop bolt..The prop bolt is plenty strong enough to drill and tap for a 10-32 spinner bolt, just don't ever use a grade 5...
Cranks are hardened on the outside, but if you use a good cobalt drill and good tap it can easily be done....
Tapped cranks are not new, old K&B glow engines and Kalt KG22s had the same setup...Hard to bend a crank when only the taper sticks out of the front bearing...

But if one keeps the nose out of the dirt there is no problem with most any crank....

I got a topflite 18/8 wood prop. I orginally drilled it for the 4bolt hub. I've since changed the prop hub to a single bolt.
Do you think it's OK to run that prop on the single bolt. It bolted right on. didn't have to do any addition drilling.