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Outdoor Free Flight Forum => Power => Topic started by: Starduster on July 10, 2014, 08:47:15 PM



Title: Sandy Pimenoff's Number 18
Post by: Starduster on July 10, 2014, 08:47:15 PM
All

I was going through my stack of drawings last night and cleaning out drawings.

I found my drawing of Sandy Pimenoff's Number 18. This airplane was flown in 1960.

I did this drawing way back in the 1990's in CAD, but I no longer have the files.

So, the question is:

If there is sufficient interest, I will take my paper down to my local Kinkos/FEDEX, have them (there are two sheets) scanned and upload the .pdf into the plans gallery.

So, what say you? Is it worth it?

Thanks

Rich

BTW - Giving the airplane another look after all these years, I am thinking about building one over the winter, but building it for electric.


Title: Re: Sandy Pimenoff's Number 18
Post by: monocoupe110 on July 11, 2014, 02:39:02 AM
I would download them!

Cheers, Nigel  :)


Title: Re: Sandy Pimenoff's Number 18
Post by: glidermaster on July 11, 2014, 02:42:45 PM
That would be my vote, too!

JB


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on July 11, 2014, 07:15:02 PM
I've up-loaded the drawing. I was not able to combine the two .pdf's, so there are two files to up=load. Give Ratz a while to approve and take a look.

The drawing is full-size.


Title: Re: Sandy Pimenoff's Number 18
Post by: monocoupe110 on July 12, 2014, 11:37:19 AM
Thanks for sharing Iceman!

Cheers, Nigel


Title: Re: Sandy Pimenoff's Number 18
Post by: Red Buzzard on August 06, 2014, 12:15:11 AM
Iceman,

I'm late on this but thanks for the offer as well. I'll look for it at the Gallery.

Bill


Title: Re: Sandy Pimenoff's Number 18
Post by: glidermaster on August 07, 2014, 01:21:35 AM
You're going to have to go some to get one ready for Tangent, Bill!

JB


Title: Re: Sandy Pimenoff's Number 18
Post by: Red Buzzard on August 13, 2014, 12:26:34 AM
John,

Wish I could but in this case, wishes are horses. I'll be there to CD and with a re-covered Altmann and some other stuff, but no Vint entry. It's on my list though, and working its way up.

Brings my best,

Bill



Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 18, 2014, 02:22:35 PM
Question for you power guys regarding the #18:

I see on the sketches (from the sketches attached) that the wing is at positive 3 (or 4) degree incidence, and the horizontal stab is at positive 1 (or 2) degrees decalage.

Is this so the airplane glides in a nose-down attitude? I've never seen a set up quite like this (Rather high angle of attack on the wing and a positive angle of attack on the stab) Why didn't he just go with 1 or 2 degrees incidence and a little negative decalage?

I'm just curious.

Thanks

Rich


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 20, 2014, 03:08:07 PM
Gentlemen and Ladies

I need some advice:

I am re-creating the Number 18 in 3D CAD. I was looking a little more carefully at the drawing I up-loaded to the Plans Gallery and comparing it to the two sketches attached in the above post, I saw that there are a few things that I would like to clean-up. (I don't think I got the airfiols quite right and the horizontal stab outline is a bit off.

So, a couple questions:

1) Of the two sketches shown above (one from Zaic and the other from Volar Libremente, which would you say is more accurate (true to the original)
2) There is no mention of the thickness of the wing or stab ribs. I would think that the stab uses 2.5mm Balsa, but 2.5mm seems thin for this size wing.

Thanks

Rich

And by the way... Once I get done with the new CAD Model and drawing, the plan right now is Bob Holman will be offering the short-kit for the airplane!


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 20, 2014, 03:42:56 PM
Looking at the CAD Model, though, it looks like 2.5mm for the wing ribs is OK:



Title: Re: Sandy Pimenoff's Number 18
Post by: applehoney on August 20, 2014, 07:42:43 PM
Rich, I feel that 2.5mm ribs would be overkill, especially for the stabiliser.

I'd use 1/16" - 1.5mm - all through, especially as there's quite a lot of wood in that wing


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 20, 2014, 07:57:24 PM
Rich, I feel that 2.5mm ribs would be overkill, especially for the stabiliser.

