NO take it off
QUOTE: completed RV-6A, 150 Lyc with wood prop and a Viscos dampening ring that mounts
to the flywheel. Am replacing wood prop with metal fixed pitch prop.
Has anyone ever used the dampening ring with a metal prop?
(Don't know but it sounds like a bad idea)
Are there benefits or hazards in doing this ?
(Little or no benefit and potential for hazard is high. If the prop was made to operate with
out one than using one is an experiment. Call the maker of the prop (Sensenich) and I am
sure they will tell you not to do this.)
Anyone else tried it?
(I don't know. These devices where popular in the 80's with wood props as a work around to
some of the draw backs of wood props.)
Your comments are welcome
With a metal prop Sensenich, you will not use the "Viscos Disk" you now have with your wood prop.
The main purpose of the disk with a wood prop, are two fold:
One - add weight to the nose for CG;
Two - give the engine more rotational inertia (flywheel) so it would idle better.
The low rotational inertia of light wood props required you to idle at a higher RPM. This was a pain to taxi with a high idle, The disk helped with the flywheel effect. As far as smoothness, wood props are already smooth because of the natural dampening of wood, God's Composite, if you will. I don't think the disk did much there and was more hype in my opinion. They where popular in the 80's, especially since wood props where used more. Now most opt for C/S props or the metal fixed Sensenich prop, made just for the RV. Wood it great but has some drawbacks, as does metal. Everything is a trade-off.
A metal prop will provide the rotational inertia and weight. Adding any extra mass on the end of the crank is counter productive and could be a hazard. I don't know for sure but call Sensenich and ask, they will know for sure. My opinion is it's a waste at best. Also, far as tensional dampening, if it was necessary and useful Sensenich or Lycoming would have done it long ago.
Wood props are as smooth as you will find. They have many advantages but there are drawbacks. Going metal is a good move. I assume Sensenich. Wood props require more maintenance and are rain restricted to mention a few.
Metal prop will be a little faster (due to thinner airfoil) and maintenance free. Metal, however does not dampen like wood and will be more "buzzy", but if well balanced (dynamically), blades track and are pitched evenly, metal props are plenty smooth.
Wood props have there own natural dampening quality that makes the pilot "feel" it as smoother than metal. Metal has harmonic frequency that can be excited by the engine's own crank-shaft natural frequency?s and power pulse at some RPM's. When you get flying you may find just a 50-100 rpm differnce will make it much smoother.
Sensenich has tested this and determined the prop / engine is OK at all RPM's. It is also made for RV's and there flight speeds.
Bottom line you do NOT need the little gizmo with a metal prop and it will do nothing but add more weight. Also some of these "disks" have cracked, especially if you do aerobatics.
EXPERIMENTING by using "The Disk" and could shift natural frequencies to be counter to safe operations, unless you do definitive flight tests.
If you do any Mod you should call the manufacture and check, including a dampening disk.
Take all the wood prop stuff off and sell it on eBay. Put on the New Sensenich prop, all new matching hardware and new spinner as needed. Enjoy the speed, safety and low maintenance.
George
(I don't work for Sensenich and am a diehard c/s Hartzell guy, however clearly Sensenich has a great product for the RV's and made their product just for us. I think it is a deal and the performance is outstanding for a fixed prop. I still like c/s better, but that comes at a premium of cost. Also not to offend any wood prop flyers. Wood props are as light, cheap and nice looking as you will find. They give good performance and are safe if operated and maintained as intended. However they are made of made natural materials, subject to normal variations and defects. The big draw back is the bolts need to be re-torqued on a routine schedule.)