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Old Nov 06, 2012, 07:00 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
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Lost foam

Hi Wingnutser,

The reason for making a mold in this case , is that at least several sailplanes will be built, and I can experiment with different layups , but the outside shape will always be the same.

Go search on my posts for my Borcian and DG505 both built as one offs with the lost foam method.



Mike
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Last edited by mikegbogh; Nov 06, 2012 at 08:53 AM.
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Old Nov 06, 2012, 07:29 AM
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wingnutzster's Avatar
Lanseria airport South Africa
Joined Oct 2005
419 Posts
Aah I didn't see those, I am going to go have a look right away. You are clearly experienced at the mold making process but until I get there I think I will churn out some lost foam fuz's I have set up a bow based on some of your pics and some tutorials I found so let's see.
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Old Nov 09, 2012, 01:05 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
1,037 Posts
JS1 B serial no 002

Hi Guys,
Last night I joined the Nimbus 4 molds and the second JS1 , this morning popped them open and all looks good. I will need to clean of the join lines but , the second one with a different layup is 900 grams so I saved about 100grams, this is good news especially as it is mostly in the tail area.

While the big stuff is curing I continue to make smaller pieces with off cut cloth,
so a third canopy frame was laid up as well as some more streamlined shrouds.

Hopefully this weekend I will start the Rudder mould as well as the tailplane, and joiner molds.
regards
Mike
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Old Nov 09, 2012, 01:23 AM
Hunting for Goat Lifters
Titus ZA's Avatar
South Africa, GP, Randburg
Joined Jul 2012
109 Posts
Great work Mike. Glad to see the 2nd fuse cam out easier than the first. 100grams less is good going. I'm fairly sure you may even be able to get it down a bit more knowing you.

Cheers
T
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Old Nov 11, 2012, 02:28 AM
WGTN NZ
WELLINGTON NEW ZEALAND
Joined Jun 2008
98 Posts
Mike, that is one sexy looking fuzz ! ! !

Woo
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Old Nov 20, 2012, 12:41 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
1,037 Posts
Wing joiner

Hi All,
Slow progress, but progress it is ,I made up a joiner out of 2 x dowel sticks, painted and polished them and glued them together with the correct, dihedral. Next I made up a splitter board waxed everything and gel/coat and glassed one side, followed by the other side.

Sunday was very hot and I layed up the first joiner with a fast harderner, unfortunately the first half had started going off before the second half was completed, all seemed ok and I clamped the two halves, unfortunately the half with no "give" was slightly overfull and as a result there was a slight mismatch in alignment, the joiner is ok and strong but just wont fit the tube, I will use it for some testing, so far if I place it between two bricks and stand on it , it flexes slightly with my 80kgs load, so a 5kg glider is unlikely to ever reach those sorts of loads.
regards
Mike,
Hope to start some foam cores soon. fuselage 3 is just about ready for popping out the molds.
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Old Nov 20, 2012, 12:44 AM
Hunting for Goat Lifters
Titus ZA's Avatar
South Africa, GP, Randburg
Joined Jul 2012
109 Posts
Nice work Mike. Glad to see that you managed to get some work done on the JS1 as I know you been pretty busy.

Cheers
T
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Old Nov 20, 2012, 01:17 AM
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Joined Nov 2008
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Argh if you start the wings soon I'll have no excuse and will have to start my ASG29 wings too!
Interesting joiner construction method - I thought you were a pultruding fan though?


Simon
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Old Nov 20, 2012, 01:23 AM
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wingnutzster's Avatar
Lanseria airport South Africa
Joined Oct 2005
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I don't know how many more times this can be said or in how many more ways....but you truly are an artist with this medium

I am quite happy with the progress of my plug and it's starting to take shape but will send you pics to get some advice on where it can be improved.
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Old Nov 20, 2012, 07:29 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
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Quote:
Originally Posted by swarrans View Post
Argh if you start the wings soon I'll have no excuse and will have to start my ASG29 wings too!
Interesting joiner construction method - I thought you were a pultruding fan though?


