Yet another Full-Comp, Full-Skip Question

[GitWood]

I know that this has been discussed adnausium, but I have a question/theory to which I have not found the answer. Even if one were to leave available torque out of the equation and assume that it were unlimited, it seems that at some point in increasing bar length, full skip chain would cut faster than full comp.

At least in my simple mind, this would occur when the length of cut was sufficient to create enough chips to start holding the chain out of the cut and acting as a wood-chip depth guage. Switching from full-comp to full-skip at that point would allow greater chip clearance and let the cutters again cut down to the chain's depth gages. This would also reduce drag, but I guess that wouldn't matter with our unlimited torque saw.

I'm not sure if the question will make sense but if so, it brings me to two questions.

1. Does this theory hold water at all?

2. If so, any Ideas at what bar length full skip would be superior with the all-powerful saw? I realize that this would vary with chain type, raker depth, etc. Just looking for a general opinion from the experts.

Thanks,
Mark

 

[fishhuntcutwood]

That's absolutely correct. Too many chips in the cut causes problems. There's a couple of threads on here in which we talk about it. There's actually a gem of a full skip thread up in the Trading post of all places.

I think most will agree that bars 28"+ call for full skip.

 

[elmnut]

skip will cut faster than comp due to friction, unless sharpened wrong.

 

[ShoerFast]

I know that this has been discussed adnausium, but I have a question/theory to which I have not found the answer. Even if one were to leave available torque out of the equation and assume that it were unlimited, it seems that at some point in increasing bar length, full skip chain would cut faster that full comp.

At least in my simple mind, this would occur when the length of cut was sufficient to create enough chips to start holding the chain out of the cut and acting as a wood-chip depth guage. Switching from full-comp to full-skip at that point would allow greater chip clearance and let the cutters again cut down to the chain's depth gages. This would also reduce drag, but I guess that wouldn't matter with our unlimited torque saw.

I'm not sure if the question will make sense but if so, it brings me to two questions.

1. Does this theory hold water at all?

2. If so, any Ideas at what bar length full skip would be superior with the all-powerful saw? I realize that this would vary with chain type, raker depth, etc. Just looking for a general opinion from the experts.

Thanks,
Mark

Mark

To me, the theory seems flawed, as I see no proof that full skip removes any more chips then full comp chain due to extra room, as it's my contention that it is the effects of the cutter moving through the cut that removes majority or the chips, the math is a wash,,,,, half the cutters, half the chips - half the chip removal ability.

The idea is cool that the chips could set the depth gauge , but there would be more drag in the real world, depth gauges ride fairly easily in the kreft, sort of like a non cutting coulter on a earth plow, it would be easy visualize the chips under the depth gauge lifting or tilting the cutter out of the cut occasionally, it is stihl the best design out available.

Here is another something for a think, as long as we found the unlimited TQ saw, what cuts faster, full comp chain with .015 DG's or full skip with .030 DG's?

 

[GitWood]

Mark

To me, the theory seems flawed, as I see no proof that full skip removes any more chips then full comp chain due to extra room, as it's my contention that it is the effects of the cutter moving through the cut that removes majority or the chips, the math is a wash,,,,, half the cutters, half the chips - half the chip removal ability.

The idea is cool that the chips could set the depth gauge , but there would be more drag in the real world, depth gauges ride fairly easily in the kreft, sort of like a non cutting coulter on a earth plow, it would be easy visualize the chips under the depth gauge lifting or tilting the cutter out of the cut occasionally, it is stihl the best design out available.

Here is another something for a think, as long as we found the unlimited TQ saw, what cuts faster, full comp chain with .015 DG's or full skip with .030 DG's?

The idea that more cutters will drag out more chips is interesting. I need to mull that one over a little.

Regarding the chips limiting the depth, I didn't mean that they simply get under the depth guages, but that they build up under the entire chain body and act as a depth guage.

In my imaginary world (at least this evening) the full skip .030 DGs wins hands down against the full Comp .015 DGs with any bar length if you consider that full skip has 2 cutters for each 3 on full comp.

Thanks for the food for thought.

 

[THALL10326]

I know that this has been discussed adnausium, but I have a question/theory to which I have not found the answer. Even if one were to leave available torque out of the equation and assume that it were unlimited, it seems that at some point in increasing bar length, full skip chain would cut faster than full comp.

At least in my simple mind, this would occur when the length of cut was sufficient to create enough chips to start holding the chain out of the cut and acting as a wood-chip depth guage. Switching from full-comp to full-skip at that point would allow greater chip clearance and let the cutters again cut down to the chain's depth gages. This would also reduce drag, but I guess that wouldn't matter with our unlimited torque saw.

