MIRO 2

[Rod]

Hi Barrie sounds like a very cool project, got any pictures? I have recently done some stator blades for a large fan at work using a similar system weight was not an issue. The laminate was foam/glass/balsa/carbon uni/glass bagged on with mylars. The foam was medium density and I used 16inHG. After curing I hot wired out all the foam. What I found was that it was very heavy (not a problem) resin from the inner layer had migrated right through the foam which starved the balsa/glass bond to some extent. Crushing wasn't an issue. Now I know Mike B has had some issues with delamination using this sort of technique. However I have read of carbon tissue under balsa for extra strength. I can see the advantage of a layer of glass on top applied with mylar for finishing reasons as well as strength. I have been making some DLG wings and you need to be carefull not to soak up too much of the resin with the kitchen towels or you get too dry a finish when using glass (kevlar seems to retain the resin better). I have a new project in the pipeline 2.6M span I plan to use medium 1.6mm balsa with the usual internal reinforcement and 25gm silk on the outside applied with dope for light weight. By the way I am looking at polyspan for this Miro project (a polyester tissue) And am looking for a local supply if anyone knows of one.

[Rod]

Barrie I havn't used polyurethane for skinning yet as it precludes the use of fibreglass and carbon reinforcement.

[brusty]

Hi Rod,
Yes you're quite right, using gorilla glue does preclude the addition of the unifibre carbon spar cap, and for that reason i will possibly stay with epoxy. It was a bit sad about mike / frazers wing, i feel a bit guilty about that as I had been expounding to Mike about building a composite laminate on the foam core instead of making a mould and producing laminated skins. its much quicker and cheaper to cut cores rather than make wing moulds!! (And you can change your design as often as you change your mind!) However I think the problem they ran into, and I also found it on one of my Raven layups was the lower pressure due to the low density foam as opposed to sucking into a mold when you can crank it up as far as your sucker will go ! I also think balsa skins adhere better than this divinicell at the lower pressure, its great in the Fuz mould where again pressure is not a problem, but over a foam core the parameters change as you also observed. My last OD F3A patternship came out at just under the 5kg, using 1.5mm kledgecell in the Fuz Laminate, and balsa skins on 16kg foam wing cores, and I reckon with knowledge gained, I could get another .3kg out of it. Its just a pity my flying ability doesn't match it, but its a challenge, and interesting talking to others and pushing the boundaries a bit.
I watch your progress and comments with great interest. Cheers, Barrie.

[brusty]

Rod,
yes I have used Carbon matt tissue, but I find it is rather like blotting paper and does soak up the resin and can add a lot of weight. Laterly I have been using a 20mm strip inside the trailing edge to give it a bit of stiffness.

Like you I now use a small foam and a cotton roller rather than a brush. Originally I carefully weighed my resin and tried to match the cloth weight, but have abandoned that idea, and now mix up plenty of resin, apply it where i can with a roller, and then get rid of it all again using a small wooden wallpaper roller over paper towels. That way I find I get a better coverage, and the weight seems to come out pretty minimal, but if I need a bit more resin, then I can be sure it is in there. I gleaned that trick from our local boy DLG hero,Rowdy. Its good talking and looking over others shoulders, you never stiop learning.

Have you seen Phil Barnes video on vacuum bagging wings, thats a great look, and well worth the investment.

Last but not least, I changed my moulding and mould release system for the Raven, and used Ultratec profiling resin, great being able to lay it up all in one go and no shrinkage. i also changed from my usual mould release wax system to the Frekote , Semi Permanent Release Agent, and found it easy to use and the plug and the model popped out of the mould without a problem, and i'm told will continue to do so.


Cheers, Barrie.

[Rod]

Here is the left (port) wing in the bag. It is in nearly the same position as it was cut. The weights are to seat the cores in the offcuts without vacuum. I managed to reuse the bag. You can see the vac pump to the right and one of the CNC foam cutter gantrys at the back.

[CSpaced]

	Quote: Originally Posted by brusty
	I am also considering applying the skins with Gorrilla glue, I did a test sample, and there was little difference in weight, and the penetration and adhesion of the polyeurathane glue was excellent. Then the ouside i might use a layer of 2.3 ounce and a layer of 0.75 under the mylars. What are you thoughts? Regards, Barrie.

For what its worth my buddy used gorilla glue on his 42% Extra 300's wings. He cut out a lot of the foam and used carbon tow to reinforce the wing. Then he glued the balsa panels on using gorilla glue. (see link - post 210)

Dalton Aviation 42% Extra 300 Mark Leseberg Edition build

[Rod]

Hi Chris thanks for the link. I have done this on .60 size models a number of times. I used epoxy with plenty of micro balloons applied with an icing syringe in beads. I will consider it for my next project. I am still liking my current system though.

Second wing panel out of bag at 235gms (8.29oz).

[brusty]

[quote=Rod;441776]Hi Barrie sounds like a very cool project, got any pictures?

Hi Rod, have a look at http://www.modelflight.regheath.com/workshopset.htm, its a summary I did for "Modelflight"

I have been making my U/Cs over a male MDF mold, covered with some plastic sheet. Then easy to lay up with rectangular pieces of cloth, wetted out with the roller. The Raven had a mixture of eight layers of 6 oz carbon cloth, 20 layers of C/Uni & 10 layers of 6oz glass, covered with a sheet of mylar and bagged at max pressure overnight, and then left on the hot water cylinder for a couple of days...like a piece of steel, but light. The beauty is I can get two legs out of a sheet of layup. On some of my smaller electrics, I can lay up a sheet for up to four U?Cs. Cheers, Barrie.

[Rod]

Hi Barrie very nice model. How do you think you would lose some weight? Am interested in your pipe setup, do you have any dimensions you could pass on?

[Rod]

I have finished the new release system on the fuselage mold. I am going to vac bag the fuse this time and am going to try to get as much coverage with the foam reinforcement. I am experimenting with these ribbed rollers to get the foam to conform to the mold shape.

[brusty]

Rod, Thats looking good, as a matter of interest, what foam are you using in the fuz layup...type and thickness ?? Just off to the field, I will send you the manifold dimensions later today. The muffler is an MTW tuned muffler. It is a bit noisier than i expected, but that may be the prop. Running a 27x10Th, but have just got a 24x10 three blade, so that should tell me. I have a couple of small mods I want to make to the plane before I fly again, and as we close the field tonight for duckshooting that will be a couple of weeks away. Cheers, B.

[Rod]

The foam is ordinary polystyrene of a fairly high density, stuff I scrounged from work. I cut it with my CNC cutter so it is nice and smooth. Even with the CNC cutter it is hard to get really exact cuts over the entire length so the thickness varies from 2.2 to 2.6mm. I have found no need for anything denser like kledgecell.