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Author Topic: P30 weights  (Read 2392 times)
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billdennis747
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« on: April 30, 2018, 11:35:40 AM »

I was just going through models for the Nationals, including a P30 (Teacher's Pet). For some reason I decided to weigh it, expecting a gram or two over the 40.
I reeled; total weight 55g as follows

fuse 21.6
wing  14.4
prop unit  13.8
tail  4.9

Is it possible to build down to 40g? Surely the prop unit weight is fixed, a mylar tail may lose a gram. The TP is not a heavily-built model so which of these componenets is too heavy, or is it all of them? I thought I'd done a good job on wood selection but obviously not.
thanks
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« Reply #1 on: April 30, 2018, 11:51:51 AM »

Yes it is possible to build a P30 to weight. Is it possible to build a Teacher's Pet to weight?  That would be a challenge. Lot's of wood in that plane!

Edit:  Woops! I mixed up the Teacher's Pet with another plane. 
« Last Edit: April 30, 2018, 12:07:20 PM by DerekMc » Logged

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« Reply #2 on: April 30, 2018, 12:02:09 PM »

Bill can you post a pic of your Teachers Pet?
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RalphS
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« Reply #3 on: April 30, 2018, 12:04:07 PM »

  Hi Bill  -  you spent too many years building those diesel powered scale models.  These are the weights of my 2007 Nats winner Wink        

             Fuz     16.14g
             Wing     9.83
             Prop      8.72
             Tail        2.60
          
            Total      37.29
              Bug        3.11

     New total      40.40  + rubber bands

Wing and tailplane largely CF.  Fuz includes Tomy timer.  Covering mylar to wings and T/P.  Fuz is tissue over mylar.

Ralph

You must have a lot of lead in that noseblock.
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billdennis747
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« Reply #4 on: April 30, 2018, 12:32:43 PM »

Crikey Ralph. You'll have to take my word that the wood isn't overly heavy, but I can't see anywhere to save all that weight.
The only way to reduce the prop is a different one - Peck?
Maybe it can't be done with a standard wood and tissue TP.
I guess I'll just have to take more notice of thermals
Here's a picture Crabby (and the weights don't even include bands!)
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strat-o
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« Reply #5 on: April 30, 2018, 01:44:24 PM »

Sorry, no help here really.  I've built two Teacher's Pets and both came out close to 40.  I used 1/32" for all ribs (per plan) but even if 1/16" were used I doubt it would add more than 1/2 a gram.  Covering was Esaki throughout.
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calgoddard
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« Reply #6 on: April 30, 2018, 06:11:19 PM »

I have six P-30 models.  P-30 is one of my favorite classes. None of my P-30 models weighs close to 40 grams.  They typically weigh 45 - 50 grams.  I am relatively new to outdoor free flight, having started in the hobby about 5 - 6 years ago.

My P-30 models include:

1)   Square Eagle
2)   Pirate
3)   HOT BOX
4)   Holiday (my own design)
5)   Bob White
6)   Air Shark

A picture of my recently completed Air Shark is attached. It flies great!

Here is a link to a video of an early trim flight of my Air Shark in my local park.  The portion of the park that I can fly in only comprises about 6 acres.  So  I had to set the DT to trigger early or else the model might have flown over adjacent houses.  The launch in the video is at very low torque.  Later on at our 88 acre field I gradually increased the launch torque to 6 inch-ounces.  I seem to recall adding more down and right thrust as I increased the launch torque. Experts somehow launch their P-30 models at 10 inch-ounces of torque. I am not there yet.  

https://www.youtube.com/watch?v=eLWX1WOUzb8

The plan included with the old Air Shark kit that I built had a 1999 date on it.  When I installed a 6 x 1/8-inch rubber motor, the GizmoGeezer (GG) would not free wheel.  The hook-to-peg distance was too long.  The Air Shark came out before the GG prop assembly.  So I switched to a longer 10 x 1/16 inch rubber motor. I did not want to add weight by adding a new motor peg location that would require two more reinforcing rings made of 1/64-inch plywood. This turned out to be a great decision, i.e. using a 10 x 1/16 rubber motor.  I get a long motor run of approximately 100 seconds, and a fairly good rate of climb at 6 inch-ounces of launch torque.  

