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Old Nov 28, 2010, 06:36 PM
The lunatic is on the grass
ridgewalker's Avatar
Joined Aug 2008
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dumas F-4F Wildcat rc conversion w/AR6400

The dumas F4-F Wildcat 17'' wingspan is the next plane i will convert from ff to rc useing the AR6400 brick...and it will have ailerons.

This is my second dumas kit build in the "walnut" size and i find there kits very good.
The wood is laser cut....not "die crushed" like some other kits i have read about (guillows).
Plans are clear as well as the directions....i would recomend if your going to build a plane and plan on useing an AR6400 or vapor type brick that the dumas kits are the way to go.

OK...so a few things i have found out when building these ff kits as an rc plane is that you need to try and keep it light as you can....especialy in the tail!

So i have decided to build the rudder and elevator in 3mm depron to save weight.
Also i have thinned the top and bottom keel as well as opening up the rear #9 former.....and also a bit was taken off all the formers behind the cockpit.

The wing ribs have also been opened up to reduce weight in the wing.

I wanted to be able to get to the Ar6400 in the event i need to unplug the main motor to change it or to for some reason need to unplug and switch the aileron servos....so i built a couple hatches in!

Now i can connect the rudder/elev linkage,install or unplug through the hatch!
The hatches have some thin cf to add strength and some tape makes the hinges...i may change the tape hinges to a small sliver of cf.

Oh ya...weight....So as it sits with the brick,ail servos,canopy,foam tail,prop,motor/gearbox and plastic nose piece it weighs in at...37.2 g.

A bit more heavy than i would like at this stage of the build.

But...the cog is spot on!!

I plan on having the battery slide in a slot on the belly.
The battery i am thinking about useing is the 500 mah 120 sr battery...it ballances perfect with that battery and with a 150 mah the cog slides back a tad and i don't know if it will be ok....so i will build it to accept both batteries and flying it will tell me which will be better.

Not planning on adding any landing gear ...i really don't like the look of it flying around with the gear hanging....just doesn't look good on this plane.
I had wanted to add another servo and have the landing gear retract but the added weight is not something i need in this model..lol

Planning on sheeting the bottom of the wing with foam plate foam...it's already white so i wont have to paint it or anything!
The top of the wing will be sheeted with 1/32 balsa...i dug through all the 1/32 sheets and found the thinnest three i could and will use those....mabey on the fuselage as well.

Now.....i know, i know, that some will say that tissue would be lighter...and i think i would agree...But,i can sand down the 1/32 sheeting if i find it heavy...mabey i could loose a .05g-1.0g i'll have to wait and see.

I did weigh a piece of foam from a foam plate against the same size piece of 1/32 balsa sheet and the 1/32 balsa sheet is lighter!!

Only by .03g but hey...every bit helps...and like i said i can sand the 1/32 balsa to try and get it lighter but i can't do that with the foam and still have a nice look...i tried..lol

All comments,questions,suggestions and ideas are welcomed....good or bad..lol

On to a few pics...
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Old Nov 28, 2010, 08:14 PM
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United States, MA, Sutton
Joined Aug 2006
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I love these Dumas walnut kits too. Just finished the Curtiss P-6E today...

I like your pin hinge door idea to the access of the RX. Good stuff. I look forward to seeing more.

Tom
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Old Nov 28, 2010, 11:31 PM
This Calls for a Sexy Party
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Minneapolis
Joined Sep 2010
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nice start, good luck with your build
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Old Dec 01, 2010, 04:40 PM
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Central Massachusetts
Joined Nov 2010
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if I build this, should I use the origional prop, or what prop should I use?
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Old Dec 03, 2010, 03:25 PM
The lunatic is on the grass
ridgewalker's Avatar
Joined Aug 2008
4,947 Posts
Scaleflyer121.........If you are building it for rc use...say with the AR6400 then i would not use the prop that comes in the kit.It is heavy and the pitch is more for a rubber power.
I am going to start off with the 4 site prop and see how it goes.

Just about done now.....a few changes were made to my original idea ,but in the end i am happy with how it looks.

Thanks StewieRC.....

ducatirdr....Your Curtiss P-6E looks good !....the pin hinge on the ailerons works well and is light.The WD-40 red tube you get with the can has come in handy for many things....also makes a good coupler between the cf linkage and the metal wire that attaches to the servo horns!


Pictures on the way....


Ridgewalker
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Old Dec 03, 2010, 04:32 PM
The lunatic is on the grass
ridgewalker's Avatar
Joined Aug 2008
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Well i got the top of the wing covered with the 1/32'' balsa...and i have to say....it sure looks good

The bottom is covered in the foam from foam plates...it went on well and looks good.
The foam really adds strength...i used ca to glue the foam skin to the wing formers and trimmed it with a razor.

Now about weight....i cut the foam pieces that i was to use and went to weigh them....

First...1.2g ok...i set it aside and weighed the wood...1.0g great...so for some reason i placed the foam pieces in my lap while i was sidetracked....then...i don't know why but i weighed them again...3.2g Whaaaat!!!

How could that be...hmmm....so i weiged em again..3.0g ????

So by now i have to check the scale....i have a an alum "standard" i use that i know the weight of and what do ya know....the scale is working fine

So i go to weigh the foam again and notice that some fuzz is stuck to it...ya know...from static electricity...so i try and brush it off and i get it off...but it was stuck...ya know how static electricity makes things stick together.

So i re weigh it and it weighs..2.5g......so i got to thinking..because of that fuzz lol

I rub the foam on my head...like you would do with a balloon to build up a static charge on the balloon to make it stick to something...anyway i rubed the foam on my head and weighed it...4.5g!!!!....then i blew on it,as if blowing dust off something and re weighed it..3.0g.

It seems to me that one of two things is going on...one the static charge is interfearing with the digital scale...or.........two, static electicity has weight to it that can be measured ,and as the charge rises the weight increases.

I need a mechanical scale....like a tripple beam used in a lab to know if it is interfearence with the scale or not.

So......i couldn't get an accurate weight on the foam pieces.
I did weigh the wing before the covering it was 12g with the two servos....but i had to have the wing in the fuselage and add the wood and foam sheeting that way so know weight of the wing after the sheeting..lol

I had planned on useing the wood and foam on the fuselage as well.....but weight had made me change that idea..lol

I used the included tissue and applied it with thinned elmers glue...lightly misted it to shrink it after the edges had time to dry and then painted....I'll be getting those pictures up soon.

For now here are a couple few more as i was finishing it up....



Ridgewalker
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Old Jan 17, 2011, 06:55 PM
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Burgeoning Metropolis of Tustin, MI!
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Perhaps the static is trying to pull the foam sections downward toward your table... try weighing the items while putting the scale on different surfaces... static electricity doesn't add weight, but the pulling force toward a plastic scale, or the table.... does add some down-force (scale interprets this as added weight)

Brandon
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Old Jan 18, 2011, 03:33 AM
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Minneapolis, Minnesota
Joined Jul 2007
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That is a beautiful build! I agree, the wings look wicked skinned with thin balsa. One observation. It appears the leading edges are blocky. If you sand them in to a nice curve it should improve lift.

Jay
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