Designing My First Airboat Need Advice and Pointers
 

I've been reading posts on this site for a while and have finally signed up and decided to throw my design out here. I've posted a picture of my computer model so far and I need your opinions on whether or not this model is feasible to build. I will continually post updates as I change the model but Ineed to know a few things first.

1. Is this model reasonable? can it be built?
2. Total length is 24" and width is 9", is a size 40 engine adequate?
3. How much room should Ileave on the engine stand for the fuel tank? (the engine stand is 7 inches tall to allow for even the largest size prop)

If this post generates some attention I will post a 3d pdf file on rapidshare that anyone with adobe reader will be able to view

RE: Designing My First Airboat Need Advice and Pointers
 

That hull looks reasonable and should be easy to build. The .40 engine would be a little bit heavy for that size hull. A .25 engine would be a better match for that hull.
As for the engine stand build it to suit your engine. You can put the fuel tank under the engine stand.
A .40 would swing a 10 inch prop so I would make the engine stand about 6" off the deck.
What material are you going to use? Ply or balsa. What type of rudder are you going to use , a water or an air rudder?

RE: Designing My First Airboat Need Advice and Pointers
 

I plan on using air rudders, however after sitting on this model for awhile I am concerned that it will drive more like a traditional boat than the slip n slide feel that Iwould like from an airboat. I want the final project to be like an "airboat" not a regular boat with a propeller on it if you understand. Iwas going to use 1/8 modeling-grade ply for the frame and 1/16 modeling grade ply for the exterior (or "doorskin" depending on which I can find easiest) I planned on glassing just the bottom and then putting 3 coats of thinned fiberglass on the whole thing to seal it.

Also Pusher or Puller? Seems its just up to aesthetics but Iplan on running this thing in a REALswamp complete with all sorts of low hanging branches, soft patches of ground, the occasional turtle and so forth. Seems to me a pusher would be most ideal because the engine stand would act is a natural guard for the prop

P.S. im not a total noob, Im a junior engineering student and the son of an avid carpenter so feel free to use all the big words and jargon you want. This is just the first time ive done a ground up project.

RE: Designing My First Airboat Need Advice and Pointers
 

1a) Yes. 1b) Anything is possible with the right engineering.;)

2) If the hull is light, you could possibly run a .25. If you building for a .40 size that you have. I would make the boat about 26"x 12".

3) About a 4"x2" is the average size for the size tank that you would be running for the .40.


When I plan a flat bottom boat, I make the bottom a few inches wider than the prop diameter I plan on using. This will give it the slide effect.

If your on a budget, you can use doorskin. I have built many out of it. If you can use the model grade ply, use it.

RE: Designing My First Airboat Need Advice and Pointers
 

24x12 would be a good size it may want to flip being that narrow

RE: Designing My First Airboat Need Advice and Pointers
 

thanks for the responses im going to post a new model a little later to incorporate these ideas.

RE: Designing My First Airboat Need Advice and Pointers
 

Ok here is the update

Total Length: 28 in
Total Width: 12 in
Hull Height: 4 in
Tower Height from Hull: 7 in (I can adjust this pretty easily)
Width between Tower struts: 4.5 in. < Is this too much? I dont really know much about the fuel tanks in terms of general dimensions, but they have to be pretty narrow right?
Engine: .41 (bought it off a crash runs great the plane and transmitter didnt make it)

Features (if you could call them that)
1. Tower is cut from the same wood as stringers rather than attatched after the fact. This is for the sake of simplicity and structural integrity
2. Pusher (the previous owner of my engine mentioned that nitro plane engines need the prop wash for cooling purposes so)
3. Dowel rods (.25 and .50 in.) have been placed around the outside of the frame to help prevent warping and to reinforce the outer hull. I will be running this in a real swamp that includes all kinds of nasty things that can chew threw an unprotected hull.
4. Lightweight Frame: A large amount of wood has been removed from the various parts however I hope the dowel rods will make up for that loss in strength

I need to model the outer skin, but once thats done i'll upload a really really sweet full 3d model that can be viewed by anyone who has adobe reader

so what say you? Is this a solid model? What are your thoughts on it?

RE: Designing My First Airboat Need Advice and Pointers
 

Looking good.

In my opinion, 4" thick is a bit much. My 40-46 size hulls are 2" think.

RE: Designing My First Airboat Need Advice and Pointers
 

Fairly new to the airboat design and build, your hull looks fairly stable. I'm currently designing a hull using old plastic tubs, more of the on-the-fly design than something built from plans. My hull is 15 inches wide, 20 inches long, and 2 inches deep. I'm using a Ryobi 18V motor pushing a 9" prop for one set-up, and twin EDFs from an wrecked nitroplanes A-10 for the other. I'm sure the Ryobi setup wil be a faster boat, but the EDF set-up should be perfect for a pool cruiser. I'll be posting the results of the build in it's own thread here soon, I'm working the bugs out on the design as well as finding out what works and what doesn't (for instance JB Weld doesn't bond to plastic tub plastic well)
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RE: Designing My First Airboat Need Advice and Pointers
 

Looks solid and the sizes are good. You could make the deck a bit thinner. I make my hulls just thick enough so they can take a standard servo. Thats around 60mm ( 2 1/2") thick.

