Scram

[Jmk89]

For my next trick, I thought I would get in touch with my inner JOD and build a Scram from Laurie Barr's plans published in Model Aircraft in 1950 (downloaded from OuterZone.co.uk).

Having created the rib templates using FreeCAD, I was wondering what airfoil that was. It isn't mentioned in Laurie's article or on the plan and it doesn't matter, but I just wondered if it has a name.  Can anyone enlighten me?

[PeeTee]

Hi Jeremy, the Scram is a marvellous model but alas I gave mine away. It's still going strong with a mate of mine and somewhere I have a photo of it which I'll try and dig out !

Peter

[Jmk89]

I took a break from uploading AeroModellers from the early 1950s today and started work on Scram's wing - I will put the ribs that are in the tips in place after the tips have been added (I decided to use bamboo heat bent to conform to the lower wing surface as well as having the round plan view).  The ribs at the dihedral breaks will be inserted once the dihedral has been set and the ply braces have been glued in place.

The little black doodads are slotted braces to hold the ribs at 90 degrees to the building board while the glue dries.

[Jmk89]

A bit more progress on the Scram wing - I attached the bamboo wing tips using a 1/4"packing strip to ensure that the tip has almost the same camber as the under-surface of the wing. 

Photo 1 shows the bamboo attached to the Starboard wing and photo 2 shows the same for the Port tip but adds the rib which is attached to the tip and not to the LE and TE strips.

The next steps are:
1. cut through the LE and TE at the dihedral breaks,
2. sand in the chamfer to LE and TE so there is a solid butt joint there,
3. set the dihedral and glue the butt joint,
4. glue the ply doublers to the LE and TE at the break points, and
5. Glue in the wing rib at the dihedral breaks sloped by 10 degrees  (the little green doodads in the photos are supports to hold the ribs at that angle while the glue dries (more 3D prining fun)

[Lastwoodsman]

Wed March 25 2026

Hi Jeremy!    Yeah,  one has to take a break from the monotony of updating files,  and  get back into some therpeutic building.    Thanks for the detailed build.      I'm following your  "Scram"  closely.    Could you post a pic of what a scram looks like?

Lastwoodsman
Richard

[Jmk89]

Here's a picture from OuterZon's page on Scram
https://outerzone.co.uk/images/_thumbs/models_more/5318/004.jpg

[dputt7]

Hi Jereny, Just a word of warning "Fit a D/T" I built Scrams  stable mate Pinocchio. Lost it on it's 4th flight, a mate found it on a road and returned it, I had another flight and promptly lost it again. I built another and still have it, Don't fly it much.

[Lastwoodsman]

Wed March 25 2026

    Sorry Jeremy -  I saw you do this before.    Your links to a pic are just needlessly filling up my recently closed tabs page,  with links that I don't need,  when all I want to do,  is just look at your pic.  Would you please post your own screenshot pics and not links?

Thanks,  I think you know what I mean ....

Cheers   

Lastwoodsman
Richard

[Jmk89]

Hi Jereny, Just a word of warning "Fit a D/T" I built Scrams  stable mate Pinocchio. Lost it on it's 4th flight, a mate found it on a road and returned it, I had another flight and promptly lost it again. I built another and still have it, Don't fly it much.

Absolutely.

You might notice in the junk in photo 1 of yesterday's post near the pencil the rotary damper that will by th timer!

[Jmk89]

Here's the photo

It isn't one of mine

[Jmk89]

For once I actually got done in a day all the stuff that I envisaged would be done.

Here are photos of the tip dihedral being installed-
Photo 1 – simple butt joint using the dihedral holding jigs I developed from an idea I saw in one of the old AMs that I put up in the Plan Gallery . There is a better photo in this post:
https://hpa.aeromodelling.gr/index.php?topic=10.msg2192#msg2192

Photo 2 – dihedral break braces (0.8mm ply) glued in place – in the background, being used as an auxiliary prop is a 10 degree sanding block that I drew in FreeCAD and printed last night –  It really makes sanding the chamfer much easier!

Photo 3 – the dihedral break ribs glued in place held by the 10 degree props I mentioned yesterday.

I will trim the bamboo off tomorrow and then store the wing somewhere safe until it's time for sanding and covering.

[Jmk89]

Did anyone who has built Scram done so using a plan downloaded from OuterZone?  That's what I did (printing it as a poster at 100% with tile marks to facilitate sticking it together).

The prop blank is stated on the plan to be 6.25" x 2" x 1.5" but when I measure it the length of the block is more like 6.0", making a requirement to increase the block to 104% of the drawn size (with the other dimensions of the block being increased likewise).  Curiously the wingspan and the fuselage length are much closer to the published figures of 28" and 28.5" respectively, although each is a touch on the short side.

Would you use the dimensions of the block as drawn or as published?

[Jmk89]

Not much progress today - I started the tailplane (see photo), laid out the prop blank (I decided to use the stated dimensions and not the drawing), bent the bamboo for the tail tips and cut out the template for the bent outline for the fin.

Not spectacular progress but ticking off steps.

[Jmk89]

A bit more progress.  Fuselage mainly constructed (see photo).

Tomorrow will be carving prop and making fin and some finishing of the fuselage - detaching and regluing any spacers that went out of square etc

[Jmk89]

Yesterday and today I spent carving and sanding the prop blade for Scram.  When Paul van Leuven came second in F1B (1979?), he mentioned that her used the ARA D 6% airfoil on his prop and said it was much better than anything else he had used.

That got filed away in my noggin and it resurfaced while I was thinking about Scram's prop, so I decided to do some research, in the course of which I found a 1977 paper in Aeronautical Quarterly which goes into detail on the whole ARA D Family of airfoils for propellers.  A 20% improvement over NACA prop airfoils suggested that this was worth looking into , so I made some templates and started carving and sanding.

The templates were 'quick and dirty'- I drew the airfoil at a 200 mm chord length and then photocopied that to the sizes from 20 mm chord to 55 mm chord in 5 mm steps.  I then laminated the different pictures and cut them out so I had upper and lower surface templates at each on those chord lengths.  Then it was just a question of carving and then sanding down to the shapes.

The proof of this pudding will be when it is eaten (flown - Phantom Batter Pudding Hurler of Bexhill-on-Sea, for Goon Show fans).  If it works, it isn't any harder than making a normal prop.  And the section is a bit beefier than some props that I have made before, so maybe it will last better!  I noticed this mentioned in the article in AeroModeller April 2026 on prop carving, so I'm moving with the times!

I have uploaded the Aeronautical Quarterly article to the Plan Gallery (under Airfoils and Propellers) so those interested can read for themselves once George has reviewed it.  The article has the co-ordinates for the ARA D sections or you can get them from the usual airfoil websites