what motor is this John. Nother skinny 24mm?

Just remember guys, air density does not fall off in a linear fashion with increasing altitude. The roughly 3000 of difference between the north site and Hartsel causes a much greater fall-off in atmospheric density than the difference between sea level and 3000'. Merely simming temperature differences between the site does NOT accomodate the difference in atmospheric pressure. Talk to Jim Amos about something called the Standard Atmosphere Model and how it affects accuracy in altimeters if you want a real earful. Rocksim does NOT incorporate the standard atmospheric model. It uses a linear progression which is NOT accurate.

Warren

Actually, from what I can find in the standard model, the difference between Hartsel and the north site is roughly a factor of 1.096:1 (for density). Between sea level and 3000 feet is a factor of 1.093:1. I wouldn't call that a "much greater fall-off". Also, as it starts smaller to begin with, the absolute fall off is actually smaller between the north and hartsel than it is between sea level and 3000 feet.

Also, on a side note, this difference is small enough that a 40 degree fahrenheit day at Hartsel is almost exactly equivalent to an 88 degree day at the north site (for density of air). So, a hot day up north is actually better than a cold one at hartsel.

Chris, just how much hotter has it to be? Ignoring humidity, can you do a 3-D plot? impulse on the z axis, AGL on the x, and T on the Y. Of course insoluble in closed eqn, only curious if you can get after this with an assumption of a given Cd., and figure out the big blob so formed.

Also, on a side note, this difference is small enough that a 40 degree fahrenheit day at Hartsel is almost exactly equivalent to an 88 degree day at the north site (for density of air). So, a hot day up north is actually better than a cold one at hartsel.

BINGO. I concur. Hence my continual musing that Hartsel is NOT that big of an advantage. It just does NOT get that warm down there. It is a wonderful place to fly, but the N site has a lot higher temps, and at 5,500' (ish) the N site ain't no slouch.

well if science backs our opinions--why not? If anything I would have suggested last summer and maybe JW will concur, that Hartsel can be a disadvantage due to the winds that attend any decent temperature. Than something really strange happened in early fall, we had two launch dates in a row that were absolutely fantastic--almost hot and at most a gentle breeze. Maybe some of the more seasoned Hartsel flyers can comment. The new high altitude is operative only for a couple hours after sunrise, so anything over a G has to be flown then when the temps are low, thus negating any advantage for the most part. I still think this is an interesting aside at best, as the majority seems to be in favor of restricting NCR records for the most part to NCR sites. I just can't agree with the logic.

I'd love to see NCR north become the place to set records--at least w/in the waiver limits/ By not recognizing field records, one can come out spend a bunch of $$, and maybe eclipse the record but not by the required 2%. I think in terms of our global strategy of making MHM and OF some of the finest events in the country, why not do what we can to attract more flyers.
JS

PS: chris, just poking your ribs in the last post.

Chris, just how much hotter has it to be? Ignoring humidity, can you do a 3-D plot? impulse on the z axis, AGL on the x, and T on the Y. Of course insoluble in closed eqn, only curious if you can get after this with an assumption of a given Cd., and figure out the big blob so formed.

I was just looking purely at density from the standard atmosphere model.

If you really want, you can (it's doable, but difficult without knowing rocksim's exact assumptions), but from what I can see, the difference should not be massive. As I said earlier (and this is a rough estimate, but close enough to be within a couple percent), if the north site is around 48 degrees warmer than Hartsel, the densities will be almost identical. Since the north site tends to be warmer than hartsel, I would bet that there would only be a couple hundred feet at most between a perfect day at hartsel and a perfect day at the north site.

I'd love to see NCR north become the place to set records--at least w/in the waiver limits/ By not recognizing field records, one can come out spend a bunch of $$, and maybe eclipse the record but not by the required 2%.

That 2% *is* a killer. It has bit me twice. I eclipsed the TRA J record by about 1.5%, and the H record by 14', but neither one counted. I could have held 4 TRA records at once, but it didn't happen. The J record was eventually crushed, but my NCR "H" record is still 14' better than the TRA record. I'm good with that 😉

Incidentally, the J record that I flew that squeaked past the TRA record was indeed at the N site. The TRA "L" record that I set a year ago was set at the N site as well, though it was short lived.

The TRA records are rapidly getting out of reach. Some really competitive guys out there...

Well Mr wilke a more stoic attitude could only be expressed by some guy in a Gulag prison and obviously I our notions coincide on some level--which is what I was trying to address. Honor those who make the effort and succeed, nearly so, or maybe not even close. I have said over and over that Joe H is like so on the beam to make this club the envy of all others... I think the best move is to encourage all record attempts and not simply a footnot if an outsiders second place effort is hundreds of meters beyond any NCR member's effort. Not sure if I have anything more to say on the subject.
We've got a chance to grab it all, very fine waivers, research launches. 2 3 dayers a year, and no it aint the playa where you could spot a dead studebaker tail pipe from several miles, not bad.
J

PS: Chris, well I'll take your word on the 44 degree temp diff. I just plugged in the best conditions imaginable at North under RS, and backtracked a match at Hartsel. Likely little diff between 90 and 110 F unless you're chasing a rocket. Let me know if you still want some help with the deuce pre-paint prep.

