Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: simple airboat plans  (Read 5875 times)

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
simple airboat plans
« on: June 21, 2009, 10:47:48 PM »

I have been playing around with a design for a simple and fun airboat. The pics show one that is quick, cheap and easy to build. It performs well and gets lots of sideways action in the turns!

Great fun on the water, and after its first outing, 2 other club members asked for the plans to build one.

So, here they are, along with the spec I used.

AIRBOAT
Sides,   nose, transom and rudder from 5mm balsa.
Deck and bottom from 3mm balsa lain crosswise with internal doublers across the joints.
Transom and nose reinforced internally with thin ply.
Motor mount from 6mm aluminium channel, through deck with supports to suit under the deck.
Motor: 1100kv, 3536 brushless motor and 25a esc  from:  http://www.giantcod.co.uk/index.php
Prop: 9x5
Battery: 8 cell Nimh
Standard servo.
Weight should be distributed so that the c of g is approx 1/3 forward from the transom.


Ian
Logged
if at first you dont succeed.....have a beer.....

OMK

  • Guest
Re: simple airboat plans
« Reply #1 on: June 22, 2009, 06:53:48 AM »

Excellent stuff! British ingenuity at its best. Nice detail and all.

Cheers!


By the by,
I don't suppose I could trouble you for a close-up of the top of the rudder? Specifically, is there some sort of anchor point at the top?
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: simple airboat plans
« Reply #2 on: June 22, 2009, 07:25:07 AM »

There is no support at the top of the rudder, I fitted one on an earlier prototype but found it unnecessary and added extra weight with the support structure. The bottom rudder tube is the full depth of the hull, from top of deck to internal top of bilge, seems to be ok.

Ian

PS. If you fix the battery down with velcro, it allows you to adjust for best weight distribution. Also forgot to mention the torque reaction from the motor and prop requires the battery to be slightly to one side so the boat is level at speed, which side depends on direction of rotation of the prop.
Logged
if at first you dont succeed.....have a beer.....

OMK

  • Guest
Re: simple airboat plans
« Reply #3 on: June 22, 2009, 07:54:52 AM »

"The bottom rudder tube is the full depth of the hull..."

Yep - I'm hearing you. Thanks.
Although, I'm not 100% clear about the steering linkage. Is that a bog-standard servo horn, somehow attached to the rudder post?

Regarding the unwanted torque, is it not possible to add in a bit of sidethrust on the motor mount itself? Not trying to sound like a know-all, but just wondering aloud if the same dodge would apply to boats as it does to planes. You say that it's more noticable at high speed. How bad is it when you're not going flat out?

Thanks, man. Hope you don't mind my bugging you with all these Qs.
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: simple airboat plans
« Reply #4 on: June 22, 2009, 08:33:22 AM »

That is standard servo horn on the servo, the arm on the rudder post is a pin from a 13a plug, they are connected by a length of bent wire out of the scrap box!

Yes the torque could be 'dialled out' with a bit of sidethrust - maybe a little fiddly but possible - my design aim was simplicity!

How bad is the unwanted torque when not going flat out? Not so bad, but you need plenty of revs to make the thing steerable! However, I ran flat out all the time so low speed wasnt an issue :}

Ian
Logged
if at first you dont succeed.....have a beer.....

OMK

  • Guest
Re: simple airboat plans
« Reply #5 on: June 22, 2009, 09:15:42 AM »

"...my design aim was simplicity!"

Absolutely. That's why I love the thing.
Anyways, you've given me plenty of food for thought. I can't help wondering if it's somehow possible to make the motor itself steerable, illiminating the rudder.
Obviously waaay ahead of myself, so I'll have a stab at your tried-and-trusted plan first.

Thanks a ton for the idea.
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: simple airboat plans
« Reply #6 on: June 23, 2009, 10:50:49 AM »

As an afterthought, after running mine its now clear it needs two bottom stiffeners. I suggest 5mm balsa, 10mm thick, glued 5mm edge to bottom bow to stern equally spaced crosswise.

Ian
Logged
if at first you dont succeed.....have a beer.....

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,721
  • Location: South Cumbria
Re: simple airboat plans
« Reply #7 on: June 23, 2009, 05:47:43 PM »

Sorry fellas, found a small error in the plan dimensions, this one is correct.

Mr mod, could you please replace the first one with this?

Ian
Logged
if at first you dont succeed.....have a beer.....
Pages: [1]   Go Up