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Oct 02, 2018, 08:36 PM
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If the huckebein flies half as well as the P1101 I'll be one happy guy.
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Oct 12, 2018, 11:56 PM
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Some small progress.

I epoxied the fuselage foam blocks together and cut out the wing slot from the fuse. I then epoxied a single layer of 6oz cloth to the bottom of each fuse half and then doubled up on the bottom of the vertical section. It is quite stiff. After the backing cloth cured I shaped the nose, rear section and canopy. I then epoxied a single layer of 3.2oz cloth over the fuse. There were some imperfections from the wire cutting and my 'man handling' the foam blocks so I filled them in with Superfil epoxy filler. I tried to blend the vertical into the fuselage, also using some superfil. I also added a 1/8 inch balsa piece to the vertical where the stab will be positioned. This will give me some additional space to work in when I connect the elevator horns to the pushrod. I did this because I cut an NACA0014 airfoil for the vertical and there didn't look like there would be sufficient room for the linkage. It also looks a bit like a fillet.

I will add some more Superfil to better blend the vertical into the fuse then I will cover the fuse halves with another layer of 3.2oz cloth. Just to be clear, this fuse will function as a male mold. After the second layer of cloth and epoxy set I should be ready to wax and pull a fuse (that's the plan anyway).

I cut the horizontal stabs and the wing sections according to the discussion found here:

https://www.rcgroups.com/forums/show...-wing-airfoils

I have not cut the sweep into these pieces yet, 40 degrees for the wing and ~ 45 degrees for the stab. This will give a wing span of ~ 40 inches and a horizontal stab span of ~ 14 inches.
Oct 29, 2018, 12:19 AM
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The horizontal tail and linkage are likely to be a tight fit so I decided to focus on this and the fuse. I cut the horizontal to its planform and then shaped the tip. I laid in a sub-TE of balsa then I woodpeckered the cores and covered them in 2.3 oz unicarbon tape and 5 mil G10FR4. The tape is 50 mm wide Textreme. I like this stuff. It is easy to handle and stays on its carrier backing nicely until you lay it down on the epoxy then the backing lifts off easily. I wiped the surface of the G10 with acetone and then sanded it some so the epoxy would stick better. I wet everything out and put it into the vacuum bag overnight. I used the carbon fiber so I can get a strong, stiff but relatively light horizontal (final weight after bagging and trimming is 46 grams).

I am also using carbon fiber on the tail area of the fuse so it is as light but stiff as I can get it. The wing sweep is so large that, according to my simple estimate, the wing's center of mass is 4 to 5 inches behind the calculated CG. I estimate the wing will weigh ~ 10 oz. If the tail is heavy also then I guess I'll have lots of lead up front just to balance. I want to try to avoid this situation if I can, hence the carbon fiber. Also, I'll cut another set of foam verticals and epoxy them into place when I assemble the fuse halves. The verticals are 9 grams total. Not a bad trade-off for the stiffness I will get by using the foam between the carbon fiber.

I sprayed a cheapy primer onto the fuse mold halves to find high and low spots. After filling and sanding (there wasn't much of either) I covered the fuse mold with another layer of 3.2 oz cloth. Next time I'll use a cloth with a tighter weave. I filled in the weave with minwax polycrylic and talc then I sanded the fuse smooth. I put a cover layer of polycrylic then waxed the mold 3 times (next time I'll do this 5 or 6 times since some of the polycrylic / talc pulled up with my fuse--see pics below). I also brushed on a layer of PVA and let dry for an hour or so. Then I laid out the cloth. The layup is as follows: 6.2oz then some 5.7oz carbon fiber, another 6.2oz layer then a cover layer of 1.6oz. The carbon fiber covers just the rear and vertical, the 6.2oz cloth is sized to overlap the carbon fiber but at different locations so there isn't too much of a bump. The 1.6oz cover layer runs the full length of the fuse.

