doxilia

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I can't recall if I posted the graphics I made up for this li'l beauty too.

Here they are:

1) Fuse decals
2) Wing decals-1
3) Wing decals-2

Also shown, a JPG of the fuse decals (but use the attached PDF at the printers!)

The 30 size plans are open in CAD... [8D]

Where have all the Shoestrings gone? Please post some pics!

David.

doxilia

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Last but not least, a 3-view and a 6-view of the full scale.

David.

wildwillie3

Doxilia, Thank you very much for posting the PDF's what size paper should they be printed on? What servo's did you use?


Bill

doxilia

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Hi Bill,

now they're there for anyone who wants to build one.

Yes, I realized that I forgot to put a scale and frame dimensions on the plans. However, if they are printed at their native PDF dimensions (no scaling on printing), they will be correct.

Just so everyone knows, the dimensions of the documents are:
[ul][*] Fuse Plan: 32" x 17"[*] Wing Plan: 32" x 11"[*] Parts Plan: 38" x 21"
[/ul]
David.

wildwillie3

Thank you, David

Bill

doxilia

My Feedback: (3)

Here's a stab at the Shoestring E25:

Fuse Length = 43"
Wing Span = 45.75"
Wing Area = 400 sq in
Wing Loading = ~18 oz/sq ft
Weight = ~50 oz
Power = High kV 25 (e.g., E-Flite Power 25 1250 kV)

The fuse plan should be close to complete. I need to make some dimensional checks but otherwise I think it should work.

The design has been altered from Pat's E10 design. Both the wing and the fuse top front are removable. The battery/esc/motor access hatch is built by making the top portions of formers F2 and F3 part of the hatch. A proper firewall has been added (3/16" ply) to allow the installation of a high kV outrunner on standoffs. The firewall is designed and placed in the fuse to provide some flexibility in terms of motor length. I designed things around the E-Flite Power 25 1250 kV using short standoffs (to allow for longer motors). An additional top hatch former (F1H) has been added to make for a 3/32" sheeted, 3 former, removable top hatch. The hatch can be held down with a dowel up front and magnets in the rear.

A horizontal 3/16" balsa stringer has been added to the fuse top along the thrust line to provide some "binding" strength between the fuse formers. This in addition to the doubled 3/32" balsa fuse sides. The top portion in the motor area is fixed and flanked by the firewall at the rear end and by a 3/32" ply front former and the area sheeted with 3/32" balsa about the top 1/4" balsa stringer. The firewall needs to be drilled for the motor mount and set at the proper distance for the drive washer of the prop adapter. The firewall is then installed with the motor mount installed making the motor mount inaccessible after the top has been sheeted. The motor is then installed through the nose where the opening is larger in diameter than the motor can. Since the fuse top front is removable, it is a simple matter to screw down the motor into the pre-installed mount from behind the firewall through the axle opening. Obviously a little thread lock is used in the final installation of the motor once the model is finished.

I haven't given much thought to the empennage construction but they could be either lightened with some holes or built up to suit. As for the wing, it remains a scaled up version of Pat's E10. I'm considering going with either a semi-symmetrical or symmetrical wing. Since the wing no longer has the LE F2 former into which dowels can be inserted, it is held down with 3 screws or nylon bolts (2 in the front, 1 in the back). The bolts can be passed into the wing from the underside of the fuse (as in the E10 design) making for a clean mount, or the two front bolts can be installed from the top with a couple of holes in the fuse section built atop the wing just forward of the canopy. I'll probably leave it designed using the installation of the bolts from the underside - cleaner, more elegant and easier to install all three bolts from the underside with the fuse inverted over the wing.

I have also drawn a fuse top view which was missing in the original MAN plans.

Any thoughts or suggestions are welcome.

David.

Mooney_driver

It sounds like you have given it quite a bit of thought and things are coming together nicely for a bigger design. Iam looking forward to the bigger bird.

Thank you.

doxilia

My Feedback: (3)

I have been unable to upload anything to RCU now for over three days. The evenings I simply can't navigate and in the mornings it's "let's hope, let's hope... arh, still not working".

I'm going to have to re-address the situation back on a thread which began earlier this year. It is rather frustrating not being able to upload the related content or post an image once in a while...

I have plans to show on the thread but can't upload a 200K file.

David.

doxilia

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Here's another try. What I wrote two evenings ago:

Well, the other day I tried to upload the fuse plan showing the changes I brought about the Shoestring 25 to no avail. In the interim, I made a few more changes and things are getting close to being done.

I need to give the wing some thought as an airfoil a little more appropriate for this size and type of model seems in order. I decided to leave the tail feathers as is to be cut from 3/16" balsa stock. If someone felt inclined to building them up, that's always an option. I may change this at some point in the future but for the time being, I'm happy with the sheet surfaces as in the SS10.

Here's the plan for the SS25 showing a Rimfire 15 being used for power on a 10x7 prop and 4s. Should turn around 500W. For those who want a considerably more spirited model, the E-Flite Power 25 1250 kV (NMPRA version) is an option turning the likes of a 8x8 to 10x10 APC-E prop.

