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Bates 1/5.5 Sea Fury Build


Nick Somerville
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Sometimes the smallest tasks take the longest. It took me several hours of fiddling and colourful language to get the little 3m nylon nuts and bolts in place for the hatch hinges. Access was particularly tight and I lost count of the number of times I dropped the pesky nuts inside the wing centre section.  Had chosen nylon as in the event of an unscheduled trip through longer grass they might break off instead of ripping the hinges out. Also the curvature of the gear doors and wing meant aligning for a free movement required some wedged shims. I have 3m steel bolts on the doors at present but think I will replace these with nylon too, once I buy some more. Now, how to go about finding the optimum location on the bay wall for the pneumatic actuating device and the ball link on the gear door. Once I do sort that out I can line out the door and move on to the upper leg cover. 

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Edited by Nick Somerville
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There is a great article by Phil Clark (Fighter Aces) on RCSB on how to get your gear door geometry correct. https://www.rcscalebuilder.com/tutorials/gear_doors/default.htm
However, I went for trial and error and as the top ball link connector has a few mm of adjustment I had some give and take. With the pivot point of the actuator set as low as possible in the well everything looks to be within a turn or two of ideal. Phew! The door horn is some copper clad pcb board silver soldered to a right angle with holes drilled to improve gluing with epoxy.

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Following on from the gear doors I have been having a go at hinging/actuating the upper leg covers and setting the main leg covers in position. The main covers are attached to the sprung/moving part of the u/c legs and the Sierra gear came with a  pair of collars with a imperial bolt protruding for this purpose. The Imperial allen bolts were not quite long enough so I tapped the threads in the collars a little larger to take some 3mm threaded rod. A pair of hardwood blocks spacers and a third fixing point nearer bottom of the cover allows for some adjustment to get it all sitting nicely. 
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There is no attachment point on the legs to fix a ball link to, so I made up a pair of ply half collars to take the link and have glued these in place with cyano. A little epoxy fillet on the edge will provide some extra support once I am certain the geometry is correct. It will be interesting to see if glue alone will be enough to hold them.  If they fail I can always add a thin alloy strap and use the ball link to hold it in place.image.thumb.jpeg.4559c2b8c48f6f3fad7121dc3953b7da.jpeg

 

With the link in place and the upper cover hinged everything moved ok, but I did need to relieve the top corner of the main cover to clear the arm during part of its travel.

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Added the alloy straps to the legs as better safe than sorry. All gear doors and covers now lined and painted. I am running out if things to do on the wings. 
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Took a deep breath and fished out the bathroom scales. With everything except the throttle servo, prop and batteries I am up to somewhere in the 22lbs region. Hard to say exactly as I had to weigh in parts and I am not sure if it really cuts the mustard that way. 
 

Wth a rod under the fus and the engine in place with the hefty spinner, but no wings, she is balancing pretty much spot on the c of g. Be interesting to see what difference the wings make. Either way I am confident that it won’t be a big difference and therefore auw is going to be no more than 24lbs. I’ll take that!

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24 isnt bad but i would expect some lead to be needed once the wing is on as most of it is behind c/g. 

 

Its funny you mention weighing the parts though. A friend and i  have a standing joke about that as it never adds up for some reason. They always end up heavier. 

 

My gut feeling is 25-26 is still a likely outcome. Still not bad considering all the details though

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Thanks Eric. Sure they are in now.

13 hours ago, Martin McIntosh said:

Final weight yet?

Soon as the weather picks up I can assemble it outside and sort out the CofG and let you know. Also a few things to add. Receiver, batteries, tank, air bottle, spinner to cut so I can mount the prop and the final gloss coat over the whole model.

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Hi Nick, 

this is my scratch built Seafury it is electric powered 56" span with a balsa and ply frame foamboard formers and sheeted with depron covered in brown paper. I scaled it up from a small plan. it fly's great and looks the part in the air, it is the 5th Seafury I have made. looking forward to No. 6 which will have a 30cc twin petrol engine. Also looking forward to seeing yours in the air, all of mine have flown well so yours should be good as the bigger ones fly better.

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Thanks Nick , 

the area where the exhausts come out was made out of a Forster's can, I heated it up to anneal it and the interior is coated with what seems to be a shellac, this burned to the colour it is now which looked about right without painting. The top of the cowl is the hatch where the battery goes it also is an air intake to cool the battery but not noticeable when in the air.  

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Everything put together today bar the propeller and the total weight without balancing is 23.15lbs/10.5kg

 

Very difficult to check CofG as I shall need to set up a proper rig of some sort or get hold of some digital kitchen scales and use the weighing at each wheel etc technique. However at a guesstimate  it is about 1-2 cms aft of where it needs to be. Batteries currently placed behind the firewall. 
 

So to move the balance forward I could install the two batteries further forward either side of the engine box, or is this unwise due to the heat in that area? Also the cowl fixing is very secure, so some flat strips of lead could be added inside the front lip giving the longest possible moment arm. Thoughts appreciated.

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