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Author Topic: Cracked Ribs?  (Read 1098 times)
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Bigbandito
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« on: June 13, 2018, 12:39:27 PM »

My next project includes cracked ribs. I'm pretty sure I know what they are, but I'm a little unsure as to the best way to construct them. I searched for a post on the topic and found none. Would anyone like to provide a little advice?

Oh, and I understand some competition classes don't allow them. This is a P-30. Am I OK with cracked ribs?

Thanks
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flydean1
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« Reply #1 on: June 13, 2018, 10:55:34 PM »

No structural restrictions in P30.

Usually my main spar was full depth and established the high point.  Sometimes I notched the bottom for the lower stick, sometimes simply glued it on top of the lower stick.

Bottom stick goes from leading to trailing edge.  Front top goes from leading edge to top of main spar.  Rear top goes from main spar to trailing edge.  There is usually a spar on top of the front stick midway between the main spar and leading edge from root to tip.  Some on larger models use two such on the front, dividing the area in thirds.

There are variations such as using diagonals to gain some torsional stiffness.  For years, I built all my scale models with tapered or elliptical wings using this method.  It works really well.
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packardpursuit
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« Reply #2 on: June 14, 2018, 07:23:08 AM »

It never appealed to me but IIRC, the usual method of cracking the rig cap stick was to crease the stick in the appropriate spot with a finger or thumbnail. Again, IIRC, a fellow named Oldencamp came up with method specifically for his early P-30 design.

Suggest trying simple excersise to learn best technique that works for you. You could create a common specific length sticks for all the tops and arrange some sort of guage to determine the point of thumbnail impression.  the idea is to crease the soft balsa so that the break is localised to a repeatable degree, but not to break off or separate the stick completely. Remaining fibers of the shattered induced failure are fixed back togeher with glue while being glued to the spar, LE and TE.
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Crabby
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« Reply #3 on: June 14, 2018, 10:57:44 AM »

BigBandito, are you getting ready to start the Spitfire P-30?
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Bigbandito
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« Reply #4 on: June 14, 2018, 12:51:53 PM »

Thanks for the explanation folks. It's just what I needed.
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Bigbandito
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« Reply #5 on: June 14, 2018, 12:55:00 PM »

BigBandito, are you getting ready to start the Spitfire P-30?

I am! And I'm very excited about it. It's for a club competition in mid-August. That's a fast build for me.

Next thing I need to do is plan how to build the spinner and keep a freewheeling prop. I was going to use a Gizmo Geezer, but no stock available right now. I guess It doesn't really have to have a spinner if I run short on time.
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« Reply #6 on: June 14, 2018, 01:03:56 PM »

I believe that the late John Oldenkamp was the person that originated the cracked rib construction technique in his Hot Box P-30 model.

John was a long time member of the San Diego Orbiteers free flight club and he was one of two fliers who were responsible for developing the rules for the P-30 class. Harry Steinmetz, another member of the San Diego Orbiteers, was the other flier that was responsible for developing the P-30 rules.

John was also largely responsible for the development of the E-36 class.

John Oldenkamp was elected to the NFFS Hall of Fame in 1998.

Do a Google search for "hot box P-30 plan".

You can click on the link for RC Groups that comes up and a pdf of the plan will be downloaded.

The Hot Box plan was first published in Model Builder magazine in the July 1977 edition.

There are cross-section views of the wing and stab on the plan that will give you the details of the cracked rib construction.

I am tempted to build the Spitfire P-30 but am put off by the work that would be needed to form a nice one-piece clear plastic canopy.  
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Bigbandito
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« Reply #7 on: June 14, 2018, 03:50:08 PM »

I am tempted to build the Spitfire P-30 but am put off by the work that would be needed to form a nice one-piece clear plastic canopy.  

Thanks Cal. I've admired the Hotbox and read of its many exploits in P-30.

Since the P-30 Spitfire has a number of other compromises for the sake of simplicity, I have no qualms with a slab sided canopy. I'll probably add outside "frames" to cover the gaps and round the front screen a bit.