I'd use 1/16" - 1.5mm - all through, especially as there's quite a lot of wood in that wing

I agree with you, thanks!


Title: Re: Sandy Pimenoff's Number 18
Post by: RobinB on August 21, 2014, 02:30:46 PM
Ribs and riblets are 2mm. Diagonals are 3 x 3 mm. Main spar 15 x 10 mantya (spruce?)
Stab ribs and riblets are 1.5 mm. Stab spars 3 x 3 mm.

Robin


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 21, 2014, 04:08:40 PM
Ribs and riblets are 2mm. Diagonals are 3 x 3 mm. Main spar 15 x 10 mantya (spruce?)
Stab ribs and riblets are 1.5 mm. Stab spars 3 x 3 mm.

Robin


You sound pretty confident... can I ask where you are getting your information? (not doubting you, just curious...)

Also, you say "Diagonals are 3 X 3 mm" Are you saying the diagonal ribs are not full depth airfoils, but just 3 X 3 mm? (see the attached picture)



Title: Re: Sandy Pimenoff's Number 18
Post by: RobinB on August 22, 2014, 03:35:09 AM
I have a copy of the plan. One of the people who started the Cranfield Classic contests
sells plans of the 5 models.
I think it is George Arnott, but I'm not sure. Anybody?

Robin


Title: Re: Sandy Pimenoff's Number 18
Post by: billdennis747 on August 22, 2014, 03:47:31 AM
Google Allan Brown Cranfield Classic plans


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 22, 2014, 08:06:37 AM
I can't find anything on George Arnott or Allen Brown Cranfield Classic Plans.

My intention is to make this CAD Model and drawing as accurate (faithful to the original) as possible.

So far, I have a couple of questions:

1) Are the diagonals in the wing full-depth ribs, or are they 3 X 3 square stock?

2) Looking at the sketch from Volar Libremente, take a look at the attached picture of the airfoils.

on both the wing and stab ribs, it appears to me that the spars are embedded in the ribs. But... there are two short lines that go from the cross-hatched spar to the top of the airfoil (except for the forward spar of the stab rib). I'm not sure how to interpret this.

(BTW - I am going to ignore the Zaic stab rib drawing, it looks like the extra spars were added later, see the second picture)


Title: Re: Sandy Pimenoff's Number 18
Post by: billdennis747 on August 22, 2014, 08:16:16 AM
http://www.sam1066.org/nc1110.pdf

Contains Allan's email address


Title: Re: Sandy Pimenoff's Number 18
Post by: mick66 on August 22, 2014, 08:26:17 AM
Hi

I'm mates with Allan Brown.  He ran a Cranfield Classic a couple of times at the BMFA FF Nats a few years back.  The Scottish lads (Jim Arnott) run one every year up there.    I think you're mixing names between AllanB and George Blair who is another well known modeller and one of the Scottish boys.

Anyway ... seems like an awful lot of effort to CAD the plans when you can probably get them off AllanB.  Check out the SAM1066.  http://www.sam1066.org/nc1209.pdf
Also, in one of the Clarions John Thompson did a write up of his No18.

In the meantime ... here is a couple of pics of the real thing.  Engine is an OS19 Max (Nelson Head and pressure venture\NVA from Ed Needham)
I'll dig out weights and trims if anyones interested .. mine goes OK but I'm about to re-engine with a Norvel 15 BB (Nelson Head and pressure venture\NVA from EdN again).  Does just under 23K on an APC 7x4.

Cheers

Mike



Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 22, 2014, 08:38:44 AM
Thanks, Bill and Mike

The (main) reason I'm doing the CAD model is to get a LASER kit done. (Besides the fact that up until this morning, I was unaware that anyone else had done the full-size drawing). As I mentioned above, Bob Holman has agreed to offer the short kit. I love the look of elliptical airplanes, but man-o-man I hate cutting out ribs for them!

I am also "hooked" on electrics, and I am planning on building a No. 18 for electric ("Burn him! He's a witch, burn him!")

Mike, can you do me a favor, though? Can you ask Allan if he has any heart-ache with me doing the plans and offering them for sale through Bob Holman?

A few pictures of the complete wing 3D CAD Model:


Title: Re: Sandy Pimenoff's Number 18
Post by: mick66 on August 22, 2014, 08:48:49 AM
Hi

don't worry about the electric thing ... they're working on a cure.