I built all of my P-30 models except for my Pirate, which was an ARF model, and my Bob White. The latter came with a pre-assembled wing and stab which, both of which I covered. I then had to do all the final assembly of my Bob White P-30. All of my P-30 models are covered with Mylar.  The Pirate and the Bob White models have carbon fiber composite spars.

None of my P-30 models was built using a weight budget.  I was not careful with wood selection.  All of them have DT’s, which include either a TOMY timer or a viscous timer.
 
My Square Eagle was my very first P-30. I seem to recall that my Square Eagle came in at around 55 grams.  I won my first P-30 contest with that model years ago, and I was flying against some very experienced P-30 fliers.  My Square Eagle obviously caught some good air and/or my competitors’ models didn’t.

My lightest P-30 wing (Pirate) weighs 11.52 grams and my heaviest P-30 wing (HOT BOX) weighs 18.95 grams!  

The next P-30 that I will build is the brand new Super Y from CB Model Designs.  I recently bought the full kit. It includes excellent balsa wood selected by Clint Brooks, a world class P-30 flier. The illustrated instructions are incredibly detailed and well written.  According to the weight budget in the Super Y build instructions the model is supposed to come in a hair under 40 grams.
 
At my last P-30 contest earlier this month I intentionally left off my Walston RF tracker off my Pirate to avoid a 3 gram weight penalty.  My Air Shark had mysteriously developed a warp in the wing which I was unable to take out without my heating iron which I did not bring to the contest. Naturally my Pirate was lost on its third official flight even though the DT triggered as planned. It took several hours and several people searching to recover my Pirate. Even Clint helped out by searching for my Pirate using an electric bicycle.  My wife and I both had an excellent line of sight on the model when it landed. Eventually she discovered that it had landed in a shallow irrigation ditch and was about 6-inches to 1-foot below ground level.  It was obscured by weeds that had grown up in and around the irrigation ditch. I had walked right past it at least once and maybe twice.
 
I don’t think I can build a P-30 to 37 grams that would be durable enough to withstand the rigors of competition, including 5 - 7 mph winds at our flying site that sometimes come up before we quit fling at noon.  A world class glider flyer at the contest said I was an idiot to invest in a Walston retrieval system and not mount its RF tracker on my P-30. So maybe I will be flying my Super Y at 43 grams, plus the weight of a near 10-gram rubber motor Smiley

P.S. - I also have a kit for the Dragonfly P-30 that I purchased from BMJR Models a few years ago. It keeps getting put off in terms of building the same.  I doubt it will fly as well as my Air Shark or my Super Y, but I like the retro looks of the Dragonfly.

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« Last Edit: April 30, 2018, 06:49:16 PM by calgoddard » Logged
mkirda
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« Reply #7 on: April 30, 2018, 08:15:39 PM »


Is it possible to build down to 40g?
thanks

I built one at 32 grams, had to add a bunch of ballast.
I think it is all the F1D building.

 Wink

Regards.
Mike Kirda
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applehoney
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« Reply #8 on: April 30, 2018, 08:39:17 PM »

P30 weighed 34 gms as pictured.  Since has had upper surface of wingtips and the outer sides of fins lightly sprayed with fluorescent colour and the tracker housing fitted.  With tracker and batteries it topped out at  41 gms.

As far as I recall my previous two (three?)  P30s were underweight when built.  No special wood, just selecting from stock that which 'felt right' for its particular purpose.
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ffkiwi
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« Reply #9 on: April 30, 2018, 08:51:29 PM »

I was just going through models for the Nationals, including a P30 (Teacher's Pet). For some reason I decided to weigh it, expecting a gram or two over the 40.
I reeled; total weight 55g as follows

fuse 21.6
wing  14.4
prop unit  13.8
tail  4.9

Is it possible to build down to 40g? Surely the prop unit weight is fixed, a mylar tail may lose a gram. The TP is not a heavily-built model so which of these componenets is too heavy, or is it all of them? I thought I'd done a good job on wood selection but obviously not.
thanks

Bill if its any consolation-my first Teachers Pet thudded onto the scales at 55g also....some 35+ years ago! [It was my second P-30...the first was a modified One Night 28-minus LG and tip fins] I remember being very disappointed with the final weight at the time. To misquote John Cleese in Monty Python and the Holy Grail..."I got better!"   .....and I'm sure you will too-but if its even more consolation to you- I still have trouble building P-30s and Coupes down to weight-and in the last 35+ years I've built quite a few of both!

