How to see a wing plan hidden by sheeting whilst building..? - RC Groups
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Nov 01, 2017, 03:26 PM
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How to see a wing plan hidden by sheeting whilst building..?


Good evening, folks...

Maybe a 'dumb' question; we'll see. I'm building, from a Svenson 'Prima' kit, a high-wing aileron trainer. I'll say from the outset that the meagre instructions are not very helpful, but I've got the tail feathers and fuselage in hand, and am about to start on the wings. These are built directly over the plan, in time-honoured fashion, but the method given in the instructions has me puzzled. The underside sheeting is to be pinned down to the plan, along with the lower spar and rib caps. In doing this, important parts of the plan are no longer visible, being covered by the sheeting. To be fair; the instructions do recommend making a photocopy before starting, as they are aware of the problem. Less fortunately, it is not explained how this helps in building the wings..!
Am I overlooking the obvious, or is there some secret, cabalistic procedure that turns sheeting transparent, X-ray glasses, Superman vision or whatever for dealing with this..?
Now retired, I'm taking up where I left off all those decades ago. At the time, the small 'planes I built didn't have sheeting; simply tissue paper and dope. Now it's me, the dope..! Thanks in advance for any advice offered; meanwhile...

Have a nice day

Douglas
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Nov 01, 2017, 04:26 PM
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DGrant's Avatar
Usually the frame work is done(spars, ribs, leading/trailing edge, etc.)... then the frame is gently lifted from the plans and sheeting is added at that point. Is there any reason you can't do that?

I Googled that plane, and it looks very conventional in construction and design... I see no good reason why you can't do it like that... as long as it's handled with care every step.

The wing once built up with ribs, spars and LE/TE will be fine if it's glued well and true... and should be fine to lift off the table... flip over and sheet... and should be easy to sheet.

Why it's telling you to pin down cap-strips is a mystery as well... as that's always one of the last steps in basic framing. Well after LE/TE sheeting is done.

There are actually ways to mark you wood and/or plans to target the placement of components... but really I've never pinned sheeting to a plan like that for wing.

I do have to say, it's not a bad idea at all in this day and age to get your plans scanned and put into digital format, as then you can output as many sets as you like(depending on your resources of course)... as many print shops have that service now.... If you have your plans in digital format, you can also share them, email them, or output them .. whatever you want... So there's another thought...

... but yeah on those wing-panels... just let build them as flat as you can, let the glue dry thoroughly, then sheet them. At least that's how I would approach it... you can double check me... and hopefully you'll get more replies here too..... above all keep studying until you're satisfied it will work..
Nov 01, 2017, 04:52 PM
Scott
Pylonracr's Avatar
That is pretty much how I do it. I scratch build most everything now. Complete the framing, trailing edge sheeting is easy with the trailing edge flat on the building board top and bottom. Doing this first will add a little more torsional strength. I glue the leading edge sheeting to the spar and wet the outside only with water and ammonia, which causes it to naturally curl. Then glue it to the ribs. Turn over and do the same thing again. Cap strips are added last. Hope this helps.

Scott
Nov 01, 2017, 07:49 PM
B for Bruce
BMatthews's Avatar
With old timer models it was easy. We'd open up the latest copy of Popular Science and turn to the rear section with all the advertising. Then find the advert for the AMAZING X-RAY GLASSES. Two weeks later they would arrive and we could look through the sheeting at the plans....

When I've done the models with lower side sheeting like that I take some time to mark witness marks on the wood for rib locations. That's all you need. You don't need to print the whole set of plans. All the rest of the stuff like spars and such follows from the ribs and the build proceeds using the marks on the wood.

Heck I designed and built one wing where it RELIED on that style. Even to the point of using a split "V" trailing edge where I made sure to have the lower side right next to the edge of the building board so I could sand in the taper to shape to match the line off the top of the ribs. This was to allow the upper sheet to have a place to glue down with no bends or lumps.

