Author Topic: Dreidecker zur See!  (Read 8263 times)

Offline Alexis

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Re: Dreidecker zur see!
« Reply #15 on: January 18, 2022, 04:05:57 AM »
What looks off to me is the front tips on the floats are dipped down to much . Set the angle of that higher , Shorten the struts by 3.5 mm . And perhaps the tail plane for the F.1 with the curved leading edge . I take it this is 48 scale ?

Okay , I'm no engineer , not even good at math to be honest but at mark one eye  ;)


Alexis
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Offline Brad Cancian

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Re: Dreidecker zur See!
« Reply #16 on: January 18, 2022, 07:18:06 AM »
Hi all,

Many thanks for the great inputs re the struts and floats (thanks also Frank for correcting my poor German – I have now capitalised the “S” in “see”). Hi Alexis - indeed this is 1/48 scale :)

I actually am an aeronautical engineer by training so I am slightly embarrassed that I perhaps didn’t think it through as much as I should have; I went more for looks than actual practicality! To be honest, I was thinking more so the way in which the Albatros set up the struts on the W4, which are long and fairly straight up and down:



That being said, that was a larger and heavier aircraft. In thinking this one through, the comments make sense regards the relationship between the engine thrust line, the centre of gravity of the aircraft, and distance to the floats (both the float centre line and centre of gravity). A bigger gap between the thrust line and the floats horizontally, and a smaller gap between the aircraft centre of gravity relative to the float centre of gravity, will indeed create a bigger rotational moment forward. The way to deal with this is to lower that gap and push the centre of gravity of the floats forward, the combination of which counters the forward rotation of the aircraft as more thrust is applied. This, in turn, necessitates the floats being angled upwards more to avoid ‘digging in’ to the water.

The Hanriot HD2 is an example of how this engineering has occurred:



The HD2 has a squat, low set and low distance between the fuselage and floats, some forward angling of the struts, and upwards angle on the floats. The squatness of this design means that these angles and relative positions of floats to fuselage don’t have to be too extreme, but they are there.

This kind of squat look would, I think, not suit the triplane aesthetically – she’s a tall aircraft so I think there’s a balance, looks wise. So somewhere in here I want to apply the adage of “if it looks right, it’ll fly right”. Accordingly, I have shortened the struts up a little, angled them further forward, and raised the incidence (angle) of the floats. I do agree this is a better look that accords a little more with some of the aforementioned engineering principles whilst still maintaining an aesthetic ‘balance’. Here it is compared with the first attempt:



Unfortunately the modified angles means that the aircraft doesn’t sit nicely all by itself on the struts, so I need to prop it up a little for the pictures, but you get the idea.



Thoughts? I may have overdone it a little, but I can still make tweaks.

Cheers,

BC

Offline kensar

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Re: Dreidecker zur See!
« Reply #17 on: January 18, 2022, 07:57:24 AM »
I think your last mod is the best, but what doesn't help the looks is the floats are too pointed at the front.  Modifying them may be more effort than you want to make.

Best of luck with this.  It's a good 'what if' project.

Offline RAGIII

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Re: Dreidecker zur See!
« Reply #18 on: January 18, 2022, 01:20:07 PM »
I absolutely love this one Brad!
RAGIII
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Offline bobs_buckles

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Re: Dreidecker zur See!
« Reply #19 on: January 18, 2022, 08:21:14 PM »
What ever you decide I'm invested!
Good luck Brad!

Bob  ;)



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Offline PrzemoL

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Re: Dreidecker zur See!
« Reply #20 on: January 18, 2022, 10:42:23 PM »
Brad, I think that you should rather tend to copy the layout of  Hanriot mechanics-wise, rather than taking care for aesthetics - HD is quite similar in weight, engine type and general layout to Dr.I (with exclusion of zwei  vs. drei-decker). Looking at HD I see that the potential location of the loaded plane gravity centre (somewhere between the engine and the pilot) projected vertically to the floats plane falls between the strut mounting points to the floats. In your last proposal, to my eyes the Dr.I gravity centre projects backwards, beyond the rear mount point - this would lead to extra moments applied to the struts-plane connection - in my opinion it would not work. And it does not look right to my sight - it will not fly right.  ;) Maybe you could incline the rear struts to the rear, as on Alb W.4.
« Last Edit: January 18, 2022, 10:50:45 PM by PrzemoL »
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Offline Brad Cancian

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Re: Dreidecker zur See!
« Reply #21 on: January 19, 2022, 06:30:49 PM »
Hi Prez - many thanks, I certainly respect your opinion on this one!

I have continued to play, but am pretty much going to stop soon as I simply want to make a little more progress. I have decided on a twin row Oberursal UR.III, so that'll move the Centre of Gravity forward a bit more. I also butchered the struts down a little further, undid some of the forward sweep, and angled the floats down slightly more. I think i'll round off the leading point of the floats a little in any case. I can't really muck with the attachment points due to the float config. Here's where she sits now (and probably where i'll leave it. Apologies for my poor photoshopping of the cowling for the UR.III):



You can see the modifications here; lower, tweaked CofG, and what the cowling will probably look like with the twin row UR.III, etc.



