Dave G

  • Slideshow

Prop Strike

By Dave G

Pics show the extent of damage to my Kiev prop

Comments

  • Dave G

    We put a 19 meter Northwing mpulse on my BB Manta 503 and were about to do some taxiing tests when the engine was revved to start movement........the prop flexed and the tips contacted the keel of the wing. We realize now that there needs to be more clearance between the prop and the keel so we will probably cut some of the keel off to facilitate.

    Does anyone here have any experience with or knowledge of how to repair a prop like this?

    The leading edge of the prop is brass and the rest is fibreglass.

    Dave G

  • Wile E Scott

    Hate to tell you this now but... My GTE has a 19M NW MPulse and I have about 1.5in cut from my keel tube to compensate for this issue. I'm told it's common to have to do this. That really sucks..... Sorry to see it.

  • Dave G

    Hey Wile, I may have to cut about 3-4 inches in total off because that Kiev prop flexes so much.

    What kind of prop are you using? does it also flex quite a bit?

  • Ken

    Pretty sure Henry had similar clearance issues when he mounted a Northwing Mustang 3 on his Tanarg, Strange thing is that my Mustang 2 fits on mine just fine. Definitely a must check though, that must have made a scary sound!

  • cburg

    Usually a quartering tailwind on the ground when you are trying to get it moving is the worst case (besides a completely wacked out landing).  A lot depends on how much slop there is in your hang block.

    I do a full twist/pushdown test with the wing/sail and have an assistant flex the prop forward to check for clearance.  This will eat up a lot of clearance you thought you had.

    I’ve had a prop flex and strike a BRS canister once on a Cosmos after flying it that way for a long time.  I had recently switched to a Chronos 12.9 wing, which must have caused a little more flex than the prior wings I flew on it for years.

     

  • jeff trike

    super glue, baking soda and sandpaper

  • Wile E Scott

    I have an Arplast Helix and no they don't flex very much. I'm always concerned about it in the back of my mind though. Not much room for error.

  • cburg

    If it chops the rear wires in flight you're probably toast unless you get a quick clean BRS deployment.  Rear wires have failed and killed the pilot.

  • GeoBlaze
    Here are some suggestions... you know the official answer is to check with the prop manufacturer for what they recommend.
     
    Keep in mind that once fixed the prop balance may be effected so you may want/need to do a dynamic prop balance.
     
    I've used Devcon Plastic Welder (5 Minute Epoxy) and this works well:
     
    Devcon Plastic Welder
     
    Retain as much of the original prop material in the damaged area including the brass on the leading edge.  Shape the brass back into its original position by carefully squeezing with small pliers.  Apply the Devcon Plastic Welder pushing it into all of the gaps.  Duct tape can be used to shape the epoxy close to the desired blade shape before it sets.  Just gently wrap the tape around the leading edge to enclose the epoxy.  This will set quickly but should provide amply time.  Allow this to fully cure at least 24 hours before shaping the epoxy.  Once cured, a dremel tool with a small cylinder sander can be used to remove excess epoxy and shape the edge.  A small file and fine sand paper can be used to finish the surface.  Sharpie permanent ink markers work well for touching up the color to match the prop.  The metallic gold color matches the leading edge brass well. 
  • Wile E Scott

    Everything Geoblaze says and then a prop balance check to make sure its really ready for prime time.

  • XC Triker

    Yeah, I agree with what Geo says.  This is more than a baking soda/super glue nick-- though that does work great and easily sandable-- I keep some in a baggie for field repairs on XC.  Make sure to work the epoxy deep into/between the fibers.  Tape will help make a dam for the glue on the curve while it sets, then you can shape it when hard. If you have to add more epoxy, rough up the epoxy surface very well for adhesion (little cuts work well for the glue to lock into).

  • Dave G

    Thank you all for your comments and tips on prop repair.

    I now have a good idea of what I need to do......however I will wait to hear from the manufactures rep to get their input before proceeding.I would also be happy if I could source a retail outlet in Canada that sells Devcon plastic weld. Ill keep looking and thank you again everyone.

  • Ken

    Got ace hardware?

  • Dave G

    Thanks Ken, we have an Ace Hardware store in a neighboring town about 20 miles from me......Ill check them out to see if they have any.

  • ULtrikepilot

    Dave, I agree with earlier comments about use of epoxy on that prop tip.  However, I have had great success with JB Weld which is a 2 part epoxy that I think is available at most Home Depots or Lowes.  I have never used the Devcon plastic weld but sounds like it would do the job as well.  Good luck!

  • John Fetz

    John Fetz here in Lake Havasu Az, I have been repairing props for a number of years, the Correct way of doing it is to use Epoxy and Carbon Fiber ,  on wood props I use a urathane filler and Fiberglass covering of the whole blade for major breaks

    https://groups.yahoo.com/neo/groups/PropellerRepair/info

  • Dave G

    Thanks John.....I have picked up some two part epoxy from a local automotive parts dealer.......it is the Canadian equivalent to Devcon plastic welder .....Its called Permatex Plastic Weld. It is tested to Temperature range -60°F to 250°F (-51°C to 121°C). Permanent strength up to 3500 PSI.

    What hints would a fellow of your experience have for a rookie like me?........I can send you more pics of the prop if you like.

    Im thinking that the brass leading edge of the prop got pretty messed up on the tip and it may be too hard to reform it to its original shape........would it be a sin if I were to cut it off at a point where it is still intact on the leading edge?

    Probably would have to cut off the same amount from each tip huh?.

