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Author Topic: Dave Clarksons SLOP formula  (Read 4285 times)
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Sandgroper
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« on: February 01, 2012, 07:28:07 PM »

Here is a list of Slop designs from Daves article in Aeromodeller Nov 1998,It shows the different approach taken by UK modellers compared to those in the US with Classic Gas models-ie the SLOPS have a very short nose.
I built and lost the 400sq version,originally powered with a Taipan 3.5,then put in a converted 21 car engine for Open Power which really made it honk-seemed better with more power,very easy to trim and never had a crash.
Sorry it`s in metric guys

Phil
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RobinB
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« Reply #1 on: February 03, 2012, 05:58:03 AM »

Phil, apologies if I'm diverting this thread a bit, but :-

That Clarkson article also has a 3-view of Graham Shacklock's SLOP ( as did his paper in the 1997 Free Flight Forum ).
I think I recall you saying that you had built on of these models.
Was I right? If so, did you get a plan from somewhere or use the 3-view?

Does anyone else know if there was any other drawing made of this model?

Robin
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RalphS
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« Reply #2 on: February 04, 2012, 06:28:30 AM »

Phil, apologies if I'm diverting this thread a bit, but :-

That Clarkson article also has a 3-view of Graham Shacklock's SLOP ( as did his paper in the 1997 Free Flight Forum ).
I think I recall you saying that you had built on of these models.
Was I right? If so, did you get a plan from somewhere or use the 3-view?

Does anyone else know if there was any other drawing made of this model?

Robin


I am a club mate of Dave Clarkson and Graham Shacklock was also in our club.  Graham sadly died some time ago at a very
young age.  Dave doesn't do computers so he wont see this.  I can pass on any enquiries to Dave if you want.

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Sandgroper
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« Reply #3 on: February 04, 2012, 07:39:15 AM »

Hi Robin,
I got as far as cutting up the rib templates  from alloy sheet and was sidetracked by other projects so thats as far as I got.I would have drawn up a plan from the Aeromodeller 3-view

Phil
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RobinB
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« Reply #4 on: February 04, 2012, 10:44:51 AM »

I am a club mate of Dave Clarkson and Graham Shacklock was also in our club.  Graham sadly died some time ago at a very
young age.  Dave doesn't do computers so he wont see this.  I can pass on any enquiries to Dave if you want.

Very kind of you to offer, Ralph, but I don't have any queries about the plan, as such. I was more interested to find out if anyone had built the model,
and how they got on with it. I believe that Graham Shacklock based it on a scaled-up 1/2A Zeus.

I was away from active FF during the period he was flying, so I never got to see the model fly.
I do remember reading of his early passing - as you say, far too young.

Robin
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Sandgroper
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« Reply #5 on: February 04, 2012, 11:56:42 PM »

It is sad to hear of Grahams passing,Graham and the model had an exceptional contest record and it should be a winner,the decalage on the plan is only +0.5 deg instead of the more usual +1.5deg to +2.0 deg,maybe a misprint?or nobody told it that it shouldn`t fly that well?
I have built three US models lately so it`s time for a UK one and this looks like it will be good match for my PAW 19SP.
It would make a nice Classic Gas A/B model as well.
No worries with crossthreading Robin there aren`t many threads on Slop models
Phil
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RalphS
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« Reply #6 on: February 05, 2012, 06:02:42 AM »

Graham and SLOP taken at N. Luffenham 2004.
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RobinB
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« Reply #7 on: February 05, 2012, 06:12:12 AM »

Phil, if you've hoarded those Dave Clarkson articles from 1998, you might also have the series by Dave Hipperson in Aviation Modeller International about SLOP model setup and trimming. In the June 2000 article there's a picture of Graham Shacklock with the model on page 45.

When I posted earlier that I didn't have a query about the plan, I was wrong. The stab seems too small - the aspect ratio is only about 3!
If you look at the pic of the model, the stab looks to have more normal proportions.

The decalage would be quite small - the CG is well back (about 90% of mean chord) and it's a 6% cambered profile. Not quite Dixielander trim, but heading in that direction.

