paulagc 0 #1 June 4, 2007 Okay, you experieced folks out there who may have built a pea gravel pit for accuracy competitions in their hay day...how do I build one? I've been running a dz for several years. We took over from the former DZO who had already built a pea pit. Now, we've moved our landing area and without "the pea" to shoot for, our jumpers are quickly loosing their accuracy skills. (plus, we have a new crew of jumpers who need to earn their "IGLOT" numbers!!). We obviously need to put one in. Now, how? How deep? Do we dig? Do we line it with sand or anything else besides pea gravel? Standard sizing? I would appreciate any help and guidence that I can get. Thanks, Paula Coody Indiana Skydiving Academy Goshen, Indiana Quote Share this post Link to post Share on other sites
billvon 2,380 #2 June 4, 2007 We built one; don't know if we did it 'right' or anything. Site it appropriately, so as to not interfere with the 'normal' landing patterns, and away from any obstacles that might cause turbulence. Dig a hole about a foot deep, line it with that weed-barrier stuff that lets water drain. Get PEA gravel, not regular gravel (we made that mistake!) Quote Share this post Link to post Share on other sites
DougH 270 #3 June 4, 2007 So did the person who built ours!!! You are better off landing in the grass because that shit hurts even after you rake it. "The restraining order says you're only allowed to touch me in freefall" =P Quote Share this post Link to post Share on other sites
stratostar 5 #4 June 4, 2007 Quote how?*** loads of pea gravel of course... How deep? Quote Foot & half deep of peas Do we dig? Quote No that leads to sprained and broken ankles when you hit the sides of the pit. Do we line it with sand or anything else? Quote Line it with some plastic or other weed control. Standard sizing? 36 ft or is 32, I can't remember..... hell make it 36 but call it 32....you can't pay for kids schoolin' with love of skydiving! ~ Airtwardo Quote Share this post Link to post Share on other sites
stitch 0 #5 June 4, 2007 Take a trip to SD Temple to see how not to do it, and go from there. "No cookies for you"- GFD "I don't think I like the sound of that" ~ MB65 Don't be a "Racer Hater" Quote Share this post Link to post Share on other sites
JerryBaumchen 1,046 #6 June 4, 2007 Hi paulagc, Make sure it is washed pea gravel. Otherwise, you get pea gravel + whatever, sand, etc that they might not have removed when it was seperated. Oh, and make sure it is pea gravel; some places like to sub crushed rock or anything else that they have on hand. I would suggest going to your potential rock supplier and see what he can provide to you. We built a pit back in the 60's without getting washed pea gravel and after a rain it was almost like concrete. Jerry Quote Share this post Link to post Share on other sites
waltappel 1 #7 June 4, 2007 Quote Take a trip to SD Temple to see how not to do it, and go from there. The peas at Skydive Temple are fine but I keep on getting that annoying pea gravel in my shoes. Wouldn't be all that bad but since I land in the peas quite often....Walt Quote Share this post Link to post Share on other sites
dragon2 0 #8 June 4, 2007 Do it like ours: we had a guy promise us free/cheap gravel for our pit (can't remember which). Turned out that was a LOT of gravel, as someone made a mistake when digging, confusing diameter with radius ciel bleu, Saskia Quote Share this post Link to post Share on other sites
riggerrob 558 #9 June 4, 2007 Yes, And pea gravel hurts less when you get it inside your shoes. I quit landing in our bowl, because I got tired of having to remove my shoes - in the middle of a busy day - to shake out crushed rock! Quote Share this post Link to post Share on other sites
rehmwa 2 #10 June 4, 2007 Apparently, you don't want to put in the middle of the swoop lanes. SHeeesh ... Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants Quote Share this post Link to post Share on other sites
JohnRich 4 #11 June 4, 2007 The official classic accuracy competition size is 7-meters radius. Consider making it that dimension so that anyone practicing on it for Nationals competition will be familiar with the proper sight picture. The accuracy landing requirement for licensing varies from 10-meters for a "B", to 5-meters for a "C", and 2-meters for a "D'. So one of those first two might be a good size also, so there would be no confusion about whether or not someone landed within the prescribed range on their accuracy requirement jumps. The 7-meter competition size seems like a good compromise between the different license requirements. Consider re-using the pea gravel from the old pit, instead of ordering new, to save cost. Just dig it up and move it. Fill in the old hole with the dirt removed from the new location. And the hardest part would be remembering your high school geometry to calculate how many cubic yards of pea gravel to order to fill a pit 7 meters in radius and 1.5 feet deep... Quote Share this post Link to post Share on other sites
