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Konrad
Very Strong User
Doc, I have to say you were right! In this thread post #13 you said to fill the void with epoxy. I have to say I didn't think it would make much difference as I thought the tube would add most of the stiffness as it was anchored at both ends of the loading port.
forum.alofthobbies.com
Well, I had some left over epoxy from this repair and needing a place to put it, so I stuffed it in the void. I came back this morning and was pleasantly surprised at how much stiffer the fuselage was.
forum.alofthobbies.com
All the best,
Konrad
Ballast tubes! How to make a fast, easy and good setup.
Hi Guys, Over the (Many) years I have seen more ways to keep ballast in ballast tubes than I can shake a stick at. Mostly they involve Nuts screws washers and bolts - and other laundry related systems. All have been ingenious - some more than others I have to say. Me? I use the...
forum.alofthobbies.com
Well, I had some left over epoxy from this repair and needing a place to put it, so I stuffed it in the void. I came back this morning and was pleasantly surprised at how much stiffer the fuselage was.
60" Molded racers for MoM
Well, I think I recovered from this fiasco. I need to give a shout out to Doc. for encouraging me to try these epoxy wipers. https://forum.alofthobbies.com/index.php?threads/servorahmen-ids-servo-mounts-etc-step-by-step-install.198/page-2 While far from perfect, I’m actually happy with the...
forum.alofthobbies.com
All the best,
Konrad
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Motowncali
Active User
Using the solar powered autoclave oven to cure epoxy... I’ve lost count as to how many projects I’ve cured in the truck or car over the years. Doesn’t need to be up in the window either... just put it on the seat. I also have a lap size electric blanket that wrap projects in and leave on the work bench. It auto shuts off after a couple hours, but works great.
Attachments
Konrad
Very Strong User
To feed the flap and aileron leads down the wing I remove the connector housing and then heat shrink the ends together. Once the leads are in the wing I reassemble the connector in the servo pocket.
Due to manufacturing tolerances, shipping and handling the root ribs (profile) almost never line up. I set my wings so that they are true to each other at about the 20% span location. I use the 20% location as it allows me to still twist the wing should flight testing show a problem. You will notice that the wing looks twisted as the right (your right) wing looks like it is high at the TE and the left (your left) the wing looks high at the LE. This twist is less than 1mm heck it was less than 0.5mm before I block sanded the wing.
For those that have built a Mefisto where did you place the wing? I get the best fit with the wing saddle with the wing LE overhanging by about 5mm. I actually like this look. I also like that it adds length to the tail boom. I’m concerned with balance and the placement of the ballast tube. I think I have enough adjustment as to not be an issue.
All the best,
Konrad
Due to manufacturing tolerances, shipping and handling the root ribs (profile) almost never line up. I set my wings so that they are true to each other at about the 20% span location. I use the 20% location as it allows me to still twist the wing should flight testing show a problem. You will notice that the wing looks twisted as the right (your right) wing looks like it is high at the TE and the left (your left) the wing looks high at the LE. This twist is less than 1mm heck it was less than 0.5mm before I block sanded the wing.
For those that have built a Mefisto where did you place the wing? I get the best fit with the wing saddle with the wing LE overhanging by about 5mm. I actually like this look. I also like that it adds length to the tail boom. I’m concerned with balance and the placement of the ballast tube. I think I have enough adjustment as to not be an issue.
All the best,
Konrad
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Konrad
Very Strong User
To support the top wing skin I added some unidirectional carbon fiber to the servo pocket. I should have oriented the fibers so that they were 90° to the sheeting grain. Really I should get some light bi-directional carbon cloth.
Also when cutting out servo pockets I try to cut as few span-wise fibers as possible. This is why the pockets have the long dimension of the rectangle going span-wise. It is also why I cut off the mounting ears on servos I plan to glue into the wing.
alofthobbies.com
As a note, I tried the flat across the top dihedral and didn’t like the look (it looked droopy). So I broke the joint and added 6mm to the center as my dihedral.
All the best,
Konrad
Also when cutting out servo pockets I try to cut as few span-wise fibers as possible. This is why the pockets have the long dimension of the rectangle going span-wise. It is also why I cut off the mounting ears on servos I plan to glue into the wing.
