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Old 04-23-2012, 01:21 AM   #51
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Floating in the clouds sounds good to me. Can't wait to get this thing airborne. Plans possibly, not sure about a kit. As I've mentioned before, lets see if she flies first. *grin*

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Old 04-23-2012, 01:53 AM   #52
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Why is it the last 10% takes 90% of the time?

So I started adding gussets to the v-tail. I carefully measured the required angle then set about making 32 of these little buggers...



Then I noticed, duh, I'd need different shaped gussets for different areas of the tail. The leading edge, for example, runs at a different angle to the ribs than at trailing edge. After a long groan I tossed most of them & set about cutting out a new set. Anyway here's a panel with the corrected gussets installed. Came out nice & strong & fairly light...



And now for the next time sucking issue...

One of my ruddervators (love that word) annoyingly appears to have developed a moderate warp along its hinge line...



So back to my damp sponge trick, I saturated the wood then using a straight-edge as a guide, secured it to my workbench. I'll let it sit overnight, fingers crossed she'll be straightened out come morning...


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Old 04-23-2012, 02:31 AM   #53
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I like your attention to detail. I now remember some of those building tips from 20 yrs ago. That's helping me now repair my sailplane from my crash last week.
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Old 04-24-2012, 04:51 AM   #54
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I'd forgotten a bunch of stuff too. Its all coming back to me though.

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Old 04-24-2012, 05:45 AM   #55
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I had a great session today, got a lot done. Best of all I'm not all grumpy like I was yesterday.

The warp in my ruddervator is better but I'm still not happy with it. Will give it another go with the damp sponge trick & see where that takes me...



So anyway, I'm not letting that issue slow me down. Time to make a V out of my tail...

I needed to add a 55 bevel to each of my tail-feathers. I spent some time scratching my head, thinking up all sorts of crazy jigs & whatnot. In the end I decided to just get on with it & adjusted the table on my belt sander to 55 & went for it...



With very little fine tuning from the block sander, amazingly she went together at exactly 110, SWEET!..



Again with the head scratching, I needed a way to attach the v-tail to my CF tail-boom. Actually that's the easy part, I'm just going to fiberglass it around the tail-boom. The tricky part was finding a way to make sure the tail lines up straight. So here's what I came up with... I temporarily tacked a short section of scrap CF tube to the v-tail making sure it ran down the joint precisely. I then epoxied two small strips of plywood either side to just the tail, not the CF...



While that set I carved a few short slots in the very end of the tail-boom. The thinking here is that'll give the glue something to index & hopefully keep the tail from working loose & spinning on the shaft. I also roughed up the CF with some course sandpaper...



Next I mounted the wing center section to the fuselage & used a bunch of clamps to hold the wing perfectly level with my work bench...



Yet another use for the amazing Quick Grip clamp, love those things. Once I had the airframe squared up I removed the temporary CF tube from the tail then went ahead & epoxied the v-tail to the tail-boom. I used a ruler to check it was square with the bench, propped it up with a glue bottle & I'm leaving this puppy to set overnight...



Tomorrow I'll reinforce the tail joint with fiberglass. Feels great to finally get the tail on there. Another major milestone achieved, YIPPY!

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Old 04-25-2012, 04:33 AM   #56
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Odds & Ends
No photos today. I didn't really do anything photo-worthy, just lots of odds & ends. Here's a quick list of what I got done...
  • Visited hobby shop & picked up nicknacks, control horns, pushrods etc
  • Finished fiber-glassing the v-tail to the tail-boom
  • Fixed the warped ruddervator by sanding it straight
  • Trimmed to length all the control surfaces
  • Installed the two ruddervator pushrods
  • Did more sanding here & there
Movie night tomorrow so not sure how much I'll get done but I believe I've arrived at yet another milestone. It might finally be time to break out the Ultracoat, WOOHOO!

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Old 04-25-2012, 05:07 AM   #57
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Possibly you've already mentioned this but what radio system do you plan to use in this aircraft?
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Old 04-25-2012, 05:19 AM   #58
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I'm planning to use the following...

Tx: Spektrum DX7s
Rx: OrangeRx DSM2 6ch Receiver
Rx: OrangeRx R100 Satellite Receiver

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Old 04-27-2012, 05:59 AM   #59
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Here's a detail of how the tail was fiber-glassed to the tail-boom...