It's probably not going to be competitive, but I think it'll be a lot of fun.
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calgoddard
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« Reply #8 on: June 14, 2018, 05:05:25 PM »

Bigbandito -

Watch this video for some inspiration.

https://www.youtube.com/watch?v=bqATqXS735s

Here is a link to a build thread for what appears to be the same Spitfire P-30 shown in the video, or one remarkably similar to it:

https://www.modelyapiyorum.com/model-ucak/spitfire-p30-gultekin-kalay/

The text of the aforementioned build thread is in the Turkish language.  I ran a sample of the text through the Google translator and it did an excellent job.  The photos should be helpful.  It appears that the Turkish modeler built a flat-sided canopy as you proposed.

Please start your own build thread so we can follow your progress.

Any P-30 can win a P-30 contest if built light and trimmed well, and if it catches good air.

Good luck!
« Last Edit: June 14, 2018, 05:23:04 PM by calgoddard » Logged
Bigbandito
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« Reply #9 on: June 14, 2018, 06:26:44 PM »

Bigbandito -

Watch this video for some inspiration.

https://www.youtube.com/watch?v=bqATqXS735s

Here is a link to a build thread for what appears to be the same Spitfire P-30 shown in the video, or one remarkably similar to it:

https://www.modelyapiyorum.com/model-ucak/spitfire-p30-gultekin-kalay/

The text of the aforementioned build thread is in the Turkish language.  I ran a sample of the text through the Google translator and it did an excellent job.  The photos should be helpful.  It appears that the Turkish modeler built a flat-sided canopy as you proposed.

Please start your own build thread so we can follow your progress.

Any P-30 can win a P-30 contest if built light and trimmed well, and if it catches good air.

Good luck!

Wow! Thanks Cal.
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« Reply #10 on: June 17, 2018, 10:40:21 AM »

Not that the hobby needs another splinter event, but WOW!!  I just entertained visions of 30" Prototype Spitfire, with this wing structure, and completely non -molded flat sided canopy. Yes,... I just invented P-30 Scale!  The real genius is that such a model would be both scale and non-scale  Roll Eyes all at the exact same time No need for thanks, people ... just send ALL  royalties to.... Grin
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Bigbandito
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« Reply #11 on: June 17, 2018, 02:14:56 PM »

... I just invented P-30 Scale!

Could we fly it in WWII mass launch?
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« Reply #12 on: June 18, 2018, 12:09:48 PM »

"Could we fly it in WWII mass launch?"

 Hey, you have my permission... but neither AMA or Flying Aces listens to me...




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Bredehoft
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« Reply #13 on: June 18, 2018, 03:52:45 PM »

If a scale model met the 30" max measurements and 40 gram minimum weight, used 10 grams of rubber, and used an unmodified 9.5" prop, I believe it would qualify for P-30 (not a P-30 expert).

For WWII, making things like the sides and canopy flat (not to scale) would disqualify it for WWII Combat.  It would also need proper colorings, markings and forward firing guns.

It could be done...

P.S. there are several ways to put a spinner on a prop and retain a freewheeler.  Search through these articles; there is at least one that covers the spinnerr subject:  http://volareproducts.com/?page_id=1686

--george
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« Reply #14 on: June 18, 2018, 06:18:25 PM »

You could also check out on my Avetek Pilatus PC9 thread http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=21457.50   replies 62 and 69 onwards - this covers a freewheel on a plastic prop with spinner that would work for a P30
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packardpursuit
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« Reply #15 on: June 19, 2018, 11:10:54 AM »

Early Spitfires had flat sided perspex  canopies well into Battle of Britain period. Compound curve added just at top profile, but sill flat sided. Full round frontal cross section appeared on Mk.V's, IIRC.

AFAIK, there is no specific rule that excludes a scale model from entering endurance events. Generally, there is no rule that excludes a non-scale endurance model from entering a scale competition. Poor scale scoring conceivably limiting their overall success. However, special event rules, such as for WWII mass launch, may limit physical and/or subject requirements of models deemed appropriate for a significant historical time period, etc.   Another possible snag maybe the final arbitrary decree of an event CD.