JX PDI-0902MG Servo - 2.6 Kg (36.11 oz in), .07 sec - High Voltage
Digital control, high torque and a metal gear train make this servo an attractive choice but the thin profile (8mm) is really where it shines. A great servo for lighter gliders, thermal ships, and entry level DLG's at a great price.
alofthobbies.com
As a note, I tried the flat across the top dihedral and didn’t like the look (it looked droopy). So I broke the joint and added 6mm to the center as my dihedral.
All the best,
Konrad
Konrad
Very Strong User
Well there it is on page 4 of Blejzyk manual. It looks like the as molded fuse is for the HN1033 airfoil. and that with the S6063 the wing is intended to be moved forward about 4mm.
Wing position on top of the fuselage:
www.blejzyk.pl
Wing position on top of the fuselage:
- HN1033 profile: as per drawing
- S6063 profile: move the wing forward by approximately the thickness of the leading edge
Blejzyk - download files
Blejzyk - producent najwyższej jakości modeli latających szybowców oraz motoszybowców RC. Poznaj pełną ofertę 2014. Zapraszamy.
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Konrad
Very Strong User
With all the weight credits 
I get making the wing a single piece by removing the wing joiner, I’ve added a 4 layers of fiber glass across the wing center line joint. These layers are arranged like a leaf spring. The first 2 are 0.75 oz (red) and the last 2 are K&B medium weight (2 oz ?) (green). I then soak up the excesses epoxy with a paper towel lightly dampened with alcohol. I want the area to have a dull mat look. Any glossy areas are an indication of too much epoxy and will just need to be sanded down. Also too much epoxy can allow the fibers to float above the surface of the wood. These floating fibers will offer no strength should they get cut while feather sanding the layup.
I get making the wing a single piece by removing the wing joiner, I’ve added a 4 layers of fiber glass across the wing center line joint. These layers are arranged like a leaf spring. The first 2 are 0.75 oz (red) and the last 2 are K&B medium weight (2 oz ?) (green). I then soak up the excesses epoxy with a paper towel lightly dampened with alcohol. I want the area to have a dull mat look. Any glossy areas are an indication of too much epoxy and will just need to be sanded down. Also too much epoxy can allow the fibers to float above the surface of the wood. These floating fibers will offer no strength should they get cut while feather sanding the layup.
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Konrad
Very Strong User
I've glassed about 1/3 the wing span. I've also allowed one layer to encompass the servo cut-out. This really is overkill, but I did it as I'm able to ballast the ship with over 470 grams of ballast. Should I fold the wing I want it to fail outboard of the flap servo. The S6063 is a nice thin airfoil as such I'm trying to give the wing some stiffness with all the glass layers and at the same time maintain some flexability.
After allowing the epoxy to cure overnight I’ve block-sanded the epoxy and glass with a rigid-backed sanding block. It is important to use a hard sanding block and not a soft foam sanding pad. You want to knock off the high fibers and not undercut the underlying fibers.
What you are seeing is about 30 minutes of work with the sanding block. I’ve pretty much feather-sanded the fiberglass layers. Now comes the hard part, feathering the layup onto the wood skin without undercutting the wood veneer. Anybody in the Aloft hive mind have any tricks to do this?
All the best,
Konrad
After allowing the epoxy to cure overnight I’ve block-sanded the epoxy and glass with a rigid-backed sanding block. It is important to use a hard sanding block and not a soft foam sanding pad. You want to knock off the high fibers and not undercut the underlying fibers.
What you are seeing is about 30 minutes of work with the sanding block. I’ve pretty much feather-sanded the fiberglass layers. Now comes the hard part, feathering the layup onto the wood skin without undercutting the wood veneer. Anybody in the Aloft hive mind have any tricks to do this?
All the best,
Konrad
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Konrad
Very Strong User
It’s never too early to think about geometry. I’m thinking of making the flaps and ailerons top driven. There is some evidence that this can lower the drag the equivalent of the drag we get from the stabilizer. That’s a lot of drag.
It looks like the push rod slot will need to be about 20mm from the hinge line and about 20mm long.
I’m thinking that I’ll need to make up a set of half jelly bean shaped servo covers. This would be a bit of a shame as the Blejzyk kits come with some very nice fiberglass servo hoods.
I’m thinking that a 7 mm horn with a 10 mm servo arm. Setup so the arm linkage is locked* with the flaps down.
What do you guys think about the threaded brass stud vs the classic fiber class control horn?
*Locked linkage is when all three pivot points align in a straight line. In this case it is the servo axis, the servo arm and the control horn.
All the best,
Konrad
It looks like the push rod slot will need to be about 20mm from the hinge line and about 20mm long.