Robin
p.s. While typing this I'm told that a pic has been posted by Spadge, but I can't see it.
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Sandgroper
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« Reply #8 on: February 05, 2012, 07:10:51 PM »

 Nice picture Spadge(also my wifes aunties nickname),yes far too young to go.After a close call last year and a bit of tune up surgery I hope to be around for a while.
Robin,I found the printout of the AMI article-again a very nice shot of Graham and yes the tailplane has a aspect ratio of about 3.6to1 scaled from the picture.Using the metric dimensions of 190mm(7.4") chord x 600mm(23.6") span on the drawing-it works out at 174sq in or 32% wing area at 3.16 to 1 and at 3.6 ratio it should be 684mm(say 27") span and 200 sq " or 37% wing area-which would you choose?.
The sections on the Aeromodeller 3-view will need to be blown up 103-104% to suit the dimensions given for the chords,the metric conversions are not very exact the rib spacings being up to 5mm out;ie 2 3/4" for the tailplane rib spacing is closer to 70mm not 75mm as on the 3 view, if you work out the wingspan using the 3" rib spacing it will be 62inches,if you use 80mm spacing you get the 65" span.
I have blown up the drawing 550% using windows paint,it took 32 A4 sheets,I will stick it together and check the dimensions.
I was brought up on imperial measurements and converted to metric in my teens so use a combination of both-I find square inchs make more sense to me than sq mm,cm, etc.

Phil
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RobinB
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« Reply #9 on: February 06, 2012, 11:34:45 AM »

The 200 sq.in. estimation looks about right, and would give the necessary stability margin using the CG position shown.
(It would also correspond to 5 complete geometric bays, not 4 as shown.)

This drawing appeared in its original form in the 1997 BMFA Free Flight Forum Report.
It only shows metric dimensions or the rib spacing. The 'rough' imperial equivalents appear to have been added by AMI.

Does anyone out there know anything of the Zeus 1/2 A that this model was based on? I believe it was published as an Aeromodeller plan,
but I can't recall seeing it.

Robin



 
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applehoney
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« Reply #10 on: February 06, 2012, 04:01:32 PM »

August 1963
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RobinB
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« Reply #11 on: February 06, 2012, 04:32:18 PM »

Impressively quick response, Jim. Many thanks.

I remember Dave Hipperson's Slowworm and Tony Young's Dynamo, but not the Zeus.

Robin
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« Reply #12 on: February 06, 2012, 08:07:42 PM »

I recall seeing Graham win a very good 1/2A f/o at Odiham in late '91 with what must have been a near standard Zeus powered by a PAW 80BB complete with (I think) a 3 blade prop.
He beat Mike Bull's all-auto surfaced model complete with Kustom Kraft TD 049.

The Zeus (or at least that particular one) having a tremendous glide performance.

John
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« Reply #13 on: February 10, 2012, 01:01:45 PM »

Hello

I can vouch for both the original 1/2a Zeus and the SuperZeus.  I fly both in their respective classes.  Won the BMFA Nats with my SuperZeus in 2010 in far from ideal conditions.  I substituted a Carbon boom for the fuse but I don't think its an improvement over the original ... balsa is way easier to repair.  I'm building a new one at the moment.  Apart from that it was identical to the GrahamShacklock 3-view.  Fora 21 diesel does lower 16k+ on a thin blade master 9x4 with a 50/50 mix of D2000/D3000.  I'll post some pics and any other info.  I also fly a DaveHipperson T34 with a Fora 21 diesel ... its another great SLOP model.  Both certainly glide very well but are at a disadvantage on the climb with their undercambered wings.   I think DaveLimbert also flies a SuperZeus to good effect.

The 1/2a Zeus is a great little model ... don't set it up as per plan.  CG needs to go further back.  Cox TD049 woth Nelson head and bladder.  35% Nitro.  I've got a couple at the minute.  Fantastic glide ... again ... I'll post some pics etc

Cheers

Mike

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Sandgroper
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« Reply #14 on: February 11, 2012, 04:58:03 AM »

Hi all,
Mike do you use any thrust offsets on the T34?,I was given one by a retiring freeflighter and it has 2.0deg downthrust and 2.5deg left-measured from bottom of fuselage,it had a weighted pivoting dragflap on the right main to help transition,I have taken this off and would like to go back to basics and retrim.It was flown with a OS20FP glow,I have a diesel conversion for the OS to get that extra two seconds run.Is there any difference in the performance of the Fora 21 diesel to glow?

Robin,I found Daves plan for the Trainer Open Power model and the rib spacing and the number of bays are the same as Grahams Slop model,I already had a couple of copies printed and modified them for the 12mm extra chord and the tappered tips extended to 65" which saved a little time,just have to draw up a fuse and tail.