All the cloth for a fuse half weighed ~ 77 grams. I mixed up ~ 90 grams of US Composites 635 and the medium hardener and wet everything out including rolling some epoxy directly on the fuse mold. I tried to really lather it up with epoxy but I guess I didn't do such a good job, the fuse half after curing weighs ~ 100 grams (3.4oz). I rolled over the area near the rear of the fuse with a hard rubber roller to try to minimize any bumps where the cloth overlapped. The fuse is a little 'flexy' so I think I will add another layer of ~ 4 oz cloth.
Oct 29, 2018, 12:59 AM
Crafter of flying plugs
Owen Hedger's Avatar
Very interesting. Keep up the good work.
Oct 29, 2018, 06:11 AM
Slow builder
_AL_'s Avatar
Nice.

Al
Nov 21, 2018, 10:01 PM
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Thanks to the guys from down under for their comments / encouragement.

A bit more progress, mostly on the wings.

Marked off and cut the foam cores to lay in the 1/2 x 1/2 inch balsa sub-TE. First I cut away the trailing edge of the cores then the 1/2 x 1/2 inch section to be replaced with balsa. I put the cores on their lower beds and then weighted them down and 5 minute epoxied in the blasa, then I epoxied the TE of the foam to the balsa. After I used a Japanese pull saw to cut the balsa close to the foam core. I used some 5 mil mylar to protect the foam as I cut. Then I gently sanded the balsa to the surface level of the foam. It came out OK without too much damage to the foam.

I used 10 mil thick G10Fr4 to cover the wings. I sized the G10 as if it were mylar. I wiped the surface that would bond to the foam with acetone then I rough sanded the surface. Afterward I covered the 'up' side with tape and wax paper. This way even if I'm not very careful during the rollout of epoxy not much gets on the side I will eventually paint. I also cut some 2.2oz kevlar on the bias and some 1.6 oz fiberglass also on the bias. The kevlar is backed with 3M double sided transfer tape (don't remember the manufacturer number for the tape now) and then the fiberglass is 3M77'ed onto the kevlar. This is used to cover the LE of the core. I also capped the end of the wing with 3/16" balsa. I then woodpeckered the hell out of the core and placed the kevlar/glass onto the LE, wet it out and then placed the G10 onto the cores and then put them into the vacuum bag.

After pumping overnight I took them out and marked up the wax paper for the hinge and torque rod location. I made the usual torque rod assembly. I cut the aileron so it is 1.75" at its widest and ~ 1.5" near the wing tip. It is 16" long. The wing came out a bit heavier than I expected at ~ 6.8 oz, but there is a lot of wing there since the TE taper is almost like the LE taper.
Last edited by ek123; Nov 22, 2018 at 01:10 AM. Reason: Deleted double posted images
Dec 06, 2018, 05:15 PM
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A bit more progress...

I added another layer of 3.2 oz cloth the length of the fuse and 1.6oz cloth to the vertical. After the epoxy cured I cut out the fiberglass on the mold where the wing slot was cut. I then placed the fuse onto the mold and traced out the wing slot, masked it off and then used a dremel and cut-off wheel to cut out the slot on the fuse.

I also epoxied in the foam support for the vertical. The support is cut with the airfoil shape of the vertical, but is in two halves so I can epoxy each half seperately into the vertical. I then traced out a path for the flexible cable I will use for the elevator push rod. The idea is to get some weight up front of the CG by placing the elevator servo in the nose area. Maybe I'll go with something different if this doesn't work well, like placing the elevator servo in the rear with a straight carbon fiber tube as linkage. The torque rod has the brass clevis offset so that the linkage makes as close to a 90 degree angle to the clevis as I can get.

After some test fitting I epoxied the fuse halves together at the vertical. After the epoxy dried I then wet out the seam area inside the fuse and then wet out the seam tape and rolled it onto the inside of the fuse. It came out well enough. After all this I weighed the fuse. Obviously it 'bulked' up, but only to ~ 10oz. Taped out the fuse hatch area but didn't cut it out yet. I also made some supports that will be used to make the fuse and hatch rigid once the large hatch is cut. The supports will be used for the lower side of the wing and the hatch. The supports were made by taking the center section of the wing to use as a mold. I took 1/8 inch blasa and covered both sides with 6 oz cloth the placed the support pieces on the wing section mold and put them in a vacuum bag overnight. The support pieces conform very well to the wing top and bottom. Hopefully they can be epoxied right in place when I set up the wing/tail incidence.
Dec 07, 2018, 01:12 AM
IT'S NOSE HEAVY!!!!
cityevader's Avatar
I can't wait for bench flight photo!