The KEY THING is to remember to remove all the pins that would otherwise become sealed in when the upper sheet goes on. And even double check... You REALLY don't want to "discover" that you missed one....
Nov 01, 2017, 10:34 PM
Registered User
^^What Matthews said. I often make witness marks on plans when I see that important reference points will be covered later.
Nov 02, 2017, 10:40 PM
Registered User
Thanks for the replies, folks; it's much appreciated. I, too, as an 'old timer' remember those X-ray specs, but never dared to send off for a pair..!
I'll try out the 'classic' method of creating the skeleton first as a dry run, to see if I'm inspired by that. If it seems too delicate, there'll still be time to unpin the lot and lay down the sheeting. I can probably mark any salient lines for component placing, but there are other notes on the plan that'll be hidden, such as wood dimensions and other notes.
As for scanning: this plan is from an original kit, but the plan is also freely available for download as a pdf from AeroFred.com (so I could consult it on screen...), or I could order a print-out from that excellent plan library. We'll see; I'll report back as to progress (or disaster..!) later on.
If anyone is interested, I've a Build Log on the forum there, with all the steps taken so far. My 'wing' progress will appear there as and when I advance it. To be continued, then...
Nov 03, 2017, 01:13 AM
B for Bruce
BMatthews's Avatar
Or, and this is just some wild and crazy idea... You could write down the notes you need on some scrap paper with an old fashioned pen?

Nov 03, 2017, 01:38 AM
Registered User
HIR/Cer's Avatar
Bruce, those x-ray glasses? Saw the ads also back then but never bought a pair myself. Remember the Johnson Smith Co. catalogs, hundreds of pages of interesting stuff including those x-ray glasses? Would spend hours browsing over the catalog but never did buy anything either.

Dad3353, nice pics of your Prima build, very neatly done!

Always interested in balsa builds, the Prima plans and instructions are also available on Outerzone (never looked at AeroFred.com before, thanks for the link).

I would build the wing according to the instructions. Seen this elsewhere already incorporated into the plans but to establish the location of the ribs and wing tip reinforcement, use a straight edge and pencil on the plans to extend the parts' dotted lines beyond the balsa sheets that will cover the plan details. Especially helpful in locating the ribs in the wing center section as the other ribs are cemented onto the center of the caps strips except for the rib nearest the wing tip.
Nov 03, 2017, 06:18 AM
Registered User
Quote:
Originally Posted by BMatthews
...You could write down the notes you need on some scrap paper with an old fashioned pen?...
Great idea; thanks..! I'll just nip out now and pluck myself a quill from a passing goose.

Quote:
Originally Posted by HIR/Cer
...
Dad3353, nice pics of your Prima build, very neatly done!...
Thanks; it's my 'first', so I'm trying to keep a record of my steps, and haven't seen anyone else do it for this model. There may be a very good reason for the assembly to be done in their manner. After all, Svenson are not at their first kit, either.
I'll soon see; I've put the fuselage to one side whilst waiting for the out-of-stock motor to become available again, so the board is now clear for the next delicate stage. Onward and upward..!
Nov 04, 2017, 12:12 PM
Registered User
Quote:
Originally Posted by Dad3353
I'll try out the 'classic' method of creating the skeleton first as a dry run, to see if I'm inspired by that. If it seems too delicate, there'll still be time to unpin the lot and lay down the sheeting. I can probably mark any salient lines for component placing, but there are other notes on the plan that'll be hidden, such as wood dimensions and other notes.
As for scanning: this plan is from an original kit, but the plan is also freely available for download as a pdf from AeroFred.com (so I could consult it on screen...), or I could order a print-out from that excellent plan library. We'll see; I'll report back as to progress (or disaster..!) later on.
The guys here are telling you true.
Build over the plans being sure to use something to isolate any glue from the plan sheet (I use plain old wax paper).
Once you have the main structure built, you have NO need for the plan sheet anymore.
So pull the structure off the table, lay down some fresh wax paper to avoid gluing the wing to the table, and then add the sheeting making sure to be using any height spacers called for in order to build in the specified washout.
Doing it this way saves your plans from anything more than some pin holes, and it allows you to hang the plan on a wall in front of you for constant reference going forward.
Good luck.
Nov 04, 2017, 01:46 PM
Registered User
I've released the ribs from their sheets, and prepared the required wood for spars and all, but am patiently waiting on the postie to deliver proper 'thumb-tack'-style pins before wading in on the next step. Yes, I have glass-headed dress-making pins, but my poor old fingertips don't like pushing them into my chipboard table too much. They're OK for balsa-to-balsa, or just one or two, but it's going to need more than that for these wings. Luckily, I've already taken delivery of a large bucket-full of Patience. ;-)
Keep the suggestions coming, please; I learn more from just about every post. One is, it seems, never too old for that.
Nov 04, 2017, 03:23 PM
B for Bruce
BMatthews's Avatar
Oh lordie... be careful with those glass headed pins. Seriously. They are prone to shattering the plastic blobs under pressure and then drive the end of the wire into your finger. They are fine for fabrics and even balsa. But if you're pushing them through the balsa and into chip board then sooner or later one of them will shatter under the pressure and you're not going to like it.