Any comments are welcome.

David.

Ahh... no dice!

Whoa! Success! I managed to get the plans up!

doxilia

My Feedback: (3)

Ok,

it seems like I might be able to upload some images now. The fuse plan above basically shows a 150% enlarged Tritle Shoestring. Since the problems began a few days ago with RCU I've made some progress and have been modifying a few things including the top view of the fuse (fuse airfoil if you will) to produce a more streamlined shape. For some reason (perhaps radio installation and/or wing mounting simplicity), the E10 Shoestring (SS10) has a square box fuse in the wing saddle area. As one can see in the plan above, it produces a somewhat angular fuse shape which I wanted to smooth out. Since the MAN plans don't show a fuse top view, it was hard to know how it actually looked until built (or drawn in CAD from the plans shown formers). The fuse now tapers uniformly from the wing LE to the aft end of the fuse - much like the full scale SS.

I also lowered the cheek cowls to a more scale position. After some thought and study, I have also converged on what I believe ought to be a good airfoil for this larger SS25 version - NACA 2411. Not the scale airfoil (which varies from root to tip - NACA 23009 to 23006) but it should produce a good flying model. The fuse side view in this post shows the new airfoil in favor of the flat bottomed SS10 airfoil.

I have also began lofting the new wing. I have made several changes to the structure to complement the airfoil better. The design is in some respects more conventional and should be easier to build for either scratch builds or laser cut versions. The ribs will have LE and TE 1/4" alignment dowel holes to permit the wing to be built and sheeted in a jig. The somewhat awkward top sheeting of the SS10 flat wing using washout jigs and "cracked" sheeting at the fuse side is no longer an issue. The wing is built right side up using the alignment dowels through the ribs. Main spars, notched TE spars as well as a LE 3/32" square hardwood spar inset into the rib centers take care of the remaining alignment prior to sheeting. The wing is no longer fully sheeted but instead cap strips are used on certain ribs to lighten the structure. Simple block wing tips also add to the build simplicity and make for a nice contour shaped tip.

Next, I will have to structure the ribs to accept the spars and sheeting.

Again, any comments are welcome.

David.

doxilia

My Feedback: (3)

Because the RCU software is not thumb nailing images at the moment, I'll post the wing plan here.

David.

doxilia

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Here's a close up view of NACA 2411 - a little easier to understand the airfoil from this view.

If the plan quality is not good enough, please let me know. I can re-scale the photos so that they are clearer. Hopefully, RCU's thumbnail software will work again soon.

Any feedback on the specifications, airfoil, design changes and planforms would be helpful. It's easier to do these things with input from others.

TIA, David.

doxilia

My Feedback: (3)

Alright Shoestring fans... (anyone there?)

I managed to get in a few more lines this morning before brunch. I bit the bullet and decided that since I was going to airfoil the wing, I might as well do the stab as well. I haven't done the vertical yet, but as I look at the flat slab of wood, it just seems to be next step. Tail feathers will be NACA 0009.

I also managed to get the wing and stab ribs structured. One cool thing I recently learned from a fellow expert designer are interlocking spar centered shear webs. As a scratch and kit builder I've always placed my shear webs on to either the front or the back of the main spars. I've also used a truss system backed D-Tube where instead of using sheet balsa I use rectangular spar material and produce a zig-zag backed set of ribs tying the wing together - a little time consuming but very strong. For this wing, I plan to use regular sheet shear webs spar centered but they won't be interlocking - I just don't have the patience for that yet (and I've got some other plans in the works). I will however design them so that the fit when laser cut will be exact. This makes for a much easier and quicker wing build with no gaps at the sides of the shear webs - the key to a torsion resistant wing under load. Even though this will be a light electric model, I'd like to be able to bank it hard!

So what's up with all you Shoestring builders!? Anyone out there building or flying a MAN SS10?

Anyone run into problems wth F2 or F5 in their builds... ? (I swear my SS10 plans are just a tracing of the MAN plan!)

Latest SS25 fuse plan below...

David.

doxilia

My Feedback: (3)

NACA 2411 Wing and NACA 0009 Stab plan...

David.

wildwillie3

Very nice David, what CAD program are you using? I use Auto CAD daily. Keep up the good work

Bill

doxilia

My Feedback: (3)

Bill,

thanks for the kind words. Believe it or not, I'm using Illustrator for this project. I have been procrastinating on the installation of AC on my computer since Illustrator is reasonably capable. I have fooled around with a couple of other CAD programs too but I'm no CAD expert. I started designing "electronically" a little over a year ago. I enjoy the precision that it gives leaving one to build the model when the design is done rather than going with the old adage of "measure thrice and then cut". I'm also a bit of a manual builder and use a minimum of power tools so having a laser (or CNC) take care of all these nice little cuts is sweet. I once built an interlocking kit from SIG and thought that it was very cool. Auto-alignment can save you from a banana plane on a day you got a bad night's sleep!

