MHester

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Ok guys, you asked for it, so here it is.

Finally, an american built wood/foam/composite kit that is easy to build and has a flight performance that is second to NONE at the time of this writing. No it isn't perfect, but it's about as good as it gets!

The flight characteristics and testing have been covered extensively elsewhere, so I am going to focus on the building of the plane in this thread.

The weight is easy to make IF you follow my instructions to the letter. If you have better or more aggressive iseas, feel free to chime in, I certainly do not have all of the answers, I only know what has worked for me so I am going to share it.

First and foremost let's talk about weight management. You can NOT build a legal electric VF3 without an accurate gram scale. Unless you're the luckiest guy alive. Weigh EVERYTHING. if you can find a place to shave a few grams without sacrificing too much strength, by all means do so! But I can tell you right now, the 2 easiest ways to control the final weight of the airframe are with the sheeting and the finish.

The majority of sheeting on the VF3 uses 1/16x4x36" contest balsa. DO NOT use any piece of sheeting that weighs over 12 grams! The same goes for the capping and blocks....weigh and hollow everything. Even the leading and trailing edges, blocks for wing tips, tail blocks etc need to be hand picked contest balsa. The lighter, the better. To hedge your bets, get more wood than you need and only use the best pieces. if none are good enough, simply save them for another project and try again. Trust me on this one, this plane flies awesome so it's worth being patient and doing it right.

I'll go into specifics on the finish and sheeting in thier respective sections, but in general, just know that on a plane like this, with a LOT of surface area, you simply can't afford to get lazy. If you do it right and are careful in your execution and equipment selection, you can come out with a 10 lb plane with batteries. The plane was designed for the AXI outrunner (24-26 ounces) and 3 lb packs. it will make weight in this configuration, but you need to follow the directions. It's not hard at all, just don't get complacent.

As a general note, this plane is draggy and has a long tail moment. I strongly suggest using a DEPS system for the elevators and mini servos for the ailerons etc. You need to be thinking of an electric set up with a higher pitched prop. If you install the old industry standard hacker C50-14 and 22x12 prop, you can go have lunch during a downline. This is neat, but wait until that Nats wind comes up....not so neat. but personal preference.

For info's sake, details on the plane can be found at www.customairframes.com

Off we go, I'll type as much as I can per day as I finish the ones I'm working on over the next few weeks.

MHester

My Feedback: (1)

Items needed:

This is what you need to complete the framing of the kit.

-PBG C/F 7/8x30" wing tube and socket
-PBG C/F 7/16" stab tube and socket
-2 gator style wing adjusters
-2 Gator style stab adjusters
-landing gear of choice (ES long gear works best, alternative is Comp ARF Integral or Impact gear)
-Wheel pants (small)
-2 BVM style hatch latches
-motor mounting system (Esprit/cambria or "X" mount)
-36 pieces 1/16x4x36" contest balsa (LIGHT!)
-2-3 pieces of 1/16x4x48" contest balsa (LIGHT)
-3 pieces 1/8x4x36" contest balsa (LIGHT)
-2 pieces 1/4x4x36" contest balsa (LIGHT!!!!)
-2 pieces 3/8x4x36" contest balsa (you get the idea)
-1 piece 1/2x4x36" contest balsa (ditto)
-1 piece 1x4x36" contest balsa (getting the picture?)
-1 piece 2x4x36" contest balsa (this one can make or break ya)
-1 piece of 1/8" light ply for misc stuff
-West system 105/205 resin for sheeting OR
-polyurethane glue (You BETTER know what you're doing with this stuff!)
-various CAs (mercury adhesives makes some really good stuff for composite bonding, M100XF)
-Straight, flat table
-72" straight edge (available at any hardware store)
-various sanding blocks, permagrit files, etc
-Fuselage jig (optional, but VERY nice!)

Now that I have been using the perma grit files, I don't know how I ever did without them. Especially the round and flat files. They can REALLY make life easy.
I use a small hard piece of 3/4" MDF board wrapped in sticky back 80 grit paper for general building, as well as various blocks, bars etc. use the hard 80 grit blocks and the flat perma grit file for general fitting. For sanding sheeting, I use 220 grit paper on a 3m block. I also have a special 90 degree block I use for truing the edges of the wing and stab cores. I'll show you this later....

Ok we'll start with the cores as this is easily almost half of the work.

MHester

My Feedback: (1)

Prepping the cores

Foam is a funny thing. it has internal stresses and 'wet" spots that make life difficult. All you need to know is that the cores were cut weighted on a flat table bottom side down, so always do sanding, weighting etc with this in mind.

When foam is cut, a hairy melted foam crap is left on the surface and the surface is glazed. This needs to be sanded off, but not yet.

