Propeller Bending
Ashely Wolfgram
The main elements of the sculpture were three sheets of curved metal, linked together to form a static work resting under its own weight, making it what Calder called a "stabile", as opposed to his famous "mobile" sculptures. It was reminiscent of a ship's propeller. Like many of Calder's public sculptures, it was painted red. The large work, 25 feet (7.6 m) high, was first installed near the entrance to WTC1 (the North Tower). It was moved in 1970 to a plaza in front of 7 World Trade Center, on the northeast corner of the Austin J. Tobin Plaza by Vesey Street and Church Street.
The work was severely damaged in 2001 in the aftermath of the September 11 attacks, crushed under thousands of tons of rubble when 7 World Trade Center collapsed[broken anchor]. About 40 percent of the sculpture was recovered from the debris in the following months. With not enough of the original remaining for a restoration, the recovered elements were stored by the Calder Foundation. Today, a portion of the sculpture can be found at the National September 11 Memorial & Museum.
My question is about techniques to bend a model propeller without melting it. I'm trying my hand a building a ditched 1/72 Corsair but don't know how I can bend the props due to the water impact. Any suggestions?
Your best bet is boiling water. The temperature is controlled and won't melt the plastic, but will soften it. Mark the prop where you want the bend to be and get some kind of mandrel to bend the blade around so as to get a realistic radius of bend. A dowel works well for this. Get a good pair of gloves and dip each blade in the pot until it softens, pull it out and bend it around the mandrel. Repeat this until you have bent the number of bades you want to. Get some good crash references, the blades don't always bend straight back, and often there will be one that doesn't bend at all. Have fun!
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I was leaving the dock today and slow through a shallow spot and must have hit a rock. One of the tips is bent a little bit, not bad and no nicks. Can I just take a small vice grip pliers and try to bend it back to match the other tips? How critical is it that it's perfect?
I guess it depends on how important your next trip is and if you have a spare. If you can, I would bend it and see how it works. I know props can be very finicky and even the smallest dings or bends not even noticeable to the eye can cause problems.
I have fixed small damage by using a body hammer and a vice. I used the vise to get the correct radius. It is now my backup but I used it after the repair and couldn't tell a difference between the old one I fixed and the new one.
Only one shop in my area and I have to drive mid state to get it done. 30+ years of experience is reassuring especially on the NiBrAl props. I rolled 2 tips on a submerged log 2 years ago and it was $230.00 to straighten and balance. It was cheaper than a new 1235, but it still hurts to sit. If you are going to get it done you better go screaming in now. Boating and fishing season will back a place up for months before you see your prop! Get it fixed before you start to see the adverse second and third order effects, vibration, cutlass bearing or shaft seal failure.
I got mine done for $100-$140, somewhere in there. Looked brand new when I got it back. It's also my back up now because I was upgrading anyway At certain rpm's I would vibrate slightly or feel a sort of cavitation effect. This forum led me to believe it was my prop. When I looked at it, I noticed some very small dings but when we actually took the prop off, and measured it against the other blades, it was obvious that it was out of pitch. Running around on a bad prop is equivalent to a bad tire on the car. If it's going low, you might be able to plug it and make it a little while, might work out okay for a good while, if it's flat or really low, and you ride around too long, it's gonna cause a lot more damage. I'm in Austin and used Nettles Props. Quick turnaround time during mid season and they had the 1235 I needed in stock already. They will even do the prop swap out right there if you happen to have your boat in tow. Just some FYI for the central Texas guys and gals out there.
Set the jaws an the wrench so it just sips onto the prop. All are now backups now but some stayed in use for more then a year. No only one was mine the others are people we ski with. All the one's I have done are on ski boats running 34 & 36 mph, so in the 5,000 rpm range.
