Hempel 50% BD5 Build
 

Just arrived by FEDX Freight this past week , my Bill Hempel BD5 J......I'd love to show you some pics..but their is apparently a problem on RCU downloads at the moment... Its a quite sizeable bird in comparison to my other jets....I think I would call it chunky. But the finish of the Freedom scheme is really nice. With James Bond in mind I'm already sizing up a scale size building to fly it through down at my club site Area 52.

Unpacked the big refreigerator size box..Everything looked in pretty good order....But upon close inspection looks like the boys at FEDEX may have stood in on its nose.. a small dime size chip of paint gone...Lucky I know a good body man who might fix it up . A few pieces looked unfamiliar..but a quick text to Bill got a few pictures emailed which explained alot. Most were interior cockpit side panels and dash.

Have started out with the tail...The rudder servo is set directly in the Vertical stab.. The real trick here was getting the servo mounting screws in place.. This was facilitated by a flex shaft screw driver and a little patience... Next cutting slots in either side on Vert fin for the rudder servo arm to extend out for push/pull set up. An 8/32 rod thru the rudder hard point along with swivel links get the pocket hinged rudder in order. Real similar to a 50-100cc airplane set up.. Will touch up with a little paint later to camo the pushrods

TONS of room inside this bird. With all your gear,adding smoke system.Would probably still have room for a regulation size football in the engine bay and 2 in the cockpit.

Moving on to the full flying stab. Still trying to post pics...

Bill

RE: Hempel 50% BD5 Build
 

Bill. That's gonna be a nice flyer. Wish you could do a good photo build of it. I hope to see it at the rally up there this year.

RE: Hempel 50% BD5 Build
 

Photos now working

RE: Hempel 50% BD5 Build
 

Finally got a little time to work on the jet....
The elevator set up is next....There is a sturdy aluminum rod that joins the two elevators..This is controlled by a bell crank set up going to 2 servos in a push /pull config.Servos are mounted almost in the center of the airframe in a mounting plate built for them . A 4mm bolt holds the bellcrank to the joining aluminium rod. I found that my tap was a little worn and the fit slightly loose..so I stepped the bolt up to 8-32...zero slop. Each elevator half is held in place with 2 x 3mm screws...simply drill/tap and bolt them up Level of course.

RE: Hempel 50% BD5 Build
 

Next comes pipe and engine....I'm using a JC Rhino...A little larger than the 120-140 recommended.... In order to get pipe and engine to align well I had to work out some mouniting brackets and spacers to raise height of engine... Also needed to make these removable in case of a plug change/maintainence.

RE: Hempel 50% BD5 Build
 

I would not raise the engine, the bd has bad habits with raising the engine. When you hit over 1/2 thottle it will push the nose down. I have experieince with this from my bd's, due to the thrust line I had to lower (angle) the front half of the motor. After that it flew alot better and you didnt have to worry about losing (or having enough) elevator when trying to pull up. I would check with Hempel before you raise the engine.

RE: Hempel 50% BD5 Build
 

Thanks for the input.....If I mounted the engine in the standard location...due to the diameter of the can, the exhaust does not "hit the hole".or even near it THe engine is moved up to get the exhaust close to the pipe. I will ask Bill about it. Thanks Again

RE: Hempel 50% BD5 Build
 

Frank,
Thanks for the input....Rhino has been moved to orginial loaction...Required some cutting to get starter by former....The Rhino must be a little longer than a JC because at this point, I'll have to cut the pipe at rear

RE: Hempel 50% BD5 Build
 

Not a problem... hate to see someone go thru the pain with this plane and the thrust line.. 50% BD is still on my list as well, maybe next year Ill pick up one. I miss the bd-5's I had.

RE: Hempel 50% BD5 Build
 

Trying to upload photos.... server error Anyway .. Robart gear has arrived....Bolting it in this evening

RE: Hempel 50% BD5 Build
 

Here we go Pics show the pipe angle out out the back..... The new engine location and the cut out for former to clear starter

RE: Hempel 50% BD5 Build
 

Bill. Looking good. You gonna try to have this ready for First in Flight??

RE: Hempel 50% BD5 Build
 

Yes, Hope to have it well flown by Joe Nall. Still waiting on a wheel mix up from Robart that may arrive today...If so, I'll be ready to test by next weekend.

RE: Hempel 50% BD5 Build
 

Great. I should have fig with the good progress you are making on the bird.

RE: Hempel 50% BD5 Build
 

Well, While trying to upload a couple of videos...Let me tell you that The BD5 flys pretty well..... Testing done today with a fairly steady crosswind....

Two points of interest..

1. YES, A BD5 flys level with DOWN trim..... Took off with about 2 clicks of up.....Rhino pushed it out at better than 45 degrees at takeoff rotation. Spent the next few min. trying to click in down trim...

2. Missed the first approach, upon applying full power and pulling flaps, plane took a downward bobble when power hit.. Probably will just apply power and climb out dirty.. I'm sure a throttle mix with elevator will fix issue.

I LIKE IT !!!!!!! Rain started heading in...But got the first flight .....Ready for the next

Bill

RE: Hempel 50% BD5 Build
 

That is the down thrust in the plane.. if you could tilt the front of the motor down maybe a washer or two it. My skymaster did it everytime when I hit full power, almost a instant nose dive.

RE: Hempel 50% BD5 Build
 

Have 3 washers in front AND pipe is tilted upward to max height at exit. "I'm tilting her all she's got captain ! " LOL

I'll get bugs out in the next week or so

RE: Hempel 50% BD5 Build
 

Good news Bill. Can't wait for the vids. Glad you held your own with that go around. That 50% has got to be impressive to watch on the sidelines.

Has anyone tried to cut the tube and put in some upthrust in it? Looks like you could put 5-7 degrees up in the tube and cover it up with a cosmetic only outer sleeve that looked straight.

Yes, UP thrust is not a good answer...I tried it....You'll find you fly level with DOWN trim...Not good.....I'm going to try a throttle to elevator mix AND and elevator gyro .....It's a smooth flyer in the air..But that take off is hairy right now

Bill

When i say up thrust that would be angling the tube exit up so as to create a downward force on the tail. This would counteract the high thrust line somewhat and would reduce the airspeed the plane would rotate at making the takeoff distance much shorter and would reduce the pitch down tendency when throttle is applied. I could care less where the trim ends up but would want to minimize abrupt pitch changes with throttle and to shorten the takeoff. The smaller sky master bd jets i have seen seem like they are up to flying speed in 150 feet but cant rotate until the plane is400 feet down the runway or if the pilot panics and chops the throttle they will suddenly jump off and go oops.... How much room do you need to takeoff?

Probably 400 ft....I have both the engine with UP Thrust and the PIPE with max up thrust..... With a level stab you climb out on about a 45 degree angle....Once in the air...trimming down to prevent the climbing and assume level flight.... is not an issue... HOWEVER , if you have to climb back out ( miss approach for example) you MUST hold elevator up until full speed is regained and altitude,,,ANY release of back pressure will result in a violent pitch over ( like a waterfall) ....I'm hoping that reducing the UP thrust shimming of pipe and engine..will reduce the need for down trim in level flight and thus will reduce the violent pitching with power.....Adding a throttle to elevator mix and the gyro on elevator should calm things down a lot as well

Reducing the up thrust will make the pitch over worse. But may make the trim changes less.

I am considering this airplane. Not much info out there. What are the pros and cons in your opinion (BillJ)?

So where's the video's already ?