ZigZagMarquis 8 #12 June 4, 2007 Quote And the hardest part would be remembering your high school geometry to calculate how many cubic yards of pea gravel to order to fill a pit 7 meters in radius and 1.5 feet deep... That's easy! That would be the volume of a cylinder; which is the area of the base times the height. I try not to do math in public, but if I get this right... you're looking about about 93 cubic yards of pea gravel... and if pea gravel runs about 1.3 tons per cubic yard... you're looking at about 121 tons of pea gravel... Quote Share this post Link to post Share on other sites
DougH 270 #13 June 4, 2007 QuoteThe accuracy landing requirement for licensing varies from 10-meters for a "B", to 5-meters for a "C", and 2-meters for a "D'. So one of those first two might be a good size also, so there would be no confusion about whether or not someone landed within the prescribed range on their accuracy requirement jumps. I don't believe that is completely correct, at least if we are talking about the USPA licenses. According to the 2007 SIM a C license requires 25 landings <2m. There are no additional accuracy landing requirements for the D license."The restraining order says you're only allowed to touch me in freefall" =P Quote Share this post Link to post Share on other sites
rehmwa 2 #14 June 4, 2007 QuoteOkay, you experieced folks out there who may have built a pea gravel pit for accuracy competitions in their hay day...how do I build one? could you repeat that? was it "pea gravel" or "pee gravel" it makes a difference ... Driving is a one dimensional activity - a monkey can do it - being proud of your driving abilities is like being proud of being able to put on pants Quote Share this post Link to post Share on other sites
ZigZagMarquis 8 #15 June 4, 2007 Quoteyou're looking about about 93 cubic yards of pea gravel... and if pea gravel runs about 1.3 tons per cubic yard... you're looking at about 121 tons of pea gravel... If my maths is right... and my WAG on how much it will cost (pea gravel + sales tax + delivery (unless you're willing to make lots of trips to the quarry in the DZ pick-up))... my WAG is you're looking at $2000 to $5000 bucks. Do you really want a regultion sized (7 meters (apx 23 ft) RADIUS by 1.5 feet deep) pea pit that badly?? Quote Share this post Link to post Share on other sites
stitch 0 #16 June 4, 2007 Quote Quote Take a trip to SD Temple to see how not to do it, and go from there. The peas at Skydive Temple are fine but I keep on getting that annoying pea gravel in my shoes. Wouldn't be all that bad but since I land in the peas quite often....Walt Just a hint, those aren't "peas". It is some kind of aggergate."No cookies for you"- GFD "I don't think I like the sound of that" ~ MB65 Don't be a "Racer Hater" Quote Share this post Link to post Share on other sites
JohnRich 4 #17 June 4, 2007 QuoteQuoteThe accuracy landing requirement for licensing varies from 10-meters for a "B", to 5-meters for a "C", and 2-meters for a "D'. So one of those first two might be a good size also, so there would be no confusion about whether or not someone landed within the prescribed range on their accuracy requirement jumps. I don't believe that is completely correct, at least if we are talking about the USPA licenses. According to the 2007 SIM a C license requires 25 landings <2m. There are no additional accuracy landing requirements for the D license. I'll take your word for it. My copy of the SIM, and knowledge of such requirements, is very old. Quote Share this post Link to post Share on other sites
JohnRich 4 #18 June 4, 2007 QuoteWell, I'll risk making a math fool of myself too... (Message edited to try and correct my mistake.) Yep, sure enough, I screwed something up. I knew that the surface area was the diameter times pi (same thing as the radius squared times pi), but I forgot to square the radius to get the diameter. Doh! So, I'll try again. The diameter of a pit with a 7-meter radius is: 14 meters, converted to feet, and rounded up to get a dimension divisible by 3, for yards = 48 feet. So that's 16 yards diameter (48 / 3 = 16). Multiply diameter by pi to get the surface area: 16 x 3.14 = 50 sq. yards. Now, since you want the pea gravel 1.5 feet deep, that's half-a-yard deep. So Multiply the surface area by .5 yards to convert to cubic volume: 50 x .5 = 25 cubic yards. So, 25 cubic yards is the number I figure. This time... I think... Quote Share this post Link to post Share on other sites
jumper03 0 #19 June 4, 2007 QuoteMultiply by pi to get the surface area: 8 x 3.14 = 25 sq. yards. pi * r^2 (otherwise you are just left with yards). That gives 200.96 sq yards. Times 0.5 for depth - 100.48 cubic yards. I think....Scars remind us that the past is real Quote Share this post Link to post Share on other sites