So, it's been almost two weeks that I've been working on the SS25 in the evenings on and off. I think it's going to be a cool model. I am close to done with the design of the fuse (is one ever done?) having gone through my "to do" list of things. Some annotations details remain I suppose.

I hope to get the wing & stab plan finished up this week. I have changed building approach yet again for good reasons with it now being built inverted on a flat table using tabs on the rib tops to produce a flat top wing with the dihedral built in and due to the tapering of the wing airfoil toward the tip. This makes it easier to build in the absence of a jig and also results in wing panels that are sheeted on the bottom first allowing one to trial fit things to the fuse prior to completing the wing top sheeting. In addition, the flat top wing aids in the construction of the fuse portion built atop the wing since the half round formers need only have a flat base rather than difficult to measure and design concave bases which would be required if the wing were chord symmetric (and without dihedral). I've found that this also aids in producing the molded balsa sheeting about the formers.

Hoping the fuse is not overbuilt for an electric model, here's the latest version of it. ESC & Battery, radio and hatch plates have been designed as well as a new wing LE retention mechanism which is part of the root ribs and enters a section of the F3 former. This makes for a cleaner and easier mount of the wing (much like using dowels) requiring only two bolts at the rear passed through the bottom of the fuse as in the SS10.

David.

P.S. Ahh... it seems like RCU is back to normal at least at this late hour. I've re-attached the plan images so they are now properly thumbnailed.

FlyDave

It's only me that can't open the image and instead see only a "loading..." message ? []

doxilia

My Feedback: (3)

Dave,

give your browser a restart or try another one. RCU has had some very strange behavior as of late and that may just help. If not, you may have to wait til tomorrow or whenever RCU decides to cooperate with you. I was unable to upload images for over a week...

David.

Chemac2

All

Happened to check this string and noticed the recent activity.... We did finish our shoestring which was built from the MAN plans using Dave's CAD version of the plans as reference as well. My brother and I co-built the model (have some earlier posts/pictures) on this string. Attached are a few pictures of the final product. We're pretty happy with the way it turned out. Haven't flown it yet.... Too chicken right now. We're still trying to perfect our flying skills on more "trainer type" models.

David,

May be interested in building the 25 size version you prepared a set of plans for..... Whats the best way to get a full sized set of the plans printed out using the files you've provided? Have you built the model your self yet?...... Or planning to with a finished set of plans in place?

doxilia

My Feedback: (3)

Excellent execution guys! Nice graphics, did you use the ones I posted?

I like the bottom hatch mods - makes access to the motor and battery easy. What finish was used on it?

The Shoestring 25

The plans for the 25 size are still in the works but I have made some further progress (see attached). The model has a few more parts than the smaller MAN 10 size so I was planning on having it laser cut - it makes removing the wood for lightness much easier especially since this version will have some ply parts compared to the 10 size which is basically all 1/16" balsa (except for the bottom balsa sheets).

The wing will build in a rather different way than Tritle's version since it has a "racing" airfoil. Basically it will have two panels (rather than three) but could in principle be built as a single piece wing. The top of the wing will be flat - not in airfoil but along the span line. This makes the construction of the wing simple as it can be built upside down on the building board using tabbed ribs. It also allows the fuse section above the wing to be sheeted more easily. Formers in that region get tricky if there is dihedral on the top of the wing. However, to provide stability, the wing has dihedral which results from the tapering airfoil. This wing design and construction approach was done with many classic pattern models back int he 70's.

If there is an interest in the laser cut 25 version, I can have a few more kits cut. I recently re-designed and drew up plans for a classic 25 size pattern model (a Bridi UFO) and had it cut and sent a few fellow modelers kits along with printed plans. Here's a thread on that project if you want to take a peek. The last posts contain some details of the laser kits:

http://www.rcuniverse.com/forum/m_9312876/tm.htm

I could do the same with this design when the plans are done. I've actually already began laying out the laser sheet so things are coming along. This month is a little busy work wise but April should be a little easier. Laser kits with plans (two sheets) of this size end up costing around $100 - not bad when one considers the amount of time put into the development.

David.

Chemac2

David,

We did use the graphicsyou provided which workedout real well. We printed them using a laser jet printeron decal paper. We ended up using primarily paint for the finish... sanding sealer dope as the base coat, then automotive spray paint for the final colored coats.

We'd definitely be interested in building the 25 size shoestring you've been developing plans for. Being able to get laser cut parts would be a big bonus.... So, put us down for a laser kit & plans. ~$100 sounds pretty reasonable to me.

I've taken a quick look at the the thread you referenced on the "25 size - Bridi UFO". Sounds like a lot of time and effort went into the development for this project as well. Do you have any laser cut kits left for this one? I might be interested in one of thoseas well.Keep up the good work!!.... And, thanks for sharing it.

Dave

doxilia

My Feedback: (3)

Dave,

glad to hear you are interested in the SS25. It's always more fun to have "partners in crime..." I'm a little busy this month but hopefully in April it might be doable to have it cut.

I'll get back to you with details on the UFO - if you like classic pattern designs, it's a real sleek machine! Can you send me a PM with your email address?

David.