Jun 21, 2013 at 6:56 am #1304452
Is there any reason why not to get the Arc Blast over the Blast? I do want an internal frame, but somewhat concerned about the "Arc" putting weight away from my back.Jun 21, 2013 at 7:38 am #1998654
I own the Arc Blast and also own a frameless GoLite Jam. For me the Arc Blast carry's the same weight as my Jam but much more comfortably with a direct transfer to the hips. The Arc definitely improves breathability. I haven't noticed any detriment of the Arc in terms of feeling like it was pulling me back or disturbing my center of gravity. Of course I haven't carried more than 20lbs.Jun 21, 2013 at 7:50 am #1998656
I'm at Kennedy Meadows – 1 month and 700 miles into my PCT thru-hike, and I haven't noticed any problems with regards to carrying / weight transfer of the Arc Blast. I've pushed it to about 35 lbs for a 20 mile stretch of two and have noticed a substantial improvement in carrying comfort vs. a fully frameless pack like the Blast or MLD Exodus/Burn. At around 20 lbs you almost don't even know the pack is on. A nice pack that has handled what I've thrown at it very well thus far. Cheers, "Naturally Caffeinated" – NOBO PCT 2013Jun 21, 2013 at 10:24 am #1998687
USA Duane HallParticipant
@hikerduaneLocale: Extreme northern Sierra Nevada
I got to talk to a couple guys at Kennedy Meadows Resort last Friday who were doing the PCT. I was using my Arc for our small group hike into Relief Reservoir and was waiting for the group to "packs Ho!". It did fine, maybe 20 lbs. with some heavier gear and almost three qts. water. I think now instead of getting the -1" torso length, I should have gone with the default as I still have a little weight on my shoulders, but it may be what is needed to keep the pack from moving around.
DuaneJun 21, 2013 at 10:25 am #1998688
@tracedefLocale: Southern California
I have experienced what you are concerned about with Osprey Exos in different flavors, but never had an issue with the arc blast …Jun 21, 2013 at 11:05 am #1998698
Speaking of sizing, my torso measurement, utilizing the standard C7 to iliac crest measurement, is around 16"-17". That means that measuring to the bottom of the desired location of my hipbelt, I will get around 18". In spite of this, Joe recommended I try the "shorter" size (16"-17"). Thoughts?Jun 21, 2013 at 1:39 pm #1998736
I did a bunch of thought and thinking hear about the Arc Blast vs the Arc and weight "perception"
I have a GG Mariposa and an REI Flash 45… I like the Flash 45 WAY better than the Mariposa and I think the actual frame was what really did it for me.
The GG Mariposa just is too.. flimsy and shifts and I can *feel* that I'm wearing something.
Further, my back just didn't evolve to carry weight like that. Keeping it on my hips is paramount.
I still have a few more weeks until I get the Arc Blast though but I'm excited.Jun 21, 2013 at 8:29 pm #1998812
Speaking of the REI Flash 45, do you have the new Flash 45 by any chance? I tried it on at REI the other day, and I liked it except that it didn't seem to have a real frame. It had an aluminum loop at the top, but the rest along the sides was some type of flexible plastic. For me, a real frame is a must, hence my interest in the Arc Blast.
I was asking about the difference between an Arc Blast with a frame and a Blast with a frame, because I had seen someone post something here about the option of a Blast (not Arc) WITH a frame. I suppose with that setup you'd want some sort of foam against your back for comfort, though.Jun 22, 2013 at 1:36 am #1998840
@andyjarmanLocale: Edge of the World
My experience with the Arc Blast is that I stuff the bag so tight the air gap between me and the bag is minimal if there is any (the bag bulges out and closes the gap).
When things get a bit sweaty I loosen off the shoulder straps and let the breeze dry my back off – this can tug on your shoulders a bit so you need to give them a rest and tighten the straps every now and then to bring the pack up to your back again.
If the bag isn't packed evenly from top to bottom (say your quilt and mat are compressed in the bottom, and your food in the top is running low and there's room to spare) you find the carbon struts start to point towards each other at the top, so they bow towards each other not towards your back.
Personally the 'arc' aspect of the struts appears to be more an idea than a reality.