Phil
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« Reply #15 on: February 11, 2012, 05:53:31 AM »

Thanks, Mike, any more info would be very useful.
Also, you're the first person I know of who's using the diesel version of the Fora 21 - did you do it for the extra 2 seconds or another reason?

Robin
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« Reply #16 on: March 14, 2012, 07:57:55 AM »

A friend recently sent me a copy of the original Zeus article.
He'd written "Dixie ripoff" on it, and I see his point.

If you scale a Dixie down about 80%, taper the tips and reshape the fin you get the Zeus.
There's one other big change, however - the CG is shown as 70%.
At a guess, I'd say that the designer fitted the 80 diesel and found the CG well forward of the Dixie
norm. Consequently, the stab was chopped down to suit.
Hence the curiously low aspect ratio stab.
Just a guess, as I said.

What's interesting, though, is that Graham Shacklock scaled this model up and it performed
really well with the CG further back. Perhaps it didn't know that it wasn't supposed to work
like that, so flew great anyway....... Smiley

Robin
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« Reply #17 on: March 14, 2012, 09:14:56 AM »

I have noticed that many Nos Gas designs work well with CG's further aft than originally built.  I put it down to being able to get more out of the engines today, especially making them more tolerant to relatively high percentages of nitro.  More engine equals more airspeed in the climb and the need to make it less pitch/airspeed sensative.

Lacking VIT systems (this is not a negative thing), there is only one way which is to run the CG as far aft as the airplane can tolerate without it lawn-darting off the top of the climb.  I think we understand more about the sufficient opposite direction roll to effect a proper transition from power to glide.

We are teetering on the ragged edge of static and dynamic stability; edging ever closer to the aerodynamic precipice(sp?) but not falling off!
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Sandgroper
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« Reply #18 on: March 14, 2012, 10:31:39 PM »

Hi Dean,
yes it`s all a balancing act,funny I was only reading an old US mag yesterday and came upon the term lawn darting,does this mean bunting over as speed increases or stalling  after cutoff and diving in?If you climb too steep without enough rolly polly a Dixielander will still bite.
The Dixielander is one of the extreme examples of rearward CG but the Yeoman version is mild compared to the John West version which is 1/4" behind the trailing edge-this was taken to 1/2" behind the TE on George Fullers 1997 model.
My Yeoman model balances 1/8" in from the TE and the John West version 1/8" behind,no lead needed at the tail on either until I swapped the OS10LA for a 15LA in the Yeoman and put alloy angle on the JW engine bearers.
The JW version has less warps the pylon is swept forward 1 1/2" and seems to flip off the top of a steep climb better than the Yeoman model.The Yeoman Dixie uses about 1/8" right rudder trim and 1 deg left thrust ,the JW a micky whisker left rudder,both have 1/32" packing under the tailplane LE and the JW has 1/32" shaved off the rear mount to steepen the climb and stop it looping off to the right and going flat.

http://www.rcgroups.com/forums/showthread.php?t=1534053&page=18      Post no 263  this is the  JW model

You have to build a Dixielander Dean they are a fun model,they don`t need lots of power the FOX15X or a OS Max 15 are fine-I use spruce for the front spars
One of the best articles I have read on trimming non gadgeted models was by Dave Hipperson titled Adjust For A Vertical Climb here are two parts-I have part one but only poor quality.
The article by Jim Baguley is very good as well
http://aeromodelismovolarlibremente.blogspot.com.au/search/label/T%C3%A9cnicas%20de%20Vuelo%20Libre

Phil
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Re: Dave Clarksons SLOP formula
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« Reply #19 on: March 15, 2012, 12:24:14 AM »

G`day Robin,
the plot thickens,so you are saying the tailplane size on the Aeromodeller 3 view of Grahams model is correct?,It is common practice to thin down the section to achieve the same thing on Dixielanders when using high powered engines.
I do not have a picture of the Zeus,is Grahams model the Super Zeus?
Fired up the Max111 .15 last week,had a unbalanced Master 8x3 on first start and almost shook the poor orange Dixie to bits,put on a balanced APC 8x4 and it ran and started well but may need to be positioned carefully on the crank to get even better balance,seems to use lots of fuel compared to the modern FP`S and LA`S even if it was rich,I have put the 15 LA back in it for the Nats in April as we don`t have a NOS event.
As I found a set of ribs and plywood parts I cut up for a 525sq Dave Clarkson Trainer years ago I will be building a SLOP based on that wing and tail  before Grahams SLOP.

