Your opinion on foam core limbs

[Troy Breeding]

Kirk,

I had heard foam was quite a bit lighter in weight which will make it faster in recovery.

Alot of people talk about increasing speed for flatter trijectory. Until they shoot arrows in the weight I use they really have no idea what increasing speed can do for them.

My normal hunting weight bow is around 60#. When your shooting 800-900gr arrows with high FOC every FPS I can increase my arrow helps me more than the person shooting normal weight arrows.

Thanks for the input.

Troy

[KentuckyTJ]

I have a Morrison Cheyenne and a Zipper SXT with foam core limbs. I have had two other sets of wood limbs (boo and maple) for the Cheyenne and the foam cores are a no brainer for me. If a bowyer offers them that's my choice every time.

Going between wood cores and foam cores on the same bow is the true test of the limb material and on the Morrison they are much smoother, some faster with less recoil. Of course design makes a difference as well but if I were your and had your talents I would definitely give them a try.

[Cherokee Scout]

Hi Troy- I had a set of the most popular (and expensive) foam core limbs. I shot them thru the chrono as I do most of my bows. I found very little difference in performance. They were smooth but nothing special. Most will say they are quieter than other limbs, but I thought mine were not as quiet as other limbs. So, my opinion was they were ok, but I was disappointed in them. I know they have some new "nano" foam and carbon materials now that they say make a more stable limb, so I would consider trying those.

[Crash]

I sent a message to Gregg Coffey about getting the foam, carbon and mystery core on the Shrew I have on order.  He said that if I shot lighter arrows, I would see an improvement in speed, but that if I shot arrows in the 11 to 12 gpp range, it wouldn't be much of an improvement in the speed department.  I am undecided as I do shoot very heavy arrows and don't know if it's worth the extra money over the bamboo.

[JParanee]

Bamboo was my fav core material till I tried a pair of foam core limbs

I am very pleased with the carbon and foam core limbs and that would be my first choice

[**DONOTDELETE**]

Originally posted by Troy Breeding:
Kirk,

I had heard foam was quite a bit lighter in weight which will make it faster in recovery.

Alot of people talk about increasing speed for flatter trijectory. Until they shoot arrows in the weight I use they really have no idea what increasing speed can do for them.

My normal hunting weight bow is around 60#. When your shooting 800-900gr arrows with high FOC every FPS I can increase my arrow helps me more than the person shooting normal weight arrows.

Thanks for the input.

Troy

Foam is a higher performance material. High performance means more than just having faster arrows and flatter trajectory too.

With less mass weight in the limb there is less weight in the limb tips. These limb tips need to stop dead at the end of the power stroke to transfer the stored energy into the arrow shaft.

When you can accomplish this, you not only get a faster arrow, you get less vibration.

Can this be accomplished with fiberglass backing with bamboo or maple cores?..... Absolutely. Can it be accomplished by self bowyer's using Osage?  You bet it can.

But the higher performance materials we are using today allows us to push performance to a different level. It may seem like we are just splitting hairs to some folks, but advancements are made one step at a time, and all those hairs we are splitting pile up faster than you think.

If better over all performance means a guy with a shoulder injury can get a lower poundage bow that is smooth as silk that is hitting just as hard, and shooting just as flat as a bow 5 pounds heavier..... That makes all this hair splitting worth while to me.   Kirk

[Ragnarok Forge]

Kirk have you tested your bows for speed increases between the carbon foam and standard cores?    Tricia and I are looking at trips to Africa and Oz in the next few years.  I want to sit down and talk about some bows that will shoot heavier arrows at the same speed we are getting now.

[**DONOTDELETE**]

For some reason folks think a limb with less mass in the outer limb does not cast a heavy arrow as well as it does light weight shafts..... it's just not true.

Now you can definitely get higher efficiency ratings out of the bow using heavier shafts with more mass in the outer limbs, but it's the arrow shafts efficiency that matters, not the bows efficiency.

Example: take a 50 pound HH bow or an English long bow with deep core straight unbraced profile.
using 9 gpp at a 6" brace height the guy standing next to you while you are shooting will feel that limb shock. you can literally watch the limbs oscillate. the best speed you are going to see is mid 170's to low 180's at 9gpp.

Now take that same bow at 70-80 pounds or higher in draw weight and you'll have a whole different bow. This is because the string tension at brace is high enough to stop the mass in the limbs cleaner and transfer the stored energy to the shaft.


A high performance bow with good r/d stores WAY more energy that a straight long bow does. a 50 pound bow shooting 9 grains per pound at 200 FPS should have no problem shooting 12 grains per pound in the upper 180's to low 190's.

10 to 11 GPP is the optimum hunting weight arrow IMO. If you've got a decent design going for you you can get the same results out of a 60 pound R/D long bow as you do a 65-70 pound straight long bow using the same arrows with fiberglass and bamboo cores. You start using carbon and foam the spread gets wider and the performance gets even higher.

yes i do have tests and high speed video that back up my opinions. guys that say that speed doesn't matter are just not looking at the whole picture. high performance means more power with less draw weight. Kirk

[Sixby]

I know I can hunt elk with a 50 , 55 lb bow now and feel just as confident as I did a couple of years ago with a 65 70 lb bow. Much of this is due to the lightness and strength of the materials being used. You use much less energy moving the limbs and you are transferring that energy into moving the mass of the arrow. Some of this is due to strength but I suspect that the larger part is simply weight of materials. A pair of carbon foam core limbs are like feathers compared to glass wood core limbs.