I’m thinking that I’ll need to make up a set of half jelly bean shaped servo covers. This would be a bit of a shame as the Blejzyk kits come with some very nice fiberglass servo hoods.
I’m thinking that a 7 mm horn with a 10 mm servo arm. Setup so the arm linkage is locked* with the flaps down.
What do you guys think about the threaded brass stud vs the classic fiber class control horn?
*Locked linkage is when all three pivot points align in a straight line. In this case it is the servo axis, the servo arm and the control horn.
All the best,
Konrad
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Konrad
Very Strong User
Here I’m making the top leaf spring. I’m using 6 layers of 0.7oz fiber glass. I omitted the med weight glass and added 2 more layers of 0.7 oz glass purely for aesthetic reasons. The 0.7 oz glass looks better.
I’m using Tap Plastic’s 4:1 Super Hard Epoxy as my laminating /finishing resin. To be clear this is mixed 20% hardener and 80% resin. I like it, but it is a short pot life epoxy. To extend the pot life I put the mixed cup of epoxy on a frozen housing brick to slow down the reaction. I then poor the mixed epoxy out on the surface. To aid its flow (wet out) I then heat the epoxy that is on the wing with a heat gun. One needs to work fast but not frantic to get the lay up saturated. Once all the fibers are wet. I then mop up the excess epoxy with a roll of toilet paper (TP is more absorbent than the paper towels I used on the bottom of the wing).
Prior to the lay up I masked the ailerons as I don’t want to epoxy them in place. Make sure you mask the hinge line and make sure you don’t allow the epoxy to puddle over the hinge line. Set aside until the epoxy has set but hasn’t cured. I wait about 4 hours at room temperature.
The set epoxy is much easier to trim than waiting for the fully hardened epoxy. While the epoxy is somewhat soft but not tacky to the touch, trim off the over hanging glass. Make sure you don’t cut the mylar hinge tape under the veneer. Un mask the aileron. Now is a good time to make sure the hinge line is free of any epoxy. I find that scrapping the hinge line with a # 11 blade will lift up any epoxy that might have gotten into the hinge line. ( had less than 5mm total of the hinge line with any epoxy in it.
Set aside over night for a full cure of the epoxy. Then block sand the top as one would the bottom.
All the best,
Konrad
I’m using Tap Plastic’s 4:1 Super Hard Epoxy as my laminating /finishing resin. To be clear this is mixed 20% hardener and 80% resin. I like it, but it is a short pot life epoxy. To extend the pot life I put the mixed cup of epoxy on a frozen housing brick to slow down the reaction. I then poor the mixed epoxy out on the surface. To aid its flow (wet out) I then heat the epoxy that is on the wing with a heat gun. One needs to work fast but not frantic to get the lay up saturated. Once all the fibers are wet. I then mop up the excess epoxy with a roll of toilet paper (TP is more absorbent than the paper towels I used on the bottom of the wing).
Prior to the lay up I masked the ailerons as I don’t want to epoxy them in place. Make sure you mask the hinge line and make sure you don’t allow the epoxy to puddle over the hinge line. Set aside until the epoxy has set but hasn’t cured. I wait about 4 hours at room temperature.
The set epoxy is much easier to trim than waiting for the fully hardened epoxy. While the epoxy is somewhat soft but not tacky to the touch, trim off the over hanging glass. Make sure you don’t cut the mylar hinge tape under the veneer. Un mask the aileron. Now is a good time to make sure the hinge line is free of any epoxy. I find that scrapping the hinge line with a # 11 blade will lift up any epoxy that might have gotten into the hinge line. ( had less than 5mm total of the hinge line with any epoxy in it.
Set aside over night for a full cure of the epoxy. Then block sand the top as one would the bottom.
All the best,
Konrad
Konrad
Very Strong User
Short of any other inspiration I masked off the wood I didn’t want to sand. I then sanded the glass with a hard backed sanding block until I started to cut into the tape. Removed the tape and lightly sanded again with a hard backed sanding block until the wood started to show. Lightly sanded the whole area with a soft back sanding block and 320 grit dry sand paper. ( Do not use wet sanding when working with wood)!
A note: Don’t try to stain or dye the wood. There is a lot of contaminated surface area with epoxy from the factory. These areas will not take the dye or stains. Just for the record I chose dye as it is a water based treatment. Most stains are oil based. My concern was that the oil base might contaminate the epoxy bond when it came to glassing the center section.