It would seem the answer to make up for lost power caused by a small venturi on suction is to just add more nitro to compensate.
The small venturi restricts airflow but the nitro releases oxygen to make up for this,it seems according to the car boys their engines are less critical to high nitro fuels negative effects with restrictors fitted,-harder to go super lean I would think?
Unusual thread on the early OS15 cranks the FP(same nut as the Mk111) instructions give it as UNF-7/32-32 , M5 on the 10FP and LA15,found one on e bay

Phil


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flydean1
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« Reply #20 on: March 15, 2012, 09:11:04 AM »

Phil,

I do have a Dixielander in my future.  Larry Davidson who has campaigned T-Birds in all sizes has switched to Dixies.

I had the same problem on the old OS 15 III and 19.  Non-standard metric threads.  I had to make my own spinner nuts.  Home made tap.  Tool steel turned to size, threaded, flutes ground with a Dremel tool, and just when I had it finished, located a #10-32 tap on McMaster-Carr's web site for US$12.00!!!

Thanks for the links to the articles.  I will download and file with my Dixielander plan file.
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« Reply #21 on: March 15, 2012, 10:54:30 AM »

Sorry , last line should have finished with- found UNF 7/32-32 tap on Ebay $5.20 delivered and from Australia,goodie I can make a spinner nut,
I wikied up nitro methane only having info from articles and hearsay and it`s interesting stuff,good for REMOVING SUPERGLUE,produces 2.3 times the power of gasoline when combined with a given amount of oxygen(1.7lb oxygen to  1lb nitro).is also a monopropellant and good rocket fuel.Also great explosive when mixed with ammonium nitrate.    

Phil

just read your post Dean very clever, did similar thing for a glowpug tap during apprenticeship,I slotted the flutes in the lathe with a ground up tool in toolpost and used manual feed  to slot it while between centers.,had a choice of a US tap for $7 or one from here for $5.20-I do like the US taps but it takes 15-30 days to get here,the supplied  nuts don`t run that well on the Mk111 or the FP crank tending to bind when tightened so I will check that,Brian Winch engine tester said the thread is U.N.E.F. 7/32-7  in Airborne no111 and the FP info sheet U 7/32-32. is that the same as #10-32? It seems it`s a gun thread used in the 19th century going by a blog site.
Thanks Robin just read yours as well.

No luck with T bird test flights yet the wind hasn`t dropped for months .
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RobinB
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« Reply #22 on: March 15, 2012, 11:09:03 AM »




One of the best articles I have read on trimming non gadgeted models was by Dave Hipperson titled Adjust For A Vertical Climb here are two parts-I have part one but only poor quality.
The article by Jim Baguley is very good as well
http://aeromodelismovolarlibremente.blogspot.com.au/search/label/T%C3%A9cnicas%20de%20Vuelo%20Libre

Phil

Scroll down that webpage and you'll see (on one of the Hipperson article pages) the Shacklock 'Super Zeus' picture that was referred to a while back.
 
Well done with that OS prop shaft, Phil.  I remember being advised not to lose those prop nuts, as they are difficult to source. I recall that size is listed under Unified Extra Fine. OS really like to go for unusual threads, don't they?

Robin
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« Reply #23 on: March 15, 2012, 11:51:33 AM »

I think those early OS prop shaft threads were 5 or 5.5 X .8mm.  Not a standard metric thread.  It is a gun thread according to the McMaster-Carr catalog.  That was a good price.  I bought mine several years ago.

The backplate and head screws are also strange.  You can convert them to 4-40 with a thread-forming tap, also called a roll thread tap.  It takes a steady hand and lots of cutting oil, but worth it to be able to use proper stainless or hardened internal hex machine screws

Strangely enough, the screws for the larger .29 and .35 OS MAX-III series engines are a perfect match for 5-40.  I bought myself a 5-40 thread forming tap in plug and bottoming varieties when I bought the 4-40's.  Absolutely unneeded!
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« Reply #24 on: March 15, 2012, 12:05:22 PM »

It was our club's first Thursday comp today at Tatton Park.  I told Richard Wykes about the interest in Dave and Graham's models. He said that Graham used 1 degree down thrust and 3 degrees left side thrust on his SLOPS.  Something about countering the right turn from the fin.  He is going to have a look to see if he has any drawings from Graham's paperwork that he holds. 
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