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Feb 14, 2011, 03:57 AM
working to the closest cm
jirvin_4505's Avatar

Pictures please


Quote:
Originally Posted by DrFragnasty
No. Bog mix. It'll be a 1st for me.
I'll be relying on Steve's expertise (he's the bog wiper master) on this one.

hang on...bog wiper master just sounds plain wrong ;0)

Chris.
Hi team SEAT
Would enjoy some photos when you make the wipers

I recall discussing this at Jerilderie and there have been some techniques developed - a revision lesson would be nice

IIRC. The use of a strip of balsa as a depth of bog control?
Handling an instillation where the hinging is already established
I think one of the team was doing formed in place carbon wipers - would like to see that done

Cheers Jeff
Really enjoying the build
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Feb 14, 2011, 05:46 AM
mmmmm....BEER
Hey Jeff,

I tried making carbon wipers on the Machine initially. Got too messy.......I had bits everywhere and the wheels were starting to fall off. It was a hot day. Cleaned it all up whilst I had the chance and went with the bog wipers. Much easier IMHO and still relatively light if you do it right. Easier to repair if you damage them as well.

Bruce did the carbon wipers successfully on an earlier Machine build. Difference was he cut the ails & flaps off completely (he used tape hinges but you could use silicone hinges as well). This made it a lot easier to layup. But I like the hinges integral to the skins (peel ply). They haven't let me down yet and I'm really happy with them.

cheers

Steve
Feb 14, 2011, 06:58 AM
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DrFragnasty's Avatar
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FYI
Ron Gijzen has a good thread on making a wing including bog wipers:

http://www.modelbouwforum.nl/forums/...eugel-tip.html

Chris.
Feb 17, 2011, 01:41 AM
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DrFragnasty's Avatar
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tape for making wipers


Not much to report except the tape I was going to use to house the wiper bog while it cured was Flash Breaker Tape FB1.

FB1 is too thin/ too light, you need FB2. I have 2 rolls of FB1 @ $AUS40 ea

Steve mentioned laminating 2 strips of FB1 together. Worth trying I reckon or look around for a replacement; it needs to be 20mm and reasonably stiff. Dunno what Ron used... (Ron?)

Also chamfered the top skin on ailerons using exacto knife and sandpaper. This is to allow the molded wiper some clearance as it scribes an arc in operation.

The layup and the short distance from wiper slot to sub-spar meant despite chamfering, the skin is still very rigid.

Also sanded the hinge on the inisde for more travel but very gingerly so as not to remove any essential anchoring balsa and cloth. Ideally there needs to be +90 deg of travel to make applying the bog easy.

Chris.
Feb 17, 2011, 02:32 AM
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ron gijzen's Avatar
Quote:
Originally Posted by DrFragnasty
Dunno what Ron used... (Ron?)
I used plain office tape (the tough and cheap clear transparent type, not the milky stuff you can write on).
I prefer the method with the carbon though.
I think the bog wipers add a lot of weight.
Because carbon wipers are flexible, you can afford to let them contact the trailing edge of the wing without creating much friction. A Bog wiper must be sanded pretty accurately to create a small clearance so the flap/aileron doesn't get jammed during launch or landing.

I copied the carbon wiper method from Larrikin:
https://www.rcgroups.com/forums/show...arrikin&page=3
My report is here:
http://www.modelbouwforum.nl/forums/...b-model-6.html
Feb 17, 2011, 06:33 AM
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DrFragnasty's Avatar
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Thanks Ron.
Feb 19, 2011, 02:09 AM
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WIP ers


Thanks to detailed descriptions of the process from Bruce & Steve and Ron's photos I jumped in.

The slivers of balsa (1mm) were easy to apply to the Diamond tape. You can re-position them as well and they still stick in place. Quite easy really. Determining how far to mount the tape is trial-error. I re-did the first attempt because it clashed with the sub-spar when closed.

The balsa slivers are there to allow you to use a bit of mylar to screed the bog mix to get an even distribution between flap & balsa.

The bog mix was medium sticky (but not runny like tomato sauce; more like porridge).

I'll check in 24hrs then do the other 3.

Chris.
Feb 19, 2011, 05:15 PM
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DrFragnasty's Avatar
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1 down 3 to go


Removed the tape expecting pefection and got disaster!

The flap wouldn't fit back under the skin. 2 cups of coffee later and 1/2 hr of 80grit and it could slip under.

Another 1/2hr and everything is OK. Finished with 120 grit and it looks good.

The beauty of making bog wipers is you can sand to get the right profile and if you use sandpaper wrapped around a metal ruler you can get a neat edge. I had to sand the leading edge of the wiper to get the reflex deflection I needed. Ultimately I took off 2mm.

This is the way I'll make them from now on. If you need to bling it up, add some colouring to the bog mix a la Jaro Muller.

Chris.
Feb 19, 2011, 05:53 PM
mmmmm....BEER
Chris,

I've found that if you deflect the ailerons at 40-45 degrees and the flaps at 45-50 degrees to cure, they should work nicely and tuck under the skin. If you have to sand the actual surface of the wiper you haven't got the amount of deflection correct.

I sand off the leading edge of the finished wiper to neaten up and get the amount of travel I want in reflex.

Steve
Feb 19, 2011, 07:21 PM
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DrFragnasty's Avatar
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Hi Steve,
Excellent tip. I'll try it for the remaining.
Chris.
Feb 22, 2011, 12:21 AM
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DrFragnasty's Avatar
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Another tip is to make sure your cheap chinese electronic weighing scales work.
I only say this since the poxy epoxy bog mix didn't cure.
I'm blaming the scales ;0)

I've scraped off the 3 wipers (it was like hard marzipan) thankfully it all came off cleanly.

Re-doing them tonight.

Practice makes perfect.

Another tip is to use a 6 hr hardener since the wipers don't need the strength of 24hr, they just need to hold their shape.



Chris.
Feb 22, 2011, 01:17 AM
Registered User
Chris do you have any suringes.
I use 1 for the resin and another for the hardner, can go wrong with the measurements that way.
Feb 22, 2011, 01:41 AM
mmmmm....BEER
Oh No! I thought they were pretty dodgy when the second batch of bog was mixed up.
Feb 22, 2011, 02:29 AM
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DrFragnasty's Avatar
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Take in a Eurotour event then go see a glider made!


If you're mixing slightly larger quantities the ml accurate scales are fine but for the low volume stuff they're dubious.

The last wiper I did is fine, I just used 5ml hardener & 15 ml resin (LY3600) plus an extra dribble of hardener. There's a heap of surplus.

In a production environment I guess they mix up a big batch and have a "Wednesday wiper day" where all they do is wipers ;0)

I'd love to have a tour of Breta/ Samba/ Nan/ Vladimir/ Baudis or Muller facilities to see how production environment differs from the hobbyist environment.

Take in a Eurotour event or two then tour the factories...Nirvana! ;0)

Chris.
Feb 22, 2011, 06:21 AM
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DrFragnasty's Avatar
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Incidence pins


Good tip on the syringes Mick but I'll sling the scales I've got and use another brand.

Steve; the poxy epoxy bog hadn't cured after 2 days and warm temps!


On a lighter note, the MK2 wipers are curing and I found a tent peg that's made from very stout but light aluminium.
Turned down by a mate of mine (thanks Wen) to match the plugs in the tip roots (4.7mm dia.).

30mm length overall means probably around 5-8mm sticking out to lock into the tip panels.

Chris.


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