monkycndo 0 #20 June 4, 2007 I can see why you hate math. Area of a circle is pi * r^2, not pi * r.ZZM is correct, +/- a yard or two. Weight of pea gravel is 1.3-1.5 tons per yard, depending on if it is hard rock or not. Yep, putting in a pea pit that size is not cheap. In Northern California, with tax and delivery, I'd say his WAG of $5K would be closer to the cost. *Edit* Steve, beat me to it. 50 donations so far. Give it a try. You know you want to spank it Jump an Infinity Quote Share this post Link to post Share on other sites
white_falcon 0 #21 June 4, 2007 Cylinder A cylinder is a space figure having two congruent circular bases that are parallel. If L is the length of a cylinder, and r is the radius of one of the bases of a cylinder, then the volume of the cylinder is L × pi × r2, and the surface area is 2 × r × pi × L + 2 × pi × r2. Example: The figure pictured below is a cylinder. The grayed lines are edges hidden from view. Sooo.... L × pi × r2 = .5*3.14*8= 12.56 I agree with John Rich on the volume Quote Share this post Link to post Share on other sites
ZigZagMarquis 8 #22 June 4, 2007 Quote monkycndo said: ----------------------- I can see why you hate math. Area of a circle is pi * r^2, not pi * r.ZZM is correct, +/- a yard or two. Weight of pea gravel is 1.3-1.5 tons per yard, depending on if it is hard rock or not. Yep, putting in a pea pit that size is not cheap. In Northern California, with tax and delivery, I'd say his WAG of $5K would be closer to the cost. *Edit* Steve, beat me to it. Woo-Whooo! That B.S. in Aerospace Engineering was worth it! Quote JohnRich said: ------------------- And the hardest part would be remembering your high school geometry to calculate how many cubic yards of pea gravel to order to fill a pit 7 meters in radius and 1.5 feet deep... Either intentionally or unintentionally, John used as typical tactic used by college profs to trip up students. He mixed units... i.e. "...a pit 7 meters in radius..." and "...1.5 feet deep...". When working the maths, one has to either convert meters to feet for the radius measurement OR convert the depth mesaurement from feet to meters. I chose to work in English units, thus, converted meters to feet... ergo... 7 meters is about 23 feet. I then worked the problem to come up with a cubic feet answer and converted that to cubic yards by dividing that answer by 27. I did a quick search on the internet to try to figure out what pea gravel weighed per cubic yard since I figured if one showed up at a rock quary, the folk working there would want to know how many tons of product you want vice a volume. QED Anyway... The next mistake some made is mistaking radius for diameter. Either because they mistakenly recalled the formula for the AREA of a circle as what is really the formula for the CIRCUMFRANCE of a circle... and/or... when John posed his question, he really meant to say a pea pit 7 meters in DIAMETER rahter then RADIUS. Thus the "R" in the calculation would have been 3.5 meters or about 11 feet vice 23. I did my maths off the top of my head without looking up the exact converstions and rounding up a lot... to account for all the pea gravel thats going to start finding its way out of the pea pit in peoples sneakers, canopies and pilot chutes quickly after its installed, mind you. Heck, we send probes to Mars (sometimes successfully) using Pi only to 2 decimal points. Quote Share this post Link to post Share on other sites
jumper03 0 #23 June 4, 2007 QuoteCylinder A cylinder is a space figure having two congruent circular bases that are parallel. If L is the length of a cylinder, and r is the radius of one of the bases of a cylinder, then the volume of the cylinder is L × pi × r2, and the surface area is 2 × r × pi × L + 2 × pi × r2. Example: The figure pictured below is a cylinder. The grayed lines are edges hidden from view. Sooo.... L × pi × r2 = .5*3.14*8= 12.56 I agree with John Rich on the volume you forgot to square your 8....Scars remind us that the past is real Quote Share this post Link to post Share on other sites
monkycndo 0 #24 June 4, 2007 Quote Woo-Whooo! That B.S. in Aerospace Engineering was worth it! Yeah, but I see you prefaced it as a WAG. Typical engineer. I pulled out my old Means and actually looked it up. Have to admit though, you were pretty close.50 donations so far. Give it a try. You know you want to spank it Jump an Infinity Quote Share this post Link to post Share on other sites
rygon 0 #25 June 5, 2007 then again why does it have to be a cylinder...why not have it as a bowl (ie half a sphere) This will save digging and gravel costs work it out... v = ((pi/3)y^2)(1.5d-y) v = volume y = 0.5d (half a sphere) d is the diamter of sphere Quote Share this post Link to post Share on other sites
