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Member postings for Lucas Hofman

Here is a list of all the postings Lucas Hofman has made in our forums. Click on a thread name to jump to the thread.

Thread: Gentle Curves - Lucas his Skywriter
17/01/2018 09:29:03

A little like ugle duck - beautifull swan:

wing tip crumbled.jpg

wing tip crimped.jpg

Upper wing done:

upper wing covered.jpg

Now I cannot postpone glassing the fuse anymore ...

Cheers, Lucas

Thread: Timís Grumpy Tigercub
16/01/2018 12:12:27

Hi Peter,

It might be a combination of more people growing up with no experience of using their on anything else then touchscreens (and maybe a game console or 2 - this makes great drone pilots) and that it is so much easier to get help compared to 20-30 years ago.

I have quite a few colleagues who have as primary reflex when something needs to be done "who do I call" instead of "what/how can I do this". In that light it is positive your man does at least not assume somebody else is going to fix it for him.

Point him to a Youtube video on soldering or to the RCM&E tutorial on the subject and he will be happy.

Regards, Lucas (who probably also has asked you a trivial question or two...)

Thread: Gentle Curves - Lucas his Skywriter
16/01/2018 07:51:05

Progress again. Wings always cover quickly, but it remains difficult not to get dustparticles under the covering. I found that if I use a tack rag just before covering a section it usually goes ok.

lowing wing started covering.jpg

lower wing covered.jpg

Cheers, Lucas

Thread: Kwik Fli 40
12/01/2018 07:06:51

Trevor, the wing profile is symmetrical but the plane is not. The center of drag is slightly under the centre of gravity, so therefore rolls may get more axial with some differential in place. And for some reason I do not understand som F3A planes do best with reverse differential (more down than up).

More down elevator than up is normal if you trim for hands of horizontal flight and a sligth pressure on the stick for horizontal inverted flight, as most pilot do. Easy to find out: the diameter of loops with full up and full down should be the same.

It is not needed if you trim so that you have to pull all the time for upright flight and push for inverted. This is what most full size aerobatic pilots do; it make the knife edge straighter. But I find a model that dives with the sticks at neutral most unnerving to fly....

Regards, Lucas


Edited By Lucas Hofman on 12/01/2018 07:07:32

Thread: Gentle Curves - Lucas his Skywriter
12/01/2018 06:55:41

At last things are moving:

tail surfaces covered.jpg

10/01/2018 07:03:19

Must be the slowest build ever, but at least the stab is covered (and the slits for the hinges opened up, using the still uncovered elevators. I once forgot to mark these before all was covered, and had a hard time locating them again)

stab covered.jpg

Covering always takes me some time getting back in to, and then it goes quite fast.


Thread: Timís Grumpy Tigercub
10/01/2018 06:31:19

Posted by Tim Ballinger on 09/01/2018 16:34:17:

Moved on to adding the 1/8 balsa in 4 inch widths. Thank heaven for cyno, this would take forever with normal glues.

I do non fancy cyano (brittle joints, glue often wicks away from the joint, leaving a weak joint). Could this be done with contact glue (like we do doublers on fuselage sides)?

Regards, Lucas

Thread: Gentle Curves - Lucas his Skywriter
09/01/2018 11:20:37

I have never done this too. Besides doing laminations this is "the new technique" to learn for this build.


09/01/2018 07:01:57

At last the hatches are completed and all is sanded. Surfaces to be covered with film sanded down to 400 grade. Next are glassing/painting and covering. I am longing for a clean job so out with the vacuum cleaner (both model and bench).

Thereafter away with the dusty clothes; a new piece of foam on board and a new razor blade for cutting the film. I use a tack-rag just before covering to avoid humps in the covering due to dust particles getting trapped.

Starting with the tail surfaces, they are easiest:

starting to cover.jpg

Cheers, Lucas

Thread: Grumpy Tiger Cub by John.
06/01/2018 21:57:56

Hurray for build up tail surfaces!


Thread: Gentle Curves - Lucas his Skywriter
05/01/2018 09:14:30

Same here, Lucas (

ps Correction fluid, that is the stuff we used when printers still had keys and hammers wann't it, some 40 odd years ago? Can you still get it?

05/01/2018 07:22:26

A lot of fiddling with the hatches. My method for getting the magnets aligned with the screws under. It is not so critical as when using two magnets, where a misalignment may result in the hatch pushed off by the magnet:

front hatch - getting magnets in place.jpg

a drop of (water based) paint on each magnet, push the hatch in place and one has circles where the wood need to be removed to sink the magnets in.


Thread: Timís Grumpy Tigercub
05/01/2018 07:16:12

Might be looking even better if the sides/bottom were not straight lines. Would it be an idea to have an outer layer of soft balsa so you can sand a slight curve in them (lengthwise)?


01/01/2018 10:51:51

And plans for the colourscheme Tim?

Regards, Lucas

Thread: Gentle Curves - Lucas his Skywriter
29/12/2017 08:42:35

​Fitting the outer Struts. I make 2 triangular plates first to check whether the upper wing would be OK. That looked good so the final struts parts can be made. Decided to have a slightly different design, where the plates from top to bottom wing are not interupted. It will not win a price in a scale contest, but simple it is:

struts in place.jpg

Thread: Timís Grumpy Tigercub
27/12/2017 12:01:31

And a few vices. Take care with the throttle, or restrain the model. I ended up at the hospital when doing this with my first electric plane. Tested the fail-safe, which was incorrectly set to half throttle. The model swiftly travelled the 40 cm to my body and broke its propeller on the bones in my hand.

cutted up hand.jpg

Nowadays I check rotation direction without a prop on the motor....

Cheers Lucas

Edited By Lucas Hofman on 27/12/2017 12:01:57

Thread: Gentle Curves - Lucas his Skywriter
26/12/2017 09:46:55

onAnd some progress. Now the lower struts fixing plate is in water again the inner struts went fine. A litte filing to correct hole being half a millimeter off centre and the place was square.

fitting and adjusting the inner struts.jpg

After the lugs in the upper wing were adjusted for length the upper wing is also on zero incidence.

both wing on 0 incidence.jpg

Edited By Lucas Hofman on 26/12/2017 09:48:25

26/12/2017 09:42:51

The cullprit is the changed airfoil. Mine is NACA 3414 ("Miller standard" versus Lindsay's 12%. If one keeps the trailing edge in place and sands the wing saddle until the lower wing lies flat on the table one gets a significant incidence. I should have kept the leading edge aligned with the bottom of the fuse.

Fixed by lifting the trailing edge and sanding out the dower hole as far down as it can go. Now the lower wing is at 0-0.2 degrees with regard to the stab. Half a days work but on track again.


23/12/2017 21:54:11

Oh the joy of changing a design! Just found out that, with the stab at 0 degrees, the lower wing is at +2.5 degrees. There goes my "perfect" wing saddle....

22/12/2017 22:42:43

Wondering how to get the upper wing fixed correctly. Many ways it can be wrong. By the way, what should the incidence of the lower versus the upper wing be? From Lyndays blog I get the impression it is 0, this means that due to the upwash of the lowet and rhe downwash of the upper wing the aerodynamical Angle og attack is not alike. The upper wing is working harder and will stall first.

What do you all think?


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