First prep the Wing, stab and rudder cores by marking and cutting away the TE 1/4" back and sanding it flush (CAREFULLY) with a sanding bar.

Now install the false ribs and run the wing/stab tube inside and check to be sure the hole is centered and clears the tube. Sometimes the hole for the socket is a bit tight, so wrap some sandpaper around the tube (not the socket) and twist this inside the hole until the hole clears the socket. it should slide freely, but not really sloppy.

Now locate the balsa insert point for the hard points. Cut them out and install pieces of balsa to fit.

Now glue on 1/4" contest balsa strips for the TEs, glue in the false ribs, and glue in the balsa inserts with polyurethane glue. This stuff needs to be FRESH and thin. Wipe off the excess with a paper towel. It should only appear damp. tape the TE in place with masking tape and let dry overnight (or while you're making the skins.)

MHester

My Feedback: (1)

On to the wings.....

On an electric, every gram counts. You don't have the vibration of an engine to worry about, so you'd be suprised what you can get away with.

I like to honeycomb my panels on electrics. I use a different technique on my glow planes, but for the electrics I build, honeycombing the panels saves at least an ounce per panel and shows no ill effects. I know some who swear they can feel the ing twist in flight (I'm not saying they can't, but this plane doesn't seem to care). At any rate, I think it's worth doing.

We can do this for before we ship for a small fee, but it's easy to do yourself if you're well versed with it. Basically you use poster board templates and a small hot knife and just cut away voids in a geodesic pattern. You need to leave at least 3/8" at the edges, and don't get over into the load bearing areas like the wing tube or spars. A little acreful planning though and it's not too bad.

Next, sand the TEs flat with the foam core. be VERY careful and patient with this step so as not to dish the foam surface. What I do is use an 80 grit bar and get it close, then sand it flush along with the entire core surface with a hard 220 grit block. This is the point to sand all of the cores. just break the glaze and get it even, don't go crazy.

The spar slots should be marked. The easiest way to do this is to use a straight edge guide (like the side of a level) and a dremel with a router cage. Use a 1/8" router bit set a hair deeper than the 1/4" spar and just guide it down the straight edge. be careful and patient when you hit the false rib. After this is done, use either your perma grit file or better yet a standard 1/8" steel file from the hardeare store and run it down the slots. Test fit the spars and they should be snug but flush with the top pf the surface.

Sand ALL cores with a 220 grit block and then blow them off with an air hose or vacuum. Keep them clean for the sheeting process.

Ricardo M.

Hey Mike, nice color you choose to paint your thumb nail. LOL


Yust kiding, no offence.[sm=biggrin.gif][sm=biggrin.gif]

MHester

My Feedback: (1)

Wife's hand

Arrgh didn't ntice that, used an old stock pic from the V2 thread for that one.

-M

woodie

OH NO!! you weren't referring to your wife as 'old stock' were you? Man, are you in trouble........ ;-)))

Woodie

MHester

My Feedback: (1)

Making the sheeting

True up the edges of the sheeting. I ususally use a long straight edge and trim the edge straight with a new (very sharp) Xacto blade. Do this to all edges.

Next with a block sander (or preferrably an edge sander if you have one), stack the sheeting about 6 pieces at a time and sand the edges true.

Using the atached drawings as a guideline, trim and glue the sheeting together.

Place a piece of sheeting on a flat table. Lay out a piece of masking tape sticky side up and place the edge half way onto the tape.

Next, lay the glued piece onto the tape, taking care working all the way down the seam to ensure a tight fit with no gaps.

Lay the seam over the edge of the table, so the exposed piece drops over the side and exposes the seam like a hinge.

Run a small bead of elmer's white glue down the seam and make sure there are no dry spots.

Close up the seam on the flat table, and wipe off excess with a paper towel. The less glue left on the surface of the wood, the better.

Repeat until the skin is completely glued. Weight down the skins with whatever you have available so it doesn't bow up and open the seam.

Let sit for about 20 minutes, then sand the seams LIGHTLY with a 220 grit block. This creates dust as a fliier to close up the seam. Do NOT try and sand the skins perfectly flush at this time, only create dust and work into the seam if needed.

After the skins sit for about an hour to an hour and a half, carefully remove the weights and flip the skin over. Carefully peel back the tape.

Place the blocks down again, and after about 10 minutes, dust sand this side as well.

Let the skins dry overnight before final trimming and sanding.

MHester

My Feedback: (1)

After the sheeting has dried, trim to final shape and sand flat.

Sometimes thicknesses vary, so you have to match this. The side the tape was on should be down against the table, and sand the exposed side first. Only then flip the skin and sand the other side.

After you have sanded the skins smooth, blow them off with an air hose or vacuum, but get all of the dust off the skins.