I'm not sure if the question will make sense but if so, it brings me to two questions.

1. Does this theory hold water at all?

2. If so, any Ideas at what bar length full skip would be superior with the all-powerful saw? I realize that this would vary with chain type, raker depth, etc. Just looking for a general opinion from the experts.

Thanks,
Mark

Good post there. The last time I was down at Stihl they explained those two chains in the simplest form. They said the all the cutters on a regular 33rs chain on a high speed powerful saw is not cutting. Some of the cutters are merely going along for the ride and clearing out the chips, which a slower less powerfull saw needs. On a high powered saw with long bars a full skip chain they said is indeed better. They said the chain is lighter due to less cutters, all the cutters are cutting in the cut and pulling out chips. They did make note it takes more power to run a full skip chain because each and every cutter is cutting and clearing out the chips, no helper cutters for clearing the cut.

 

[fishhuntcutwood]

half the cutters, half the chips - half the chip removal ability.

True, but your bar is twice as long. And it's not as much about removing the chips, as having room for all of them riding the chain in the cut. More chips will be produced in a 36" cut than there would be in a 16" cut, regardless of how many cutters you have. You need to have room for those chips to ride on the way out. Too many chips can actually clog a chain, and bog the saw, or worse come to worse, kick the saw out of the cut. This is the reason for reaming on deeper cuts. You've got to keep your cuts clear. Full skip helps here. It's really the only way to go on long bars. I run it over 24".

 

[Lakeside53]

Not sure about the chip clearnace issues..

If you have the HP (for a given bar length) to keep the chain speed up, full comp outcuts skip.

It's all about chain speed and cutters/second... More cutters and more speed cuts faster. Skip just reduces the cutter load by 1/3 and allows faster chain when the saw is running out of HP.

Try a 32 inch full comp and then a full skip on say a 440 cutting 8 inch wood. The full comp will be faster... Then try it on say 30 inch wood - the skip will be faster...

On my 066 I run full comp on my 28, full skip on my 32 and above. The 66 work great with full comp on a 32, but too many damn cutters to sharpen!

 

[rbtree]

Good post, Andy...sounds about right. To know for sure, we should ask Rotax Robert, Tommy Fales, Dennis Cahoon, or any west coast saw racer that gets to cut in 24 inch and larger wood now and then. Naturally they all use custom race chain, but I'm sure the analogy would apply.
Check out my latest escapades...routine tree and crane work, but hey, it's all fun, and produces some nice greenbacks.
http://www.arboristsite.com/showthread.php?p=491781&posted=1#post491781

 

[SawTroll]

Mark

To me, the theory seems flawed, as I see no proof that full skip removes any more chips then full comp chain due to extra room, as it's my contention that it is the effects of the cutter moving through the cut that removes majority or the chips, the math is a wash,,,,, half the cutters, half the chips - half the chip removal ability. ....

I think the theory hold some water; Full skip have more room between the cutters, so it can carry more chips without it interfearing with the cutting action.

Full skip has about 66% the cutters as full comp, and semi-skip about 75%.
The exact numbers will depend on the DL count.

 

[John Ellison]

On 28 to 36" bars I like semi-skip. Smoother cutting.

 

[Ed*L]

IMHO it depends on the wood you are cutting. The west coast guys cutting big pine & fir use it. It works better in soft wood.
For the midwest (hardwood) folks I see no advantage to it unless it's on a really long bar.
I use full skip on my 60" bar & 084 combo. The 36" bar uses full comp. I've run 066 & 395xp saws with 36" bars with full comp. that had no trouble cutting thru hardwood.
It's something that nees to be determined by bar length & saw torque more than anything else.

Ed

 

[Big Woody]

Don't tell my Makita DCS 9000 that it's slow with a 36" full comp round chisel chain. It would be a very unpleasant experience. On the other hand my 3120 with the 60" skip generated quite a pile of chips in a hurry on a 48" cherry log some time back.

Quite a few self contradictory comments in the posts above. Its like those comics/puzzles where you find the hidden images. Once you get good they jump out at you.

 

[ShoerFast]

It's all good!

As I see it, the majority of the chip removal takes place buy the cutter action in the wood, and the scoup of the inside of the cutter.

Picture an earth plow with all the bottoms plowing in the same ferrow, with each plow botton cutting a little deeper, but with each mow-board taking a little more dirt forward with each cut.

I'm not fallowing how having more distance between the plow bottoms, or saw-chain cutters would remove more chips, as it wouldent push chips past the DG, as it seems?