Added some stylish wingtips...



Bare-Bones
And with that the airframe is complete, wO0t! Before she's covered I thought I'd take a few bare-bones photos to help celebrate...













Feels great to have gotten this far.

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Old 04-27-2012, 12:53 PM   #60
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Default Scratch Sailplane!

Nodd!

Very nice build!
Very nice Craftsmanship!!

Regards
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Old 04-28-2012, 02:48 PM   #61
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Beautiful bird with excellent looks. Nice build log, very informative.
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Old 04-29-2012, 04:26 AM   #62
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Thank you, thank you.

Wrapping Things Up

Well we can't have this glider parading around naked, time to do some covering. I chose to use Hanger 9 Ultracoat as I've worked with it before & like the way it applies. Low temperature to activate the adhesive then switch to higher temp to do the shrink-wrapping. Its also pretty forgiving & most wrinkles can be eliminated with some heat...



I wanted to show off the built up structure so I'm using transparent red on the open areas & opaque white everywhere else...



Before I got too far into the wing covering I performed another balance check...



I centered the wing on my balance stand & added weight to the light side...



Three small nails on the left wingtip & she balances perfectly. There is a school of though that says its a mistake to add weight at the tips as this adds unwanted mass way out on the ends of the wing, not where you want it. Its often better to add weight further in & keep the tips as light as possible. The down side is you need more weight to achieve the same result. As my wing was already balanced fairly close & needed just a few grams I felt it was fine to just stick the nails into the end of the wing...



If you use nails for weight you should pre-drill the holes. Don't go hammering away at your wingtips, bad idea. Once in place a drop of CA glued keeps them secure...



Here's my home-brewed CG balance stand. Simple & because its in two pieces it fits just about any airplane. Note the spiffy rubber tips to keep things from slipping while balancing...



Anyway with the wing balanced I covered over the nail holes & turned my attention to the v-tail...



I'm trying something new on this model. I usually use CA hinges but I noticed one of my ARF gliders uses just the covering its self as a hinge joint. The result is a gap-less joint that's fairly sturdy & doesn't seem to bind at all. If my ruddervators start to fall off in a month or so I guess its back to CA hinges but my other glider has been around for years & no signs of hinge fatigue yet. So I thought I'd give it a try. Here's how my hinges are laid out...



From the top at least the joint looks totally seamless. Obviously there's a small slot on the under-side to allow the control surface to move downwards but aerodynamically its pretty clean. I like...



Well that's enough for today. I'll tackle the rest tomorrow...


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Old 05-03-2012, 12:25 AM   #63
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Where's Nodd?
I must apologize for the lack of progress this week. I've been feeling under the weather & not at all motivated to do much more than sleep & doddle about the house. Anyway I appear to be getting over the hump & expect to be back in the workshop tomorrow (fingers crossed). Thanks everyone for their patients.

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Old 05-03-2012, 02:07 AM   #64
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Looks great. Thanks for posting all the construction details.

It's never too late to have a happy childhood.
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Old 05-04-2012, 01:29 AM   #65
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Okay I'm officially back in action. Woohoo! Although I can't say I got a whole lot done today, it was great to be working on the project again. Illness sucks.

I picked right up where I'd left off on the covering. These are the ailerons...



The guys at Ultracoat were having a laugh when they chose which side of the roll to put the backing material on. For normal opaque UltraCoat the waxy backing paper always ends up on the topside when you unroll it. I guess they thought it'd be fun to mix things up by reversing that for the completely invisible clear-backing used on their transparent rolls. I spent an hour going out of my mind trying to figure out why everything I cutout for the transparent areas kept coming out backwards. I finally noticed the discrepancy in the backing materials but not until wasting a fair amount of my red roll. Oh well, now I know & so do you.

Hinges
As I discussed a few days back, I used UltraCoat to make my ruddervator hinges for the v-tail. Seems like that worked pretty well but someone on another forum suggested I give plain-old Scotch tape a go...