Yeah ... I can ask AllanB but I'm not sure he owns the rights or anything.

Cheers

Mike


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on August 22, 2014, 10:34:07 AM
Suomen Ilmailuliitto (the Finnish Aviation Federation) published in early 1960's a book called "Suuri Lennokkikirja" (The big book of model airplanes), where the section of FF power models was written by mr. Pimenoff himself. The article also has a small drawing of the #18. In the picture the diagonals are marked to be 3*3mm, and it seems that they are slightly thicker than the ribs. Also there is another picture of wing structure, where the text mentions that the forward end of diagonals should be glued as high as possible, and the aft end as low as possible. This seems to suggest to me that the diagonals are indeed square. (I think the original #18 is at display at the Aviation Museum in Helsinki Airport, so I could go and check. However I think that mr. Pimenoff has restored the model with new, opaque covering, which would make it impossible to check the structure...)

The last picture from the book shows a launch of a D-2 power model, and from the rudder shape I conclude that the model is #18, so I think the picture is of mr. Pimenoff himself.


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 22, 2014, 11:01:02 AM
Thanks, Tapio

That drawing from the book and your explanation answers my questions. It looks like neither the Zaic or the Volar Libremente got it quite right.

It's interesting that the drawing in the book shows a built-up vertical stab.

Also, I can't quite make it out, but does the drawing or the article mention the incidence and/or the decalage angles?

I'll have to go back and change a few things in the CAD model....

Rich


Title: Re: Sandy Pimenoff's Number 18
Post by: billdennis747 on August 22, 2014, 11:08:16 AM


on both the wing and stab ribs, it appears to me that the spars are embedded in the ribs. But... there are two short lines that go from the cross-hatched spar to the top of the airfoil (except for the forward spar of the stab rib). I'm not sure how to interpret this.


I would say the spars are dropped in and the gap filled with little bits of balsa. Much easier build.


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on August 22, 2014, 11:37:07 AM
The drawing does not indicate the angles, but the attached picture suggest the angles, and the article says "the decalage should be 2 to 3 degrees as in picture 54, the final value is established during trimming."

About rudder, the article says that "the rudeer should be built-up instead of sheet, to avoid warping."

To me it seems that the spars are inset into the ribs, and the riblets have a flange coming over the spar.


 


Title: Re: Sandy Pimenoff's Number 18
Post by: mick66 on August 22, 2014, 12:17:23 PM
Hi

looking at my trimming notes ... all angles wrt bottom of fuse.

CG:                         83%
LeftThrust:             +1.5 degrees
DownThrust:           +2.0 degrees (as in down)
Wings:                    +3.0 degrees
Tail:                        +1.5 degrees (giving +1.5 decalage)
PRT tip washout:       +2mm
PRT inner panel:        flat
STB panel washin:    +2mm
STB tip washout:      +2mm

On the actual plan the rigging angles are Wing (+4 degrees) and Tail (+2 degrees).
I've trimmed it out at little under ... +1.5 degrees as noted above.

Tip washout measured at TE behind last rib.

Cheers

Mike



Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on August 22, 2014, 12:38:28 PM
Gentlemen:

Thanks for all the help.

Thanks also to the power of "parametric" 3D modeling, it took me all of about 5 minutes to change the diagonals, see attached.



Title: Re: Sandy Pimenoff's Number 18
Post by: hastf1b on August 22, 2014, 02:58:35 PM
Sandy Pimenoff with "Ascender".

Heinz


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on August 22, 2014, 11:04:38 PM
Different tailplane!


