HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Apr 25, 2011, 11:18 AM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,858 Posts
Good luck to you.
I'm looking forward to your pics and also pics of the new lighter contructed project, if you are going to share those with us.

R,
Target
target is offline Find More Posts by target
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 25, 2011, 10:44 PM
Registered User
Sydney
Joined Apr 2009
716 Posts
Good luck in the Eurotour Roydor and thanks for the update. It would be a great feeling to have come up with a world class performer with the Gremlin.
John
OZPAF is offline Find More Posts by OZPAF
Reply With Quote
Old Apr 26, 2011, 01:26 AM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,474 Posts
yes share roy we all follow
jojoen is offline Find More Posts by jojoen
Reply With Quote
Old Dec 29, 2011, 04:14 PM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
865 Posts
I am finally starting work on Gremlin #3.

This one will be a full carbon spread tow wing. I'm hoping to finish it around 1.8 kg.

I started today by making the joiner boxes and the web material for the spar.
The joiner boxes are 200g/m^2 carbon in 45 deg, wrapped with Kevlar tow and finished off with peel-ply.
The web material is 5 mm balsa (end grain) with a layer of 90 g/m^2 carbon on each side. I will be using two webs in the root going down to 1 web towards the tip.
I'll get some pics as soon as I get the stuff out of the vacuum bags (probably on Sunday) and try to make a detailed build log.

Roy
roydor is offline Find More Posts by roydor
Reply With Quote
Old Dec 29, 2011, 06:23 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,858 Posts
I'm looking forward to the pictures.

R,
Target
target is offline Find More Posts by target
Reply With Quote
Old Dec 29, 2011, 10:03 PM
working to the closest cm
jirvin_4505's Avatar
brisbane australia
Joined Nov 2002
2,127 Posts

This is exciting
looking forward to the pictures

cheers Jeff
jirvin_4505 is offline Find More Posts by jirvin_4505
Reply With Quote
Old Jan 02, 2012, 08:45 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
865 Posts
Pics of the joiner boxes and web material.
I calculate that the web for the spar should weigh around 70 grams for the entire wing.
With the spar caps, joiner boxes and glue, the spar weight should be around 250 grams.
This means around about 100 grams less then my previous models and I believe it should be strong enough.
I'm also planning on building a lighter joiner (20 grams lighter) with most of the weight savings taken from its tips as I believe my existing joiners are way to strong at their ends where the forces are relatively low.
roydor is offline Find More Posts by roydor
Reply With Quote
Old Jan 03, 2012, 02:26 PM
Registered User
jojoen's Avatar
Norway
Joined Dec 2003
1,474 Posts
Hi Roy!
What do you use on the joiner as release compound when you make the joiner boxes. Only wax or something else?
jojoen is offline Find More Posts by jojoen
Reply With Quote
Old Jan 03, 2012, 04:10 PM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
865 Posts
Quote:
Originally Posted by jojoen View Post
Hi Roy!
What do you use on the joiner as release compound when you make the joiner boxes. Only wax or something else?
I put a thin layer of Vaseline and wrap it with a thin nylon wrap (like for sandwiches only a little thicker) This allows the boxes to slide off REALL easy after hardening and provides the necessary thickness difference to allow the joiner to fit into the boxes without getting locked in on hot days or in the presence of dust and moisture.
roydor is offline Find More Posts by roydor
Reply With Quote
Old Jan 03, 2012, 05:42 PM
Registered User
Phoenix, Arizona
Joined Dec 2008
271 Posts
Hurry up I want to see pic of this beauty in the air!
Big Browns is offline Find More Posts by Big Browns
Reply With Quote
Old Jan 03, 2012, 07:27 PM
Detail Freak
target's Avatar
Harbor City, CA
Joined Oct 2003
21,858 Posts
No, I want to see all the build pictures!
They all are photos to learn from.
Thanks, Roy!

R,
Target
target is offline Find More Posts by target
Reply With Quote
Old Jan 04, 2012, 05:09 AM
Registered User
Sydney
Joined Apr 2009
716 Posts
Quote:
Originally Posted by roydor View Post
Pics of the joiner boxes and web material.

II'm also planning on building a lighter joiner (20 grams lighter) with most of the weight savings taken from its tips as I believe my existing joiners are way to strong at their ends where the forces are relatively low.
How are you tapering the carbon caps in the joiner, Roy? Will yo do them separately and then assemble with foam spacers in a joiner mould?

