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Author Topic: My first F1D  (Read 5493 times)
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Skymon
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« Reply #50 on: July 03, 2018, 06:44:37 AM »

I made a small stub to join the boom to the motor stick.
Built up on a little former with dimensions based on the internal wall diameters of the boom and stick minus the wood thickness.
It works, although I would use at least two slits in the tapered end next time as just one seems to give an uneven taper.
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Skymon
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« Reply #51 on: July 18, 2018, 05:29:36 AM »

Work on the motor stick continues. I added the metalwork. For some reason I opted for the torture of a wire nose bearing. I completely forgot I have four Harlan bearings in my box, ordered for exactly such an occasion. By the time I’d remembered I had got this far.
I am an absolute expert at wire pigtail bearings. It can take me as few as fifteen tries to get a good one. I end up encased in a pile of discarded guitar strings, my local music shop must thing I am a thrash metal lead guitar soloist with a very busy gig schedule…
Despite being difficult, I do enjoy a bit of metal bending.
I made up the rear hook and front bearing and got ready to add them to the webbing for insertion in the motor stick.
I used motor stick thickness wood and full strength cement. I have just built an F1R, so I stuck my rear hook in the end of the motor stick and the front bearing in the front. All fixed in pretty solid and neat.
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Skymon
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« Reply #52 on: July 18, 2018, 05:30:44 AM »

It was at this point that I glanced back at the plan to see that the rear hook isn’t at the end, it’s 30mm down it.
Oh.
Lesson learnt again, keep an eye on the plan if you want to know what you should actually be doing.
I soaked the webbing out for the rear hook and cut a slot in the motorstick where it should be.
I built in a little web as part of the webbing and added tissue over the top. I went ornate on the top fixing for the bracing wire, this will probably be trimmed to a hook rather than a loop later. Let’s see what my weight ends up at first.
The front end could possibly have done with the integral web as well, but as this was constructed in one of my build ‘sprints’ where I even forgot to look at the plan, I didn’t do it.
I will add a web at some point, possibly from something a little harder than balsa.
I added a bracing post at the point mentioned on the plan, the plan shows it canted over, so I canted it over.
I’m guessing this means the motor stick will be subject to a little twist under tension. I have no idea what that will do. I’ll build up the spare stick with the bracing post vertical, see if that makes a difference.
I took the boom off of the former and it has a curve to it. I painted a thin line of cement along the boom on the opposite side to the curve to see if that would ‘shrink’ the balsa against the curve and it helped. The curve was about 3mm along the 500mm length and mostly in the last third. Not exactly spaghetti.
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Skymon
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« Reply #53 on: July 18, 2018, 05:41:12 AM »

Next up are the wingposts. I opted for square section as I needed to gather a bit of experience putting boron on to such vital parts.
I’m still not keen on just sticking wire on to wood.
The use of dissimilar materials seems high risk of failure.
Sticking to a curved surface compounds this risk.
I went square. Probably another error, but onwards and hopefully upwards. Making square tubes is gonna be a pain.
Next up – fitting the wingposts so they are upright and square… Jig building required.
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Skymon
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« Reply #54 on: July 25, 2018, 03:51:20 AM »

Wingposts fitted.
I opened a hole in the marked area with a pin, then used a new number 11 scalpel blade to square it off and open it out.
No real issues with fitting these apart from lining them up in all directions and then working through the lower skin without popping the seam or ending up with a volcano effect.
Once fitted and liberally fixed with thinned adhesive I sanded the lower part level.
Maybe this was a mistake, but I like the clean look.
Front post here shows pre-sanding condition.
Next task is to seal the front end off and add a web to the prop shaft bearing wire.
Right now my stick is 2mg underweight according to the plan I'm 'following'.
That'll be used up on the web and cap no doubt.

After capping and webbing I'll add some bracing wire.

Si
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Skymon
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« Reply #55 on: July 26, 2018, 06:19:41 AM »

Starting to gather info and materials for making a prop.
Despite my pathological fear of sticking wire to wood, I am going to attempt a boron reinforced outline.
I have a nice doc from Tony Hebb that details the method.

Here are my materials:
A carved prop form made from a balsa block and Bob Baileys neat spread sheet that spins the form axially to reduce wood removal.
Some wood from Nick Aikman for outline and spars.
Some boron kindly donated to me by my friendly local indoor free flighter, Ian.
and a bunch of shapes ruthlessly culled from various plans.

Next steps are tapering the wood.

Si
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Skymon
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« Reply #56 on: July 27, 2018, 06:23:59 AM »

The method for making boron re-inforced prop outlines is well documented, I’ll not repeat it all here. What I will do is detail the issues I had and the areas where I went wrong.
First issue was deciding whether to go around the tip with the metal or not. Both have pros and cons.
Wrapping around the tip means one piece of boron and no exposed ends to ping off. But it also means the boron is constantly in tension, meaning it’s more likely to ping off.
I went for two bits in the end, mainly because of the fear of bending boron and the nagging doubt of making a propeller blade featuring a permanently spring loaded construction.

Step one was to measure the outlines and cut them from the wood.
I cut in the appropriate taper as recommended, from 045 to 022. Nice straight edge and new razor blade and I have two sets done.

