Scratching a B-52

[nchrome]

Hi guys I need a little help in finding some fan units of about 5" diameter. I'm going to need eight of these cause I plan on putting them on some TT40s to propel my B-52 that I plan on building this winter and hopefully have it ready to taxi around by Laborday down at Taylor Mo. next year. Wing span will be about 11' to maybe 13' a little big but I've allways wanted to build one so now I'm going to do it. So a little help would be welcomed. :D

[easytiger]

The TT40 is not a DF engine, it's not going to work in a DF. Maybe try eight of them as props, sure would simplify the project.
If you want DF, get proper DF engines. Maybe try electric, too.
Dehavilland Models has a prototype kit, a semi kit, for a B52, but smaller than yours.

[PhilLin]

Nchrome, go for it as myself have not seen much of this type this side of the pond. I'm not an expert on this, so please take my comments accordingly; but I hope it will induce the real experts to jump in.

As I understand, the biggest problem with such models is assymetric thrust. Synchronizing all drives on each side of the fuse will not be a small matter with internal combustion engines. Hope Chris won't mind (or he can move this post) as he also moderates the other side. Electric ducted fan is getting more acceptance as the way for multi-engine models; as demonstrated by G. Maroiyama's B29/TU4; for reliability & control.

For EDF cost & wide apps, 90mm fans may be the way to go. There are at least 4 sources of 90mm EDF on the market from $70 to ca. $350/ea that can do the job; WeMoTec Midi being the most common @ $80, but is also slightly heavier. Sure, cases can be cited for failed EDFs. But one can pick the motor, controller (ESC) & battery conservatively for 3 to 3.5-lb thrust each; 8 of which I heard should be good for up to 45 to 50-lb bomber model.

I'll be watching for your model posted here next year.:)

[easytiger]

Synchronization is waaaay overstated in importance. Having flown a bunch of twins, I have learned that it is NOT that important to have the engines running at the same speed, what IS important is to have them all running WELL.
All that aside, I would not be even SLIGHTLY interested in building a plane with eight ICDF units. Your chances of landing with eight still running are pretty slim, they are just not that reliable. And you get some pretty funky vibrations with multi ICDF.

Go electric, and you can have a really successful project. That's right, Chris Golds has a plan, and his flew very succesffully. Build his.

[dcairns]

Any progress on your B-52 project? I have a 11 foot span, slope soaring B-52 under construction (no engine worries for me :D ). It is blue foam and fiberglass construction. Just not getting into the fiberglassing.

B-52 Project (http://www.rcgroups.com/forums/showthread.php?s=&threadid=173652)


http://www.thecairns.com/pss/HPIM1037.jpg