...but with the cutie holding it.
Dec 07, 2018, 01:23 AM
DWA
DWA
1Corinthians 13:1-8
DWA's Avatar
Looking good!


Dave
Dec 07, 2018, 01:40 AM
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Quote:
Originally Posted by cityevader
I can't wait for bench flight photo!

...but with the cutie holding it.
Well I'm pretty sure I can have the bench fly in the next couple of days
...but I don't know where I'm going to find such a cutie to hold the plane.
Dec 09, 2018, 10:16 AM
It's not going to build itself
TRISME's Avatar
Nice work Eusebio! Your skills are impressive!
Apr 20, 2019, 06:51 PM
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Yowee! it's been more than 4 months since my last post on the build! Anyway, I have managed to push things along some.

Thanks to everyone who has been following this and making comments!

First things first; there was a mishap in the garage that led to the destruction of my original tailfeathers that make up the v-tail so I had to redo them. I made the v-tail a bit larger and especially the elevator a bit larger.

I rethought the plan for the flexible pushrod for the elevators. Somehow I never managed to get it to work to my satisfaction so I decided on a 'straight' shot from the elevator linkage to the servo. I used some 4mm ball links at the clevis connected to an ~ 10cm length of wire. The wire, one from each elevator half, was then soldered into a single tube which was then epoxied into a graphite tube that had a short piece of wire at the other end. I mounted the servo just behind where the wing trailing edge lies. I think this set-up will work well enough despite maybe leading to a bit more overall weight for the plane.

After cutting out the hatch I epoxied into place some 6 oz cloth as a hatch support then taped on the hatch and then used a small nylon roller that fit through the nose to roll out the cloth. I then 'tacked' in the lower wing support with CA and then used 6 oz cloth to anchor it to the fuse. The cloth was placed below the support inside the fuse and after it was wet-out it was rolled it up against the fuse using the nylon roller. I also used some 1.6 oz cloth on the top of the support to help further anchor it to the outside of the fuse. The piece meant to act as the hatch support was cut so that the mounting screws and servo plus linkage assembly would not interfere with the fit. I then taped the hatch support onto the bolted in wing and then ran some splooge along the edges of the support and dropped on the hatch and taped it down.

I also decided I didn't like the look of the nose so I made a small foam insert that I will use as a mold to form a nose-section. The nosecone section is recessed about 1 inch so this will be the location of the air block to reduce drag.

Next I need to fill in the fuse weave (maybe with epoxy and talc?--any suggestions?), and then trim the vertical section behind the v-tail. I will do this after setting incidence.
Last edited by ek123; Apr 20, 2019 at 07:00 PM.
Apr 20, 2019, 06:57 PM
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Question about setting incidence: I posted some time ago about what to do about setting wing / tail incidence since the wing has about 3.5 degrees of washout. someone replied to use the midpoint of the wing and set the tail incidence to that, which seems reasonable. The question I have is how do I set up the incidence meter on the wing? It seems to me that the correct way, given what little I know about the pressure distribution and lift across the wing, is to set the bar perpendicular to the LE of the wing. Practically I think there is little difference between to the two ways indicated in the pics. Does it even matter?
Apr 20, 2019, 11:29 PM
It's not going to build itself
TRISME's Avatar
Looks great Eusebio! I would think you need to set the incidence meter parallel to the fuse, because that's the path the air will take over the wing?
Apr 20, 2019, 11:50 PM
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Thanks Tom.
The way I understand lift for these swept wings is the pressure distribution perpendicular to the LE generates lift, the distribution along the wing does not. In fact it was with this in mind that prompted me to cut the wing the way I did (I think my first or second post refers to several threads that discuss this). This would lead me to set the incidence bar perpendicular to the LE. Anyway, practically it probably doesn't matter much and given the fact that the v-tail has an airfoil it won't be easy to accurately set the incidence, I think.


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