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RodneyFord 06-30-2015 03:59 PM

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Faceted the bottom of the fuselage. Going to experiment with a dorsal fin as an add on and this will help integrate it into the rest of the fuselage.

RodneyFord 06-30-2015 04:00 PM

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A more chiseled look to the nose. Will keep working on this.

RodneyFord 06-30-2015 08:28 PM

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Blending in the fin.
http://www.rcuniverse.com/forum/atta...mentid=2106688

serious power 07-02-2015 01:27 AM

Hi Rodney,
Interesting project !!
What density Rohacell are you going to use ??

Brian

RodneyFord 07-02-2015 01:38 PM


Originally Posted by serious power (Post 12064282)
Hi Rodney,
Interesting project !!
What density Rohacell are you going to use ??

Brian

Hi Brian
It is Rohacell 51. A group of us got together and imported a good batch of 800 x 1200 sheets from Clarasonic in Thailand NZ$50 (US$40) a sheet. We got a range of thicknesses 1-3mm in .5mm increments, I am thinking 1mm for this model. Interestingly if you google thermo forming Rohacell there is plenty of info out there. I usually use a heat gun to form the PCV foam we have been using but will try going further and get the Rohacell to form to the full canopy shape.
Rod

RodneyFord 07-02-2015 04:14 PM

1 Attachment(s)
Got the front and rear lining on the canopy. It's spaced from the fuselage a little for something to come and go on.

http://www.rcuniverse.com/forum/atta...mentid=2106963

serious power 07-03-2015 12:25 AM

Hi Rodney,
An idea might be to keep the plug for thermo-forming.
Any reason why you did not go for the 31 ?? A M\2 of 31 at 1.5mm weighs less than a 1mm M\2 of 51. You can use the 1.5mm in the big flat areas for extra stiffness in the section.
We found the 31 plenty strong enough in compression for all our lay-up purposes and out of the sandwich it is way stiffer than the same thickness honeycomb.
I have never used carbon veil in a mold lay up but I am using it instead of glass for finishing.
It might be worth your while to try ; 0.5oz outside and 0.3oz on the inside on a 10cm X 10cm test piece - I pretty sure it would be great.
However glass on Rohacell looks nice.

Brian

RodneyFord 07-03-2015 12:53 PM


Originally Posted by serious power (Post 12064769)
"Hi Rodney,
An idea might be to keep the plug for thermo-forming."

Yes I thought that too. Although I usually do it into the mold. I might need to get some high temp vaccuum film And heat the foam through that.

"Any reason why you did not go for the 31 ?? A M\2 of 31 at 1.5mm weighs less than a 1mm M\2 of 51. You can use the 1.5mm in the big flat areas for extra stiffness in the section.
We found the 31 plenty strong enough in compression for all our lay-up purposes and out of the sandwich it is way stiffer than the same thickness honeycomb."

Actually I never thought about getting the 31. We were mainly interested in doing the 40% IMAC models with composite wings. I think the 51 is for a better surface finish when pulling full vacuum. You are right about the big flat areas, am thinking about a honeycomb ladder down the fuselage.

"I have never used carbon veil in a mold lay up but I am using it instead of glass for finishing.
It might be worth your while to try ; 0.5oz outside and 0.3oz on the inside on a 10cm X 10cm test piece - I pretty sure it would be great."

I will do some test pieces. It would be interesting to see how the carbon veil handles. The CL guys use it on their wings, which might be worth thinking about. I wonder how it would effect the RF. Mind you I'm flying Jeti with dual path so with the telemetry would probably get it sorted out.

"However glass on Rohacell looks nice."

This is plan A however I have enough 1oz Kevlar if I decided to go that way.

Brian

I'm thinking 2 layers of glass on the outside. Either 25gm-50gm or 2x 50 gm and 1 layer of 50 inside. I will do a test with the Kevlar though.
Probably use lacquer as the gel coat for the weight saving over epoxy undercoat.
I had better see if I can find some finished weights to aim for.
Rod

RodneyFord 07-04-2015 08:35 PM

2 Attachment(s)
Made this setup to hold the fuselage straight while I glue in some stiffeners.

http://www.rcuniverse.com/forum/atta...mentid=2107517 http://www.rcuniverse.com/forum/atta...mentid=2107518

RodneyFord 07-05-2015 02:45 PM

2 Attachment(s)
Glued the other stiffener in. The first one was already holding things straight. Here is the laser on a magnetic stand. The laser is also great for marking out rudder cable runs.

http://www.rcuniverse.com/forum/atta...mentid=2107679 http://www.rcuniverse.com/forum/atta...mentid=2107680

RodneyFord 07-05-2015 03:55 PM

Thoughts on a counter rotating drive system.
 
2 Attachment(s)
I like the idea of building my own drive system modeled after the Adverrun design. The concept has been around for a while, here is a diagram from 2000 for an air boat drive.
http://www.rcuniverse.com/forum/atta...mentid=2107710
The Brenner and Adverrun systems seem to be running props around 4000 rpm. This will determine the gear ratio given the motor Kv and the battery voltage. Out runner heli motors look to have the right Kv, light weight and reasonable cost.

Example
Kontronic 650-62 Kv 620 so it will be doing a nominal 22940 rpm on 10 cells. so it will need a ratio of 5.735/1 to run the props at 4000 rpm.
I have been looking at gears and belts to see what is required. It looks like 1mod for the gears and GT3 for the belts. A 14 tooth belt pinion is a good number so that 6 teeth are always in contact with the belt so we get a pulley of 80 teeth. Minimum distance between centers is around 47mm. A 14 tooth 80 tooth 1 mod gear drive is 49mm between centers so they look pretty closely matched.
Here is a quick sketch of the basic dimensions to see if it will fit in. Looks OK.

