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S1581 Hawker Nimrod MkI

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Martian07/12/2018 12:06:35
1988 forum posts
943 photos

Hi Danny a question gay 😏 i,ve seen a reference to the fin being offset by 3.5 degrees why is this is it necessary on e electric is it to reflect scale or to compensate for torque of an ic motor

Danny Fenton07/12/2018 15:09:39
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8841 forum posts
3699 photos

Apart from the ply reinfocing plates and some trailing edge sanding the lower wing is complete. I am quite pleased that the final weight is 203g as that includes an additional 28 leading edge riblets.

I have been doing a bit of research. The cutouts in the wing panels at the root of the lower wings are supposedly for carrier launching. There is also another anchot point just in front of the tailplane.

These didn't seem right to me as tradiotionally catapults are mounted closer to the c of g and drag the aircraft to speed. Then I realised that could not work with the sort of undercarriage the Nimrod has.

Then it dawned on me that the aircraft must be affixed to a craddle of some sort. Eventually I found and image that does indeed show a cradle.

nimrod cradle leuchars.jpg

mev-10841824.jpg

Fascinating stuff

Cheers

Danny

Danny Fenton07/12/2018 15:12:07
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8841 forum posts
3699 photos

Hi Martian the offset is to allow partly for the torque on the big prop of the fllsize, and to compensate for the spiralling propwash as it moves back along the fus. For the model you dont really need it, unless you are using a great big prop (as I am) its more for the model to be accurate. Often something that is looked for during static judging

Cheers

Danny

Martian07/12/2018 15:18:34
1988 forum posts
943 photos

Thank you Danny, I'm almost certain to be using a big prop, so from the rear of the plane is 3.5 to the right or the left

Danny Fenton07/12/2018 16:43:14
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8841 forum posts
3699 photos

Hi Chris, this should help

fin offset.jpg

Cheers

Danny

Andy Sephton 107/12/2018 17:06:58
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98 forum posts
183 photos

For interest, the fin offset is to allow the aircraft to be in lateral trim at its cruise speed. Therefore, the pilot would need to hold some right rudder during the climb and left rudder during the descent. For the majority of the flight, the aircraft should be in trim laterally.

Luckily for us, the Kestrel prop rotates in the same direction as most of our model engine props, so setting the fin leading edge to the left will help to balance the torque and spiral flow of our engines as well as on the full-size.

Martian07/12/2018 18:13:55
1988 forum posts
943 photos

Much appreciated Danny Andy

Danny Fenton08/12/2018 20:33:50
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8841 forum posts
3699 photos

I have been asked to create a cad drawing of the tool for shaping the leading edges. Which I have done. If anybody wants a copy of the dxf file to give to a laser cutter then just let me know.

leading edge shaping tool.jpg

I have tweeked the design to make the tool longer (100mm) and included two end pieces that are added after the tool is lined with 1.5mm balsa and the 120 grit aluminium oxide paper. The end pieces act as a guide and stop the tool digging into the balsa.

Cheers

Danny

Danny Fenton11/12/2018 20:55:57
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8841 forum posts
3699 photos

A little more progress today though I have been working away of late.

I drilled the centre section wing bolt holes. It is fairly important these are true to the drawing or the bolts wont allign with the plates in the fuselage. I made a jig to get the angle right, and chocked the wing to make the drill edge of the jig vertical to my pillar drill.

026.jpg

Imagine the drill bit is in the pillar drill.

I thought I would look at alligning the lower wing to the fuselage. I was really pleased that the centre section fitted the leading edge shaped cutouts in the fuselage, however when I measure for the tail to the tips it was a little out. So twisting the wing in the seat slightly sorted it, only took a fraction. Once alligned I carefully marked the wing. No idea how I am going to clamp the centre section to mark the tapped hard wood blocks.

027.jpg

028.jpg

You may just be able to make out the small black mark on the carpet thread.

030.jpg

The centre section alligned, and the upper sheeting marked.

Cheers

Danny

Danny Fenton12/12/2018 17:22:14
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8841 forum posts
3699 photos

I believe it was a hero of mine Martin Fardell that said just a few minutes a day is all you need.

So I spent my few minutes today making a tray for the wing anchorage. Not as heavy as it looks. I think the wood is called basswood and adequate for this task.

031.jpg

Cheers

Danny

Danny Fenton13/12/2018 16:26:41
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8841 forum posts
3699 photos

Managed a little more at lunch time.

Tidied up the sheeting around the nose and added some blue foam, as you know I don't like wasting block balsa.

032.jpg

033.jpg

Thought I had better look at the speaker installation before I go too far, good job I did, the foam was close to blocking access.

034.jpg

035.jpg

Cheers

Danny

Martyn K13/12/2018 16:33:27
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4760 forum posts
3436 photos

Hi Danny

Why have you cut the side sheeting square around the lower wing?

Martyn

Danny Fenton13/12/2018 17:03:07
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8841 forum posts
3699 photos

Hi Martyn, I will deal with those areas later, I plan to use Proskin for the seat and then fill between the Proskin and the sheeting. Not essential to do just yet.

Cheers

Danny

Danny Fenton14/12/2018 11:43:35
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8841 forum posts
3699 photos

Added some blocks to secure the speaker.

038.jpg

Thought I may as well close up the fus sides as Martyn had mentioned it. Still some tidying to do.

037.jpg

Cheers

Danny

Danny Fenton15/12/2018 00:28:17
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8841 forum posts
3699 photos

Okay those following me, there is a better way to do the wing seat. Add the 1/8 cross grain following the 3/16 fus side along the wing seat, using a 90 degree block (tape covered lego brick) to make sure it is fitted vertically.

039.jpg

If you add the sheeting first it gets tricky around the rear of the port seat, where it joins the rear stringers. Once the cross grain is in place sand it to follow the contours of the side formers, then add the sheeting. I can recover the situation but it will be fiddly cutting the cross grain bits to infill the gap.

I had intended using proskin for the seat, but alas that leading edge curve means it will have to be wood.

This design is proving trying to say the least......

Cheers

Danny

Colin Leighfield15/12/2018 09:37:30
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5552 forum posts
2269 photos

Hmm. Exactly where I am stuck at the moment. I’m glad that you said it is trying! However where’s there a will! - - -

Danny Fenton15/12/2018 10:25:09
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8841 forum posts
3699 photos
The cutouts in the fus sides are accurate, so adding the cross grain wing seat, perpendicular to the edge should be fine. As somebody already mentioned you may have to shorten/extend some side formers.
Cheers
Danny

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