Simon
Hi Simon,
Mike (yyz) is a big fan of pultruded carbon rods and I think builds up the spars, with multiple lengths, my theory besides the fact that its not available here , is that yes it is accurately made and stronger than any hand lay up , but I guess if they are round in profile then any weight saving and or strength may be reduced because of the resin in the gaps , between the rods, resin on its own is maybe not that strong, but its one way of building with carbon.
I layup my spars in situ with 40k carbon tow and work the resin well into the carbon, on the joiners the same, except the first 10 tows into the mold are UHM 12k carbon which has a glossy sheen and makes a nice outer finish.
regards
Mike
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Old Nov 20, 2012, 07:50 AM
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North Yorkshire UK, on a big hill facing the prevailing wind. Coincidence?
Joined Oct 2007
915 Posts
Do you gently stretch the tows before the resin sets to ensure they are straight and parallel?

I've read this increases strength significantly by making every carbon fibre share the applied load more evenly when stress is applied, instead of some of them needing to unravel a little first. Makes sense to me but I've never tested samples to prove it.

Rog
Still loving the build!
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Old Nov 20, 2012, 08:00 AM
Caravan driver
wingnutzster's Avatar
Lanseria airport South Africa
Joined Oct 2005
419 Posts
Great piece in SA Flyer this month of mountain soaring with some lovely Nimbus shots. There are just so many beautiful performance gliders to choose from it makes sticking to the project started really tough, the JS1 must be one of if not the prettiest bird though
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Old Nov 20, 2012, 09:04 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
1,037 Posts
Quote:
Originally Posted by Sutton Bank View Post
Do you gently stretch the tows before the resin sets to ensure they are straight and parallel?

I've read this increases strength significantly by making every carbon fibre share the applied load more evenly when stress is applied, instead of some of them needing to unravel a little first. Makes sense to me but I've never tested samples to prove it.

Rog
Still loving the build!
Hi Rog,
I dont make any special attempt to pull on the tows at all , but you are right ,but must say I wet out each tow and they lay fairly straight in the molds.

But I have found that once your gloves get sticky if you dont handle this tow carefully it all pulls apart and becomes fluffy, those accidents I bin.(fluffy carbon just dont cut it]
I also believe that at 16 mm diameter this joiner is overengineered so not too worried .
I am going to try make another joiner tonite with an epoxy that has 1hr pot life its stinking hot and 15mins pot life is courting disaster.
Work has ticked up as has flying so progress has slowed but wings start in the next week or two.
cheers
Mike
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Old Nov 20, 2012, 02:01 PM
Registered User
Blenheim, NZ
Joined Dec 2007
1,164 Posts
Rod spars

Quote:
Originally Posted by mikegbogh View Post
Hi Simon,
Mike (yyz) is a big fan of pultruded carbon rods and I think builds up the spars, with multiple lengths, my theory besides the fact that its not available here , is that yes it is accurately made and stronger than any hand lay up , but I guess if they are round in profile then any weight saving and or strength may be reduced because of the resin in the gaps , between the rods, resin on its own is maybe not that strong, but its one way of building with carbon.
I layup my spars in situ with 40k carbon tow and work the resin well into the carbon, on the joiners the same, except the first 10 tows into the mold are UHM 12k carbon which has a glossy sheen and makes a nice outer finish.
regards
Mike
For what its worth....I built my Vertex Electric saiplane using pultruded rods. http://www.rcgroups.com/forums/showt...ghlight=vertex They are glued into grooves in the foam made with a soldering iron tip with no webs then filled and bagged in Kevlar (did I say I hate this stuff!)straight over the top. It worked well although sat a little proud. Relatively cheap and easy and I would use the method again.

Allan
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Old Nov 21, 2012, 01:57 AM
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mikegbogh's Avatar
Roodepoort, South Africa
Joined Aug 2007
1,037 Posts
Bulls eye

Hi All,
Just 3 shots and its in the zone
Fuselage 1 nice layup super strong and 1004grams

Fuselage 2 slightly lighter around the tail
spread tow carbon, carefull resin 914 grams

Fuselage 3 off cuts of hybrid and Arimid/Kevlar cloth
very carefull with resin. 804grams

The join seam was excellent , I got the timing just right and joined just when the glass tape went green but was still tacky.
cheers
Mike
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