RE: Designing My First Airboat Need Advice and Pointers
 

Ok here it is the FINAL version. Rendered using solid works in loving 1440x810 resolution (HD Widescreen). Final dimensions are unchanged but I made the hull a bit simpler to make production easier.

28 in long, 12 in wide, 3 inch tall, 5 in tall engine mount.

Questions:

There are gaps between the outer coverings. How do you fill these? Iwas thinking wood filler or some kind of putty or even epoxy putty but which one?
How do I run the control lines from the radio box to the rear of the hull?
How do Imake a radio box cover? Iwas thinking plexiglass
Any other good advice is appreciated.
What is a good name? :)

Also total weight: 7lbs if Iuse pine. Calculated using solid works mass calculator.

Also Selph- Inflicted I signed up at your forums under the same username as this. So I'll be looking for some good advice there.

RE: Designing My First Airboat Need Advice and Pointers
 

That looks cool, i cant tell you much about how it will perform because i dont have any airboat experience.

Also, what design program is that? Can i have a link?

RE: Designing My First Airboat Need Advice and Pointers
 

Its a program called Solid Works and unfotunately it is probably above the casual airboat builders pay-grade. It costs a few thousand dollars for a license. Ihave access to it through my university. I can do some more renders from different angles if anyone is interested.

However there is a program called Sketch Up that is a fantastic (and free) program that will do everything you need, Ijust use Solid Works because Ihave access to it on school computers. Solid Works is a pretty proffesional program and you have to invest alot of hours (in my case a few college courses) to learn how to use it so Its not worth getting it even if you did have some cash to blow.

RE: Designing My First Airboat Need Advice and Pointers
 

I use sketchup for random boredom things like ships and stuff. I also used it to design my hovercraft.

RE: Designing My First Airboat Need Advice and Pointers
 

I saw that thread. Its a very nice design. I havent built too many things but Iam being educated in machine design so I'm interested in all kinds of interesting vehicles and projects.

RE: Designing My First Airboat Need Advice and Pointers
 

I teach at a High School as a shop/technology instructor. We replaced Autocad with Solid Works a few years ago. GREAT program! If you already have a little background in CAD, than it's a fairly easy to learn program. No background, may take a little longer. Great built-in tutorials to get you started in making you first parts rather quickly.

RE: Designing My First Airboat Need Advice and Pointers
 

Yes Solid Works is awesome but I need to get this thread back onto the original topic so im quoting my last thread-relevant post.

RE: Designing My First Airboat Need Advice and Pointers
 

LOL yea the Solid works subject kinda derailed the topic....you'll have that. LOL

Mix sawdust with epoxy to make a paste that will fill the gaps.
make the radio box cover out of wood. Plexi looks really cool and all, but any water vapor in the box when sealed will condense against the plexi in the sun and drip onto your electronics....been there, done that.

For the control cables, a real good way is to bury them in the hull using the "double sheath" method and seal the ends with pushrod seals.
If you only use the single sheath and the sheath cracks or breaks, you have to open the hull to replace it, with a double sheath you just pull out the bad one and run in a good one.


Seriously...you DO NOT want ME to name your boat. The regulars here know why. [:'(] :)



EDIT: I forgot to ask what year Solid Works do you have? I have 2004 but don't use it much. I'd really like to get that file and look at your boat from all angles.

RE: Designing My First Airboat Need Advice and Pointers
 

Ask and ye shall recieve...

http://rapidshare.com/files/40660511...bly_Final.EASM

make sure you have eDrawings it should be free on solid works website

RE: Designing My First Airboat Need Advice and Pointers
 

Any chance I could get it in sldprt? I understand if you don't want to.

RE: Designing My First Airboat Need Advice and Pointers
 

I would have done that originally but im concerned about compatibility... im running 2009

RE: Designing My First Airboat Need Advice and Pointers
 

Ok here is the update:

Changes: Engine stand is not as wide. I made it 3" wide instead of 4" and reinforced it.

Name: "The Spirit of Lake Charles" - after the city that inspired me.

Paint Scheme: Blue base and yellow pin stripes

Questions: How thick should the ply that I mount the engine to be?
How do universal engine mounts work? Specifics for a .41 nitro motor would be great.

Thanks for the help so far. Here are two more amazing renders, one with a section view also.

RE: Designing My First Airboat Need Advice and Pointers
 

I would suggest making the main runners out of 1/4" ply and also making the motor mount plate out of 1/4" ply. Use 1/8" for the remaining bulkheads.

RE: Designing My First Airboat Need Advice and Pointers
 

I corrected some dimensions. For example, I modeled the runners as 7/32" instead of 1/4" because that is the true dimensions of the ply you get at the hardware store. I also modeled a 10 oz fuel tank based on the dimensions of a fuel tank found on tower hobbies.