Chip board as used for covering up the framing on new house construction isn't a very good "pin board" for building anyway. The pins don't want to go into it easily enough as you're finding. Some like a sheet of dry wall and say that the gypsum takes their T pins neatly and that it holds well. Others go for a large tile from a suspended ceiling. Turn it over if you can't find any without holes or use the white face side if you can fild a "solid" tile. With either of these you can even get by with the beaded pins... although I still suggest you buy some "T" pins.
Nov 04, 2017, 04:44 PM
Registered User
Quote:
Originally Posted by BMatthews
Oh lordie...
Thanks, Bruce. I'm aware of the fragility of the pins I'm using, and had no issues with my previous builds, which were for smaller 'planes, on a smaller softwood building board, and had no problems pinning to that. The much larger plan for the Prima, however, necessitated the scaling up. I had the chipboard panel (I've others, too...), which is not as hard as all that, but too much for my fingertip's comfort (a daily blood-sugar level test doesn't help, of course...), and your safety concerns are part of the equation, too..! These are the pins I'm waiting for...



I considered a softer material for the worktop, and considered hunting down a roll of cork; that's still an option, I suppose, but was a bit concerned about keeping the surface flat with such a layer. Same for polystyrene tiles or such. Our local hardware store doesn't offer a great range (a small town...), but I could take a trip to a better-stocked outlet. I'll see how I get on with the new pins first, though. Thanks for your concern; I can't say it brought a tear to my eye, but your advice could save me crying over split fingers..! :-o
Nov 04, 2017, 05:21 PM
B for Bruce
BMatthews's Avatar
I've used those pins as well. They do work great. But oddly enough I found a lot of the heads pulled off if the pin got stuck in the wood due to excess CA glue bonding them in place. But a bit of attention to keep the pins further form joints where the glue can wick through the wood pores and they are fine.

Side note... my personal "best" for the thin CA wicking along the capillary tubes and sticking either my pins or my fingers to the wood is just a bit under 2 inches.... Some days it simply doesn't pay to get out of bed......

I do love those pins though for another reason. The wire is VERY thin and on models where the pinholes from the heavier gauge T pins would still show the holes from these close back up neat as a ... er... as a ... pin? So even if you find that you eventually buy some heavier T pins for some uses I think you'll find that these light gauge pins come in very handy.

One good thing with the colourful plastic heads is that on wings with lots of sheeting it's far more obvious if you missed a pin before sheeting the top side. I wasn't joking about forgetting a pin or two inside the "D" box. I spoke from personal experience. I double and triple check now before risking another occurrence of THAT embarrassing moment...
Nov 04, 2017, 05:43 PM
Registered User
Another good reason for me not to use CA glue, it would seem. I've never had much luck with the stuff (although most of my attempts date well back, when it was perhaps not yet perfected..?). I hold the view that it works by telekinesis; that's to say 'will-power'. To those that believe in it, it works fine, but for sceptics such as myself, it 'knows' that we have little faith, and so fails (except for skin adhesion, of course...).
No, plain ornery PVA is what I use, systematically, with very rare spots of epoxy, mostly on non-wood jointing. I used to get on well with balsa cement, but it's a bit brittle, I find, for the (to me...) larger build presently on the board.
Of course, the main advantage of the coloured pins is to be appreciated when hunting for those dropped to the floor..! :-)


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