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Old Nov 26, 2009, 12:04 PM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
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Evolution of an FPV Maxie Swift

This is my second Maxie Swift FPV build. The first was a tri-gear design that I posted earlier on the flying wing board.

http://tinyurl.com/yebaq6o

During several builds with EPP I found several things that work and some that did not. Perhaps some of this may be of help to new builders.

Kit parts
If your going to use the wing as delivered whatís in the kit is fine but if you plan on investing a lot of time and money my suggestion would be to remove the wing and winglets from the box and throw everything else away. Much better parts are available or can be made. If you use the OEM motor mount be aware that this isnít the strongest of designs. While maybe OK for the motor size intended it needs to be strengthened for a larger motor. The manual shows mounting the servos on the bottom but the top surface makes more sense to me for everything.

Wing Strengthening
Out of the box I donít think the wing needs anything more than what is in the kit but if you hang on more FPV weight you might want to think about adding some strength. The standard methods are fiberglassing the exterior, adding internal tubes or external taping. Fiberglassing adds a lot of strength but also weight and it is a time consuming process. Much of the physical advantage of EPP is its ability to absorb impact and return to pretty much its original shape. Any strengthening method that prevents the EPP from compressing under load loses much of that advantage. Not that it wouldnít make sense to use the method but realize the consequence. If however you are after extreme speed you need a very stiff wing and thatís how you get it. Internal tubes also work well but I would stick with wrapped fiberglass tubes rather than pultruded CF which are best employed for tension loads. Pultruded tubes have all fibers running lengthwise and are prone to cracking from beam loading or compression. They are made by pulling epoxy soaked fibers through a die rather than wrapping the fibers around a tube form. Cheaper to make and the process can accurately control dimensions but only strong in one axis. CF also isnít the best material choice for use with FPV electronics
Iíve used all of these methods in the past but now lean towards the simplest approach which for this wing which is external filament taping but have found that a good tape bond requires surface prep. I lightly sand the entire wing surface before doing anything which removes the roughest part but it is still a poor surface for a good adhesive bond. If you mask off the area that the tape will sit on it can be prepped by applying a coat of micro-balloon/epoxy slurry. This coating should be lightly sanded after curing. I use 1-inch fiberglass filament tape for the spar areas and 2-inch 3M extreme tape for the edging edge. In the pictures the filament tape is hidden under the decals. I fiberglass at least the edging edge from the nose to just past the battery boxes as that area will take the most punishment.

There is another strengthening method that I tried for the first time on this wing. It involves using tensioned Kevlar cords embedded in the wing surface. Using a sharp exacto blade you cut a ľ inch deep line the length of the wing. The cord is embedded and then pulled tight from the exposed ends. It is bonded in place using gap filling CA. The picture shows there are two cords on the top and bottom of the wing. The result is a wing that still has some flex since the EPP will compress a little beneath the cords when bending force is applied but the more the wing is bent the more resistance the cords provide. If your application can tolerate some wing flex this method combined with the natural resilience of EPP will make for a pretty durable wing with almost no added weight. Note that employing the cords as shown requires the use of a hard fixed center section which is covered next.

Wing joiner
I used a plywood wing joiner as shown because it provides several advantages over just bonding the two wing halves together.

1) It adds center strength especially at the equipment bay where a lot of EPP has been removed.
2) It provides a camera mount hard point.
3) It provides a strong motor mount.
4) It allows you to add a bottom fin for landing, tow hook mounting and/or a gripping surface for hand launching.
5) Lastly it provides a hard point for the previously mentioned use of Kevlar cords.

Elevons
The stock elevons are pretty flimsy as delivered and will bend under hard use. The best method Iíve found to strengthen them is to apply light weight 2-inch fiberglass tape with epoxy resin to both sides starting at the hinge line. It doesnít cover the whole surface but adds a lot of strength.
The stock EPP hinge works ok until you bang the wing into the ground. The fix is either Blemdern tape or CA hinges.

Equipment bay
One nice thing about a flying wing is that you can have a large equipment bay with all of the hardware accessable.
I use a very light weight 1/8 inch thick composite board for the floor made of 8oz fiberglass/6lb foam because it provides a flat hard surface for mounting components. The material is available from APC Composites -
http://www.acp-composites.com/home.php
This is bonded in place with urethane adhesive or epoxy. If your mounting servos with double sided tape it can also be used to make a nice top bridge between the servos to add stiffness.

The hatch cover for the bay which exactly matches the wing surface was made by laying up fiberglass on the area before cutting out the bay. I did the lay up on a lightly lubricated piece of poly sheeting.