Apparently he's been using Scotch brand Transparent tape for years with good results. He even claimed it holds up on his 100mph planes. I poked around a little & there's no shortage of suggestions on what tape is best. This guy's transparent Scotch tape suggestion seemed as valid as any so I figured I'd give it a try. After a quick trip to Walgreens I had a roll in hand. Its robust stuff with a slightly thicker vinyl feel not a lot unlike packing tape, only not as wide. It sticks well & most importantly, so far, stays put. Here's the flaps installed using the Scotch tape...



While waiting for my covering iron to warm up again after unplugging it during dinner tonight, I decided to spray paint the servo hatches. I could have covered them but this seemed simpler... pshhhh pshhhh pshhhh done...



Still not feeling 100% so that's all for today. Oh & yes I did remember to unplug my iron again.

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Old 05-05-2012, 04:14 AM   #66
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Gotta love how you build two ailerons identical in every way, one installs in 10 minutes, the other takes almost two hours!

A poor decision early in the wing's CAD design process set me up for much toil & headache today. The first aileron went on great & had plenty of travel without any nasty binding. The second bugger however, even after three complete install attempts, refused to give me more than a couple of degrees of down travel. On the computer where everything is perfect, I'd designed in just enough bevel on the aileron's LE to allow them to move downward exactly the desired amount of travel. The idea was to keep things like slots & whatnot in my spiffy airfoiled wing to an absolute minimum. Apparently the real world is not perfect. Subtle variations in both the aileron & the wing's TE were causing it to bind up. My initial solution was to open up the gap between the wing & aileron so the joint had more room to flex but when I flipped the wing over for a look-see & saw the big gaping gap needed, it was obvious this wasn't going to do. So I was forced to remove some of the aileron's covering & rework the bevel until it behaved its self. Long story short, she's finally on there & moving freely but what a hassle. Next time design in some wiggle room stupid!

So anyway with that finally behind me I started to setup the control horns...



This was not going to be my day I could tell. Next issue! I've run into this before with DuBro control horns. Seems they give you these silly little short screws that work fine for a rudder or elevator but almost always seem to come up short when doing ailerons...



There's no way I'm getting the other plastic doohickey thing that goes on the other side threaded using these screws. Will have to hit the hardware store tomorrow. Unfortunately that put an end to my linkage hookup aspirations for today. Combined with the frustrations of the aileron that wouldn't, I wasn't in the mood to switch my mindset to some other part of the build. So that'll do for today. I did assemble the wing so I could take a look at her all covered though...


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Old 05-07-2012, 04:13 AM   #67
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The Wing is Done
I hooked up the electronics to the wing & began setting up the flaps & ailerons...



All the linkages are in place. Nothing too fancy here, just a z bend & an adjustable clevis...



Here's an aileron all set to go. Note the extra travel allotted for the crow mixing function...



The programming could stand some tweaking but so far I have 25% differential on the ailerons & the crow mixing is functional, flaps go down, ailerons go up. I'd like to also have a setting where both the ailerons & flaps reflex up a couple of degrees for added speed between thermals.

Crow Mixing on the Throttle Stick or Flap Switch?
I've discussed this with the glider guys at my field & have done lots of forum searches & it seems everyone has an opinion on where this control should be on a radio. Here's my thoughts: I do a lot of powered flying & I really want to keep the throttle where it belongs, on the throttle stick. I think it'd screw up my mussel memory if I have the throttle doing something else on some of my planes. So for me it makes sense to place the crow mixing on the flap switch & leave the throttle where I'm used to having it. Now for a pure glider, I might be talked into sticking the crow mixing on the left stick, might.

Anyway, next I need to get the fuselage covered & the v-tail hooked up. I did install some trim tape on the canopy but I notice its not staying put in the curvier areas, kinda wrinkling. Will worry about that later though, looks good enough for now...


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Old 05-07-2012, 04:39 AM   #68
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The main advantage to having the crow (or spoilers or flaps) on the throttle stick is fine control for precision landings. On a switch its either full on or off. In full on mode, your plane is likely to be less responsive to aileron inputs which further reduces your ability to make precision landings.

On sailplanes you normally dont need that kind of control with the throttle. Its full on to climb then it stays off for the vast majority of the flight.

It really doesnt mess with your muscle memory all that much. Set it up so that full back stick is full crow ON - so OFF throttle coresponds to full braking. ON throttle position is still the GO position with no crow for minimum drag. Its still go on forward stick and stop on full back stick.