RodneyFord 07-05-2015 09:19 PM

3 Attachment(s)
I need to fillet the base of the canopy cutout to reduce stress risers. A handy piece of tube and some bondo does the trick.

http://www.rcuniverse.com/forum/atta...mentid=2107742 http://www.rcuniverse.com/forum/atta...mentid=2107743 http://www.rcuniverse.com/forum/atta...mentid=2107744

RodneyFord 07-08-2015 05:55 PM

3 Attachment(s)
Masked to the center line then put 2 layers of 200gm glass on one side. This goes down nicely in one piece so the only join is on the hard center line.
http://www.rcuniverse.com/forum/atta...mentid=2108137 http://www.rcuniverse.com/forum/atta...mentid=2108138 http://www.rcuniverse.com/forum/atta...mentid=2108139

RodneyFord 07-08-2015 06:26 PM

2 Attachment(s)
Here is a technique I use when glassing wings. Before the resin goes off spread micro-balloons over the surface and rub in. Fills a lot of the weave and doesn't need sanding.
http://www.rcuniverse.com/forum/atta...mentid=2108142 http://www.rcuniverse.com/forum/atta...mentid=2108143

RodneyFord 07-08-2015 10:19 PM

More thoughts on a contra-rotating drive
 
3 Attachment(s)
Well it looks like the biggest challenge with this drive is juggling all the variables and sourcing the parts. I now know a lot more about timing pulleys and belts. The design gradually comes together. It looks like a 520 kv motor is necessary. I could rewind a motor as I have built quite a few CD rom motors for indoor and have a winding machine, however not too keen on that as I know the difficulties:D. Looking like I need 1 mod spur gears and 3mm GT2 tooth belt drive with the whole thing made to work with a 80 tooth belt 9mm wide. I'm kind of thinking the rear prop can run at a (slightly) faster speed than the front one.

http://www.rcuniverse.com/forum/atta...mentid=2108153 http://www.rcuniverse.com/forum/atta...mentid=2108154 http://www.rcuniverse.com/forum/atta...mentid=2108155

RodneyFord 07-10-2015 04:12 PM

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Trimed the first side down the center line, re-masked and got the other side glassed. It will get a bit samey for a while as I go through the surfacing procedure but I will keep posting anyway.

RodneyFord 07-11-2015 06:40 PM

1 Attachment(s)
Mounted the fuselage on the paint stand. Will get some epoxy undercoat on tomorrow. Still need to glass the canopy.
http://www.rcuniverse.com/forum/atta...mentid=2108609

RodneyFord 07-11-2015 07:31 PM

1 Attachment(s)
Glassed the canopy. 2 layers of 200 gm again. Got them on in one piece on the 45 degree bias.
http://www.rcuniverse.com/forum/atta...mentid=2108610

RodneyFord 07-11-2015 10:57 PM

1 Attachment(s)
Forgot this little detail at the bottom of the fin. It is cold here so the epoxy for the canopy was still ok to use with a bit of heat gun treatment.
http://www.rcuniverse.com/forum/atta...mentid=2108627

RodneyFord 07-13-2015 08:38 PM

1 Attachment(s)
Applied a coat of epoxy/micro-sphere all over. I will be wet sanding from now on so will need to seal any exposed MDF.
http://www.rcuniverse.com/forum/atta...mentid=2109087

RodneyFord 07-13-2015 08:55 PM

More thoughts on a counter-rotating drive.
 
Well I can get the the system meshing with a 16 tooth/72 tooth belt and a 17 tooth pinion 80 tooth spur gear. This gives 4.75:1 on the front prop and 4.5:1 on the rear prop. This would suit a 520kv motor. The fly in the ointment is that there are only 4 teeth of the belt meshing with the 16 tooth pulley, 6 is regarded as a minimum. Perhaps that would be a good reason for using a 15mm wide belt rather than 9mm. I will see if things can be improved by re gearing for a 450kv motor, 3.6:1 should give a good belt mesh.
Many thanks to Brenner for his work and posting it here. As well as the correlation of Kv to prop rpm he has shown a correlation between KV and gear ratio. Most useful.

RodneyFord 07-17-2015 08:08 PM

2 Attachment(s)
Sanded off the micro balloons It is looking OK. Put on some more but only where necessary. Hopefully will get a dark colour on tomorrow so I can get a good look at it.

http://www.rcuniverse.com/forum/atta...mentid=2109767 http://www.rcuniverse.com/forum/atta...mentid=2109768

RodneyFord 07-18-2015 05:15 PM

Contra-rotator
 
1 Attachment(s)
Got a good mesh with 19-72 3Gt timing belt and 20-76 tooth Mod 1 spur gear (0.1mm difference) . This is possible due to the 95mm diameter spinner. Ordered a Scorpion HK 4035 450 Kv motor. Have a set of Mod1 gear cutters coming from China. 3GT belt and pulleys are from BandB in the USA. Here is a more complete preliminary drawing.

http://www.rcuniverse.com/forum/atta...mentid=2109875

RodneyFord 07-18-2015 06:16 PM

1 Attachment(s)
Took a bit of work to sand the green epoxy/microballoon mix off. Got a coat of epoxy undercoat on. Not too bad a surface, I will start in with the polyester filler now. This is pretty fast to work with.
http://www.rcuniverse.com/forum/atta...mentid=2109880

RodneyFord 07-19-2015 09:52 PM

2 Attachment(s)
Got some bondo on the top of the fuselage where it was looking a bit lean. Sanded. The black is a good indicator, still a few low spots.

http://www.rcuniverse.com/forum/atta...mentid=2110045 http://www.rcuniverse.com/forum/atta...mentid=2110046


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