MarkPrima

Hello everyone,
This is my first post on RCU. I have been searching this section of RCU for built plans and need some help coming up with dimensions for an airboat I would like to build. I plan on using a OS 25 glow engine with a 9" prop.

Any feed back on the dimensions?
I was going to use the dimensions of the Dumus mid sized airboat

Thanks

1QwkSport2.5r

Are you looking to build a flat bottom boat or a hydrofoil?

MarkPrima

Hi 1QwkSport2.5r,

I'd prefer flat bottom so that I can use it on snow, our winters are very long up here and need something to use in the snow but a hydrofoil design sounds interesting.

My first prototype using an electric motor - here are the plans - http://flyingblog.primaveraphoto.com...type-and-plans

Here is a photo of the motor mount I made for the OS 25


The airboat that you are using for your Avatar looks really good.


Mark

1QwkSport2.5r

Thank you! It was designed by Hooty301. That one was designed around a .61-.91 engine. If you like the design of it and are willing to spend some time to build the hull, you could try building one. I built the big one for the big engines and I also designed a smaller scaled down version for a .29 engine. See my thread here: http://www.rcuniverse.com/forum/rc-a...-stepboat.html

If I were to build this boat again, I would build it as a flat bottom instead of a stepped hull. I have not gotten it to run 100% perfect yet - the balancing of the boat has eluded me to run properly. The hull size is 26"L X 14"W X 2.5" thick I believe.

MarkPrima

Definately willing to build, planning this to be my winter build project.

Thanks for the link to the specific thread, helped alot and now starting to feel that things are falling into place.
I'll use the dimensions you mentioned: It is close to my original dimensions.

I'm not sure but I think our internet here at work is blocking images in your 4th boat build thread.

Are plans available?

1QwkSport2.5r

Unfortunately, I don't have any plans in print that I remember. I will have to look in my photo file and see if I photographed them or not. I will take a look and if I do have copies of the plans, I'll post them here.

MarkPrima

Oh OK, sounds good.

1QwkSport2.5r

I'll have to look on my computer to see if I have them saved there. I am doubting I still have my drawings since its been so long since I built the boat. I could easily take some of my pictures and add dimensions and lost my materials used.

arcdude

MarkPrima, nice to see a fellow Canadian onboard. I can relate to the winter blah's and one suggestion that may be of interest is an rc snow board airboat. It can be custom made out of foam to your desired plan, is cheap and easily replaced. The only concern with wooden airboats on snow and ice is they get beat up pretty quickly and you end up having to adhere some form of skin on the bottom to help extend their life span. Whether wood or foam a surface material adhered to the bottom such as the crazy carpet for sliding can provide a good bottom skin to toughen them up. Just google "rc snow board airboat" or "rc boogie board airboat", you'll find pretty much anything the imagination can come up with. Good luck with your plan!

MarkPrima

Hi arcdude, thanks for the feedbac/posting! Snow is a way of life up here, but can be fun.

My first prototype (snow-water-bug-prototype-and-plans) is made out of pink foam insulation and an electric engine. The pink foam is nice to work with, can be easily shaped and sanded. I have only been running the prototype on water and fresh snow, I try to stay away from hard ice.

This was my build plan... (1) to make one out of foam insulation and (2) to make one out of wood, what I call the traditional method with ribs and sheeting just for water. Since I recently purchased 2 OS MAX .25FP engines I was going to make two airboats.

arcdude

MarkPrima, I wasn't trying to sway you from your plans, merely pointing out the alternatives. Another option is to do the traditional style boat minus the wood ribs and form it out of foam and cover with sheeting, the end result is a very strong light weight boat. My avatar is constructed in this fashion. The fellas you're currently in contact with have extensive knowledge of the particular style your considering doing and are a wealth of knowledge. I'll be most happy to contribute in any way and if you have any particular questions feel free to contact me. I'm down in Ottawa so winter isn't much different here compared to yours and it's nice to have a pass time to get through the colder months.

1QwkSport2.5r

I looked and looked through both of my computers and did not find copies of my "Minikaze" plans. Should you decide to build that model, I'll have to supply you with some dimensions that aren't listed in my build thread. You may want to try the wood over foam first to get your feet wet though. The Kamikaze design isn't for the faint of heart - there are several compound bends required and plywood (even the 1/32" birch I used) does NOT like to bend in more than one direction. The hardest part of the build is getting the skin to lay right which requires a sort of "Y" type cut. I did the Kamikaze as my fist ever airboat build and it's still in one piece today, so it's not *that* hard.