Title: Re: Sandy Pimenoff's Number 18
Post by: john thompson on August 23, 2014, 04:19:32 AM
Zaic 59/61 , shows 2 versions No; 18 and the Ascender , 18 had rectangler tailplane .
My set up is 82 % cg ,+3.8 wing +2.3 tail . 4 down 1.5 left  ( these are approximate but as measured with a digital gadget ) . No warps except both tips washout by about 1.5 . Power Oliver Tigre replica 9x 5 Master about 12 k . Model flies beautifully, nice spiral, A/R not really needed . Dihedral is on low side for windy UK weather .
I have tried with more power without success ,( the problem I believe,  lies with the wing section having the undercamber starting immediately from the LE ) the model being extremely erratic in pattern and unreliable . I have built another wing with this section for another model and had same erratic pattern . On other models where this apparent problem has arisen , I have covered in the bottom of wing to make a flat bottomed section and the problem has gone away . So I must, with this limited testing assume that the undercamber was the problem , but with so many variables who knows ?
On page 47 of that Zaic is also shown, what I think is a rather good model !!
 All ready for the 2 days at Middle Wallop . Forecast fine Sunday, but rain Monday . At least I will (with others ) not be stuck on the gate this time, as we are not charging SAM 1066 entry fee this time , as we do not want to built up funds just sitting in the bank doing nothing . With a bit of luck we may get up to 150 or more freeflighters in attendance on the fine day . I suspect that there are not many places in the world where that number gather . lots of walking and hiking sticks on view from folks determined to have a go.
John 


Title: Re: Sandy Pimenoff's Number 18
Post by: hastf1b on August 23, 2014, 11:04:33 AM
Different tailplane!

Hi Tapio, I have not written it is "Number 18". It is the "Ascender" like the left drawing in post # 8.

Heinz


Title: Re: Sandy Pimenoff's Number 18
Post by: Red Buzzard on August 27, 2014, 02:45:19 PM
John T. in #18 above,

Okay, I'll bite. Two questions: Are plans available and why "Zimbabwe". I've looked at the drawing numerous times and never quite figured out why the name.

You are correct. Nice proportions, flat bottomed stab, and could build fairly light for duty in both Nos A and Vintage FAI with a bit of ballast. Interesting.

Bill


Title: Re: Sandy Pimenoff's Number 18
Post by: Starduster on September 05, 2014, 09:25:23 AM
Tapio:

Quick question:

In the scanned image of the drawing from your book (post #22), can you take a look and tell me the dimension that is from the trailing edge of the wing to the leading edge of the stab? The dimension in the image is right on the fold, and I can't make it out.

Thanks

Rich



Title: Re: Sandy Pimenoff's Number 18
Post by: Brian J Y on September 06, 2014, 02:41:57 PM
Hi Rich,

If it's of any use the Zaic yearbook gives 600mm for the Ascender & 629mm for Number 18.

Brian


Title: Re: Sandy Pimenoff's Number 18
Post by: mick66 on September 07, 2014, 02:21:54 AM
Hi

the plan I have ... which is the one in the book ...  says 628mm for the #18.

Cheers

Mike


Title: Re: Sandy Pimenoff's Number 18
Post by: glidermaster on September 09, 2014, 10:09:53 PM
What's a single millimetre between friends?
Sorry, 40 thou!


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on November 06, 2014, 05:40:51 AM
Five years ago we had a meeting at the Finnish Aviation Museum (next to the Helsinki Airport), where some previous World Champions were presenting their models. Mr Sandy Pimenoff among them. Pentti Reinas took the attached photo of Sandy presenting his model. I think the model currently is at the museum.

 


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on November 14, 2014, 07:18:26 AM
Inspired by this thread, I also launched my CorelDraw and imported one of the digitized drawings to it. Here in Finland we do not fly vintage power (nor much of any power), but I felt like the #18 might be an interesting subject for E-36, thus I reduced the size down to 36 in span. Next I would need to send the patterns for laser cutting... I have not figured out the nose length yet, but plan to cut the nose to final length with semi-assembled model, motor and battery in place. I suppose Mick's notes for angles and CG location would be a good starting point.


Title: Re: Sandy Pimenoff's Number 18
Post by: FF Bruce on November 14, 2014, 08:18:29 PM
Tapio,very nice should work well.I've done the same thing but with the Eros FAI model from the late 60's


Title: Re: Sandy Pimenoff's Number 18
Post by: Tapio Linkosalo on April 12, 2015, 05:55:47 AM
I met Sandy yesterday in a model fair here in Helsinki, and asked about the different versions. He told me that the two models were otherwise similar, but "Ascender" had the rectangular tailplane, while #18 sported the elliptical one. He said he used them both at the World Champs, started with Ascender, but at some round was timed an over-run (with big difference in the times of the two timekeepers), and had to fly #18 for that round and then sticked to the latter for the rest of the contest. #18 was called that as it (or he) made 18 maxes in the competition (counting in that one over-run).