It's a great pack, tough and practical, comfortable and light, and will take much more load than Joe will let on.Jun 22, 2013 at 2:21 am #1998843
"If the bag isn't packed evenly from top to bottom (say your quilt and mat are compressed in the bottom, and your food in the top is running low and there's room to spare) you find the carbon struts start to point towards each other at the top, so they bow towards each other not towards your back. "
I think that was addressed with the latest version where he added a horizontal strut at the top to provide more lateral stability.Jun 22, 2013 at 4:38 am #1998847
I briefly experienced both those problems when I was experimenting with different levels of tension on the Arc stays. If your stays are straightening when the pack is full, it is because they are not under enough tension. If they are twisting towards each other then one of the stays is under more tension than the other. When the adjustment is off (in my case this was caused by screwing with the tension when I first received the pack, thinking it needed to ride closer to my back) then it can take some time and finessing to get it right – especially because you cannot effectively make adjustments with the pack full. You'll need to completely empty it each time you make an adjustment.Jun 22, 2013 at 8:53 am #1998882
Indeed, no pack design can ignore physics and a bowed suspension puts the centre of gravity away from optimum. Won't be a huge issue with light loads but ….Jun 22, 2013 at 9:26 am #1998892
"no pack design can ignore physics and a bowed suspension puts the centre of gravity away from optimum."
Then again, almost all other pack designs also put the centre of gravity away from optimum, either through the use of padding or through the use of a sleeping mat between the back and the pack (or its contents).
It seems to me that the Arc Blast has the advantage that you can adjust it to leave the minimal gap between the back and the pack.Jun 22, 2013 at 10:10 am #1998904
But at least it is closer to the back with no arc. Sheesh.Jun 22, 2013 at 11:38 am #1998919
I remember the very first thread on the Arc Blast, before anyone here actually had one. There was considerable speculation then about center of gravity. But here we are a full year in, with a LOT of reviews and testimonials from actual users, none of which have cited it as an issue…
My experience is that the pack carries decently with the stays straight, but weight transfer and overall comfort increase dramatically when the stays are tensioned properly.Jun 22, 2013 at 12:33 pm #1998928
The weights that most people would use in the Arc would likely not cause an issue (reread my post, ie light loads), but stability will always be compromised with this sort of frame. Think how a contact patch works with a tire.
Damn physics. Stupid biomechanics. I feel your pain.Jun 22, 2013 at 12:45 pm #1998931
– -K.T.- –Participant
Don't crank down too hard and break the adjustment buckle. Oops. Sorry.
True story.Jun 22, 2013 at 1:04 pm #1998932
"But at least it is closer to the back with no arc. Sheesh."
The pack may be, but the centre of gravity isn't necessarily closer, depending on the thickness of the padding or mat in comparison to the depth of the arc. Or are we misunderstanding each other?Jun 24, 2013 at 5:23 pm #1999417
@tracedefLocale: Southern California
@davey Jones: I had about 35 pounds plus in an arc blast when I have to carry 7 or 8 liters of water and didn't have any issues with displacement of load due to the arc …. ymmv …. :)Jul 3, 2013 at 8:38 am #2002035
It is always a comparison perspective. If you had of used a pack without the bow in the frame concurrently (and all things being equal in terms of design apart from the bowed suspension), you would have felt a measurable difference.
I can provide the torque figures to support the physics if you would like.
Don't misconstrue what I am saying. You like the pack and it works for you. That is half the battle. I am only commenting that the bowed suspension will not carry as effectively.Jul 3, 2013 at 9:38 am #2002050
@m-lLocale: W-Never Eat Soggy (W)affles
If the frame is rigid then it's safe to assume that the weight is carried on the frame.
If the contents are pushed back 1-2 inches away from the back like the blast that is simply not enough to throw any balance off. Go ahead and provide your physics.
The only thing I can think of is swing weight. But then again the difference will be minute.
The bottom and top are close to the body, the only difference is a few inches in the center of the pack.Jul 4, 2013 at 10:03 am #2002405
I know I can feel the change in balance when I put a 5 lb platy of water in the front pocket on my packs, about 10" away from my back. But even with 20% of the pack wt located that far from the back, its still OK.
Many packs have a gap to keep the pack off the back. Exos, most heavy packs, internal and external frames. Only lightwt packs hug the back really, and they are the ones that least need to.
I wouldnt worry about it personally.Jul 4, 2013 at 9:49 pm #2002592
"Go ahead and provide your physics. "
I think you mean physics, rather than "your physics.". Sadly, I didn't construct the laws and am only forced to obey them. Just like you.Jul 5, 2013 at 6:05 am #2002639
I just received my new Arc Blast and so far I really like it. I haven't had a chance to fully load it and wear it for awhile yet to see how I want to adjust the frame tension. So I would be interested in Davy's input and others as well to make sure I do it correctly.
One thing I will say is that I like my hip belt lower and around my hips at the iliac crest. That position and the fact that women have a lower center of gravity than men will certainly be factors in how I adjust mine to get the proper weight transfer to the hips. I do notice that Joe and a lot of guys posting on this site tend to wear the pack with the hip belt located higher at their natural waist. This also affects the torso length that you order.Jul 5, 2013 at 5:17 pm #2002831
But the smaller shorter pack is ……lighter
So we learn to wear it higher.
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