MarkPrima

Thanks guys for the reply. No worries arcdude, I understand. Oh Ottawa, I did a 9 month contract in Ottawa many years ago for NRCan (Booth St.), it was great fun being in Ottawa. I lived in the Glebe (Gleeb) not sure of spelling.

1QwkSport2.5r - you have a good point by mentioning: I'll go that route. Thanks for that information. What thickness of wood would you cover the foam with? It would be great to get dimensions for the airboat.

Thanks again for the information

Mark

1QwkSport2.5r

If you're gonna run the boat on really coarse surfaces like pavement or gravel, 1/8" would be probably minimum. I'd use 1/4" wherever you need something bolted down like the engine mount. Top sheeting could be 1/32" or 1/16". Look at this build for ideas on rake angles and hull sides: http://www.rcuniverse.com/forum/rc-a...at-bottom.html

This design might be better for a first time wood build. If you have all the pieces cut out, it goes together quick.

Use Epoxy to build your hull. 15min and 30min Epoxy for assembling the hull and Finishing resin for covering the hull or fiberglass.

arcdude

Morning MarkPrima, As you may have discovered trying to uncover a set of plans is a tad frustrating, believe me we've all been there. The best I can suggest is to acquire basic dimensions which 1QwkSport2.5r has given you as a good starting point and a basic design that is of interest and draw your own plan. When constructing out of foam and covering with sheeting it is quite simple once you have a basic idea of the steps involved. Here is a link to my outrigger build which is foam core, (http://www.rcuniverse.com/forum/rc-a...foam-core.html) at least it'll give you the process step by step, this is a concept design and I haven't had any time to devote to it for testing and so on. What I suggest is using the dimensions provided and with a sheet of newspaper folded in half, draw your desired shape for the top surface and make a smaller copy for the bottom depending on rake desired, there's your basic plan and everything else just falls into place as you go along. Next transfer the plan to sheeting, I'd put 1/16" birch aircraft ply on the bottom at least or cover it completely with this thickness, it's tough as nails, then with grid lines drawn onto the foam that is over size cut place and clamp the top and bottom sheets in place and trim the sides of the foam stopping in line with the edges of the sheeting. Then do over size cuts for the side sheeting, to be glued later. Next you embed reinforcement blocks for the motor mount and so on into the foam and transfer mounting holes to the upper sheet as well as and if desired a radio box carved into the foam. Then glue top and bottom sheets onto the foam and then the sides and trim and sand them to match the top and bottom surface. That's basically the process, all you need is the desired shape and dimensions. I've come across an interesting build that is suitable for wood over foam construction with detailed pics and descriptions throughout all the steps, at least it'll help you get your head around the process (http://www.wattflyer.com/forums/showthread.php?t=69417). Hope I didn't confuse the heck out of you.

MarkPrima

Good day 1QwkSport2.5r and arcdude,

Wow, what great information and thanks
I'm just posting a quick reply until I fully read the thread links you sent.

As a starting point for my OS .25 the dimension will be 26"L X 14"W X 2.5" as mentioned.
Quick question... do you think the dimensions are too big for the motor size?

I'll be back with a good reply this weekend.

Thanks again guys!!

Mark

An update...
I called our local specialty lumber store and they have 1/8" and 1/4" Baltic Birch plywood in stock. A 30"X30" 1/8" piece is $5.59.

arcdude

MarkPrima

Seems a bit overwhelming, lots to absorb for sure. The size stated is a good starting point however, that is only one part of the equation. Size and weight go hand in hand so materials need to be chosen carefully otherwise it'll only end in disappointment. I would strongly advise against using 1/8" or thicker birch ply, this is heavy stuff. What I would recommend is 1/16" for heavy load surfaces and 1/32" or 1/16" for light abuse/non structural areas. What I've done to keep things at a minimal cost until a design has proven itself it go to Home Depot and buy a covering sheet of ply that is used to cover other more expensive sheeting for shipping, usually free and is less than 1/8", don't know what type it is though or a door skin out of mahogany which is also less than 1/8" and very light.

As an experiment take a piece of thin ply as stated and adhere it to a piece of foam then try to break it, it is exceptionally strong. Another idea that may help you out and if you have a history in rc airplanes it to take monokote and cover the bottom of your desired foam shape to experiment with size and design. That way you can experiment with different ideas, your only running it in fresh snow anyway, something to consider. I've made different snow vehicles out of the pink foam and used fiberglass gel to cover them and they worked great.

1QwkSport2.5r

Monokote will probably rip and tear on a rough surface. You're probably better off to cover the bottom in thick fiberglass if you don't sheet it with wood. 2 layers of 2oz cloth and 3 coats of resin would make it pretty tough. If you have a little 5" random orbit sander, you can always sand the rough spots down on a wood sheeted keel should it get beat up and cause drag.