Now to join them using a scarf joint.
I have a dislike for joining materials, ideally the whole outline will be one piece.
It is quite tricky to make that single piece with this type of taper. Effectively double butting the ends.
This particular scarf joint is also at the point of highest stress at the tightest radius point on the outline.
I was also concerned about the longevity of a joint right at the end where it is most likely to suffer impact.
Only one thing eased my mind somewhat and that as the addition of some Kevlar tow around the end.
This could add a bit of durability to the section.
It’ll also add mass at the longest moment arm available, which will add a tiny bit of flywheel effect that may smooth the rotation somewhat.
hopefully.

I finished off my templates and there was no going back.
I soaked the outlines for ten minutes in hot water, I added my bandaids to the former and I got ready to bend my outlines.
They both snapped in the middle on first contact with the former. The scarf joints both failed.

I went back to the table and tried to understand the failure.
Maybe I was too quick to soak? I decided to rejoin the parts and leave for a day before having another go.
I wondered if I had enough area for my scarf joints, so I recut at a more acute angle and then re-bonded the joints.
I left them over night to set and I will have another go tomorrow.

S
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cvasecuk
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« Reply #57 on: July 27, 2018, 06:49:11 AM »

The angle for a scarf joint should be at least 1:8, yours is about 1:2!!!!!
Ron
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Skymon
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« Reply #58 on: July 27, 2018, 07:37:30 AM »

Ron
You're dead right. I don't think I got to 1:8, but I did get flatter on the second go.
I'll keep going and maybe try even longer if this one breaks again.

S
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Skymon
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« Reply #59 on: July 30, 2018, 08:00:08 AM »

Here's my prop block ready to be marked up.
Got to soak the form on it over night and then spray mount it down for the addition of ribs to the outline.
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mkirda
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« Reply #60 on: August 02, 2018, 07:56:08 PM »

Go with a fin. It's much easier to build a good fin and flat stab than a stab with tip plates. Most importantly, you can easily change the fin angle if needed. I use 1-2 degrees.

For wing posts, I suggest wood and boron. square cross section. wing end rounded for the wing tubes. stick end rounded for easier construction.

1mm carbon is not stiff enough if the post is longer than 2".

1mm wing posts are way large. 0.026" pultruded carbon tube is what I use.

Works great.
I use shorter ones than most for weight savings.

Regards.
Mike Kirda
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Skymon
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« Reply #61 on: August 03, 2018, 02:48:21 AM »

MIke
Is that sanded down from 1mm, or straight forward 0.7mm tube?
S
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mkirda
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« Reply #62 on: August 03, 2018, 07:30:14 AM »

Just straight tube I sanded.
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« Reply #63 on: August 03, 2018, 06:40:19 PM »

Simon,

I think you're following Ivan's plan from Slanic 2017. That model has 80 mm wing posts. I would not shorten the wing posts. At that length, I would not use the .7mm tube. A number of us have experienced this. For comparison, Ivan uses a 1mm tube, molded himself for weight savings, and substantially stiffer than 0.7 mm.
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Skymon
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« Reply #64 on: August 06, 2018, 02:48:21 AM »

My posts are in post 53. They are balsa and boron. I went for the same length.
I read the detail for the 1mm carbon posts and assumed it was something strange, so went for traditional balsa.
The only detail on the posts is HM, which I guess means high modulus.
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Skymon
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« Reply #65 on: October 03, 2018, 05:27:44 AM »

At last an update.
I've had a few distractions including the UK Nationals and fitting a kitchen.

My pace has been sedate to say the least!
Prop bones are now built.
I had no major disasters on the way, it's all straight forward, if a little fiddly.
I added an outline form to the prop block and then pinned the outline around it using soft balsa blocks to hold it down.
Then wetted and dried it a couple of times. Added the spar and ribs and then all of the boron around the outline.
I used a tiny length of carbon tow on the outer section instead of Kevlar.
I'm not that happy with the tips, they look a little lumpy, I can see why people use a sharp corner out there, with a join.
It avoids the horrid scarf joint and looks a lot neater. I think that'll be my next plan.
I am going to be covering these this week.
After that I am halting construction of the plane to concentrate on the storage box.
That way I can store anything I make rather than let it hang about the house and get damaged.

Thanks for sticking with me on my plod of a journey Smiley

Prop spars are different lengths, then need a trim.

S
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Skymon
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« Reply #66 on: November 13, 2018, 04:12:52 AM »

I’ve started on the flying surfaces.
Wing is first. I cut the spars to the dimensions detail on the Treger plan.
I used a glass sealed unit that I had lying about to build the centre section on.
The wing was built in the standard way with boron added to the top and bottom of the main spars.

The outer ribs are fixed with white glue to allow me to drop the tips by melting the Duco later.
The plan says to add boron to the outer ribs, so I did.
Tips were soaked in hot water and then hot formed about a tip former.
They were added after the main section corner extensions were trimmed back to about 3mm.

This is what my F1D looks like so far.
I’ve got some covering to do after the stab get built.
I am running out of boron and film. Time to order some more bits…
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Skymon
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« Reply #67 on: December 04, 2018, 08:22:35 AM »

Yes, I am still slowly progressing...

I've made up and covered the stab.
Learnt a bunch of things doing this part.
I will have to make another to employ those lessons.

I am flying tonight, probably F1N, but I hope to get an hour before hand to add the covering to my wing...

Wish me luck, I've already tried once :~(

In other news; I hope to finish my kitchen this weekend and get back to serious hobbying.
If only those Christmas decorations would put themselves up

Best regards
Si
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