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Old Jul 05, 2001, 08:36 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
Dare Fokker D-VIII help

I am starting a Dare Fokker D-VIII I plan to power with a speed-400. Can anyone reccomend a prop and gearbox for this plane?

Also any pitfals I should look out for?

Thanks,
Al
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Old Jul 05, 2001, 09:09 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,717 Posts
Yes I have some suggestions-

This experience is based on my Sopwith Triplane, but I suspect it's applicable unless the D-8 is a lot bigger. First- Pat has already pointed out that the recommended motor/gearbox is more power than these planes need. The problem comes in that these power combinations are too heavy. My Triplane tips the scales at 17 ounces using the following gear- MTM S300 geared 8:1 (speed 280BB) 11 x 7 APC slow flyer prop, and an 8 cell, 720 mAH NiMH pack. I get flight of over 8 minutes duration easily- I still haven't really pushed it-while the airplane climbs with authority. Pat didn't pick this combo I suspect because it's not widely available and not as cheap.

Also, if he's using the same arrangement of landing gear on the D-8 change it- I went to a single load bearing wire sewn to the firewall- the aft struts are strictly dummies so I haven't cracked the fuselage longerons.

Sam Brauer
Norwalk, CT
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Old Jul 05, 2001, 09:16 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
The D-VIII is a 46.75" span. I'll definately take your advice on the gear. I'm also planning on springing it like the real plane with bingees on the axle.

So a 280BB is plenty of power? Damn, I built this as my first 'real' speed 400 plane (I have a Dymond Dolphin Glider as my only other).

By 'too heavy' what do you mean? If I go for a speed 400 with 7 or 8 cell 600ma nicads will I have a brick on my hands?

What about an astro 010? Although with that I'll still be using the 600 mAh nicads so weight savings won't be much.

I was planning on covering it with Ultracote, is this a mistake? I wanted something more opaque than litespan.

Thanks,
Al


[This message has been edited by Allan Wright (edited 07-05-2001).]
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Old Jul 05, 2001, 10:45 AM
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Canada, ON, Ottawa
Joined Mar 2000
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Ultracote is too heavy for this application. It will also warp the frame unless you are very careful while shrinking the covering. Litespan is probably the best covering. Paint it if you don't like being able to see through it... Just watch out for weight gain.
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Old Jul 05, 2001, 01:23 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,717 Posts
Al

What I found with the Tripe was the construction was very light. I did wind up substituting some wood to lighten it further and reduce the sanding chores, i.e. trailing edge stock. This was one of the first electric airplanes I built, (I've built lots of rubber and glow though) and I got very nervous when I pictured the 5 ounce pack of nicads floating around, so I began looking for a lighter power system. Remember that a geared Speed 400 flies an SR X-250 quite well at 22-24 oz. therefore it's overkill for a WWI bird at 18-20 oz.

Unless you're flying in really cold weather, I'd get away from nicads on this airplane- NiMH batteries are lighter (about 1.5 ounce) and with better duration.

The motor I recommended allows you to swing a big prop (effectively scale)and will keep the airplane to a scale looking speed. The Astro 010 is a more expensive geared alternative, which will still not let you swing the prop of the MTM unit.

All of the above is predicated on whether the specs. on the D-8 are similar to the Sopwith Tripe. Pat's website doesn't show the specs on the D-8, but if the airplane is around 20 ounces or under, the system I recommended should work fine. If it's a bit higher, then you can go to nicads on the MTM motor for more oomph. Note that you will have to move your batteries forward of what's on the plans- the MTM motor is lighter than a speed 400 geared. Keep it light and you'll have an airplane that's just a joy to fly on calm summer evenings, and will look very realistic in the air.

Sam
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Old Jul 10, 2001, 10:59 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
The landing gear mounts on the D-VIII seem to be an improvement on your plane. There are 2 plywood crossbraces that tie into the frame. The front one is epoxied right to the firewall as well as the sides. The rear one just glues to the fuse lower longerons, but at a place where there is a sheet covering for support. If I make the front of the gear carry the load it should do the trick.

Question, is your fuselage rear portion only 1/8" square stock and laminated 1/16"x1/8" stock? The D-VIII is and it seems a bit weak, although I still have to finish it.

Al
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Old Jul 10, 2001, 11:01 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
Also, what did you use for a batter mount? There is a 1/4" balsa sheet in the kit that appears to be for that. Mount with velcro?

I'm thinking of making up a balsa battery box to further coral the batteries and keep them from bouncing into something weaker....

