Search found 401 matches

by David Jones
March 14th, 2010, 11:21 am
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The flaps on the outer wing panels are operated by a wire linkage connected to the inboard flaps. We decided this was a non starter and that the outboard flaps would have their own servos. The outboard flaps were cut out and fitted in the same manner as the inboard flaps. As ribs 10 to the wing tip ...
by David Jones
March 14th, 2010, 11:19 am
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

An access hatch was then made up on the underside of the wing. For any adjustment and routine maintenance, the plate can be unscrewed from the hardwood rails and the whole assembly removed from the wing.
by David Jones
March 14th, 2010, 11:18 am
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The next job was to sort out the servo bays / mounts. The horn, linkage and servo are all concealed inside the wing. As the servos were replacing a bell crank system I had to devise a way of mounting the servo. I decided to glue 1/2” x 1/4” hardwood rails, supported by 1/2” balsa triangle to ribs tw...
by David Jones
March 14th, 2010, 11:16 am
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

I know it’s been a while since my last update, through a number of circumstances beyond my control, added to an illness in the family, I’ve not been in the workshop as much as I would have liked. Anyway, here’s what bit of progress I’ve managed to make. I left off where I had cut out and fitted my f...
by David Jones
February 24th, 2010, 9:40 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

In order to ensure correct alignment, I “jigged” the flap section in position by gluing a piece of stock balsa along the top spar. Hinge points were then measured off and holes drilled for the large Robart hinges. In order to ensure the drilling angle was the same for all hinges, I made up a small g...
by David Jones
February 24th, 2010, 9:38 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

Hinge blocks are then added, the plan shows two hinge points, I’ve catered for three. All the edges of the flap section were then cleaned up and the hinge blocks rounded to profile. The trailing edge ribs of the wing were then sanded to profile and 3/32” sheet added to form the flap instep. Hinge bl...
by David Jones
February 24th, 2010, 9:36 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

Before proceeding any further, I think it would be advisable to cut the flaps and ailerons out, starting with the inboard flaps in the centre section. Slots are cut in the sheeting between the bottom spars. The ribs are then cut and finally the spars and the flap section is separated from the main b...
by David Jones
February 24th, 2010, 9:34 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The centre section was then sheeted; again I made up balsa skins and cut them to shape prior to gluing to the framework, starting with the outer most sections, outboard of the nacelles and then the leading edge from the main spar. Ribs 5 and 7, either side of the nacelles, had to be “cracked” and be...
by David Jones
February 24th, 2010, 9:31 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

It was now time to start sheeting the wing bottoms with 3/32” balsa. Starting with the outer panels, I firstly sheeted the leading edge from the main spar. I then made up skins by joining several sheets of 3” wide sheets and sanding them smooth before gluing them to the wing framework.
by David Jones
February 24th, 2010, 9:30 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

Servo boxes were then made up for the aileron servos. The design is such that the whole of the top of the servo is exposed below the surface of the wing. The flaps are driven by either one servo (with bell cranks), or two servos in the centre section. An elaborate linkage with bent wire and tubes is...
by David Jones
February 24th, 2010, 9:29 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

I want to get the bottom sheeting on the wing panels as soon as possible to stiffen them up, but more importantly, to protect the rib trailing edges. Wielding something this size in a confined space does tend to lead to hangar rash. I could start sheeting now, but it would be easier to sort out the ...
by David Jones
February 24th, 2010, 9:27 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The wing panels are joined by an aluminium tube in a cardboard sleeve, and there are 1/4” dowels at the front and back to keep the structure aligned. The dowels were fitted first. The plans show the wing joiner tube is 1” diameter by 12” long. As these plans are blown up, the tube needs to be at lea...
by David Jones
February 16th, 2010, 7:31 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

I’ve put all three sections together as a trial fit and I am very happy with the results. The whole structure looks true and aligned, and both wing tips are exactly the same height high above the board when measured at the main spar. So, that’s the basic skeleton of the wing completed, the next stag...
by David Jones
February 16th, 2010, 7:28 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The outer wing panels are pretty much straight forward. The main spar is pinned to the board and the ribs glued onto it. A 1/4” square shim is then inserted under the rear of the ribs, about a third of the way in from the trailing edge, this causes approx two degrees of washout to be built into the ...
by David Jones
February 15th, 2010, 9:29 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The top spars are then added along with the square leading edge spar and 1/8” false leading edge. I was disappointed to find that a lot of the pre cut notches were not aligned and needed to be re cut and packed. The ribs are cut as per the plan, so it is obviously the profiles that are not accurate....
by David Jones
February 15th, 2010, 9:25 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

It was now time to turn my attention to the wing. Zirolli supplies several A4 pages of building notes with the plans, each step having its own tick box to make life easier. Although not as thorough as a booklet that comes with more popular kits, they are very useful and save a lot of head scratching...
by David Jones
February 15th, 2010, 9:15 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

With the fins and rudders completed, my next task was the tail plane and elevators. The tail plane is of basic construction, but the 1/2” thick tip ribs are short of the end of the trailing edge spar, and are shaped to fit the curvature of the fins. The remaining length of the spar inserts into the ...
by David Jones
February 15th, 2010, 9:09 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Re: Zirolli B25 Mitchell build

The rudders are built up with a 5/8” leading edge and 1/8” ribs, tapering to 3/16” x 1/2” at the trailing edge, with pre cut profiles for the top and bottom. The plan recommends blocking the trailing edge up on the board, lay sheet balsa in for the ribs and then sand to final shape. I didn’t like th...
by David Jones
February 15th, 2010, 9:02 pm
Forum: Your New Projects
Topic: Zirolli B25 Mitchell build
Replies: 118
Views: 49488

Zirolli B25 Mitchell build

For the past couple of years a small group of us have been talking about building a large model as a joint project. It was discussed numerous times and then shelved, that is until Alan Greaves took the bull by the horns and decided he was going to invest in a B25 Mitchell. I would build the airframe...
by David Jones
January 24th, 2010, 9:43 pm
Forum: General Discussion Topics
Topic: New member
Replies: 4
Views: 2370

Re: New member

Thanks Dave, I do have his 'phone number, we had a chat with him at the Nats when this project was in its infancy, he actually recommended we go for the bigger one. I'll certainly be contacting him in due course once I've got the build registered and started. Does Tony Hooper take registration detai...

Go to advanced search