If you don't already have a spare/alternate size prop ask the shop you end up taking the damaged prop to if they have a "refurb" (repaired) prop for sale. It's amazing how many people show up to a prop repair shop, find out it's going to take more than a week to get their prop back, and just buy a new one and leave the damaged unit there. Last time I was at a repair shop the "repaired/for sale" shelf had 20+ propellers ready to go.
My local prop shop (Northern Ca.) wanted $300 to fix a prop. I sent it to www.Propmd.com (Minnesota) and they fixed it for $160 which included shipping both ways. It was worth it for me to get a second opinion.
It is nice having them less than 10 miles away, with quick turn around. They did a lot of aluminum i/o props for me as well as my first messed up acme. Hoping to not give them as much business in the future.
For anyone looking for a great deal, Ben at PropMD just sold me a new 1235 for $530 (less than Wakemakers more than Bakes) and threw in a free refurbishment of the 537 I bent. Great deal I'm very happy.
Hi folks,
One of those irritating little questions has come up. When an aircraft's props hit the ground (or water) which way will they bend? We expect to see them bent aft, but apparently when hitting water at speed, it's common for them to be bent forward. Anyone got chapter & verse on this?
Cheers
Just a guess but with a propellor blade entering water the blades are still working in the same way but water being far denser exerts a greater pressure on the blade bending it in the direction of least pressure on the blade i.e top surface ala aerofoil.
May be one of those questions without a simple answer
Some of the variables might be....
Airspeed,Groundspeed(or waterspeed?),prop RPM(if any)
Angle of entry of prop or aircraft.
Prop RPM would also cover power on or power off entry.
Marius Eriksen of 332 Squadron during WW2 took off from North Weald once and retracted his undercarriage a bit too fast...the props barely touched the ground and they were bent forward, not backwards. They didnt see it until he came back from his sortie.
James, I photographed this the other week at Wigram. Though it wasn't signposted and I didn't ask, I am certain thi is the engine from a crashed Hudson that was pulled from the Tasman Sea last year. The aircraft struck the water and disappeared.
Sorry to go off-topic but having flown up front in Consul G-AIKR during its time with the Rapid Flying Group at Baginton UK, I was delighted to see it's still safe as depicted in the background to your shot. I became reacquainted with it only a few years ago when I photographed it in store at Ottawa. I've looked at the Wigram link from your own excellent website but what progress can you report on its restoration to Oxford status - the Wigram site only illustrates the wing centre-section?
The blades are still working when they touch the water, unless they are feathered, simply put they are pulling at the air in flight and continue to do so as they enter the water,it being denser than air, exerts a greater force on the blade than it can take resulting in the bend; the ground on the other hand isn't just dense its plain hard! the blade reaches its critical point almost instantly, it has no chance to pull or claw at the ground and is forced back ,although marshy land by definition falls somewhere between the two ,and the wetter it is the more likely that the blade will get purchase on contact and bend forward. (of course I could be wrong!)
it probably depends on when the prop itself stops spinning..
If the prop hits the ground while the plane is advancing they will surely bend backwards, but if the plane impacts a surface like water, which of course is less dense than ground and allows the props to spin even when the plane finally comes to a stop, it is plausible that they may bend forward. But I guess this is only possible in water..Unless u r taxiing backwards (pilatus anyone?) and yr landing gears collapse :rolleyes:
Dave Burke and Stuart gowans, you are both correct. If the engine is producing power when the propeller comes in contact with less resisting media such as water or boggy terrain, they tend to pull the tips forward in relation to the propeller arc. Hard terrain tends to bend the blades rearward due to the stopping of the propeller, then dragging the blades.
Tony King sent me this photo of a Hastings TG52? I reproduce it with his kind permission The Hastings was flying from Cyprus very low over the Med, there was a glassy sea, the pilot decided to see how low he could go, he got more than he bargained for.
The Sunderlands we worked on received a lot of prop damage from water, I was a young erk at the time aged 18 and one of those jobs was to 'feather file' the chips out of the tips of the leading edges of the blades
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