yak 55 32" hobby craft foamboard build - Page 5 - RC Groups
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Sep 27, 2017, 08:51 PM
Registered User
Quote:
Originally Posted by BHOFM
I think your +55% is dead on. Bare air frame is 104g, no electronics, no firewall.

your still going to be under 200g with electronics installed possibly with a 2s battery aswell. light as a feather. I might have a go at removing the paper see what saving in weight there is. strength is an issue though, the foamboard isnt very flexible it tends to crack when you bend it without the paper.

what thickness of foamboard are youusing?
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Sep 27, 2017, 08:54 PM
Kimbers Keeper.
BHOFM's Avatar
I am going to check and see what it would cost to ship to you.

They say 3/16th.
Sep 28, 2017, 01:50 AM
Registered User
Extreme Sports's Avatar
Quote:
Originally Posted by bazsound
I found anothe rpost stated about 40% heavier, maybe too heavier for floaters but peole have used it succesffully , jsut needs a little more power sometimse and doesnt fly as slow. For the 3d profile planes, yes its too heavy Im currently looking at several other options XPS foam possibly, trouble is i dont want 20 pieces. I dont have the space to be keeping a box full of 1200mm long sheets of foamboard that will sit for a year.
Had much the same problem here. My eventual solution was to buy a 30mm thick sheet of XPS ceiling insulation foam (I'm sure you will get it in the UK, since you must use roof insulation far more than we do) and hot wire cut it to 6mm sheets. Lately I've found they will give me their off-cuts for free - small pieces, but easier to hotwire than the full sheets, and usually large enough to make a wing or fuselage (off-cuts typically 600mm x 200mm). Once set up, hotwire cutting is a 5 min job. Expect a few booboos along the way, so get extra foam.
Sep 28, 2017, 03:51 AM
flyin' fool
goldguy's Avatar
If you expect to be successful in this hobby, 'start off' with finding a successful design and do exactly the same. Then venture off in the world of model aviation exploration now that you have a basis to work from.

Oh and buy a wattmeter. The most important tool you need if your playing around with electrons. Without one, your just guessing.
Sep 28, 2017, 07:37 AM
Kimbers Keeper.
BHOFM's Avatar
AUW is 244g with 3s 500. With a 9X4.7 about 80W. Or, about 160W per lb. The double KFM
is a new thing for me? I do have a wing with that configuration.
Sep 28, 2017, 10:44 AM
Registered User
Quote:
Originally Posted by BHOFM
AUW is 244g with 3s 500. With a 9X4.7 about 80W. Or, about 160W per lb. The double KFM
is a new thing for me? I do have a wing with that configuration.
Pretty good with a 3s battery and kfm wing. without the kfm what you think closer to 200? So how does it fly with a proper kfm? Is the extra weight worth it??

Looking forward to seeing results, didnt have time today to try a sort of KFM on my battered yak. will do it tomorrow. its all of 20 minutes work.
Sep 28, 2017, 11:06 AM
Kimbers Keeper.
BHOFM's Avatar
Going to try to fly it later today, taking the v-cam, but it's not dependable.

I had a piece of foam left about the size of the KFM section and it weighed 24g. That would
be 48g plus the glue add the weight of a spar and glue. I did put a strip of filament tape top
and bottom.

I just did a wild guess on the CoG at 33% at the fuselage. Put it just at the front of the canopy.

I also have a new 1000mm Edge 540 to fly today.
Sep 28, 2017, 12:46 PM
Registered User
Quote:
Originally Posted by BHOFM
Going to try to fly it later today, taking the v-cam, but it's not dependable.

I had a piece of foam left about the size of the KFM section and it weighed 24g. That would
be 48g plus the glue add the weight of a spar and glue. I did put a strip of filament tape top
and bottom.

I just did a wild guess on the CoG at 33% at the fuselage. Put it just at the front of the canopy.

I also have a new 1000mm Edge 540 to fly today.
Yeah so that lines up with what others were getting using the nice and lite stuff, some even managed to get as low as 140g flying weight. I found a possible cheap solution although i need to find the size of the sheets

http://www.trade-point.co.uk/departm...1570772_TP.prd

8gbp for 800x6000. it looks like it is 6 sheets that fold up so could be 800x1000m for each section.
Sep 28, 2017, 04:06 PM
Kimbers Keeper.
BHOFM's Avatar
CoG was dead on, three clicks up trim for perfect flight. No rudder or aileron trim needed. Flies
like a dream. One problem, flight time is 4 minutes with about 10% left in the battery.

Plenty of power but is slows very quickly. The leading edge is a square, three thickness of
foam board. I am going to round it off nicely and see if that helps.

