2018 Flite Test Forum Challenge: WWII Design & Build

[PsyBorg]

More like this

 

[SlingShot]

Strictly speaking, you just need some compressed air or CO2 to displace the water in the tank. To flood you just vent to the sea.

 

[PsyBorg]

Back when I was thinking about building a sub I learned you HAVE to power suck water to fill the ballast. Just venting takes far too long and there is no place to vent the air out of the tank to. If you vent it into the sub you just change where the buoyancy resides. The shaft drive turkey baser method (can use reservoirs for PC liquid cooling as well) is the most effective way to do it and the mechanicals add the weight in the lower part of the sub to help keep it upright on the surface as well as aid in getting it under water.

 

[Hai-Lee]

Whilst the suggestions or solutions to ballast pumping are interesting the simple truth of the matter is that the plane must weigh more than the water it displaces or it simply will not be able to submerge. Additionally whilst the displacement of the FB itself is one issue the displacement of the electronics compartment will also need to be allowed for.

Allowing the wings, Etc, to fill with water when submerging will mean some delay in surfacing as well because the water will need to drain before surfacing will be possible. Trapped water will cause severe balance problems and increase take off weight unnecessarily.

For those wishing to persue it I would suggest a source of compressed gas, (such as the CO2 cylinders used in a soda siphon). Given a strong enough structure the gas could expel water from ballast tanks without the need for heavy pumps and their battery supply.

Would be a nice candidate for an all CF structure covered with thin AL, (old drink cans).

Just a few thoughts!

Have fun!

 

[Sir Fly]

Lol I love how that one picture essentially hijacked this thread! XD

 

[Fluburtur]

Well finding easy solutions to complicated problems (or the opposite) is fun.
I spend a lot of time on the kerbal space program IRC channel and the guys there often spend hours calculating legit solutions to nonexistent problems like powering a rocket with candy or whatever, that's where the fun is!

 

[Sir Fly]

Well finding easy solutions to complicated problems (or the opposite) is fun.
I spend a lot of time on the kerbal space program IRC channel and the guys there often spend hours calculating legit solutions to nonexistent problems like powering a rocket with candy or whatever, that's where the fun is!

Oh no don't get me wrong: this is awesome! So many great minds and designers here debating and bringing up ideas I never thought of.

 

[ItMightFly]

Team "Zero" with ItMightFly, and my Dad
Build: J7W1 "Shindin"
Thread: http://forum.flitetest.com/showthread.php?36756-FTFC-18-WWII-J7W1-designed-by-ItMightFly

 

[Fluburtur]

Woooo, familly project and a cool plane!

 

[ItMightFly]

Woooo, familly project and a cool plane!

Yeah! Should be a fun build!

 

[rockyboy]

Team "Zero" with ItMightFly, and my Dad
Build: J7W1 "Shindin"
Thread: http://forum.flitetest.com/showthread.php?36756-FTFC-18-WWII-J7W1-designed-by-ItMightFly

Welcome aboard! :applause:

 

[FoamyDM]

Thinking about the plane-sub too much.

So really, we need to look at the plane volume, weight and displaced.

Using my SAM-7 as an example
52si x 0.25in H avg (Wings) (213ccm) + 21.6 , 2.55in H (Fuselage) (902ccm)= 68.08 in^3 or 1,115 cm^3.

This means it displaces 1,115 Grams of Water
Which means to be bouyant it must Be able to hold 929g (1115g - 186g) or a holding volume of 929 cm^3

Considering the Fuselage Empty skin volume is 902cm^3, The SAM-7 couldn't sink. Really. (Neat).

I'm sure the answer lies in two things, having a larger wing volume and a heavier wing loading. Anyway, Those are my musings for today.

 

[Hai-Lee]

Thinking about the plane-sub too much.

So really, we need to look at the plane volume, weight and displaced.

Using my SAM-7 as an example
52si x 0.25in H avg (Wings) (213ccm) + 21.6 , 2.55in H (Fuselage) (902ccm)= 68.08 in^3 or 1,115 cm^3.

This means it displaces 1,115 Grams of Water
Which means to be bouyant it must Be able to hold 929g (1115g - 186g) or a holding volume of 929 cm^3

Considering the Fuselage Empty skin volume is 902cm^3, The SAM-7 couldn't sink. Really. (Neat).

I'm sure the answer lies in two things, having a larger wing volume and a heavier wing loading. Anyway, Those are my musings for today.

When you add a waterproof compartment for the electrics the buoyancy issue compounds.

Additionally there is the matter of the radio control! Most modern RC systems use 2.4GHz which is unique in its properties. Water absorbs it! That is why most microwave ovens use a 2.4GHz magnetron as the cooking energy source. So if you submerged too far and the antenna became submerged you would need to go diving to recover the model!

Just a few additional thoughts!

Have fun!

 

[SlingShot]

Thinking about the plane-sub too much.

So really, we need to look at the plane volume, weight and displaced.

Using my SAM-7 as an example
52si x 0.25in H avg (Wings) (213ccm) + 21.6 , 2.55in H (Fuselage) (902ccm)= 68.08 in^3 or 1,115 cm^3.

This means it displaces 1,115 Grams of Water
Which means to be bouyant it must Be able to hold 929g (1115g - 186g) or a holding volume of 929 cm^3

Considering the Fuselage Empty skin volume is 902cm^3, The SAM-7 couldn't sink. Really. (Neat).

I'm sure the answer lies in two things, having a larger wing volume and a heavier wing loading. Anyway, Those are my musings for today.

You could cheat. With a jettisonable lead weight you could get it to submerge. After you blow ballast, jettison the weight and fly.

 

[Hai-Lee]

You could cheat. With a jettisonable lead weight you could get it to submerge. After you blow ballast, jettison the weight and fly.

You are correct but the idea of landing on the water submerging and then surfacing and taking off would still be impossible if made out of FB. The problem is not the weight or the size of any model but rather the buoyancy of the FB material. Additionally before the submerge the plane would taxi very low in the water, (possible prop strikes), and upon surfacing, (dropping the additional ballast), it would sit on top of the water like a cork!

This plane would be better rendered in a material that is denser than water and so able to sink! Perhaps a good project for the 3D printer fraternity!

Have fun!

 

[foamtest]

For those looking for other Russian/Soviet X-planes, look through this book here for ideas!
soviet-x-planes

It's where nearly all the pictures I've seen around have com from, Hope it helps someone

First off thanks for the source! I would love to get into this contest but I simply don't think i have the CAD skills or the time required fro such a build. And for those who are looking to enter this, here are some of my personal favorites from the Soviet X-Planes.
Alekseyev-218

Belyayev Babochka

Belyayev DB-LK

Bolkhovitinov S


Please note, I have not actually checked the eligibility of these aircraft, I just found them from the source in the quote.
I also hope this helps inspire anyone who wants to join the build off!

 

[MrFowl]

The Belyayev Babochka was a close second to my choice. Those wings would look fantastic in the air I think.

 

[willsonman]

Belyayev DB-LK... Looks like the Pond Racer.

 

[FoamyDM]

It sure does! Does that mean you're in? with that one too MrFowl? you can do more than one - I'm living proof.

@Foamtest - Glad you found it useful.

Here's a link to a German Plane archive mostly on flying wing experiments. I'm trying to use this to figure out the Sam-7.
http://www.nurflugel.com/Nurflugel/Lippisch_Nurflugels/lippisch_nurflugels.html

 

[willsonman]

Check Post #2