With this size of hull, shoot for a 5-6lb weight MAX. Any heavier than that and she might be a little doggy with a .25 and 9" prop. If you stick with a 9x4 or 9x5, it should make enough thrust to move 6lbs, but how fast I'm not sure.

MarkPrima

Great points!!!!!

Now going to digest this info...

I wanted to share this with you guys:

Here is my first prototype that I linked to in the above link at the start of this thread - runs quite well I go and run it on my lunch hour


24"(L) X 11-3/4"(W)

Motor:
Type: GT2218/09
RPM/V: 1100 RMP/V
Weight: 80g
Dimension: 28.5mm (Dia) x 36.5mm (Length)
Shaft diameter: 4 mm
Max thrust: 1200g
Cell number: 2-3S Lipo
Recommended prop size: 12x6 10x4.7
http://www.lazertoyz.com/GT221809_p_26.html

=========================================

arcdude

If that is your very first design and build, my hats off to you on a great effort . The only concern I'd have is the bottom bow would have a tendency to plow whether it were running on snow or water. An improvement would be to do a lengthened gradual curve. Do you find the rudder gives adequate control response?

MarkPrima

Thanks arcdude, yes you are right the bow tends to plow into the water at mid throttle but planes out at high throttle, but does well quite well in the snow. I would have to say the rudder is not bad, two would have been better but I went the 'easy way' and just did the one on the motor mount support.

You guys were mentioned plywood thickness, so 1/16" is good for base with fibreglass?

1QwkSport2.5r - thanks for sharing the link the the thread - 9th RC airboat build - Selph Inflicted .40 series Tapered Flat Bottom - it gives me ideas on the bow shape I am thinking with the foam. Oh and thanks for looking for the plans and info about the weight.

We had our Flying Club meeting last Thursday and I ended up buying a OS MAX 4-stroke FS48 SURPASS from one of our members that was liquidating some of his engines. I may use this engine on my second build - "I think I am out of control now" LOL

Last night I Epoxied two sheets of 1" pink foam insulation to give me a 2" thick piece of foam, I'll shape the hull from that then design the radio box.

Here is the second one I made, but don't have props for the engine yet. This one is pink foam covered in Monocoat, it measures 10"(W) X 15"(L). The red areas are painted with Tremclad. This is my first experience with prop-saver engines and I plan on abandoning this one and using the receiver for my glow engine air boat

MarkPrima

For some reason it posted my Reply Twice?

arcdude

I see you have tried the monokote idea, how'd it work out? The 1/16" ply can either be finished with a couple coats of epoxy or 1-2 layers of light cloth, lots of people just epoxy and seem to have good results. One thing to bear in mind with the 4 strokes is they don't have the same response as the 2 strokes and are heavier. One thing that I've been tinkering with is a self contained engine pod that can be easily transferred from one hull to another, I'll add a photo of my idea.

When gluing the sheets of foam together I usually have a good idea where the cuts will end up and avoid putting glue in that location so it can be easily shaped after. If your cuts end up where the glue has been placed the glued area doesn't sand as easily as the clean area and you may end up with a deformity if you're not careful.

1QwkSport2.5r

4-cycles are very responsive, they're just a little different to tune. I usually recommend guys new to 4-cycles to pick up a tachometer and use it to tune the carburetor. I have a 4-cycle on my big Kamikaze currently and it works very well albeit being WAY overpowered. My buddy strapped his GoPro to his brushless E-Maxx and chased my boat around in a big field. It was pretty fun. http://youtu.be/36ZYaC84ikA

MarkPrima

Well, I haven't tried the yellow Monokote one yet, still looking for props - not a fan of prop-saver motors.
For the foam one that I am now making I think I'll use the couple coats of epoxy or 1-2 layers of light cloth. The Epoxy that I can get locally and use is G/flex by West Systems, my friend who repairs canoes told me about it and have been using it for a few years.

Ahhhh, good point about the 4-stroke, I wasn't aware of that. I'll just hang on to it for now and maybe use it in a plane.

Yes the self contained engine pod would be nice, they look so slick!!! Would it be like the Big Swamp Buggy by Dumas?

Thanks for the mentioned about the glue, but too late... I epoxied the two sheets and dried over night, I am now shaping. For very fine tuning and sanding I am finding a medium course sand paper on a nice sanding block works well. I also tried the disposal nail files from the Dollar Store work well.

That is a pretty sleek engine mount! Is that something new that you are working on?