    Let me know what you think. Thanks John

    Dave G

  • John Fetz

    Dave what you day will PROBABLY WORK, but thats not the way I do it give me a call 928 680 4994 or give me a phone # I have free calls to canada, (skype)

    John Fetz

  • YFT

    Hi Dave G, I am a level 2 maintenance person. You will have about 4 seconds to shut your engine down in flight when your epoxy gives way. If you are lucky the blade will hold together, if not you will be in a world of hurt. GET A NEW BLADE. As XC what I did to the P&M GTS450 at HAY. It is not worth the risk. Think about your RISK assessment before you use a glue.

    YFT

  • acetrikesusa

    I would have to echo YFT's comment. 3 years ago I watched a "repaired" 3 blade prop disintegrate on a kitfox 4 (fixed wing) that was warming up on the ramp. It got ugly quickly... A piece nearly hit a guy that was standing 40' away and the resultant vibration (if you want to call it that, more like gyration...) immediately tore one of the motor mounts cleanly from the firewall. Thankfully the guy hit the mags quickly and saved the plane from real damage. Needless to say I think he had to change his underwear after that one! Bottom line is how much is your life worth? I have never witnessed it personally but im sure there are plenty of stories of trike wings getting mangled from a prop disintegrating in flight. Whatever route you choose, I hope you get back in the air soon.

    AC

  • John Fetz

    I have been repairing Ultralight Propellers since 2005, I do about 3 per week, NONE have failed,  they will break if they hit something or if something hits them (exhaust springs, rocks etc.)

    There is a lot involved in what material goes into the rebuild, carbon fiber ,EPOXY and preparation of the repair sight.

    John Fetz

    928 680 4994

     

  • XC Triker

    Lots of experience here.  Part of the info that YFT was referring to is HERE in CSI.  Small nicks can (and should in my opinion) be repaired.  Superglue & baking soda works great for those.  Bigger (small) ones might require epoxy, bigger ones still should have the factory / pro take a look at them for repair (I've seen very nice factory repairs by Bolly).  Even larger prop injuries should be grounds for throwing them out entirely and replacing.  I've never come near to doing a prop repair that needed fibers embedded into the matrix-  though I've done that type of repair on non-critical generic fiberglass pieces and could see how it would definitely help--  if mine was approaching that, I'd have a pro take a look at it and err heavily on the side of caution as to replacing it entirely.

    As noted, a disintegrating prop can cause a world of destruction and tear the engine completely out of the aircraft.  I believe the trike referenced above in CSI crashed-- though not all the details are there in that report-- is it on here somewhere else-- seems like I remember that ...

    I don't know that there have been plenty of trikes props disintegrating though-- it seems to be a very rare experience-- possibly because most people are very careful about their props.  As they say though, one is all it takes--  you shouldn't be the one.

    Good points from everyone above.

     

    Here's an interesting thing I noted in Oz, that I forgot to add to my list of different things I experienced there:    In the US, as far as I know we always insist on pushing trikes only from the prop hub.  In Oz, they regularly push trikes (and have for years and years, day in & out) by the prop TIPS, using the torque of the tips to steer the trike as they push it forward !!!   :0     --  I would've been freaked out if anyone in the US tried this on my trike--  but nearly everyone in Oz does it that way and there are ?1000's? of hours on the props handled that way.

    Conversely, most people I know in the US often leave their brakes on while the trike is parked.  I leave my brakes on and locked in the hangar (in case a weird gust comes under the door and tries to blow the trike into the wall).  In Oz, they only leave the brakes on briefly (maybe an hour if it is on the ramp at a rest stop)-- otherwise they leave the brakes off due to concerns that the constant pressure will damage the hydraulic seals and cause leaking.

    In both cases, thousands of hours of experience say that that is not necessarily the case. ...

     

    Lots to learn from each other the world over.  So grateful to have sites like this where we can share and enhance our collective experience.

    Blueskies Dave !!!

  • madmik

    Dave...

    For what my 2 cents is worth, I'll echo the sentiments of (safe) reason from acetrikesusa and YFT. During rotation, centrifugal and longitudinal pressure forces are focused outward towards prop tip. The prop tip repair will therefore always be trying to separate from the prop. A small or minor repair along the length is fine provided the entire prop (incl the other blades) are equally balanced prior to refitting. Best left to the prop pro's. Saving a few dollars sometimes won't save our lives...

  • ULtrikepilot

    OK, when I responded earlier I only saw the one broad side picture and amount of tip damage did not appear major.  But now I saw the other 2 pics and it appears a bit more major than what I thought earlier.  I must admit that dings and divots I have repaired with epoxy have been quite minor and on leading edge down away from tip.  This level of damage should be assessed by manufacturer or a professional prop repair person.  I still believe it is repairable.  Epoxy is incredibly strong.  Quite likely the key for such a tip repair is to have receiving surface sufficiently roughed up and scored so that new epoxy has plenty of nooks and cranies to grap on to.  Unless you see one or more cracks propagating down the blade the integrity of core portion of blade is likely sound.  On the other hand, a brand new blade might give the kind of piece of mind you need.  Although I have no first hand experience with John Fetz's repairs, I have heard from plenty of folks that have and they all seem to be very pleased with his work.

  • white eagle

    hey Dave  sorry to see the prop strike   but wow truly some great support from all trikes members. i think its hard to tell from pictures how bad it is so all advice hear i think is great. even though some advice is different its just great that all these people took the time to politely way in. (proof that all trikes is accomplishing it desired purpose) super glue and baking soda is a great fix for small strikes but iam not sure where id draw the line and maybe just replace it?may some of the more knowledgeable members here will add some more about when you should seriously start thinking about a new blade.looking forward to seeing you in polsen montana. i just talked to nathan and it looks like were all a go and the airport will have some grass field available for us to camp and park.