Some dangerous props sold from Aliexpress
- Thread starter Crazy Crow
- Start date
That is a very naive statement. China is a source for a huge number of counterfeit and inferior products of all types.
That might be so but illegal branding is an offense even the chinese won’t burn their hands on. They sometimes change the logo or swap letters in the brand name but these are definately genuine yuneec blades.
I just ordered two sets of Maytech MTCP9060H carbon props at the same company that Crazy Crow provided a link to earlier in the post. Frankly, I am disappointed by the balance of these props. Of the 12 props, only 4 could be considered to be balanced. Strangely these were all props which had no trace of sanding on the underside of the blade. Generally, I check the balance on any prop I use but the balance issues on them were far beyond what I would expect from a "Hand Balanced Propeller" as Maytech claims to deliver. In fact, one of the props was actually gauged (see photo). I wrote to MCHobby but no reaction. Maytech themselves have a non-working link to their "Online Feedback" so that is a dead end as well. At the end of the day I am sure I will be able to salvage these props and get them balanced but in all, my expectations have been lowered by the failure of this product to live up to promises made.
That’s really odd. I have 6 of them and all but one came perfectly balanced. It needed a little bit of sanding but it took me less then 5 minutes to get it perfect. Maybe you got a “friday 4:45 batch”
PatR
Premium Pilot
If you guys are sanding on thin, plastic blade props you’re courting disaster. I would expect any that had been sanded ti fail at some point. Balance by adding weight, not subtracting. Use strips of thin, clear packing tape on the convex side of the blade.
Edit: I meant to say concave, not convex.
Edit: I meant to say concave, not convex.
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Pat, please clarify for me... I also add weight... just a touch of CA glue... but everything I have seen on prop balancing says to apply the added weight to the underside of the prop... the concave side. You do not want to disrupt the airflow on the convex top side of the prop, as to not interfere with lift, correct?
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Why would it be bad to sand your props? Even the factory sands their props for balance. Also it’s beter to lose weight than add weight imo.
And if it makes any difference, they are carbon props.
I’ve had the opposite experience with using tape. It came loose during flight causing drag on the prop. This in turn caused irregular behaviour which affected the aircrafts stability.
I used to add tape all the time but switched to sanding after that incident. Never had a problem since. No prop failures or anything
PatR
Premium Pilot
You are correct, my apologies for using the wrong word. Concave is correct.
PatR
Premium Pilot
Crazy Crow:
Can you establish with no doubt H props are carbon? There is no discernible weave and if you break one there is no evidence of carbon fiber. At best H props might consist of a carbon paste which is weak without the cloth as supporting structure. If you’ve done any work with composite laminates you would know it’s strength is in large part obtained from overlapping and bias of the fibers. H props have no fibers.
As true CF props have very few layers of laminate it’s quite easy to sand through a layer and weaken the prop. Sanding works well on thicker wood and stranded fiber props but not so well with structure as thin as ours.
Sure, Chinese prop manufacturers sand props to balance them. They only have to be in one piece when you get them. If they break you’ll buy another from them. Guaranteed repeat business. OTOH, you’ll never receive a sanded prop from quality manufacturers of larger props.
Can you establish with no doubt H props are carbon? There is no discernible weave and if you break one there is no evidence of carbon fiber. At best H props might consist of a carbon paste which is weak without the cloth as supporting structure. If you’ve done any work with composite laminates you would know it’s strength is in large part obtained from overlapping and bias of the fibers. H props have no fibers.
As true CF props have very few layers of laminate it’s quite easy to sand through a layer and weaken the prop. Sanding works well on thicker wood and stranded fiber props but not so well with structure as thin as ours.
Sure, Chinese prop manufacturers sand props to balance them. They only have to be in one piece when you get them. If they break you’ll buy another from them. Guaranteed repeat business. OTOH, you’ll never receive a sanded prop from quality manufacturers of larger props.
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@Crazy Crow
Being a former Helicopter AH-1G mechanic we would never consider removing material from the blades, think about it! If your propeller on your airplane is not balance or if your rim on your car is out of balance what is the appropriate procedure? Add to balance the blade!