Of course if you dont need to make precision landings than its not such a big deal.

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Old 05-07-2012, 07:20 PM   #69
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Larry you're correct as are a bunch of other folks on another forum who also responded to my goofy thinking. Here's my response:

You guys make some really good points & I'm finding my self doing some serious rethinking here.
You're right of course, this is a glider first & foremost & should be setup as one. Here I am all worried about it messing up my powered flying but I guess that's a little like suggesting I should avoid driving my car because it might make me forget how to ride a bicycle. So I think you have me convinced, the left stick on a glider, even a powered one, should be used for the flaps.

I really like the sound of the first 50% for flaps & then the second half adds in crow. That's pretty neat.

So back to my motor. How to set that up... Other than the two main sticks, my Spektrum DX7s only has one other proportional control & that's a knob on the top right side. I find it hard to get to while flying so that's not an option. I've seen radios with a throttle slider on the left face of the radio which would be very nice. But mine doesn't have one so that means no proportional motor control, oh well. I can however use the next best thing, my three position flap switch. Set it up something like...

Flap Switch
Position 0 - 0% throttle
Position 1 - 30% throttle
Position 2 - 100% throttle

That'd at least give me some throttle management so I can run at partial power for hand launching & say if I want just a little help penetrating sink. For the most part though the motor's job is purely to chew through altitude running at full-boar. A concept as a powered flyer, who's usually all over the throttle, needs to get used to.

Anyway I'm sure I'll be playing around with this stuff for years to come. Thanks for not letting me start out goofy-footed.

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Old 05-08-2012, 04:09 AM   #70
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Oh yeah we're getting close *starts to practice his maiden flight dance* Not long now...

Time to cover the fuselage. I may have been putting this off, kinda dreaded all those evil compound curves. The covering started out a little shaky but overall I'm pleased. Once again UltraCote saves the day. Love that stuff...



A few scary wrinkles at this point...



After a few passes with the heat gun all my wrinkle worries shrank away...



Next I installed the motor. Apparently someone snuck into my workshop during the night & replaced it with a slightly larger motor. She was rubbing against the nose pretty badly...



Two minutes trimming with the Dremel tool & all was well. Next I checked for correct rotation of the motor using some patch chords...



Rotation looked good so soldered & heat-shrank the motor & ESC together...



Because I needed both hands & was more concerned with safety I don't have a photo of the folding prop test. Basically I ran her up to around 50%, she was already pulling like a train. I then did a quick blip up to maybe 80% then shut her down. All I can say is OMG this thing has balls & then some. Scary thrust, I likes!

With visions of giant propellers still spinning in my head I got back to work & installed the v-tail servos. It looks like I may need to change the spacing where my push-rods enter the rear bulkhead. Currently they are precisely where they won't work [note for next build: don't glue in the push-rods until the servos are in]. Will have to do a little x-acto knife digging to move them, no biggy though.



Wrapping things up for the day I decided to see how she'd balance. Fingers crossed I tossed her up on my CG stand, drum roll please... she came out pretty darn close to where she needs to be. Just a tad nose heavy with the battery all the way back, easy fix by adding a few grams to the tail. Very pleased with that, it could have easily been way off. I got lucky...



My to-do list is getting pretty short, woohoo!..
  • Hook up v-tail
  • Secure battery & electronics
  • Devise a system to keep the canopy on
  • Heat-shrink some washout into the wing
  • Set the CG
  • Finish programming the radio
  • Toss all my hard work into the air

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Old 05-09-2012, 04:12 AM   #71
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Well every Wednesday (that's tomorrow) I head down to the "big field" & fly RC with a great bunch of folks. I was hoping have the glider ready for her maiden but a couple of setbacks today have made that unlikely.

Setback One
While hooking up the v-tail I noticed my push-rods were binding pretty badly. After some exploratory surgery I found the culprit. Apparently when I drilled the hole for one of the wing mounting dowels I also drilled through my push-rods. Well technically I just nicked the nylon outer sleeve but that was enough to cause a problem. So those need to be replaced.

