What is the best why to repitch a carbon prop. I thought it would go good with Steve pitch gauge question. plus I never repitched one yet thanks. and can it be done at field

Thanks Tom

Hi Steve I repitched my 12/4.25 bolly using hot water. hot coffee my work to

I use sort of a "refined" version of Howard's approach.  Instead of pouring boiling water on the prop I purchased one of those coiled heaters from the household section of a grocery store.  You plug it in and drop it in a tall glass of water and just wait for the water to start boiling.

While waiting I fill another tall glass with water and ice and set it beside the one that's trying to boil.

I then do the same thing Howie does with the Prather gauge and the silver or gold pen and mark each station on each blade (I'm the "fussier" sort to which he referred)starting at three because that's about as close to the hub as you can actually make a change.  Finally, mark each blade with a name so you don't end up wondering which one you've already done and which one(s) you haven't.  I use 1, 2 and 3 but you could name them after your kids or ex-wives; Whatever works for you.

Once the water is boiling start with blade number one (or Alice, etc.) and emerse it a half inch or so beyond the station three point so that it softens beyond the point you're going to tweak.  Start with about a 30 second emersion, taking it out and twisting (at the station desired) hard in the desired direction and then dunking it in the ice water to set the location.  With luck you will have twisted it a bit beyond the desired pitch.  This is good because you then get it to the desired pitch by simply emersing it in the boiling water for a period of time (long if it needs to come back a long ways or short if it's just beyond where you want it).  I've found that by tweaking beyond the desired pitch and then coming back to it by releasing the tension just a bit-with a "touch" of heat-the new pitch seems to stay much longer...sometimes never needing to be repitched.

Once you've got that innermost station pitched, check the next couple of stations because you will have, of course, changed them as well.  Sometimes you'll find that you won't have to do much for the next couple of stations although generally they will need to be slightly tweaked as the pitch angle required as you go out the blade is much less than close in, thus small changes at the root tend to make bigger changes as you go out the blade.

Now you'll discover the superiority of the Fancher vice Rush method!

At each subsequent station you only emerse the blade into the boiling water as far as the station you need to tweak (not pouring boiling water all over your previous hard work!).  As you move out the blade you'll need shorter amounts of time in the hot water to allow the desired repitching because the blade gets thinner and the amount of twisting necessary is dramatically reduced the further out the blade you go.

Do NOT get lazy as you get toward the tip.  If anything, you need to be even more precise in your measurements as the prop efficiency becomes greater as the blades' airspeed for a given RPM increases.  You can make big changes in the way the prop propels the airplane by making tiny tweaks to the outer 1/4 or so of a blade after you've pitched the entire prop to get the plane speed where you want it when the engine is operating at its optimum RPM and mixture settings.  Tweaking the pitch higher at the tips ("wash in" of a quarter inch of additional pitch is a "lot" at the tip) will generally improve line tension and performance above 45 degrees ("wash out", the reverse) and will have only modest affect on lap times.  This is of particular value in airplanes that might be a little "power challenged"--which is not generally an issue with today's powerplants.  I did this sort of thing regularly back in the Tigre .46 days, however.

Oh, yes.  One last thing.  After you've finished with Alice don't forget the other exes!

Ted

In case you like wood props you can do the same re-pitching with either the hot water or heat gun to them. I like to use the heat gun with wood as it doesn't delaminate and its quicker. When I re-pitch I measure at station 7 for 10" props and 8 for 11", select the desired pitch and clamp the gauge bar in place. This insures that you get the same pitch on both blades. When you pitch wood you need to heat near the hub, keep slowly rolling the blade to get heat all around, after about 30 sec stop and let it heat soak in, then heat again for 13 - 20 sec, grab the hub (should use a glove, it gets hot) and twist and hold for 10 sec, release and check the pitch. If you miss it you can try and tweak it while it is still warm. If you go over it takes less force to de-pitch. Different woods and blade thickness need more or less heat time. You get a feel for it. I have not had any change back due to sitting in a hot car or on the field in summer.

Best,    DennisT

I agree with Howard and Ted ,hot water is the safest way to re pitch a carbon prop ,But I have been re pitching speed props from .049 to nelson 65;s and racing  nelson 15's and 36;s and plenty of stunt props with a heat gun for the last 20 years and as far as I know I have never had one de laminate or break 

You shouldn't really do that, heating & tweaking works only with twisting torsionally. If bent, the compression side will buckle. L