If you want to sand off excess weight then go ahead and do so
Once you remove excess amount you need to sand it down using1000 grit or better sand paper or you will have disrupted the airflow. t
Top blade is low pressure and bottom blade is high pressure.
I see now where this conversation has taken a wrong turn. I was talking about the carbon Maytech props.
The original yuneec props are indeed a regular plastic.
But maytech does sand their props to balance them before they are sold. They are what I concider a quality manufacturer.
PatR
Premium Pilot
Not trying to get on your case, but to educate. Maytech, like Sunnysky, Turnigy, and most Chinese manufacturers, is in business to make as much money as they can while expending the least amount of capital possible. The only thing they care about is making money. They are not in the business of customer care.
Most of them fail to provide accurate or well thought out user instructions although they have the ability to do so. In that failure the stage is set for those lacking experience to make mistakes that end up costing the users more money to replace what they broke or caused to break trying to figure things out.
Where props are concerned I hope you’ll at least listen to advice provided by people with many years of RC and full scale aviation experience. They share knowledge of common maintenance principles applicable to both types of aircraft. Of course you can do what you want of feel is best for you, nobody is trying to prevent that. All we are trying to do is give you information that will help you do things better over the long run and eventually save you money.
BTW, if you clean props with alcohol to remove mold release agents before applying tape it tends to stick better and longer.
Most of them fail to provide accurate or well thought out user instructions although they have the ability to do so. In that failure the stage is set for those lacking experience to make mistakes that end up costing the users more money to replace what they broke or caused to break trying to figure things out.
Where props are concerned I hope you’ll at least listen to advice provided by people with many years of RC and full scale aviation experience. They share knowledge of common maintenance principles applicable to both types of aircraft. Of course you can do what you want of feel is best for you, nobody is trying to prevent that. All we are trying to do is give you information that will help you do things better over the long run and eventually save you money.
BTW, if you clean props with alcohol to remove mold release agents before applying tape it tends to stick better and longer.
Thanks for the advice Pat. I will definately take it with me for future purposes.
No disrespect intended for all you seasoned pilots.
PatR
Premium Pilot
A story from when I was repping for a giant scale RC airplane designer/importer.
The manufacturer changed their method of making carbon fiber wing tubes for large planes. They ceased making them to accurate dimensions, electing to sand them down to the right diameter. During flight testing of a new 35% Edge 540 design the carbon fiber wing joiner tube snapped in flight. Destroyed a $4000,00 airplane. $3,500.00 worth of components in the plane were my money. Manufacturer was advised and said they would correct their procedures. Months later while performing a flight demo for a group in WA state with a later 35% Edge 540, after the so called corrections were made, the wing tube snapped during knife edge flight. The break occurred in the center of the wing tube, a location that had the additional support of an outer tube surrounding the wing joiner tube. Destroyed another $4,000.00 airplane where everything was my money. Happened with a few others as well. Pretty much ended the importer/distributor as they picked up a lot of losses from their customers, and nobody wanted to buy planes that would snap the wings off in flight. The actual (Chinese) manufacturer didn’t accept any responsibility at all.
All because they sanded through the carbon weave. The remaining bonding agent will not tolerate a bending load.
The manufacturer changed their method of making carbon fiber wing tubes for large planes. They ceased making them to accurate dimensions, electing to sand them down to the right diameter. During flight testing of a new 35% Edge 540 design the carbon fiber wing joiner tube snapped in flight. Destroyed a $4000,00 airplane. $3,500.00 worth of components in the plane were my money. Manufacturer was advised and said they would correct their procedures. Months later while performing a flight demo for a group in WA state with a later 35% Edge 540, after the so called corrections were made, the wing tube snapped during knife edge flight. The break occurred in the center of the wing tube, a location that had the additional support of an outer tube surrounding the wing joiner tube. Destroyed another $4,000.00 airplane where everything was my money. Happened with a few others as well. Pretty much ended the importer/distributor as they picked up a lot of losses from their customers, and nobody wanted to buy planes that would snap the wings off in flight. The actual (Chinese) manufacturer didn’t accept any responsibility at all.
All because they sanded through the carbon weave. The remaining bonding agent will not tolerate a bending load.
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