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Author Topic: Newcomer to P30-advice sought.  (Read 1733 times)
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calgoddard
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« Reply #25 on: January 21, 2021, 02:09:18 PM »

Thank you for the complement Kevin.

Here is a picture of the orange Chinese prop. It has a larger hub bore than the Peck prop and may need to be bushed. No alterations to the prop are allowed under the P-30 rules except bushing, adding weight to one blade for balancing, and removing flashing.

The approximately 9 1/2-inch diameter orange Chinese prop costs $2 (US) from Volare Products.

The Gizmo Geezer prop is re-pitched to a higher pitch so that its P/D is 1.25 I believe.  Long ago the powers that be ruled this alteration to be legal under the P-30 rules.

I used Peck style P-30 props on my lightweight P-30 models because they had the lower pitch I wanted for the thinner (longer) 6 x 3/32 and 10 x 1/16 rubber motors.

The green prop was super light as I recall so I used it.  

I have tried pretty much every legal P-30 prop. I have read the detailed technical analysis in FFQ re the prop choices.  I think I have eight flyable P-30 models.  I have tried flying the same P-30 with different props.  So far I cannot discern an appreciable difference in flight duration.  There is one prop in my collection that may be legal which I have not tried. It is no longer available as far as I know.  

My friend Stan Buddenbohm flies his P-30 with the Czech (IGRA) prop and he is pretty much unbeatable in the P-30 event except perhaps occasionally by Don DeLoach. The plan for DeLoach's Polecat MK 10 P-30 appears to show the Peck prop.  I think these two fliers would both be pretty much unbeatable in the P-30 event regardless of which prop that they flew with.

Be aware that Stan and Don could both beat me flying your P-30 design at 45 grams.  

I might pull off a lucky victory if their models flew into a downdraft.

Have fun Kevin.

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Re: Newcomer to P30-advice sought.
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DerekMc
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« Reply #26 on: January 21, 2021, 02:31:30 PM »

If I remember correctly Stan B's record setting P30 wasn't that close to minimum weight.  Something to think about for sure.  And it used Boron to strengthen the stab.  I'd include Clint Brooks with Stan and Don. 
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billdennis747
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« Reply #27 on: January 21, 2021, 02:33:50 PM »

...and use Ezewind lube (Aeromodeller) for extra duration.
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Kevin M
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« Reply #28 on: January 21, 2021, 03:21:54 PM »

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...and use Ezewind lube (Aeromodeller) for extra duration.

Will I get more duration the more I use? May need several grams of it.....
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DerekMc
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« Reply #29 on: January 21, 2021, 03:33:15 PM »

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...and use Ezewind lube (Aeromodeller) for extra duration.

Will I get more duration the more I use? May need several grams of it.....

AMA P30 rules state the lubed motor must weigh 10 grams or less so you don't want to use lot's of lube. My motors are weighed to 9.7 grams and then lubed.  They end up up around 9.95 grams.  I use 10k -15k wt. silicone lubricant. 

The ezewind lube looks interesting and I see there is a write up on it in the latest Aeromodeller.
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atesus
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« Reply #30 on: January 21, 2021, 03:46:27 PM »

Excellent recommendations from everyone. I will add a couple more of mine. You may consider slimming down the fuselage a little and also using 1/32" ribs and/or lighter wood in the outer wing panels. I suspect the weight reduction may not be significant but since you're literally working on shaving grams so everything helps Smiley. I do agree with the strategy of reducing the weight wherever it can be done and then moving the wing to balance the plane at the end. My P-30s have a movable pylon, which I glue in place once I'm satisfied with the performance. Not sure what kind of DT you'll use but if you're going to use a viscous timer, or an electronic timer, that is a good bit of weight which you may shift around for optimizing the wing location.

Handsome design, I like it a lot.
--Ates
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OZPAF
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« Reply #31 on: January 22, 2021, 12:44:10 AM »

Another late edition to all these good suggestions Kevin.I like the 2 spar approach for your wing as it tends to induce a slight bit of washout at the tips and also turbulates the front of the airfoil however perhaps the spars may be reduced in size - definitely in the tips - say 3 square?

It's a nice looking model and deserves a bit of development!

Good luck with it.

John.

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Kevin M
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« Reply #32 on: January 22, 2021, 09:23:17 AM »

Today I have been trying to incorporate some of the above helpful suggestions; some others will have to wait for the next version.

Most of the fuselage sheeting has been removed, a saving of 0.66g. Most of that was at the front end, removing the bits where the fins attach only yielded 01.g, but it all adds up.

I made a new shorter nose-block and left off the ply facing, used a shorter brass tube bearing for a total saving of 1.34g, certainly worth having.