 ChrisM
 'ffkiwi'
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« Reply #10 on: April 30, 2018, 09:35:47 PM »

I've built two P-30s from scratch.  Both came out 42-43 grams, and I don't have a lot of experience with stick and tissue.  My wings are my heavy part, at close to 15 g, even though the wood was carefully selected.  But it has too much wood.  It is covered tissue-over-mylar.  Stab is only 3g (covered mylar only), and the fin is Depron, so quite light.  For front end and prop I am using the Gizmo Geezer assembly.  Fuselage is a rolled tube of 5 pcf balsa, tissue covered inside and out.

Your fuselage seems very heavy.   

My next P-30 WILL come out under 37g so I can add RDT and still be near weight after trading off the viscous timer for RDT.

Put your P-30 in a thermal and it won't care.  But I like flying P-30 very early in the day, so I want to be near minimum weight.

--Bill
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RalphS
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« Reply #11 on: May 01, 2018, 11:18:25 AM »

Crikey Ralph. You'll have to take my word that the wood isn't overly heavy, but I can't see anywhere to save all that weight.
The only way to reduce the prop is a different one - Peck?
Maybe it can't be done with a standard wood and tissue TP.
I guess I'll just have to take more notice of thermals

If you look at the pics below you may be able to compare with your model re weights.  Large wood sections rather than CF, tissue instead of mylar, heavy coat of fluorescent paint on wing and tailplane, big spring and longer shaft on prop assy obviously add weight.  JOD's obligatory underfin adds more weight and one wonders why he found it so necessary, but few others do. I and JOD, used the peck prop with 4 strands of 1/8th rubber.  The down side of this is that 2000 turns are needed to get a good climb - the up side is that the prop runs for about 2 minutes making maxes that bit easier.  A geared up winder helps speed up the winding process.  

The coupe in my pics was made in 2004 and has had lots of flying in all conditions.  I hope to fly it next week in our club P30 contest.

As you say, put your Teacher's Pet in good air and it should max.

 I don't know what JOD's last Teacher's Pet weighed.  I know he covered the flying surfaces in striped silver mylar (lighter than the ordinary 5 micron mylar, he said).  Perhaps you know where it went and it would be nice to know what it weighed.
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billdennis747
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« Reply #12 on: May 01, 2018, 11:32:05 AM »

Thanks Ralph, and others. Yes I can see where the cumulative weight comes from and I think the mylar must make a big difference. It seems a lot of care must be taken to get down to weight, and I wonder why such a low weight was set for what was supposed to be an 'entry' class.
I will keep flying it but I won't make another. I picked up John's light version at his send-off and yes, it was light. As for the subfin, at least it's easy to spot in a cloud of models!
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« Reply #13 on: May 01, 2018, 12:16:57 PM »

Hi Bill, just to stick my thruppence worth in, I have built 3 Teachers Pet models,  first one as to plan, the next two I used 3/32 wood for the fuselage spacers instead of 1/16 as specified, they came out lighter! but I have to agree, there is a hell of a lot of wood in it( biggest culprit is the trailing edge. I did hear a roumer that J. O/D developed a lighter version to fly, anybody know about this one, or got a plan.
Ralph, is that a Goerge Hollingdale winder in your photo? 
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billdennis747
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« Reply #14 on: May 01, 2018, 12:31:10 PM »

Mike, I saw John's 'E-Type' P30 at his funeral - geodetic, mylar surfaces, maybe a carbon TE
I suspect my orange prop is much heavier than a Peck.
To add insult  to i, my weights are minus tracker and with fuse DT
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calgoddard
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« Reply #15 on: May 01, 2018, 12:49:54 PM »

The P-30 event originated with the San Diego Orbiteers free flight club in the late 1970s.  I understand that John Oldenkamp and another Orbiteers member were largely responsible for creating the event.  The other member may have been Harry Steinmetz.  Perhaps someone will correct me if I am wrong because the people who came up with this marvelous event should get full credit.