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Old Jul 10, 2001, 01:18 PM
Designing on the edge
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United States, OR, Portland
Joined Mar 2001
1,521 Posts
Hi:

I am currently building this plane after the Dare Fokker DVII. The longerons are the same as the D7 and in that model they work fine. The D7 also has a 1/4" sheet of balsa that I used to make a mini wing between the wheels. I sanded the piece to an airfoil shape then epoxied it to the axil. I plan to use a 6v speed 400 with an MJ 4:1 gear box and a 11x7 apc slow flyer prop. I am adding ailerons (full strips on the trailing edge each with an HS-55 servo in the wing).

Kurt
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Old Jul 10, 2001, 01:42 PM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,717 Posts
Al

Sounds like the same style of construction- effectively 1/8" square laminated longerons. Not very sturdy, but if you fly slow- to quote Dave Aronstein- Zero mass needs zero strength.

I suspect that in a hard landing, if you don't use a dummy rear landing gear strut- you'll crack the longerons. just use a little music wire and slide it into a plastic tube.

With respect to a battery box- since I went to a lighter motor, I knew my batteries would have to be forward of the c.g. I also didn't care to try to change packs- the airplane is too fragile for lots of handling. I just glued in a 1/8" sheet balsa floor in the middle of the fuse and glued my batteries to that. Access to the connector is at the back of the cowl, at the cowl fuselage break.

In terms of a motor mount- I used a Sonic Tronics unit that I dremeled down to take some weight off.

Hope this helps

Sam
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Old Jul 10, 2001, 03:16 PM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
Hmmmm the more I learn about this plane the more I think it's not what I thought I was getting.

I really wanted a speed 400 WWI plane I could fly day-to-day with several battery packs.

Now I hear you've had good success with a 280 and a permanently affixed battery. Hmmmm.
Well I'll keep building and see where I get. At least if I end up with it not working I have a powerplant/ESC/radio gear that can go in almost anything out there.

I'll keep you informed of how I go. Fuselage is 33% finished at this point.

You don't have any advice for bending the wires for LG and wing mounging do you? How well did the templates on your plans work for you?

Thanks for all the help BTW....

Al
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Old Jul 10, 2001, 03:43 PM
Designing on the edge
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United States, OR, Portland
Joined Mar 2001
1,521 Posts
Al:
I found that the templates on the drawings were OK for landing gear but were not very useful for the wing mounting. For my wings on the D7 I used an artists foam board to build a wing mounting fixture that holds the wing in proper relation to the fuse then use a caliper to measure the exact distances from the hard points to the wing fixture location. Then bend the parts to this length. I plan to repeat this for the D8

Kurt

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Old Jul 10, 2001, 07:17 PM
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J Bergsmith's Avatar
Concord, NC
Joined Jan 2001
1,044 Posts
Bengtson: Your right about the wing cabanes on the D-VII, I thought it was just me, the templates just are not right. My D-VII flies great on the titanic airlines gear drive with 8 cell 600ae with a flying weight at 19oz. I also have the D-VIII kit looks good. I would consider adding ailerons, I think with rudder and elevator only it might be sluggish. Everything else on the D-VIII I will build stock, I have also built Pat's Cessna Skyhawk which flies great also but would be better with ailerons.

[This message has been edited by J Bergsmith (edited 07-10-2001).]
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Old Jul 10, 2001, 11:39 PM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
Good idea about making a foam jig to hold the wing while you measure the true distances - I'll do that - thanks!

I got the fuselage pretty much finished tonight - turtledeck and top stringers on, all the blocks installed for the wing mounting wires. I just have to drill the holes in the blocks and build the cowl/motor mount and bend and solder the wires. So far so good!

Thanks for the encouragement. I was getting a tad bit discouraged there.

Al
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Old Jul 11, 2001, 06:45 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Lee, NH, USA
Joined Jun 2001
5,185 Posts
I was thinking of using epoxy to hold the struts in their holes rather than CA. I find CA tends to shear off wood to metal joints if there is any torque stress on them. What did you use?

Al
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Old Jul 11, 2001, 08:18 AM
Balsa Flies Better!
Stamford, CT
Joined Oct 2000
6,717 Posts
Try Zap a Dap a Goo II- flexible, strong, and if it gives in an impact, it saves you from breaking wood. I actually managed to bend music wire with pliers, but I might have dropped down a notch in size. I threw out the stock templates and I sewed the gear to the firewall.

By the way- I've flown my Tripe a fair amount- it looks wonderful in the air, and it's easy enough for a beginner to fly it. My style is to show up with several planes, so charging one while flying another is not a big deal to me. The Tripe is a calm weather flier, but you can get it off in a small space easily- just don't whack powerlines (I did this- I'm doing some rebuilding.)as well as having an easy to control descent.

Sam
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