Thanks also for all your info and pics.
John
OZPAF is offline Find More Posts by OZPAF
Reply With Quote
Old Jan 04, 2012, 07:17 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
865 Posts
I use rohacel as the foam for the joiner, sanded to the correct taper and then I put everything into the mold in one go.
I use UD fabric cut down to different lengths, longer at first then shorter so as to get the required taper.
The joiner is also wrapped with 120 g/m^2 carbon in 45 deg, one layer around each half of the rohecel, one around both, an additional layer in the center and one which wraps the entire layup including the UD fibers. other joiners I made hade 200 g/m^2 with a layer removed (was easier to work with)
It’s about 1 hour to put it all into the joiner mold and after it hardens it requires trimming to length and it’s done.
My taper is 3 mm in the root going down to 1.5 in the tip. the next joiner will be 2.5 at the root going down to 1 mm at the tip.
roydor is offline Find More Posts by roydor
Reply With Quote
Old Feb 24, 2012, 08:49 AM
In F3J size does matter!
roydor's Avatar
Israel
Joined Nov 2006
865 Posts
I was hoping to get the plane done by now but work and family got in the way (imagine that )
Finally I managed to find a few evenings to myself and I demolded the wings this morning

I used 80 gr/m^2 spread tow for the outer layer, a horrible fabric to work with when comparing it to the 90 gr/m^2 ďregularď fabric. Still, after developing my own methods based on some information and suggestions given to me by Philip Kolb I managed reasonably well with it and the molding process went well. However, my batch of fabric wasn't what I consider grade A, probably due to shipment and handling on my side. As a result some of the tows got a bit messed up and I had to be a little creative in order to get reasonable cosmetic results without having to toss half of it away to the garbage. Again, not the friendliest of materials to work with, especially if you want a carbon finish, If going for a colored finish, it isnít as bad. For the wings I used Rohacell 71 for the cores, a very nice material to work with. In order to reduce some work load I used 3M adhesive to attach the inner fabric to the core. I used 25 gr/m^2 glass for the inner fabric and after placing the cores in the mold I used a brush to very lightly wet out the fabric.
I added carbon tows in the leading edge to take the necessary radius and prevent air bubbles, an added advantage is reinforcement of the leading edge
For the spars I used a 0.3 mm UD fabric. 3 layers for the top spar (30 mm down to 5 mm at the tip) and for the bottom spar I used 3 layers for the first 80 cm then reduced to two layers for the rest of the span. I used 90 gram carbon to ďcloseĒ the UD of the spar and to transfer the loads to the wing skin to prevent spar bulge. 90 gram carbon reinforcement at the root servo bays and linkage attachment points and then into the vacuum bag.
After trimming I made all the sub spars and webs. I used a carbon sock for the ailerons and flaps and the spar in front of the ailerons, for the spar in front of the flaps I used a balsa-carbon-balsa-glass-balsa sandwich material I used for the previous Gremlins, reason was my carbon sock wasnít the right size for the tall spar.

I added a carbon rod to the leading edge to help hold the glue in place when closing and to strengthen the leading edge, with the carbon tows I used in the leading edge when molding, I suspect Iím going to get nasty leading edge in case of midairís

I used a sponge wetted with epoxy and squeezed as dry as I could for the ribs. It ends up as fairly light ribs and donít need shaping at all as it gets squeezed into shape when closing the two halves.

Demolding was very easy and the finish is excellent with no pinholes. I have a minor cosmetic issue in the tip bet otherwise Iím happy with the result.
Before painting I asked a friend for his opinion on my color choice (was going with yellow and black only at first) and he said it would be a little boring and suggested adding some red. When I opened the mold I was a little surprised to see the German flag . In any case, I had a lot of help from Philip Kolb on this design so it sort of proper

As for weight, the weight difference after trimming the leftovers (flaps and ailerons still closed) is 1 gram and I am still on budget for my 1.8 kg goal

More updates when I get more building time.
Roy
roydor is offline Find More Posts by roydor
Reply With Quote
Old Feb 24, 2012, 12:33 PM
Registered User
Joined Nov 2009
1 Posts
Very good work !!
giammi77 is offline Find More Posts by giammi77
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
My Firefox project slowjoe170 Electric Ducted Fan Jet Talk 10 Mar 19, 2005 02:03 AM
My Electrajet project slowjoe170 Foamies (Kits) 66 Dec 11, 2002 07:26 PM
My next project....the RAKE Tres Wright Parkflyers 12 May 20, 2002 11:55 AM
My Python Project squelchF18 High Performance 4 May 01, 2002 09:54 AM
-= Pics of my latest project =- Jensst High Performance 15 Jun 05, 2001 05:51 PM