Embedding control rods/electrical wiring
A thick micro-balloon/epoxy mix was used after protecting any exposed parts that I may want to salvage at a later date.
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Old Nov 26, 2009, 12:08 PM
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That is very nice work. Thanks for posting it.
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Old Nov 26, 2009, 01:00 PM
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You should post a picture with you near that Maxi. The first time I had that thing near me I was stunned.
This is a very good sample of a beautifull work, your Maxi makes me ashamed of my Own build. The only thing I dont like is the way you placed the RC Rx antennas. They should be away from all those cables and servos.
Too bad the Maxi was Out of stock for quite long time. It seems like MScomposit does not want to make any more.
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Old Nov 26, 2009, 01:05 PM
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In other words you've made it into a Ritewing Zephyr
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Old Nov 26, 2009, 01:16 PM
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Here is a video of my Maxi Swift for a local News interview.
http://www.youtube.com/watch?v=nH-M1D0D12U
I have lost count of how many flights I have on my Maxi, I have a new one in the box waiting for the day when I retire this one, but she just keeps going.
I fiber glassed the center of the wing about 3 inches wide over the wing joiner. As far as strengthening the wing, I just have not seen any reason for it I would rather spend the weight on batteries.
Beautiful job on your build, keep us posted.
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Old Nov 26, 2009, 01:19 PM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
2,451 Posts
I agree on the antenna placement. That is a 433 MHz antenna mount on the left wing so hopefully that Rx is a temporary situation. I don't plan any long distance flights with that Rx.

There was a US dealer change during the last year. No one had any stock when I wanted one so I bought some directly from the manufacture in the Czech Republic. I think Common Sense batteries is a distributor now.

Quote:
Originally Posted by Elcheapo View Post
You should post a picture with you near that Maxi. The first time I had that thing near me I was stunned.
This is a very good sample of a beautifull work, your Maxi makes me ashamed of my Own build. The only thing I dont like is the way you placed the RC Rx antennas. They should be away from all those cables and servos.
Too bad the Maxi was Out of stock for quite long time. It seems like MScomposit does not want to make any more.
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Old Nov 26, 2009, 01:20 PM
FPV Desert Beta Test Center
Mesa, Arizona
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Really and how is that?

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Originally Posted by trappy View Post
In other words you've made it into a Ritewing Zephyr
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Old Nov 26, 2009, 01:30 PM
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Wing joiner, fiberglass wing strengthening, reinforced flaps, improved motor mount and strengthened electronics bay.

Those are all the characteristics I have on my Zephyr ontop of the traditional Maxi Swift. I chose to glass mine additionally because I wanted it to go fast (my max speed was 180mph in a vertical dive from 2000m).

What's missing is slimmer winglets (too draggy) and you've basically turned the Swift into a Zephyr if you disregard the difference in airfoil.
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Old Nov 26, 2009, 01:37 PM
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Quote:
Originally Posted by trappy View Post
Wing joiner, fiberglass wing strengthening, reinforced flaps, improved motor mount and strengthened electronics bay.

Those are all the characteristics I have on my Zephyr ontop of the traditional Maxi Swift. I chose to glass mine additionally because I wanted it to go fast (my max speed was 180mph in a vertical dive from 2000m).

What's missing is slimmer winglets (too draggy) and you've basically turned the Swift into a Zephyr if you disregard the difference in airfoil.
I love my Maxi, it can handle what ever weight I throw on it and it is still a blast to fly.
Weed wacking with my Maxi Swift (1 min 58 sec)

Do you have a video of this 180MPH dive I would love to see it, that is sick.
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Old Nov 26, 2009, 01:40 PM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
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I haven't seen that type of a wing jointer with a built in motor mount used on a Ritewing nor elevons glassed like this. If someone has mod'd one this way I haven't seen it or I would have given them credit. I thought the large RW version used wood elevons and a plate motor mount bonded into the wing. Please lets not turn this into another who "sells the best" debate. I don't sell anything or care what anyone else buys.



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Wing joiner, reinforced flaps, improved motor mount and strengthened electronics bay.

What's missing is slimmer winglets (too draggy)
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Old Nov 26, 2009, 01:47 PM
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Not my intention Gary. I like how you noticed the shortcomings of the Maxi Swift and modified to address them. I'm merely pointing out that these shortcomings are already adressed on the Ritewing - not in the same style but just that they're solved. The motor mount on the RW are glued/bonded to the wing joiners. The elevons are balsa, so they don't need glassing.

Tarro, I can't find the one where the speed was properly indicated, I'm uploading one now where the GPS fails on the vertical dive. In any case you can see it's fast .... will take a couple of mins to get it uploaded

http://www.vimeo.com/7839405
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Old Nov 26, 2009, 03:17 PM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
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Correct RW addressed their design aspects in a different way. There are no shortage of RW build threads on RCGroups if anyone wants to see how they are put together. The purpose of my post was to show some construction techniques that I haven't seen used before in this particular application not to try and sell anything. What I have done can be used on most any FPV EPP wing. This was intended for the designers/builders not buyers.



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I'm merely pointing out that these shortcomings are already adressed on the Ritewing - not in the same style but just that they're solved.
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Old Nov 28, 2009, 02:43 AM
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What are those servo arm connectors? Never seen such model until now...
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Old Nov 28, 2009, 06:52 AM
FPV Desert Beta Test Center
Mesa, Arizona
Joined Nov 2006
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Sulllivan metal clevis.

http://tinyurl.com/ykdwnfk


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Originally Posted by RENATOA View Post
What are those servo arm connectors? Never seen such model until now...
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Old Nov 28, 2009, 07:13 AM
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Dumb mode this morning... that rubber collar fooled me and not recognised.
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