All the best,
Konrad
A note: Don’t try to stain or dye the wood. There is a lot of contaminated surface area with epoxy from the factory. These areas will not take the dye or stains. Just for the record I chose dye as it is a water based treatment. Most stains are oil based. My concern was that the oil base might contaminate the epoxy bond when it came to glassing the center section.
All the best,
Konrad
Wow - you are a crazy engineer guy.. 
Looking good.
I would be shy of doing a top drive on this wing as it is lightly built and taking out the trailing sub spar may allow for wing flutter should you ever put her into a high speed dive. Also adding complexity to an otherwise easy build. I have the normal and very easy control horns on the bottom and am very pleased with the performance from this plane. If I was going for some sort of speed, then I would be more interested in a top drive or IDS, but this is not a fast plane. For me KISS wins out. With that said, it is your build, and if you heart says complex is the right way, then it is the right way!
The wing joint is massive overkill and lots of extra work IMHO. You pulle dit off very nicely, but really not needed based on my experience with my 2 piece wing version of this plane. I would have suggested simply gluing the wing togther with the wing joiner in place, or some sort of similar joiner bridging the joint. Then a 2 oz glass around the outside of that joint, maybe 1 or 2" wide. Then call it done. 2 bolts in the center to attach to the fuse. (or 1 bolt and a clip if you want to be fancy.)
I'm only commenting on this for those that think this was a complex process to join the wings.. it was. But well done.
Looking good.I would be shy of doing a top drive on this wing as it is lightly built and taking out the trailing sub spar may allow for wing flutter should you ever put her into a high speed dive. Also adding complexity to an otherwise easy build. I have the normal and very easy control horns on the bottom and am very pleased with the performance from this plane. If I was going for some sort of speed, then I would be more interested in a top drive or IDS, but this is not a fast plane. For me KISS wins out. With that said, it is your build, and if you heart says complex is the right way, then it is the right way!
The wing joint is massive overkill and lots of extra work IMHO. You pulle dit off very nicely, but really not needed based on my experience with my 2 piece wing version of this plane. I would have suggested simply gluing the wing togther with the wing joiner in place, or some sort of similar joiner bridging the joint. Then a 2 oz glass around the outside of that joint, maybe 1 or 2" wide. Then call it done. 2 bolts in the center to attach to the fuse. (or 1 bolt and a clip if you want to be fancy.)
I'm only commenting on this for those that think this was a complex process to join the wings.. it was. But well done.
Konrad
Very Strong User
Hum?
Well the wing joint with glass fibers over the center line is what I think of as a the default setting for most woodies and stressed skin designs. The "joiner" to my way of thinking is more complex.
I kept with the stressed skin idea all the way across the joint as I was thinking that I might over load the wing with all the ballast I can install. If taking the time to glass I see no reason not to carry the benefits of glass (stiffness) out to about the 1/3 span mark. I felt that the servo pocket was the weak point in the wing and wanted to be able to spread the loads around the opening.
I have to say that the Tap Plastic 4:1 super hard epoxy sands very well. There is little or no loading (gumming) up of the sandpaper. Some hobby grade epoxies load up rather easily. With the Tap Plastic epoxy the feathering out of the glass was easy, dare I say fun.
I too had concerns about cutting into the TE sub-spar. But with a 7mm control horn it looks like the pushrod tunnel will start 20mm behind the hinge line. I think this will clear the sub-spar.
How is the top drive more complex than the bottom drive? Ok, I have to burn a push rod tunnel and maybe make a jelly bean servo cover. But this is a much easier actuation system than say the RDS (Rotary Drive System) we sometimes see. No, I don't like complexity. I'll add it in the build if I think it will add performance or take away complexity at the field.
I was going to use 4 bolts to hold down the wing mainly to be able to use the Elf 60" wing. I may re-think this as I think the Elf will also have a one piece wing.
While lower cost can be a benefit to building "kit". I find adding ones "improvements" to be the real reward in building kits. Unfortunate I've been known to improve things to the point that they don't work!
I should make it clear that this is a build thread, the way I build, not a review of the the kit. So guys take away what you will and use it in good faith.
BTW; Thanks
Konrad
Well the wing joint with glass fibers over the center line is what I think of as a the default setting for most woodies and stressed skin designs. The "joiner" to my way of thinking is more complex.