Heck, if it still doesn't look right, let's just call it one of Fokker's 'unsuccessful' experiments  ;D



Cheers,

BC
« Last Edit: January 19, 2022, 06:35:20 PM by Brad Cancian »

Offline PrzemoL

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Re: Dreidecker zur See!
« Reply #22 on: January 19, 2022, 06:34:29 PM »
Brad, the current version looks spot-on to my eyes. I do not see that problem with gravity centre anymore. Go for it - it looks right, it will (would) fly right ;)
Ash nazg durbatuluk, ash nazg gimbatul,
Ash nazg thrakatuluk, agh burzum-ishi krimpatul.

Offline Brad Cancian

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Re: Dreidecker zur See!
« Reply #23 on: January 19, 2022, 06:36:37 PM »
Brad, the current version looks spot-on to my eyes. I do not see that problem with gravity centre anymore. Go for it - it looks right, it will (would) fly right ;)

Thank you my friend! I shall stop my worrying and get on with the project ;)

Cheers,

BC

Offline Stuart Malone

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Re: Dreidecker zur See!
« Reply #24 on: January 20, 2022, 12:41:09 AM »
Brad,

I have been following along and absolutely love it.  Then again, I have a penchant for float planes.

Stuart

Offline KiwiZac

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Re: Dreidecker zur See!
« Reply #25 on: January 20, 2022, 01:26:04 AM »
That's it! That's the configuration I was thinking of, bravo Brad! She looks Awesome (note the capital A for true Awesomeness).
Zac in NZ

Offline hrcoleman66

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Re: Dreidecker zur See!
« Reply #26 on: January 20, 2022, 08:37:03 AM »
Hi Brad

Interesting project.

Reading through the discussion on the COG and Thrust lines etc etc, I'm reminded of discussions I had with colleagues when looking at building flying models of float planes.  My memory is a bit foggy about it now, but I seem to recall there was a necessity for negative angle of attack on the floats simply to allow them to unstick from the water on take off.  Obviously the floats need to be situated in such a way as to not prejudice the air-frames COG and Center of Lift.  But the angle of attack of the floats is just as important from the point of view of how they behave IN/ON THE WATER. 

I was building a Supermarine S6B in 1/6 scale at the time and was surprised at just how much the floats appeared to be pointing DOWN.  I was also VERY concerned about how heavy the floats would end up being and how the weight of them would affect the model in turns.  Another friend had built the same model years before, and although it got off the water fine, it stalled on the first turn and was a complete loss.

Your "Further Amendment" above "Looks" right.

Cheers,

Hugh
« Last Edit: January 20, 2022, 08:56:30 AM by hrcoleman66 »

Offline Brad Cancian

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Re: Dreidecker zur See!
« Reply #27 on: January 26, 2022, 06:02:24 PM »
Not a particularly exciting update, but the 'big pieces' are getting close to coming to fruition.

I've now cleaned up the floats (well, mostly... still some spots to fix). This involved quite a bit of filling and sanding, and ultimately re-skinning of the top surface of the floats (long story, but whisky helped). I still need to add the 'ribs' and hatch(?) things that seem to pervade the tops of the floats on German float planes, but I'm yet to work out exactly what pattern i'll do for that. Any thoughts or suggestions?

I've also extended the kit cowl using heat-bent sheet styrene to accommodate the Oberursal U.III 160hp twin row rotary engine. I kept the front face of the cowling 'as is', to keep that distinct Fokker look, but tapered it back to still meet the fuselage underside at the right point. I also started construction of the engine itself, mainly to see if it would fit nicely within the cowl. The engine is from Small Stuff and so far it looks like it will look very nice when done. I've only glued the 14 cylinders to the crank case, but only after drilliing right through the middle of the crank case to allow the whole thing to be slid onto a brass tube. I did this to help with alignment; but I also mounted the engine on a single tube as i'd like it to still be able to rotate when all finished. Thankfully, it looks like it should all fit without any clearance problems:




So here she roughly takes her 'final form':




Next is finishing the last few blemishes on the floats, and adding the details to the top surface, once I work out what that will look like. Then, I think I can get properly started!  ;D

Cheers,

BC
« Last Edit: January 26, 2022, 06:29:22 PM by Brad Cancian »

Offline PrzemoL

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Re: Dreidecker zur See!
« Reply #28 on: January 26, 2022, 06:25:26 PM »
Very fine touches! It is always so in the modelling, perhaps not only, that the less attractive and most tedious tasks decide the final look. Great you are now passing over these - the final result will be the award, I am sure.
Ash nazg durbatuluk, ash nazg gimbatul,
Ash nazg thrakatuluk, agh burzum-ishi krimpatul.

Offline DaddyO

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Re: Dreidecker zur See!
« Reply #29 on: January 26, 2022, 08:49:09 PM »
Love how this one has developed and really enjoyed the progress so far.

Next and obvious question will be the colour scheme - naval lozenges anyone?

Paul
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