I have some questions about record rules:

Is a "boosted dart" an unpowered payload section that recovers separately from the booster? I checked out the Tripoli rules and boosted darts aren't disallowed from single-motor records, though they are disallowed from the staged records. I also found an account of a 2001 single motor F-record flight that fits this idea: "It used a single Adept ALTIM05-50K altimeter and used motor delay deployment with one parachute for the booster section and tumble recovery for the payload and nosecone." It seems that a rocket which was designed specifically for a motor deployment charge to be a piston launcher for a nosecone could give a significant advantage, especially in the D class, which doesn't have any motors with a very long deployment delay. It also seems to violate the spirit of limits on the total impulse, which normally wouldn't include the ejection charge. Will there be a separate category for boosted darts?

Where is the line drawn on motor modification?
I assume wrapping the motor in tape for a friction fit is o.k.?
How about drilling a hole in the un-filled forward end of a SU motor for the purpose of tying on a shock cord?
Or gluing a shock cord onto the forward end?
Can some or all of the deployment charge of a SU motor be removed?

Also, does the motor case have to be recovered with the rocket for the record to count?

Thanks for bringnig the newbie up to speed

Is a "boosted dart" an unpowered payload section that recovers separately from the booster? I checked out the Tripoli rules and boosted darts aren't disallowed from single-motor records, though they are disallowed from the staged records. I also found an account of a 2001 single motor F-record flight that fits this idea: "It used a single Adept ALTIM05-50K altimeter and used motor delay deployment with one parachute for the booster section and tumble recovery for the payload and nosecone." It seems that a rocket which was designed specifically for a motor deployment charge to be a piston launcher for a nosecone could give a significant advantage, especially in the D class, which doesn't have any motors with a very long deployment delay. It also seems to violate the spirit of limits on the total impulse, which normally wouldn't include the ejection charge. Will there be a separate category for boosted darts?

Where is the line drawn on motor modification?
I assume wrapping the motor in tape for a friction fit is o.k.?
How about drilling a hole in the un-filled forward end of a SU motor for the purpose of tying on a shock cord?
Or gluing a shock cord onto the forward end?
Can some or all of the deployment charge of a SU motor be removed?

Also, does the motor case have to be recovered with the rocket for the record to count?

Thanks for bringnig the newbie up to speed

Darts... that is a major change in the rules (that I was not aware of) as there was a real knockdown-drag out argument about it a year ago. Tom Rouse was adamant that they were not allowed for single motor recordss. I am really surprised to see that the rules have changed. I'd double-check w/ Tom. as the web page may have been modified and that section dropped. I can tell you that he felt *very* strongly about it a year ago.

Motors... You may remove powder, but not drill the casing. You must recover the casing with the rocket. This falls under the "safe recovery" section, i.e. you don't want a spent casing hitting someone in the melon.

Hope that helps. Corn is still growing in Iowa. Sigh.

JW

As a club, NCR is usually considerably less rigorous about the rules surrounding altitude contests - a big for instance is Tripoli expects the bird to recover in certifiable and reflyable condition. NCR doesn't insist on that, we just consider it good form.

As for boosted darts, I personally feel that they are not the same thing as a single motor bird. A boosted dart is effectively a 2 stage bird with no motor in the second stage and weight optimized for coasting. A completely different animal than a single motor rocket that retains the motor and booster sections throughout the flight. I'll have to check the detailed rules, but I don't believe we currently recognize boosted darts. If we do, I'm going to move that they be a separate category from single motor birds.

You can remove the powder and plug an SU motor for altitude events. In fact, many NCR altitude records have been taken on semi-legal motors that have non-certified forward closures (Aerotech motors with a modified plugged forward closure with an eyebolt installed), and non-certified rear closures (partial tailcones machined as replacements for the stock knurled rear closure. These would never make it in a Tripoli altitude record as they must use certified motors only for certified altitude events. Modifications that are not certified by the manufacturer and Tripoli disqualify the record if these parts are used. This isn't intended to knock down standing records, just to make it clear that what qualifies for an NCR record doesn't necessarily qualify for a Tripoli record.

Warren

Is a bossted dart really different then a single motor vehicle? You could say that the dart drifting is similar to a single motor rocket drifting, the only difference is the dart breaks apart. I think a boosted dart should be allowed. And if they are moved to a different category which one would it be? There are not many if any 2 stage records, and there are not enough boosted darts to make there own category.

Boosted darts have a significant advantage on standard 3FNC single motor rockets in terms of altitude. Basically my half=assed boosted dart could almost certainly beat the crap out of your super-optimized 3FNC bird on the same motor any day of the week. I believe a Boosted Dart category is called for.

Warren

Agreed, though below about K impulse or so, the problem with a boosted dart becomes squeezing the recovery components into the tiny dart...

I suppose I should be asking Tom Rouse this, but do you think that the ejection charge reduction/elimination would disqualify a Tripoli attempt? When I go for the F record I want to make sure I tag all the bases.