God bless you all, Steve

[FerretWYO]

I have a foam core pronghorn and have compared it to similar bows of comparable weight. There is most certinaly a differance in the way the foam draws and shoots. Very smooth and quite fast.

[Troy Breeding]

Kirk,

I'm glad to hear you say all those things. I've been mulling this over since the foam core material really took off. I understand all the stuff about different efficiency in different style bows. Dr Ashby pointed that out in some of his test. He found that his 67# ACS would shoot the same arrow the same speed as his 84# Hill.

Makes more since to use the lighter bow.

Troy

[ozzyshane]

Kirk do you think there is much dif in the eff of a recurve or RD long bow when shooting heavy arrows say over 800grns will one pack more punch all things being the same .Thanks Shane

[**DONOTDELETE**]

Ozzy,

It all boils down to the stored energy in the limbs and how much of that energy is actually transferred to the shaft. typically a well designed r/d long bow that stores good energy will transfer more of that energy to the shaft than a recurve bow does. if it's timed well, and has enough preload to stop the string dead you got a winner. Keep in mind.... all r/d long bows are not created equal.

The recurve bow stores more energy in a shorter section of working limb. especially a static recurve or semi static tip. You would think the recurve would be more efficient and have a better cast, and in some cases they do.... But typically a well built r/d long bow in the 50 pound range will out perform a recurve bow of same weight.


The RC limb because of the extra width it needs to stabilize the limb laterally, you end up with a much thinner limb, and vertical stability and limb bulge comes into play on some designs.


The issues that you run into on the RC limbs with lost performance is the parachute effect for one. those wider limbs have a lot more wind resistance as they come forward than a narrow limb does.

The second issue is a recurve limb typically has more mass weight in the tips moving forward than a deep core long bow limb....If you try and use a faster taper rate and thin the limbs down too much, you end up with limb bulge issues that siphon the stored energy instead of transferring it to the arrow shaft. The limb tips are stopping but the working limb oscillates.

This is what is so exciting about using these newer carbon composites and foam. It's making unbelievable advancements possible. We are not only shaving a lot of mass weight in the limbs, but are now able to narrow our limbs up considerably with these carbon composites. We are also eliminating stability issues that are commonly an issue using glass and wood.

These new Static tip RC bows with carbon composites are closing the gap on the hot rod long bows.


Sorry for the getting long winded here guys... but for a bowyer, this is good stuff we are talking here.  

[mooseman76]

kirkll, you talk about the foam being fragile until laid up.  Once used in a finished limb how does the foam hold up to a direct blow?  Say you fell and hit your bow on a hard object?  I know any limb can fail in this situation, but has it been your experience that they are less durable than wood cores if this were to happen.  Thanks...Mike

[stickbowhntr]

Not kirkll but I would like to try to answer that. I believe that the sandwich between the glass would protect and make the foam much more stable and a lot less prone to breakage.

[2treks]

Originally posted by Kirkll:


Example: take a 50 pound HH bow or an English long bow with deep core straight unbraced profile.
using 9 gpp at a 6" brace height the guy standing next to you while you are shooting will feel that limb shock. you can literally watch the limbs oscillate. the best speed you are going to see is mid 170's to low 180's at 9gpp.

Now take that same bow at 70-80 pounds or higher in draw weight and you'll have a whole different bow. This is because the string tension at brace is high enough to stop the mass in the limbs cleaner and transfer the stored energy to the shaft.


 

Does this mean that ALL Hill style or American Longbows(or ELB) are created equal?
I have shot a few bows that caused pain. But when you shoot one that is made proper,the shot is smooth,sweet and quiet. No jarring.
I don't know why the ALB/ELB has to always get a bad rap or worse yet a bad stereotype. I just do not think its true.
I have a 57@30 Straight limb bow with about a 1/2" of backset that will send the arrow off with no worries what so ever. Is it the most efficient? Don't know. but I do know it is quiet and soft and will send that 500-525gn arrow nearly 300yds down range and it will bury the same shaft in the target or the critter.
Not,arguing with you Kirk you have valid points for sure. I think the waters are to quickly muddied when we try to compare too many fruits at one time. The fable about staright bows is a burr under my saddle pad,thats all. If it is true though, Are all the MANY hill bow shooters really that tuff,numb or ????

Just my morning thoughts

CTT

[katman]

I am  not a bowyer but have liked the carbon foam limbs I have shot; shrew, border, winex, flutes. Since the material has been out for a while now and limbs from oly shooters have many cycles thru them if there was a durability problem you think it would have showed up.

[katman]

Also, must be exciting times for bowyers getting to try different limbs designs due to the advancement in materials available allowing them to do things they could not before.

[beyondmyken]

I will let you know my opinion on foam cores in 3-4 months.  

[jhg]

Not an expert.
 I have shot a couple foam core long bows with carbon matrix and I didn't like them for  the same reason I don't like carbon fly rods. There is something very "quick" about how both behave and I simply prefer the slightly slower feel of  standard glass with standard materials in the core (or a bamboo fly rod).

Anyway, this bias in no way relects on performance of foam. For me it was just a feel thing. I don't know if its the foam or the carbon or the combo, but I didn't like shooting them as much. Try some out. You may like them.


Joshua