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TigerTail

Old 10-14-2014, 04:22 PM
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whatnext
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I have a Southern R/C Tigertail.I am trying to sheet the foam wings.The leading edge on the wing's are very sharp.Will the balsa sheet bend around this sharp leading edge?I know to wet the balsa first but that leading looks mighty narrow...


regards jp
Old 10-14-2014, 06:07 PM
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RCDENT
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Depends on the thickness and weight of balsa you are using. 1/16 in should not be a problem if it isn't too hard (lighter color generally indicates softer and "bendier" balsa).
Old 10-15-2014, 03:02 AM
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What about a 1/4" or 1/4 x 3/8 leading edge piece and start the sheeting behind it?
Old 10-15-2014, 09:01 AM
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I've never seen the plans for the Tiger Tail but if it builds up similar to any other foam winged plane, the sheeting will be glued down first and trimmed even with the leading edge and trailing edge. Flat balsa pieces are then glued to the leading and trailing edges and shaped to form the rest of the airfoil.

I've done one giant scale plane that had formed balsa leading edges and it was NOT fun to do. I had to make two seperate jigs in order to form the wood.



carl
Old 10-15-2014, 10:37 AM
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doxilia
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JP,

it sounds like your cores are intended to be "wrapped" rather than "capped". That was not an uncommon method to cut cores with some of the older kits. Recently, some of us building classics have gone back to that core approach with the knowledge that the resultant wing LE is more accurate when precision cut than when it is hand carved and sanded. It is also, in principle, less work than the more common capped approach.

There are a couple of threads on the RCG Classic forum discussing the wrapping technique. Look for Super Chipmunk and Deception threads with posts by Kevin G and by myself. In a nutshell, our approach is to skin the cores in a composite fashion using both CF and/or FG and balsa. Our balsa skins are 1/32" rather than 1/16" or 2 mm. The LE is wrapped first with a 2" to 4" wide strip of 1/32" and allowed to cure in the shucks. The remainder of the core is sheeted afterward by mating the top and bottom skins to the LE wrap. The LE can optionally be first wrapped with CF veil and epoxy in order to make it considerably more dent proof.

The trick to the LE wrap is to pre-mold the wood prior to gluing it to the core. Depending on the wood used this can entail hot water and/or ammonia as well as repeated molding passes for thicker wood. That said, if the LE is too sharp, sometimes it is not possible to wrap it (e.g., stabs) and skinning the core in a standard fashion is the better option. You can skin to within 1/4 or 3/16" of the LE and then, once cured, saw and/or sand the core LE back to the sheeting and cap it with a balsa strip.

I hope this helps.

David

Last edited by doxilia; 10-15-2014 at 10:43 AM.
Old 10-15-2014, 07:25 PM
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Timthetoolman1
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JP,

I use Gorilla Glue because it's lighter.

I cut my sheeting 1/4" larger all the way around the wing, put the GG down on the skins and scrape as much off as I can get with a credit card. Put as much glue down as you need but it will mostly come off when you scrape it.

Then mine goes in a vacuum bag but you can use weight, just use a lot! The LE wraps around and actually bunches up but after it's dry I cut off the excess and then sand the LE down till I get to where the foam and skins make a good tight bond. Then I put a small cap strip, usually 1/8" or less because the vacuum bag does a good job at squeezing it down. Then I round it to match of course.

The stab photo shows the LE before shaping.

I use the sticky back sand paper on my glass top to sand the LE flat.

Tim
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Old 10-16-2014, 10:22 AM
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whatnext
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Thanks you all very much for taking the time to try and help.Skinning the wings is the only thing holding me up with this build.I have all winter to come up with a method.

regards jp
Old 10-16-2014, 12:15 PM
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JP,

another thing to to consider is that traditionally the skins used to be glued up from 2" to 4" balsa sheets. Once the sheets were bonded to form the skin, it was sanded smooth on both sides, vacuumed and tack clothed prior to adding glue to the side bonded to the core. This method works but can have the disadvantage of producing hard edges at the sheet splice joints.