I kept with the stressed skin idea all the way across the joint as I was thinking that I might over load the wing with all the ballast I can install. If taking the time to glass I see no reason not to carry the benefits of glass (stiffness) out to about the 1/3 span mark. I felt that the servo pocket was the weak point in the wing and wanted to be able to spread the loads around the opening.
I have to say that the Tap Plastic 4:1 super hard epoxy sands very well. There is little or no loading (gumming) up of the sandpaper. Some hobby grade epoxies load up rather easily. With the Tap Plastic epoxy the feathering out of the glass was easy, dare I say fun.
I too had concerns about cutting into the TE sub-spar. But with a 7mm control horn it looks like the pushrod tunnel will start 20mm behind the hinge line. I think this will clear the sub-spar.
How is the top drive more complex than the bottom drive? Ok, I have to burn a push rod tunnel and maybe make a jelly bean servo cover. But this is a much easier actuation system than say the RDS (Rotary Drive System) we sometimes see. No, I don't like complexity. I'll add it in the build if I think it will add performance or take away complexity at the field.
I was going to use 4 bolts to hold down the wing mainly to be able to use the Elf 60" wing. I may re-think this as I think the Elf will also have a one piece wing.
While lower cost can be a benefit to building "kit". I find adding ones "improvements" to be the real reward in building kits. Unfortunate I've been known to improve things to the point that they don't work!
I should make it clear that this is a build thread, the way I build, not a review of the the kit. So guys take away what you will and use it in good faith.
BTW; Thanks
Konrad
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Konrad
Very Strong User
Wayne, looking over the thread I see I didn't mention or show how the wings are joined. I'll address this when I glue together my Elf's wings. I still need to make up a wiring harness before I do that. What I learned from this build was to gouge out the foam under the veneer at the face of the the wing root by about 2 mm. This allows for a nice epoxy bead joining both wings together. But this bead is out of sight being as it is under the veneer. Rather clever, I'll need to do this for all my foam core wings.
I got the crazy idea to glass the center section from you in post #2. Did I misunderstand your comments? Ok, I took it to an extreme with the glass leaf springs going out to the 1/3 span point. But if glassing the center section at all, it really is no more work going out past the flap servo pocket....
If I was to build mine again, I would probably glass the wing center and not bother with the wing joiner setup. I can fit this plane inside my little hatchback without taking the wings off.
-Wayne
All the best,
Konrad
Konrad
Very Strong User
I just learned that not all 1/2 oz fiberglass is fiberglass! It looks like some brands have been marketing light polyester as fiberglass. Going through my scrap bin I see what looks like three types of very light fiberglass. I think they are K&B 0.5 oz, Don Parson’s 0.6 oz and CST 0.7oz fiberglass. Two of the three samples respond to the fire test the same. That is they melt and leave a nice ball at the end of the fiber. The other one does the same but the ball often is brown to black like it burned. This tells me that one of these is not like the other. I’ve lost the labels years ago but I recall hearing rummers that the 0.5 oz K&B finishing cloth wasn’t fiberglass.
I can say that while sanding the glass on the Mefisto I did get the fiberglass itch. So I think I was using fiberglass as my light weight cloth.
The only place I now know where to get this light glass is at CST and ACP
store.acpsales.com
I did find a label for the “2oz”, it looks like it was Sig medium weight glass.
All the best,
Konrad
P.S.
The wife, a scientist, tells me that my test really isn’t very conclusive. She is suggesting that the burning (brown) might be contaminates like dust, most likely balsa dust.
P.P.S.
I've found that Carl Goldberg wing tape is Polyester and not fiberglass.
I can say that while sanding the glass on the Mefisto I did get the fiberglass itch. So I think I was using fiberglass as my light weight cloth.
The only place I now know where to get this light glass is at CST and ACP
Fiberglass Cloth - CST The Composites Store, Inc.
Light weight fiberglass cloth available in small 2 yd pkgs up to full rolls at very low prices. We also offer chopped strand mat, fiberglass tapes and heavier fiberglass cloth.
www.cstsales.com
Shop High-Quality Composite Materials | ACP Composites
Explore the ACP Composites online store for premium composite materials and components. Find high-quality and cost-effective solutions.
store.acpsales.com
I did find a label for the “2oz”, it looks like it was Sig medium weight glass.
All the best,
Konrad
P.S.
The wife, a scientist, tells me that my test really isn’t very conclusive. She is suggesting that the burning (brown) might be contaminates like dust, most likely balsa dust.
P.P.S.
I've found that Carl Goldberg wing tape is Polyester and not fiberglass.
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