Setback Two
I have two of these 50amp HobbyKing ESC. One I've been using in an AT-6 Texan & the other I was planning to stick in this glider. I noticed these ESCs would go through their musical start-up routine at seeming random intervals. This didn't seem to be an issue until last week when I shut down the Texan's throttle mid flight to lose some altitude. After gliding (like a brick) for a bit I got back on the throttle... nothing... DEADSTICK... AHHH! I ended up stalling her around 20 feet up & the result wasn't pretty... CRUNCH...



So last night I decided to look into why this quirky ESC does what it does. Well apparently, turns out its a helicopter ESC, doh! For whatever helicopter reasons, when it receives a 0% throttle signal for more than 10 seconds the ESC goes into some bizarre start-up/setup mode, musical beeping, silliness. During which it refuses throttle input (actually I think full throttle input sent it deeper into setup mode which is what doomed my poor Texan). Anyway, long story short, its sorta usable in my Texan as long as I avoid any gliding but for my glider... well yeah you get the idea. So that needs to be replaced also.

A case of one step forward, two steps back. Possible maiden flight opportunity this weekend but I think its best to just keep working on her & she'll be ready when she's ready.

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Old 05-10-2012, 09:08 AM   #72
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Out with the old, in with the new
I picked up a new ESC today. This one comes with a manual so it can actually be programmed, what a concept. At just $21 the price was right too. I've decided to install a UBEC as well. I like the idea that if I fry the ESC I'll still have control, plus the UBEC, rated at 5 amps, should deliver plenty of juice for the six servos...



Because the UBEC will be supplying the power for the radio & servos I disabled the power coming from the ESC...



The ESC & UBEC have been installed & are working like a charm. I also repaired the damaged section of the v-tail's pushrods. The v-tail is now hooked up & functional...



I feel much better about the electronics now, feels like a pretty solid system. Was a good day. Hope to wrap things up & get her airborne real soon.

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Old 05-11-2012, 04:31 AM   #73
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I picked up some crazy-strong rare earth magnets to hold my canopy in place. Couldn't resist playing with them first though...



I'm using two at the front & two at the rear of the canopy. My worries about these not being strong enough were totally unfounded. It takes considerable effort to remove the canopy...



Not something I can really photograph, the rest of my time today was spent programming the radio...



The motor is now controlled by my three position flap switch. It runs at 0%, 30%, 100% power. My throttle stick now operates the flaps with the last 25% feeding in the crow mixing. I may add camber control too but for now this setup should get me flying.

Very little to do now. I still need to add a smidge of weight to the tail, plus I want to makeup some short servo extension cables that I'll plug into the receiver so that when I remove the wing I can unplug stuff from the extension cables, not the receiver. I figure the less the receiver is disturbed the better.

The weather has been terrible this week, raining & windy so I don't feel too bad about these delays, I couldn't have flown anyway. The forecast for the weekend looks promising though.

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Old 05-11-2012, 09:34 PM   #74
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I Need Help with the CG
Okay I'm trying to figure out where my CG needs to be. I've visited half a dozen online CG calculators, plugged in my numbers & of course they don't seem to agree with each other...

Wing Only CG Calculator Results
Calc A: 1.71" back from LE
Calc B: 1.71" back from LE
Calc C: 1.71: back from LE

Wing & Tail CG Calculator Results
Calc D: 4.48" back from LE
Calc E: 3.22: back from LE

Here's the glider's data if you wanted to give this a try...

Wing Root Chord: 9"
Wing Tip Chord: 4"
Wing Sweep: 0
Wing Half Span: 55"
Tail Root Chord: 7.25"
Tail Tip Chord: 3.75"
Tail Sweep: 8"
Tail Half Span: 12"
Distance between Wing LE & Tail LE: 32.5"
Please enter what ever %MAC or Static Margin you feel would be good.

I'd appreciate help with this as I'd like to avoid having an iffy CG for the maiden flight. Thanks.

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Old 05-11-2012, 10:13 PM   #75
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Wing only calcs are worse than useless unless you have a wing only (tailless) plane.

Of the two other calcs using 10% static margin the first gave me 4.12" and the second gave 3.22"... Use 3.22" to be on the safe side. The difference is probably down to the fudge factor they use for tail effectiveness. If you use 'low' in the tail efficiency on the first calc is comes out almost the same as what the other once predicts.

Steve
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