Next, spray the skins with aqua net hair spray (just regular old hair spray in an aerosol can). Don't spray them soaking wet, just damp. The skins will curl up and bow like crazy, this is normal so don't freak. let them dry for at least 3-4 hours or longer.

Block sand the sprayed side with a 600 grit block just enough to be smooth to the touch (only knocking down the high spots). After cleaning the dust off the skins, you're ready to sheet the cores.

MHester

My Feedback: (1)

Sheeting the cores

Once this step is complete, you're almost halfway to a framed VF3!

There are a zillion ways to do this. The only things you really need is a hard flat table that won't bow under a few hundred pounds of weight, and some weights. you need at least 200 lbs for the wings. Various clamps and such are nice for the turtle decks too, just use your imagination here.

Here is the simplest way to sheet a honeycombed foam wing core.

Use a good, low viscosity laminating resin like west systems fast or slow cure.

Use a glue syringe for the honeycombed section.

Lay the core on the skin, and mark where the solid section begins. This is the only area you will apply glue to the skin. Always do the bottom skin first.

Glue in the spars with polyurethane glue. You don't need them more than damp.

When you are ready, mix about 18 grams of resin for the solid section per skin, less is better, but this is aceptable.

using a playing card or something similar, spread the resin on the skin in the marked area. To hedge your bet, next roll the skinn area with a foam roller to get it even and soak up the excess resin.

Using a glue syringe, apply a bead of resin to the honeycombed structure. You shouldn't need more than a 1/16" wide bead. on the LE, TE and Tips, apply 2 beads side by side to ensure adequate bonding. Do NOT get crazy here.

Also add a small bead to the tops of the spars, false rib and hinge line area.

Place the skin on the core carefully. Now flip the core, place it in the bottom shuck and repeat for the top side.

When both skins are in place, install the top shuck and begin weighting the core. Take care to align all corners.

As you apply weight, check the LE and TE with a traight edge to make sure the panel is not bowing under the weight.

200lbs is what I would consider minimum. The more weight you can use, the less glue you have to use. The amount of resin you can get away with would scare you.

Later I will demonstrate a vacuum/ carbn veil technique that I have been using.

Let the cores cure in place for at least 24 hours before removing.

MHester

My Feedback: (1)

Do the rudder and stab cores the same way.

For the turtle deck cores, these are a PITA.

I have started using polyurethane for sheeting these parts. However, there are a couple of things you need to know or you will mess up big time.

First, when using polyurethane for sheeting, use ONLY fresh glue. Use elmer's ultimate, and make sure you have JUST opened the bottle. Why? because this stuff thickens as it's exposed to air.

First wet the outer side of the Tdeck skin with ammonia and water.

Flip the skin and weigh out 15 grams of polyurethane.

using a spreader, spread the glue into a thin layer on the skin. It will appear almost dry, but that's ok. If it looks wet or shiny, there's too much glue and hence, too heavy.

After the glue is all down, soak up any excess because it doesn't evaporate, it's there to stay forever.

Place the cores in the shucks and weight them down. Use folded poster board, playing cards, clamps and/or weights to make sure the skins are contacting the cores and there are no gaps. This can be tedious the first time you do it, just be creative here. The moisture from the wet skin will kick the glue nicely so don't spray it.

let this cure overnight. When you remove the sheeted cores from the shucks, if the skins are still wet the core will be slightly bowed. Don't freak out, let it dry and it will assume it's normal shape.

MHester

My Feedback: (1)

By the way, if interested, we've added a few items and options to the lineup.

Go to www.customairframes.com and hit the refresh button.

-Mike

woodie

Mike, (or anyone else)

Has anyone tried using polyurethane glue and vacuum bagging the assembly instead of weighting it down? I have used epoxy and vacuum bagging but haven't tried polyurethane yet.

thanks Don

MHester

My Feedback: (1)

Sure have. I think I've tried everything at this point. Ok, everything I can think of.

It does work, but to me, it's not as easy to control the amount of glue. The viscosity of polyurethane can vary greatly, and that can get complicated when you're trying to keep it really light.

I also have vacuum bagged the cores with honeycombing. If you bag the whole shuck you can get away with it, but you can't pull a lot of mercury or you'll still crush the wing.

In the end I still prefer epoxy. A good low viscosity resin for the solid portions, and a slightly thicker resin for the honeycomb section.

-Mike

LCHelilover

My Feedback: (15)

Mike,

Are the measurements on the sheeting diagrams accurate enough that I can go ahead and cut the surfaces out of the sheets? Should I add any "overhang" or cut to the exact measurements on the diagrams?

I thought I'd glue up the sheeting while waiting for the foam to get to you.

Thanks,

George

MHester

My Feedback: (1)

Go ahead and cut the sheeting, it's accurate enough. leave a good bit of overhang, and then when you get the cores, just trim it to about 1/8" around overhang.