You guys interested in specific events, really need to READ the rules of the event BEFORE building any model for that event. I'd bet EVERY rule is pretty much available on line and only a few key strokes away.  A failure to plan, is a plan for failure!
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Bigbandito
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« Reply #16 on: June 19, 2018, 12:34:44 PM »

Thanks for the tips on prop and spinner set up guys. Don't know if I can make that work by August.

My suggestion of P-30 in WWII mass launch was strictly in jest.  Grin Although I might be tempted to launch a secret attack and wreak havoc on their carefully sculpted and adorned little hides. Wink Cheesy Grin
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Bigbandito
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« Reply #17 on: June 19, 2018, 01:01:55 PM »

"Early Spitfires had flat sided perspex canopies well into Battle of Britain period. Compound curve added just at top profile, but sill flat sided. Full round frontal cross section appeared on Mk.V's, IIRC."

I think you're right packard (see attached photo).

Speaking of which... After agonizing over the underside paint scheme, I've decided that I'll have a better chance of keeping my Spit' in sight if I do it the old fashioned way. Im 99.9% certain I'll use the early Battle of Britain scheme with the port wing painted black with the rest of the underside white (see attached graphic). That means it would be a MKI or MKII, right? I'm specifically looking at modelling the KLB P9398 "Kiwi" flown by New Zealand's Al Deere as Callie Graphics has a nice set of vinyl for it that Callie says can be scaled down to 1:15.

By the way, what do you think of my use of vinyl graphics on this? Too hard to apply? Too heavy?

Does anyone have experience with vinyl graphics on tissue?
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Re: Cracked Ribs?
Re: Cracked Ribs?
« Last Edit: June 19, 2018, 01:27:33 PM by Bigbandito » Logged

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Crabby
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« Reply #18 on: July 01, 2018, 10:12:04 AM »

Hi Bandito. You can make esaki markings by mounting esaki, prespray the back white with floral paint, apply thin front mount adhesive, and print away they come out great, very light, and pressure sensitive. I can do a set for you if you PM me too. I have a roll of front mount.


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« Reply #19 on: July 01, 2018, 11:21:22 AM »

Crabby,

Help me understand a little more.  The white backspray gives contrast to the printing. The light adhesive is to attach to the backer sheet for printing. Does the spray adhesive also serve to attach the "finished" decal onto the covering tissue or is glue stick or another adhesive used for the final attachment onto the model?

Tissue printing was discussed at yesterday's lunchtime gathering, but I have only done it a little for 4 models and not for scale models.

Fred Rash



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Crabby
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« Reply #20 on: July 01, 2018, 01:06:32 PM »

Good am Fred. What I was prescribing to Bandito was a method for making tissue markings such as roundels for his Spitfire. The adhesive I was prescribing is known as "front mount adhesive" in the graphics industry. You can get a sample roll 10'  x 30" for $50 from Drytac. I bit the bullet and bought one because a friend needed markings. To answer your question though, I don't use spray adhesive in this case. I adhere the the adhesive sheet to the back of the tissue, then print, then comes the fun part: cutting the markings out with a compass-cutter. It takes practice to cut through the tissue and the adhesive layer and not go all the way through. Its a skill that is in your wheel-house as a modeler though! In the end you have your markings neatly Roll Eyes cut out and still fixed to a the clear backing film. Peel off and carefully apply. You get no second chances on tissue!
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Bigbandito
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« Reply #21 on: July 01, 2018, 02:58:28 PM »

Hi Bandito. You can make esaki markings by mounting esaki, prespray the back white with floral paint, apply thin front mount adhesive, and print away they come out great, very light, and pressure sensitive. I can do a set for you if you PM me too. I have a roll of front mount.

Thanks for the offer Crabby. It’s very generous of you. I got a set of markings in vinyl form Callie Graphics, though. Much heavier, but easier for me.  That and the floral spray camo scheme are gonna make it a good bit heavier than it has to be.
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« Reply #22 on: July 01, 2018, 03:01:49 PM »

Floral spray is one of the lightest ways to go.......good luck with Callie
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