For a spur of the moment build, about four hours total time, two sheets of foam, some
used electronics, it is a pretty nice plane.

Three flights today, no video, and the motor mount pulled loose, no damage, just not a
good glue joint. Working too fast I think.

BTW, wind was 10 to 15 mph.
Sep 28, 2017, 05:15 PM
Registered User
Quote:
Originally Posted by BHOFM
CoG was dead on, three clicks up trim for perfect flight. No rudder or aileron trim needed. Flies
like a dream. One problem, flight time is 4 minutes with about 10% left in the battery.

Plenty of power but is slows very quickly. The leading edge is a square, three thickness of
foam board. I am going to round it off nicely and see if that helps.

For a spur of the moment build, about four hours total time, two sheets of foam, some
used electronics, it is a pretty nice plane.

Three flights today, no video, and the motor mount pulled loose, no damage, just not a
good glue joint. Working too fast I think.

BTW, wind was 10 to 15 mph.
Odd i get almost 10 minutes on my heavy yak although it is 850mah, 10 minutes is really draining the battery down too low though 7 minutes more realisting leavin gbattery at 11.2-3v
Sep 28, 2017, 05:32 PM
Kimbers Keeper.
BHOFM's Avatar
I am hoping the rounded leading edge will improve the flight times. I only do five or six minutes
tops. Age thing.

Motor mount is fixed and the wing is rounded, and covered with packing tape. Just the leading edge.
1" tape.

Another thing, the wind today required aggressive flying.

Tomorrow maybe.
Sep 29, 2017, 05:29 AM
Registered User
Quote:
Originally Posted by BHOFM
I am hoping the rounded leading edge will improve the flight times. I only do five or six minutes
tops. Age thing.

Motor mount is fixed and the wing is rounded, and covered with packing tape. Just the leading edge.
1" tape.

Another thing, the wind today required aggressive flying.

Tomorrow maybe.
could have been the wind.

I just fitting my "kfm" airfoil on the top of the wing. It is adding some strength to the wing but they can still flap from presure on the tips of the wings, better than it was before. Noticable weight increase.

Discovered that thepaper on hobbycraft foamboard (west) is really easy to remove. Just soak it in water for a couple minutes and the paper just peels off, if anything remains you can roll it off with your fingers. theres still layer of something left behind, looks like another layer of paper but i guess thats the glue. Definate weight saving could be as much as 50% removing both sides.


I cut out a 10cmx10cm piece, weighed it on my terrible anologue scales (5g increment markers) the square weight what looked just under 5g. Once the paper was removed there was n oticable weight difference looked almost have to maybe 2g. Might be worth building one with the paper removed (and using larger carbon rod spars), the only worry is this stuff i think is quite brittle, without the paper im sure it cracks easily.

Hopefully get out today to test the new airfoil although it is quite windy.
Sep 29, 2017, 08:31 AM
Registered User
managed to get a flight today after doing the wing . quite windy today but plane seemed to handle it very well and i think my wing rocking at slow speed has improved greatly. will need a calm day to test properly. i was able to float into the wind with minor aileron corrections.

flight times seem not to be effected.

Unfortunately on my 2nd flight i decided that i could move the CG back (pretty sure im nose heavy) and had the battery eject itself mid flight... I though there was till enough friction in the battery tray with it sticking out to hold it in place, obviously not.

When i turned round to start heading back into the field, there was the distinct passanger abandoning ship and then it went dead. Thought i had gotten away with it as they plane just seemed to float level until it disapeared behind the folage. well, it managed to land nose first onto path which is surrounding either side by miles of soft stuff....

Battery is gone (no chance finding it in long grass and bushes).

I think its time to build a new one, i weight it and its coming in a 420g!!!! plus im sure its not flying right due to everything being crooked in some way and the creases giving way in flight.....

I mght just go ahead and give a go at building a paperless version and see how it stands up.

Last edited by bazsound; Sep 29, 2017 at 12:21 PM. Reason: Correct poor phone typing
Sep 29, 2017, 07:39 PM
Kimbers Keeper.
BHOFM's Avatar
Flew mine today with the rounded leading edge. Whole new game. Flies beyond great. Two flights
in wind similar to yesterday and battery was at 29%. Did a five minute flight with aggressive flying
and it was 9%, which is fine.

I am going to build another 35" Laser with the double KFM wing.

My Laser

Sep 29, 2017, 07:51 PM
Kimbers Keeper.
BHOFM's Avatar
Yes, time for a new air frame. With a double KFM and some filament tape you won't need a spar.
Any bigger and I would recommend one.

Keep us posted on the new build and ask if you need any help.


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