Nowadays, some of us, have gone to an approach which carefully splices the sheets together but they are held together with painters tape rather than glue. The skin is flipped and the same prep is given to it after which it is bonded to the core. If one uses laminating epoxy rather than expanding polyurethane, the glue just seeps in enough into the joints to keep everything together once the painters tape is removed. This works especially well with thin skins such as 1/32". The use of foaming polys might also be possible but I haven't tried it. The risk is that it may seep out of the joints leaving a hard line of glue that doesn't sand well. The use of epoxy leaves a virtually seamless uniform balsa outside surface which sands and finishes quite nicely. That said, expanding polyurethane glue has its virtues and advantages but I feel it might require the skins to have pre-sealed joints along the splice lines.

A few more things to think about... ;-)

David
Old 10-16-2014, 12:40 PM
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David,

I only tack my sheets in 3 spots and the glue bonds them well and I've had no issues. I have done both methods of epoxy (since I buy it in 5 gallon containers and have plenty) and GG and I personally prefer the GG. I have wanted to strengthen the elevators and used carbon veil so I used epoxy in that case but it's rare, I just find poly glues easier to work with...but that's my preference so definitely try the different methods and see which one works for you.

I will say occasionally a small amount of glue seeps out but I've had that issue with epoxy too. Either case it's not really common. Tacking the skin with CA does require sanding a bit before gluing on so I'll try the tape method. I saw someone putting it on the inside and using sanding sealer...not sure if sanding sealer makes it that much lighter and was wondering if anyone put the tape on the outside of the skin.

Whatever method is used, make sure you match the thicknesses because most balsa sheets are not uniform in thickness. If it's off a bit make sure to sand it before you glue it on the cores. You don't want to sand it after it's on the wing. However, I've had to do some light sanding in some spots that bled through...it happens, just be careful.

Tim

Last edited by Timthetoolman1; 10-16-2014 at 12:43 PM.
Old 10-16-2014, 05:09 PM
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flywilly
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Wrapped sheeting leading edges have long been popular with the C/L stunt aficionados. I'm pretty sure Bob Hunt has written about it in one of the magazines. They have some very good techniques, but as David pointed out in his post it can be an iterative process and the sharpness of the leading edge can be a limiting factor (C/L stunters often have fairly blunt/well rounded leading edges, too).
Post some photos of your efforts, please!
Old 10-19-2014, 05:45 AM
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Hi Guys,

Here is a quick way to sheet wings.. I learned this from Dennis Hunt (zimpro marketing) He produced the viper ama pattern planes and the daddy rabbit along with a lot of others.

Anyhow after matching the wood (weight) and truing up the edges he would use the clear magic tape, like for packages every 3 -5 inches with a small 1" piece the length of the sheeting.

Cut the sheeting 1/4 - 1/2 inch larger than core, don't forget to allow for the airfoil

Next use minwax sanding sealer and go over the sheeting the taped side. no wiping down or tac cloth not needed.

Next we currently use Elmers Glue - ALL MAx - drizzle on wood, (tape side) use a old cc or piece of old sheeting and spread glue out to the point of being almost gone, you will feel a light wetness,

Next run a bead of the glue for the 1/4 wide x .007 carbon pre peg carbon fiber tape to be placed on.. Set the carbon in place and then use old cc to push carbon into bead, then run another bead of glue on top of carbon and lightly spread glue out. This it done on both top and bottom of wing.

Next spray core with fine mist of water and mate balsa skin to core, do same for other side and either vacuum bag or use the old weight system.

Allow glue to dry 4 hours and trim and sand edges. The glue with seal the sheets together and any that might come thru the joints is very easy to sand , no hard spots.

We could do 3 or 4 sets of wings in the morning and by after lunch be facing them and cutting out control surfaces and facing.

Just another way to do them.

Well back to more bootleggers.
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Old 10-19-2014, 05:36 PM
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OK, here's my way. True up the edges and run plain old masking tape the full length of the joint. Flip over and open the joint slightly, the apply hardware store Du Pont "Duco" Household Cement. Lay the sheet back down flat and cover with wax paper if doing multiple sheets. Weight the sheets down with books or similar. Let them dry overnight, then remove the tape and bond the sheets to the cores with epoxy or contact cement. The joints will be almost invisible and sand VERY easily.

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