The c/s sheeting on the horizontal stab only came to 0.08g, so I’ll leave it on this one but not bother with it on the next, similarly with the wing c/s sheet.

I managed some trivial savings with some minor wood removal from both fins.

My fuselage is now down to 11.3g, so 2.1g saved. On the next one using 1g vs. 1.4g sticks for the longerons would save another 1.2-1.5g, and I could use even lighter stock for uprights and cross-pieces than I did on this (when balsa becomes available again here). Thanks to your advice I think I am on the right track.

Do people generally use 18swg (.048”/1.22mm) prop shafts on these?
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lincoln
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« Reply #33 on: January 22, 2021, 11:24:52 AM »

You might try moving the motor peg forward if you're worried about nose weight. Maybe this would allow a lighter prop. Coupe d'Hiver models have the peg quite far forward, but they don't use heavy plastic props.

If it was my model, I'd put something over that nasty wire up front before flying it. Or else use a finish that's blood-proof.
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Kevin M
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« Reply #34 on: January 22, 2021, 11:43:42 AM »

Lincoln, the Mk 1 balanced without nose weight; this one will be lighter up front but also hopefully at the back too. The current plan is to complete the model and adjust the wing position a little if necessary to balance it. At the moment the rubber distribution about the C.G. is roughly 46/54.

Yes, my Coupe has the peg at the wing TE.
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dosco
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« Reply #35 on: January 22, 2021, 12:08:20 PM »

Lincoln, the Mk 1 balanced without nose weight; this one will be lighter up front but also hopefully at the back too. The current plan is to complete the model and adjust the wing position a little if necessary to balance it. At the moment the rubber distribution about the C.G. is roughly 46/54.

Yes, my Coupe has the peg at the wing TE.

Kevin:
If I understood your description correctly (quite possible I did not) ... you mentioned removal of several widgets of noseweight, as well as plans to keep several widgets of tail weight.

While the suggestions here have indicated you should place the wing "at the end of building" so as to achieve a natural state of balance (and avoid addition of noseweight), wouldn't you want to seek to eliminate the tail weight (due to lever arm considerations)? I'm not sure I see the need for keeping the sheeting on the horizontal stab.

Anyhow, probably nitpicking, as you indicated that sheeting = 0.08g.

Regards-
Dave
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Kevin M
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« Reply #36 on: January 22, 2021, 12:18:22 PM »

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I'm not sure I see the need for keeping the sheeting on the horizontal stab.

Laziness. It won't be there on the next stab.

No, just trying to keep it light everywhere and hope the balance works out somewhere near.
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gman
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« Reply #37 on: January 22, 2021, 01:52:08 PM »

Hi Kevin, if you're interested in Orange plastic P30 props you might try..
https://www.ebay.co.uk/itm/5pcs-Orange-Plastic-9-5-17mm-Hub-Thick-RC-Airplane-Propellers-Vanes/362791382206?hash=item54780d2cbe:g:9agAAOSw7XFf8pa0
regards wire gauge, 18swg will be fine for a P30, maybe make your "Gray Hooks" from 22swg. It's about saving a little bit of weight wherever you can.
Gavin

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Kevin M
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« Reply #38 on: January 22, 2021, 01:58:35 PM »

Thank you Gavin. I'll look into that source, and I would have gone for 18 swg for the Gray hook, good to know it can be lighter.
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calgoddard
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« Reply #39 on: January 22, 2021, 05:41:36 PM »

Kevin -

For P-30 models the standard prop shaft diameter that I use is .047-inches.

Do yourself a favor and install a 9 ½-inch Gizmo Geezer prop assembly on the current P-30 you are building. It will provide three distinct advantages:

1)   Precision thrust line adjustments that are easy to make;
2)   Reliable free-wheeling of the prop during the glide; and
3)   Avoidance of rubber motor bunching and CG shifting where the prop hook-to-motor peg distance is substantially less than the length of the rubber motor.

Normally no. 3 is not a factor in P-30 as the typical prop hook-to-motor peg distance is set up to accommodate a 6 x 1/8-inch rubber motor that is approximately 19-inches long.  
Someone mentioned moving the motor peg in the fuselage of the P-30 you are building forward to improve the moment arm.  If you are going to use a shorter 15-inch prop hook-to-motor peg distance, for example, a 19-inch rubber motor might bunch in the rear toward the later part of the motor run, causing a stall.  Or it might bunch in the front, causing a dive.

