1/3 scale Nimbus 4D gear doors

[LRFitch]

I have an old Rosenthal Nimbus fuse that is missing it's gear doors. Anyone know of a simple method of making new ones? Not sure how to make a mold that has the same contours as the fuse. Any help will be appreciated. I do have the kinds of fiberglass needed for the construction in the shop, but not sure what to use to get the shape. The entire opening is currently about 8" long, and 4" wide, and the area of the fuse where the opening is located changes in diameter along it's length quite a bit.

[Stew]

I've worked similar situations in the past by stuffing the door opening with pink or blue Dow insulating foam and shaping and sanding it down with the perimeter opening protected with masking tape. After removing the foam form, I would add a perimeter of foam and carefully sand that down to carry the curvature for a larger form than the door opening. I cover the form with Saran Wrap and lay up glass cloth on the outside. Careful squeege work with the resin and tighter weave cloth on the top layer(s) would give me a set of doors I could at least prime and sand to smooth. I also would weasel out of any color match by purposely designing a color scheme where the doors are a different color than the body of the fuse. I have also turned the foam form into a female mold by wrapping the foam in Saran Wrap and burying it in a pile of plaster of paris contained within whatever is necessary to contain it. The plaster mold will come out surprisingly smooth. I would coat the plaster mold with 10-15 coats of car wax and lay up doors in the female mold. All of this is pretty amateurish and good for 1 run, but it worked fine in the end. Maybe it will spark a few thoughts for you.

Scot

[Steve P]

Here's $0.02

I would take a piece of heavy Mylar (better than typical .014 thick) like that used in bagging composite over foam core wings and span it across the opening so that it follows the contour of the fuselage.

Several coats of mold release or high quality auto wax on the Mylar each buffed out and repeated, again like a composite wing bagging procedure, would permit you to do a layup of layers of cloth on top of the Mylar to make a blank that would match the existing hole contour.

Tape the waxed Mylar to the fuse to hold the shape and prevent it from moving. Go with probably a few layers of heavy S-Glass, maybe a layer of carbon cloth, with a final layer of 2 ounce satin weave cloth so that the finished outer surface is smooth. West System epoxy with 206 slow cure. Don't go crazy with the epoxy, just wet each layer and then blot with a a paper towel.

Wax another sheet of Mylar and place that over your wetted cloth face down, tape that to the fuselage and let cure. When cured, the waxed Mylar will come right off, leaving the cured composite blank, trim to size and cut in half to form the two curved door blanks.

It may also be possible to do all this procedure immediately in front or behind the existing retract hole if the fuselage contour is very close. That would be much much easier and allow you to tighten down the top Mylar for a better finished product. If the fuselage area in front or behind is close but not exact, some careful heat gun on the finished blank would permit some tweaking by hand to adjust the curve.

Steve

[Asher Carmichael]

Larry,
If the contour isn't too exaggerated in 3 dimensions(front to back and side to side) you might get by with laying some 6-10 mil mylar over it and taping it down. Otherwise, cover the fuselage with masking tape around the opening(single layer and no overlapping) and fill the opening with balsa sheet or pink foam with sufficient thickness to allow you to sand to shape. The masking tape should help protect the glass around the opening. Replace the tape as needed during sanding. After shaping, leave everything in place, including the masking tape, overlay with Saran or other plastic wrap and tape that in place. Apply some liquid mold release and lay up your doors. I usually make the first layup thick and relegate it to "mold" status. You never know when you might need another door.

[Swiss1]

That answers the question how to lay up doors for the Hanger 9 ASW 20, as I know of 3 people who have lost the doors due to inadequate adhesion, due to not sanding the inside weave for the hinges! Yes I'm talking about you

Jeremy and Ben
SCC AAA TT NT

[LRFitch]

Guys, thanks for all the great suggestions. Now nothing should be standing in my way of getting something done on the Nimbus. It's been over 100 degrees every day for about 8 days, so staying in the air conditioned shop has been an easy decision.
Thanks Again,
Larry Fitch

[LRFitch]

Guess what I found on my door step this morning! Nicely packaged in a somewhat flat square box about 12" square is a pair of fiberglass and carbon fiber gear doors. Michael Deleo ( also known here as YYZ) made and sent them to me. Talk about a nice fellow giving back, or paying forward. Mike is the best! Mike, thank you very much! Mike said he has a mold for a Ventus fuse and layed these up for me. Man, is this a great hobby or what!

Larry Fitch

[Swiss1]

Nice work Mike, no matter what people say about you
Do you have an ASW-20 Mold

Jeremy and Ben
SCC AAA TT TN

[yyz]

You're very welcome, Larry. How about a build thread for the Nimbus? I'd like to see some pictures.

It's all true what they're saying Jeremy, including the part about having a '20 fuse mold. Asher is ahead of you in line though...

[LRFitch]

Mike, Thanks again. I'd put up some pictures (not sure about a build thread), if I had any idea how to do that. I have an old digital camera and a no-so-new smart phone, but no idea how to upload/download, and/or post them to this (or any other) forum. I can barely type words into this computer/forum. I'm not completely computer dumb--but pretty darn close.

[lenb]

Hey Larry,

The camera should download to your computer with a cord.. You're phone will usually do the same.

Once on the computer, save them to a file, either on desktop or in you're photo program

To upload, you see the square thingy in the upper right corner of this box.
Just click on it and it will allow you to upload pics.

LEN

[LRFitch]

Len, Thanks for the instruction. I hope it works.
Len/anyone else: I'm trying to round up all of the servos needed for the Nimbus. The flaps are each 51" X 3" in size, or 150+ square inches in area. How much power do I need for the servo driving each flap panel? I'm thinking 150 oz-in or so, like a HiTec HS5645. Does that seem reasonable, or is more really needed?

[Mac Powell]

Here is a link to a servo torque calculator

http://mnbigbirds.com/Servo%20Torque%20Caculator.htm

Mac

[LRFitch]

Mac, Thank you very much for the link. It is very useful

[Tom]

Larry, Here is how far I took my cockpit so far......this winter I'll do the joysticks and microphones and other details.......I also bought two pilots for it......