P-30 was originally envisioned as an entry-level outdoor event. This explains the requirement in the rules for a commercially available plastic prop of particular dimensions, basically a 9 1/2-inch plastic prop.  The rules allow weight to be added to one blade for balancing and for the hub to be drilled and bushed.

Clarence Mather (AMA Hall of Fame Inductee) was a long time member of the San Diego Orbiteers.  I understand that originally, when the P-30 rules were being developed, they did not include a minimum weight for the air frame.  I was told by another long time member of the Orbiteers that Clarence then proceeded to build a super-light P-30, possibly 30 grams.  He blew everyone away in competition and then it was decided that it would be appropriate to add the 40 gram minimum weight to the original P-30 rules.  If it was not Clarence that did this, someone please correct me.

In my own experience, a 50 gram minimum weight (excluding the rubber motor weight) would be more appropriate for P-30 since it is supposed to be an entry level event.  It seems as if considerable building skill, excellent balsa wood, a good design, lightweight Mylar covering, and/or use of CF composite materials are typically needed to build a reasonably durable P-30 that weighs 40 grams or less.  I am in awe of applehoney's gorgeous tissue-covered 34 gram P-30 that apparently does not have any CF composite material. I bet it is a fantastic flier.

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« Reply #16 on: May 01, 2018, 02:10:52 PM »

Interesting thread.  In some parts of the world 50g is indeed the required minimum weight.

Ralph's Garami clutch bound to the prop is not legal in the USA - I rather wish it was, to obviate cobbling up a similar contraption on the shaft.

Cal, none of my airplanes, of any type/size, contain any composite material in the structures, or any type of plastic covering  (other than a Blue Ridge Special which has kitchen wrap)  I still use fuses to d/t all except gliders but most everything carries a tracker.
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RalphS
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« Reply #17 on: May 01, 2018, 02:52:10 PM »


Ralph, is that a Goerge Hollingdale winder in your photo? 

It is my design and manufacture.  I made a shaft and bearing for a winder for JOD (his overworked winder was just about worn out) and traded it for a donor drill and made this P30 winder.  To get it to wind in the right direction I added the extra gear and it is a nice compact unit that saves a lot of elbow and shoulder joint wear. Grin

For those who don't know, JOD had a large modelling building in his garden.  Inside were multiple items of all descriptions either tied up and suspended from wall hooks or stored in large old baby food tins,etc.  I don't think he threw anything away.  Another "trade" was an old hacksaw frame.  "What sort do you want?" he asked,  "the heaviest one" I replied.  I was using it the other day.  Excellent tool.
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RalphS
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« Reply #18 on: May 01, 2018, 02:58:07 PM »

Ralph's Garami clutch bound to the prop is not legal in the USA - I rather wish it was, to obviate cobbling up a similar contraption on the shaft.

It used to be a subject of discussion over here.  What is legal?  No-one ever challenged my version but I seem to remember that JOD used some other solution.  The only thing we were not supposed to do was induce more pitch or modify the blades in any way.

Nice model Jim.
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« Reply #19 on: May 01, 2018, 04:41:05 PM »

Here is a picture of the Super Y P-30 mentioned in Reply #6.

I really like its retro look.

It has a pop-up wing and pop-up stab DT system for increasing the odds that the model will come down if it gets caught in a strong thermal.
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« Reply #20 on: May 01, 2018, 06:19:05 PM »

Nice colour scheme Cal Goddard...!

 ffkiwi
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applehoney
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« Reply #21 on: May 01, 2018, 06:23:34 PM »

Has two fins .... gotta be good !!!   Grin
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« Reply #22 on: May 01, 2018, 10:13:08 PM »

My Souper 30 came in at 34.5 grams complete minus only rubber.  Nothing special but careful wood selection.
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« Reply #23 on: May 01, 2018, 11:37:36 PM »

P30 weight is important but only one factor among many. There are many P30's in the 45-50 gram range that have won contests.  All my P30's are around 45 grams. The best i've had contest wise was 49-50 grams depending how much tape I had on it when it flew Grin
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« Reply #24 on: May 02, 2018, 02:43:02 AM »

In Finland we have a national rule for minimum 50 grams airframe weight. The reasoning was to give leverage to beginners, and make sturdier models that can handle landing in trees better (our fields in Finland are quite small and surrounded bu woods). That rule works good, added weight does little harm for performance but makes solid models.

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