Like everything else in free flight, shortening the motor hook-to-motor peg distance is a trade-off.  You either have to use a braided rubber motor or a spring tensioner, like the Gizmo Geezer prop assembly includes, if you substantially shorten the prop hook-to-motor peg distance. The spring tensioner in the Gizmo Geezer prop assembly will leave you with about 50 or so unused turns, and that is why the rubber motor will not go slack and bunch.  However, those unused turns would have very little torque and would not increase the flight time very much.

Personally, I wouldn’t use a short motor hook-to-motor peg distance in a P-30. If it provided a significant benefit, others would already be doing it.

Motor bunching becomes a big problem with scale models where the rubber motor can be 2X, 3X or even 4X the prop hook-to-motor peg distance in order to get a reasonably long motor run.

I am aware of two extreme P-30 designs that use a very short motor hook-to-motor peg distance. Each has a rubber motor with more than six strands of 1/8 rubber. One uses a 14 x 1/8-inch rubber motor and a 1:4 gear drive. The other uses -a 10 x 1/8 rubber motor that is wound to a ridiculous launch torque. The gear drive is inefficient and trimming a P-30 to launch at 20+ inch-ounces is not a viable strategy in my opinion.

Keep up the good work.  Your P-30 is a very good looking design.
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calgoddard
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« Reply #40 on: January 22, 2021, 05:46:29 PM »

Kevin -

The motor peg holes in your sheet balsa wood uprights will quickly wear and the motor peg will have a sloppy fit. These uprights may fail as the holes enlarge and/or the motor peg may dislodge. Each such failure can cause major damage to the fuselage of your model.

You need to glue two ½-inch x ½-inch squares of 1/64 plywood over the inside surfaces of your motor peg uprights. Reinforcing the motor peg holes is standard practice in constructing balsa wood model airplanes.

Pre-drill holes in the center of these squares that are the same size as the OD of your motor peg. White glue, carpenters glue, or nitrocellulose cement (e.g., Duco brand) should be used to glue the plywood squares to the inside of the uprights. Don’t use CA for this purpose. The former types of glues will give you time to adjust the location of the small squares. Use the motor peg to align the holes in the squares with the holes in the uprights.  Pull the motor peg out of the squares while the glue is still uncured, taking care that the position of the squares does not change.

On my P-30 models that have a rolled sheet balsa fuselage, I boil the squares in water and form them over a forming mandrel so that they conform when glued to the outside of the fuselage. It’s not practical to glue these reinforcements on the inside of a sheet balsa wood tubular fuselage.

Switch to a 1/8-inch OD Aluminum tube for a motor peg for your P-30.  It looks like you are using a larger diameter motor peg like 3/16-inch which is overkill.

« Last Edit: January 22, 2021, 05:59:42 PM by calgoddard » Logged
Kevin M
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« Reply #41 on: January 22, 2021, 06:09:48 PM »

Thanks Calgoddard, all good thoughts. My plan is to use 6 strands of 1/8" with the motor length you see. I always do .4mm ply around those holes, I like your idea for making them fit on curved fuselages. You are right about them being sized for a 3/16" tube.I have been used to stronger motors recently than these use. I will reduce to 1/8"
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gman
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« Reply #42 on: January 23, 2021, 10:06:16 AM »

I would have gone for 18 swg for the Gray hook, good to know it can be lighter.
Hi Kevin, now I see that you're using 6x1/8th for the motor then maybe 20swg for the hook, I use 22swg on 10x1/16th or lighter. Best is to try it and see. Do keep the hook nice and "compact" though, big open loops will distort even on these small motors, and weigh more!
As if all this weight chasing isn't enough don't forget there's 3.5g of tracker....
Gavin
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Kevin M
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« Reply #43 on: January 23, 2021, 11:14:49 AM »

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don't forget there's 3.5g of tracker....

Yikes!

I'll try 20 sag, thanks.

K
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flydean1
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« Reply #44 on: January 23, 2021, 09:54:28 PM »

Derek,

Re: pop-off wing DT.

I'm kind of curious as to where you fasten the line between the wing and the end of the fuselage?  On my grandson's Souper 30 about a dozen or more years ago, we fastened the line to the DT break on the right side.  there were a couple over-sized gussets for an anchor point.  Some said he should have put it on the wing tip.  Only used it once and it was so far away, I couldn't see how well it worked.  Got the model back as he was under it with his chase bike.

We were careful to route the dt line across the top of the stab and it had very little slack.  It seemed that if it was under the stab, the line would probably damage the stab when the wing popped off.

Still, maybe the tip would be better as the usually slightly heavier tip rib would be sufficient and not make a huge gusset necessary.
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DerekMc
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« Reply #45 on: January 26, 2021, 12:48:05 PM »

Dean I'll post a few pictures of the dt line attachments and swivel when I get back home. It will be in early February. 
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« Reply #46 on: January 26, 2021, 06:37:29 PM »

Thanks Derek, that's soon enough.  Building my Jetstream first.
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atesus
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« Reply #47 on: January 26, 2021, 07:05:04 PM »

Derek,

Re: pop-off wing DT.

