Assembly sequence for building up good wingtips.

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Assembly sequence for building up good wingtips.

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Assembly sequence for building up good wingtips.

Postby 9JL » Fri Oct 16, 2009 6:25 pm

The wingtips mentioned elsewhere need careful planning,go ahead as per the Hachette instructions will result in a lumpy looking wingtip,after lots of dry runs and clamping I came up with the following sequence,the problem lies mainly in the choice of basswood sheet for the tips,it is very brittle when formed into a compound curve,so a little work beforehand sorts this out.
1/ Pre prepare the upper and lower wingtip pieces by chamfering the wingtips as shown here,keep doing dry runs until the chamfer is correct,a solid sanding block is what you need make one up by sticking medium grade grit glasspaper onto a wooden block,then take a large tablespoon and glue onto the back a piece of coarse grit paper with a impact adhesive such as Evostick,use this to carefully remove a bit of wood one inch inboard from the edge of the tips ( on the inside areas ) this makes the tips more pliable in all four axis,you will need to keep going until about 1/32nd is removed or scooped out,this really does make a big difference.
2/Place the wing overhanging on the bench or if the engine frames have not yet been added right over the bench,place a small piece of polythene sheet under the tip area to avoid sticking everything to your workbench ! now butt join the lower tip making a good joint,pack up the leading edge where it curves with scrap wood placed under the leading edge,allow to dry overnight.
3/ glue the inner ribs in place as per the instructions taking care to get the gap right by placing scrapwood into the slot between the end rib and the wingtip rib,add the mini spars and the additional rib and make sure they are correctly set up,allow to dry out.
4/ Take your sanding block and make sure all inner ribs and spars are sanded down enough so when the upper skin is in place it sits snugly,keep sanding until you are happy.
5/ Next apply adhesive to the upper skin and the ribs and mini spars,clamp everything up with something like clothes pegs etc (see my build diary for illustrations of the constructional stages and details http://groups.google.com/group/build-a-lancaster-bomber ) where the skin goes over the inboard rib just aft of the gap you can apply a small g-clamp or similar to hold everything together at the high spot created by the curvature of the rib.
6/ Allow the whole thing to cure,when dry remove the clamps and pegs,take a sanding block and run it all around the perimeter of the tip blending in the shape first,next align the wingtip nav light/formation light positions with a warding file,hachette have not allowed for the difference created by the difference in the two skins probably a good idea as it allows more juggling for us,now sand the trailing edge top and bottom and blend it in nicely,same as the leading edge round this off to conform with the aerofoil shape.give a final sand with fine abrasive paper of your choice,I then applied auto grey primer three coats to seal the wood,finally touch in any blemishes with Squadron model putty,re-sand.
I did consider other work arounds but this one utilises all of the parts as suppled by Hachette,the prepartion of the parts prior to assembly is the key.
Any questions please feel free.

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9JL
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