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  • August 17, 2017, 07:25:38 AM

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Author Topic: Shoestring build  (Read 1948 times)

Offline Dwayne Donnelly

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Shoestring build
« on: April 10, 2017, 07:16:44 PM »
Got started on the Shoestring by doing the two mods allowed, replaced the 1/8" stock doublers  with 1/16" and as suggested added basswood leading edge.
Now as for the wing it's only 1/4" thick, how much of an airfoil can I carve into it before it weakens?  n~
maac 44334


Offline Matt Spencer

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Re: Shoestring build
« Reply #1 on: April 10, 2017, 08:25:20 PM »
Depends on the Covering .

Shapewith a plane OR 60 / 80 grit on a BLOCK .

Pecikl Lines fore & aft on centerline . over & under at say 20 % & 50 % chord .

Your LE line is TWO 1/8 or 3/16 apart . The TE one is 1/16 thick .

You can go for a 2/4 - 1/3 airfoil rather than 50/50 symetrical .

Sand the flats , THEN curve . / round off ,

A few coats of dope , finish sand , a few more %^@ then the 320 or 240 paper blocked .

THEN ,  (051) H Wt. Tissue , or F'glass cloth . You can put it on with Thinners ,

A cunning trick is to warm aryldite , Spread it on & out , roll Paper Towels over it to get it to a minimum ,
And youve got a tough epoxy base for the paint , but likely requires a second coat , scraped out thin .

Best to cover wing & Fuse BEFORE fitting , however you go .

Doing a 74 Shoestring at the moment , 5 / 16 sht. wing , tapered down to 5/32 @ tips . H&R airfoil .
Definately needs the epoxy trick , with a OS 21 M / FSR type in it. said to pull 30.000 .

You can get the controls INSIDe a 1/4 wing . You cut out the blank between the leadouts ,
carve a groove central ea side in the center piece , for lead out travel , dope the grooves,
& pva back in place .

Lots of G/Y articals in the NCLRA mag .

http://stunthanger.com/smf/rat-racing-and-team-racing/n-c-l-r-a-good-year-articals-2005/

referances to em , here .

Mainly just make good secure joints , and keep it straight & aligned , a lot use flat bottomed airfoils,
Which is a good idea on the TAILPLANE , to stop hunting into & out of wind .

Wots under the hood on yours , I whittled out the mounts so a 21/35 will slip in mine , too.  >:D


Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #2 on: April 10, 2017, 09:17:25 PM »
Hi Matt thank you for the reply. It is a new spec fun  racing event my club is starting using either the Shoestring or Buster and uses a stock LA 15 with any 7X6 prop. In the thread "Fuel shut off" It was suggested that the wing be made symmetrical to avoid the plane wanting  hunt or fly nose down. Not sure what finish yet, I like the glass cloth idea, we will see.
Thanks again

Edit: I think I miss read your post, your saying put a flat bottom airfoil on the H-Stab?
« Last Edit: April 11, 2017, 06:42:40 AM by Dwayne Donnelly »
maac 44334

Offline Paul Smith

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Re: Shoestring build
« Reply #3 on: April 11, 2017, 08:00:29 AM »
If I was building one of those with a club engine I would definitely build the airframe feather-light.

That's the only way to gain advantage.  If it falls apart & crashes, it's only a club engine.
Paul Smith

Offline Paul Smith

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Re: Shoestring build
« Reply #4 on: April 11, 2017, 02:37:47 PM »
A 1/4" piece of wood isn't much on an airfoil no matter how you sand it.  I typically just round the LE and sharpen the TE. 

For a spearmint, weight the whole piece of wing wood, then sand it all you can.  You will need a good scale to measure the difference. 
Paul Smith

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #5 on: April 11, 2017, 05:49:26 PM »
Hi Paul thanks for the replies.
I'm in agreement about keeping it light, I'm now thinking Ultrakote wings and tail with just a couple of coats of auto rattle can on the fuse. I tapered the TE and put a bit of an airfoil on the LE but yeah being only 1/4" it aint much.
maac 44334

Offline Paul Smith

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Re: Shoestring build
« Reply #6 on: April 11, 2017, 07:40:46 PM »
Using plastic covering on solid wings & tails usually results in warpage.  Better to use paint.

Racers get a lot of fuel dumped on them.  Epoxy.
Paul Smith

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #7 on: April 11, 2017, 08:00:53 PM »
Moving along, wing is not glued in yet but it's starting to look like an airplane. y1 #^
Have to start thinking about covering, I'm pretty good with an iron but a nice dope rattle can finish is also appealing, decisions, decisions.  n~
maac 44334

Offline Motorman

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Re: Shoestring build
« Reply #8 on: April 12, 2017, 06:41:42 AM »
I would glue a piece of 1/8" balsa to the bottom of that wing then use the glue line to carve to giving you a 1/3-2/3 airfoil and a wing that won't flex and warp.


MM
There will be a sunny day and we will fly our airplanes.

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #9 on: April 12, 2017, 07:18:41 AM »
I would glue a piece of 1/8" balsa to the bottom of that wing then use the glue line to carve to giving you a 1/3-2/3 airfoil and a wing that won't flex and warp.


MM

That's an interesting idea and shouldn't add to much weight.
maac 44334

Offline Ken Burdick

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Re: Shoestring build
« Reply #10 on: April 12, 2017, 09:02:02 AM »
it looks assembled, what did you carve the wing to? I agree with Paul and do not believe there is any difference for what you intend to do with the model. I built one for my kids once, it was abused greatly but with wing carved as paul described and epoxy finish, it set Jr. Record at the NW Regionals.