I'm kind of curious as to where you fasten the line between the wing and the end of the fuselage?  On my grandson's Souper 30 about a dozen or more years ago, we fastened the line to the DT break on the right side.  there were a couple over-sized gussets for an anchor point.  Some said he should have put it on the wing tip.  Only used it once and it was so far away, I couldn't see how well it worked.  Got the model back as he was under it with his chase bike.

We were careful to route the dt line across the top of the stab and it had very little slack.  It seemed that if it was under the stab, the line would probably damage the stab when the wing popped off.

Still, maybe the tip would be better as the usually slightly heavier tip rib would be sufficient and not make a huge gusset necessary.

Although not a P-30, I used pop-off wing DT on my late Square Bird with great effectiveness. It brought the model down so fast that on that one day, I took my eyes off of the model for a moment, and it had already fallen out of the sky and I lost it  Grin.

The DT line went from the TE at the wingtip to a hard-point at the tail. A swivel was included in the line. Although the photos don't clearly show it -particularly after the requisite compression- the line was routed above the stab for the reasons you also mentioned. Keeping the line just long enough makes sure that the line cannot move under the stab in flight. Another concern was the wing potentially hitting the fin but in practice that turned out to be a non-issue. Once the wing pops off, the nose quickly dives, and the wing flies upwards so the separation of the two pieces is very fast. I had a video clip where I was able to see this clearly, but I couldn't locate it. If I find it I'll post. I found this video (link below) which shows the DT operation towards the end.

https://youtu.be/TBe_axZQHGo

Best,
--Ates
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calgoddard
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« Reply #48 on: January 27, 2021, 12:14:21 PM »

If you employ a pop-off wing DT in a P-30, one end of the line should be connected to a first swivel connector mounted in one wing tip, midway between the LE and the TE.  The other end of the line should be connected to a second swivel connector mounted in the rear end of the fuselage.  The line should be 10# monofilament fishing line and should have a length that is only slightly larger than the distance between the connectors.  The line should run over the top of the stab when the model is launched. The swivel connectors are the type that are typically used as part of a rod and reel fishing line set up.

I am not a fan of the pop-off wing DT as the fuselage comes in very hard, nose down. This can lead to a bent prop shaft and/or broken fuselage if your flying field has a hard pack dirt surface with no vegetation, such as one experiences at Lost Hills, California and Eloy, Arizona. The grassy flying fields of the UK would present no risk of such damage if a pop-off wing DT were used.

I prefer use of a combination pop-up wing and pop-up stab DT on a P-30.  The model descends gently in a horizontal orientation.  See the end of the video at this link:

https://www.youtube.com/watch?v=L10YLPjZq38

Details of the pop-up wing and pop-up stab DT set-up are provided in the instructions for the excellent P-30 kits sold by CB Model Designs.
 
I have attached a picture of my P-30 model that I am flying in the video. This model has no moving surfaces except for the DT.
 
Note that the P-30 in the video is flying with a 6 x 3/32 rubber motor.  It DT’s early, with the prop still being driven, and when the model is still climbing.  Even though this P-30 was only launched with 1,500 turns at only 3 inch-ounces of torque, the flight would have easily been over two minutes had the DT not triggered early.  I could probably wind the same rubber motor to 2,000+ turns and perhaps 4-5 inch-ounces of torque before breaking. I might be able to wind this motor to 6-inch ounces of torque, but that would be pushing the envelope.

Note that use of a 6/32-inch rubber motor in a P-30 necessitates the motor peg being located under the stabilizer. This leads to challenges in mounting the model on a winding stooge.  Use of a thinner rubber motor in a P-30 gives you a long motor run. However, the model must be very close to the 40-gram minimum to get a good climb.  Also, lightweight P-30 models like the one in the video only perform well in calm conditions.  In the UK, I would fly a sturdier 45-gram P-30 with a 6 x 1/8-inch rubber motor.
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Kevin M
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« Reply #49 on: January 27, 2021, 01:52:44 PM »

Calgoddard, I'm keeping notes of your excellent advice and experience of P30. I'll investigate the pop-up wing and stab system.

Quote
In the UK, I would fly a sturdier 45-gram P-30 with a 6 x 1/8-inch rubber motor.

Pleased to hear you say that because that is what i planned, although I was wondering about 3/32. I'll now stick to 6 X 1/8" (albeit my model that started this thread looks like it is going to finish at 48g or 49g; hopefully the next will make 45).
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