-Mike

dreadnaut

My Feedback: (5)

Any one finish one of these? What are you using for power? Has anyone had good results with AXI? I will be flying intermidiate.

LCHelilover

My Feedback: (15)

Dread,

I have been flying intermediate this year with an AXI 5330 FAI in a Pinnacle E- with good results. I plan to put either an AXI or a Dualsky in the BM V3 when I get it finished. The Dualsky is priced right, but I'm still waiting to see how they hold up- there seem to be some "issues" with them so far. I've been very pleased with the AXI- The Plettenberg Evos are great, but I just don't think they are worth the additional money unless you have to save the weight. Of course, I've spent enough sorting through "heavy balsa" to pay the difference between the AXI and the Pletty - OH well, I didn't say it had to make sense.

George

MHester

My Feedback: (1)

The AXI 5330 F3A is pretty hard to beat, in fact this plane was designed around it. There may be some better/cheaper options on the horizon, but only time and testing will tell.

As for packs, the Vampower pro 5s4500s are the best I have seen yet as far as weight vs power vs reliability. If you need the utmost power (FAI) the 5000s are even better, but you had better pay attention to the weight on this plane. It was designed to accept the heavist set up available, and that includes the 5000mah 5s packs, but if you get lazy or complacent you COULD be close on weight.

For intermediate the 3700 5s packs would work just fine...then you have the best of both worlds, power out the wazoo AND low weight! my guess is with this set up...this plane would be around the 10-10.25 mark easily. I could break under 10, but I admit it would be a lot of work for those last 4 ounces.

I like the Vampowers so much I'm going to run them in my own electric VF3!

An no, I am NOT "going electric". There is no substitute for a YS DZ in my book....But I want one to play with for sure, and there's only one way to get it...just build it! because I do intend to fly it in competition some next year IF I can get used to it.

-Mike

LCHelilover

My Feedback: (15)

Mike,

Sorry to be dense, but I can't decipher your answer Are you saying that the dimensions given on the sheeting templates include adequate overhang, or I should add additional overhang to the dimensions shown?

Thanks,

My Dad always said Measure twice, Cut once!

George

MHester

My Feedback: (1)

The overhang is adequate, as far as I know.....I've done quite a few of these, and those numbers work...some require a good bit of trimming but just follow the diagrams and you'll be fine!

PS yours will ship as soon as I get the new foam and get it cut, one day this week. ALL of the electric kits are getting the new foam which will shave an additional few ounces. This is stuff I couldn't get until last week. So I ordered it, they cut it up and now I have to get the trailer and go pick it up and cut it. Foam foam foam!

At any rate, I'll get down hard and heavy on this thread pretty soon, but I have to get these kits all shipped before I have any real time....

-Mike

matt13

Hello Mike, thanks for all the effort on the build thread. I have a NBM (non- black magic) pattern kit to build which has honeycombe wings like yours. The question I have is what did you make your spars uot of? Carbon firbre? Matt

MHester

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Front spars are 1/8"x1/4" spruce, or basswood. About 16" long.

Rear spars are .007" c/f sandwiched by 1/16" balsa, cut to 1/4" tall and about 16" long.

-Mike

dreadnaut

My Feedback: (5)

A note on honey combing. I don't do it because I think you save as much weight vacuum bagging. It lets you get away with using less epoxy, and still get a good, if not better bond. The problem I have always seen with honycomb is that you have to use a thicker film of resin to insure good contact accross the joint. Added to that is the fact the you are gluing a sizeable amount of sheeting to air.

Something I have considered trying is sheeting the wing with vaccum, as I have done in the past, then using a dremel to cut out ''rib bays'' afterward. I don't know how much effect this would have on stiffness. It would definatly be lighter. I think that if I used 1/2'' thick ''ribs'' in a truss pattern (like they use in powered free flight) it should be all right. Has anyone tried this?

Pardon the sketch, it was a quickie.

MHester

My Feedback: (1)

Nope, I've tried it every which way you can think of, and honeycombing is still the lightest by a good .75 ounce per panel. but you have to do it a specific way, like I outlined earlier. You have to be VERY sparing with the resin/glue. It's actually pretty amazing how little you can get away with, but the less you use, the more critical the weight applied in the curing.

The best way I have found to date is a combination of both. Honeycomb the cores, apply the resin sparingly, and then bag the whole shuck. Pull about 7 in mercury and it won't crush the core. What I did was kept sheeting wings and cranking up the vacuum until it started to crush, then backed off.

I have also tried the way you just outlined. It works. Not my farorite method but it does work!

They ALL work to varying degrees and it all depends on the person's ability. The key is using just enough resin/glue to get the job done and NO MORE, and applying enough force to bond the skins without crushing the panels.

-M