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 How to repair Okaer 5m Blades? « View previous topic :: View next topic » 
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gerd30kwselfbuild
PostPosted: Tue Jun 03, 2008 12:05 am    Post subject: How to repair Okaer 5m Blades? Reply with quote



Joined: 17 May 2008
Posts: 11

Hello,

Thank you erik for the datasheets of my rotorblades, now i can start to repair my blades.
Of couse, by the long time of use the blades have some failures and craks which i have to repair.
I have uploadet some pictures of the blades to show where my problems are:


http://img374.imageshack.us/done.php?l=img374/8320/hpim0619hn5.jpg

http://img374.imageshack.us/done.php?l=img374/1928/hpim0620iy6.jpg

http://img374.imageshack.us/done.php?l=img374/202/hpim0621vt3.jpg

http://img374.imageshack.us/done.php?l=img374/8625/hpim0624oy7.jpg

http://img126.imageshack.us/done.php?l=img126/3947/hpim0625zd1.jpg

http://img126.imageshack.us/done.php?l=img126/3163/hpim0626yk8.jpg

http://img374.imageshack.us/done.php?l=img374/7315/hpim0628bi5.jpg


Now I need to know how I could repair this craks at the blade hup, the rest of the blade has no real problem, only a few scratches..
I have planed to laminate a few plies over the big craks on the adhesive reas,after I had opened the craks a litte bit with a sharp knife or a angle grinder.
Can you say if that is the right procedure?

Also I need to know what kind of synthetic resin I should use for the repair? Do I need epoxy resin or polyester resin? And I don´t have the experience, how many plies should I laminate?

The other problem are the craks directly in (through) the flanges of the blades. Can I do something to repair them?
Does it help to fill the cavities next to the holes of the flanges with resin? The one blade witch is delivered one year later than the others doesn´t have this cavities anymore..

And at last, I need to know with which kind of painture I could do the painting of the blades, to get more protection from the weather?


I´m sorry for my bad english and for the lot of questions, but I hope you could help me!
thank you very much!!


Nice greetings from the very hot germany; ))


gerd
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gerd30kwselfbuild
PostPosted: Mon Jun 16, 2008 8:10 pm    Post subject: Reply with quote



Joined: 17 May 2008
Posts: 11

hi,
isn´t anybody here who ever worked with GFK, and could help me?
so please add an reply...
thank you very much; )



greetings
gerd
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erik
PostPosted: Tue Jun 17, 2008 7:40 pm    Post subject: Reply with quote

Site Admin

Joined: 28 May 2007
Posts: 35

Hi Gerd

Sorry, that I did not see your posting before today - I briefly looked at your pictures, and it all seems possible to repair. I will find the time tomorrow to give you some hints on repair of the 3 different crack locations on the blade..


best regards

Erik
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erik
PostPosted: Wed Jun 18, 2008 10:08 pm    Post subject: Reply with quote

Site Admin

Joined: 28 May 2007
Posts: 35

Hi Gerd,

If you could find a nearby fibreglass shop/ boatbuilder or repair shop, you could perhaps buy materials and learn a little from them. But anyway -

The easiest would be working with polyester and 2 % Mekp for curing.
Working temperature - outdoor or in well vented shed - must be 20 degrees C. For the cracks that runs between the two half shells from the root, you should sand an aerea of - ca. 10 cm width and 5 cm longer than the crack.
Sand to remove the Gelcoat layer ( ca 1 mm) .
For each crack - cut 5 pieces of chopped strand mat (300 gram/m2 type) in 6 cm width and the length of the sanded area. Use a roller to place the polyester - Start by placing one ply to the right side, then one one the other side , overlapping part of the first ply. Move the next ply 1 - 2 cm from the side, and so on - the last ply placed in the midlle. (That way the thickness wil be maximum at the midlle.) Each layer is rolled with an aluminium roller (don't remember the name) to remove air from the laminate. When finished and cured - sand the surface, and cover with boat type enamel/paint. ( Polyurethane or epoxy.)

The holes in the root flange area could be filled with Plastic Padding (Car repair type Smile ). I did not see the metal flanges on your photos - don't forget to place them. If a bushing is missing, stainless steel tubing or water pipe half inch galvanized can be used. Be sure that the length is less than the flange thickness - otherwise the sensible blade root system (Hütter flange) will not be corectly "compressed" between the steel parts.
Use Sicaflex 221 or similar polyurethane compound to seal around the blade root flange assembly.

The real dangerous cracks for this blade type, are circumferential fatigue cracks starting to separate the blade from the root bushings part. Such cracks would normally leave some dust in the crack area. They would be just over the rim of the metal flange.


Good luck with the repair !

Erik
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gerd30kwselfbuild
PostPosted: Thu Jun 19, 2008 4:49 pm    Post subject: Reply with quote



Joined: 17 May 2008
Posts: 11

hi erik,
thank you for your anser!
now i can start with the rotorblades..my plan is to mount the turbine in the autum/ winter this year.. and i still have mutch work...

the metal flanges are lying in an rack i will not forget them..
is the crack arount the inner side of the flange really dramatic?
http://img126.imageshack.us/my.php?image=hpim0626yk8.jpg

i thougt inside of the flange (where the bdt numer stands..) is only a kind of laminatet cover so that anything could fall into the blade?? isn´t it?
for me, this crack seems to start going arount this " laminatet bdt.. cover" and maybe i should replace this area with a new laminat?

the really interessant crack is the crack through the flange,:
http://img374.imageshack.us/my.php?image=hpim0624oy7.jpg

and the back side of this crack:
http://img126.imageshack.us/my.php?image=hpim0625zd1.jpg

this crack is exactly on the blade! is it possible, that there a coherence between the two half shells and this crack? I meen is the flange also like the main blade made of two parts?


thank you for your help,
when you come anytime to north germany (neer the netherlands frontier) i would invite you for a tee; ))


greetings
gerd
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erik
PostPosted: Thu Jun 19, 2008 8:38 pm    Post subject: Reply with quote

Site Admin

Joined: 28 May 2007
Posts: 35

Hi Gerd,

The crack at the bottom of the blade : http://img126.imageshack.us/my.php?image=hpim0626yk8.jpg is not a big problem. The "BDT-plate" is just a cover to ensure that water does not enter the blade interior.. (seal with sicaflex). The next crack, that parts the blade shells and root in two, should be secured - mostly by laminating, as I described earlier with 5 pieces of CSM mat at the leading edge and the trailing edge position (round part of the blade).

At the "Hütter root" the longitudinal crack is not dangerous, but should be filled with padding or sicaflex. The Hütter root - is originally made by glass-roving bundles - running from the blade ( 40 cm from the base (if I remember right) into the root, where it runs around the bushings and again runs back for 40 cm into the main blade. These bundles are compressed between the hub and the steel back flanges, when the root bolts are tightened. ( I will upload some pictures on this ... later).

Thank you for the invitation to tea ! I will drop by, if I go to that area...

Best regards

Erik
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gerd30kwselfbuild
PostPosted: Sat Jun 21, 2008 7:15 pm    Post subject: Reply with quote



Joined: 17 May 2008
Posts: 11

Thank you, your explanatory notes, now i am confident that i could repair my blades. I hope they would be solid for a few -more- years..

Very Happy
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alvinpark
PostPosted: Tue Jan 24, 2017 1:16 pm    Post subject: Reply with quote



Joined: 24 Jan 2017
Posts: 1

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kirril
PostPosted: Sun Jun 25, 2017 10:04 pm    Post subject: Reply with quote



Joined: 22 May 2017
Posts: 3

Kinda interesting forum. I like it a lot
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