K

Offline Matt Spencer

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Re: Shoestring build
« Reply #11 on: April 14, 2017, 07:17:04 AM »
Quote
Edit: I think I miss read your post, your saying put a flat bottom airfoil on the H-Stab?
in the land of the wrong white cloud , Aeotearoa , known to some as N Z !

Rod Brown weote a letter to Clarkson that appeared in the Aeromodellor Control Line Section ,
Descibing the state of thing in ' B ' T/R in Kiwi Land . about 1975 .

Was Whitness to their latest attempt , timing near 120 ( mph ) solo , down Taranaki .

ANYWAY , the ADVICE was a FLAT BOTTOM AIRFOIL for the TAIL PLANE .

the 2/3 - 1/3 H & R ( Hustead & Roy ) U. S. speed aifoil ( Fwd high point , 20 top 15 under ?? )  and this was the set up they used .

So , as Eienstein was unavaliable , I used their advice , on my secong ' Ginny ' G/Y in N.Z. .
apparently the gutter tin elevator horn ( a replaceable item ) wore out down their in their hands ,
and the thing circulated at 3 or 4 Ft. altitude from the remainder of the tank . so where told .

ANYWAY ( Again ) My Miss Dara , Wharfdale Twin Boomer (of 1963 ) and others under construction have the flat bottom stab ,
set ' O ' - ' O ' on the thrustline .

As its often blowing a trifle in N. Z. , into Wind it keeps the Nose Down , or at least it dont climb into wind , like many ( most ?? ) do .
Which is the justifiction for its place in the universe ! ,

A few A1 top notch ( even tho theyre Australian  LL~ ) Pilots having Flown the D.A.R.A. where pleased with its handling .
The Ginny would even fly inverted at the Ton with it. after youd bypassed the Cut Off .  ;D Gotta one of them justa bout done .
Put the monowheel U/C Leg Boxes in em last week , gotta find some F'Glass Cloth for the 74 Shoestring. Only got appaling L wt Stuff,
Aeromuddler recond to use that triplled with the aryldite for the FAI team racers in the late 70's ( Clarkson ) from the Ducth Chaps ,
weave @ 45 Deg. across the span .

--------------------------------------------------------------------------------------------------------------------------------

sounds like a good fun class youve got going there . A ' Sunday Afternoon at The Races ' rather than the more Cut throat Pommy version .
Our Aussie version here is 27 ( sec ) for 10 ( laps )  , which is fair enough too . You can whip & hold back , i.e. the pilot infringement
stuff dosnt apply , penalties for ' Too Fast ' is a mandatory stop & reset , or + Laps ( I think ) for repeat occurances .

Most Planes if on song seeem to top out at about the right pace . DIESELS on Suction  . Usually TBR Schneurle MVVS , Nelson etc !  %^@

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #12 on: April 14, 2017, 06:43:43 PM »
She's on her wheels, wing glued in, just waiting for epoxy to dry and then it's a dopin time.  y1 ;D
maac 44334

Offline Motorman

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Re: Shoestring build
« Reply #13 on: April 14, 2017, 07:37:55 PM »
Looks good. If you're going to be catching it on the nose for pit stops I would try to get an acorn spinner nut for the prop. I've seen guys get holes punched in their palms from a prop shaft.


MM
There will be a sunny day and we will fly our airplanes.

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #14 on: April 15, 2017, 05:30:58 PM »
2 inch or 3 inch bellcrank?
« Last Edit: April 15, 2017, 06:05:45 PM by Dwayne Donnelly »
maac 44334

Online Brad LaPointe

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Re: Shoestring build
« Reply #15 on: April 15, 2017, 06:54:48 PM »
2" ...less drag and stronger .

Brad

Offline Matt Spencer

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Re: Shoestring build
« Reply #16 on: April 17, 2017, 09:35:26 PM »
Finished Yet .  S?P H^^

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #17 on: April 18, 2017, 07:00:45 AM »
Finished Yet .  S?P H^^

Nah not yet, have to work and the Toronto Maple Leafs (hockey) are in the playoffs for the for the first time in years. Priorities ya know  LL~ #^ y1

Seriously though just put the last coats of clear on it and will shoot the colour on friday.  y1
« Last Edit: April 18, 2017, 07:21:27 AM by Dwayne Donnelly »
maac 44334

Offline Ken Burdick

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Re: Shoestring build
« Reply #18 on: April 18, 2017, 04:31:52 PM »
a little money ridin on the maple leaves....
along comes a lady in lacey sleeves.

Gotta root for the Cubs and the leaves.


Ken

Offline Mark Knight

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Re: Shoestring build
« Reply #19 on: April 18, 2017, 07:23:19 PM »
Do you have to use the stock wire landing gear?  The stock wire gear we had on our Brodak Buster looked the same as yours and bent under the weight of the engine on landing.  After a few flights (and belly rash) we switched to aluminum sheet stock landing gear.  A lot more ridged.  Other wise looking good!

Offline Mark Knight

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Re: Shoestring build
« Reply #20 on: April 18, 2017, 07:48:36 PM »
I meant Sig Buster not Brodak.

Offline Dwayne Donnelly

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Re: Shoestring build
« Reply #21 on: April 23, 2017, 06:54:20 PM »
Here ya go, it doesn't show up well but that's metallic purple auto paint, sparkles real nice.  y1 y1 Flying surfaces are ultrakote and dead straight.
Weight as you see it minus bellcrank, pushrod and few little things is 15.3 oz. I'm very happy.  #^ ~> y1
maac 44334


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