martno1fan

hi im new to air boats i currently have an os 46la engine that i had in a plane id like to build an airboat for this engine.there are so many to choose from and id like help in choosing.i think id like to try using foam ,has anyone got any advice on building one or any plans i can have?.also do i need to glass the foam or not i know glassing it will make it stronger but is it needed?.
i also have loads of coro from a spad project left over does anyone have any good plans for one built using coro!!.ive seen threads on builds and such but nothing really detailed for a beginer like myself.i have experience of building planes but not boats help!!

Selph-Inflicted

[link=http://rcairboats.net/v-web/bulletin/bb/viewforum.php?f=6]Simple Foam Plans[/link]

If your gonna be running on water only...you could get away from glassing it, but you still want to seal the foam with some epoxy.
If your planning on running on ground any, you better glass it in.

Here is a boat built from coroplast, its built by Jasper. He can help you with the coroplast build....he has done quit a few.
[link=http://rcairboats.net/v-web/bulletin/bb/viewtopic.php?t=930]Coroplast boat built by Jasper[/link]

martno1fan

hi i was planning on using it on water mainly but also on grass and maybe sand at the beach so maybe id better glass it !!.i was thinking maybe putting some skids inlayed into the foam on it too ,good idea?.thanks for the link cant wait to get it started !!

Selph-Inflicted

I would recommend using 5 oz cloth on the bottom and sides. I put 2 oz on the deck, but 5 oz will be fine there also.

Good luck with your project! Keep us posted.

martno1fan

thanks mate also i have a small thunder tiger gp10 what size boat do you think would be good for this?might be good for my young lad whos 9 yrs old maybe i can get it done for christmas lol!!

jasperrc

Welcome to airboats! SPADS are where I got the inspiration for building airboats from coro. I have expanded some of the techniques used for SPADS to build my boats.

The one Selph-Inflicted linked to is my newest and fastest boat.

As with any material, there are advantages and disadvantages to using coro. What I like about it is that it's already water/fuel proof. It's easy to work with. There is a pretty steady supply of it for free (election signs... after the election of course). It's great for water and grass running, but watch out for rocks or sticks, which brings up another positive, it can be patched at the waterfront in 2 seconds with electrical tape.

If you have any questions, holler!

martno1fan

thanks for the welcome jasper glad to be here ,i was thinking of trying a foam boat 1st but i agree about coro its great stuff and pretty tough just as my dps lol.your boat looks cool maybe ill try that one too.i dont know if this sounds like a daft idea but i was considering a cross between the two.i was thinking of a 2 mill corro sking glued to the hull all over sealing any gaps with silicone sealer im using white foam the type used for insulation and its pretty light .what do you think of this idea ?.i was also planning to put a ply base inlayed to the aft end for mounting my engine mount to.its wierd actually building a boat after a break of 20 yrs as i used to build boats when i left school mostly wooden boats from scratch the old way clinker built using copper nails for the planking real boats that is from motor cruisers to rowing boats god makes me sound ancient lol !!.i cant wait to get started on this thing any advice or tips would be very welcome !!.

jasperrc

I have seen coro boats done with foam inside before and it shouldn't be a problem as long as the coro is really watertight. If the foam is not sealed with epoxy and water gets inside the coro, the foam will act like a sponge and soak it up. The good thing about this setup is that it will provide some structure for the coro. You probably saw the foam blocks I used in a couple of locations in my last boat for just that reason, structure.

Putting plywood in the back to mount the engine stand is a good idea. I like the coro, but you can see that I use plywood for strength at the mount points.

I have used silicone sealer with pretty good results, and one advantage is that if something serious happens and you need to get inside the hull, the silicone can be removed without destroying the coro. But I only have one hull that is truly watertight and the stuff I used on it was a marine grade epoxy patching material. Great stuff! Wish I could find some more...

One of the things I try to do with a coro boat is design it so there are as few seams in the possible. I try to figure out how to make the desired hull shape out of a single piece of coro with as few thru cuts as possible. This helps cut down the number of seams I need to worry about sealing.

martno1fan

hi mate i was thinking of 15 inches wide by 26 inches long what you think?,the foam i got is 15 inch wide so seems simplest to go with that width.is it wide enough?,also my son wants one and i got a small gp size 10 i can use any ideas of the size hull i should build for this?.i was thinking of using water proof wood glue watered down and sealing the hulls with it 1st also.i was thinking of maybe just putting a cpl of coro skids underneath the hull for the smaller one so he can run it on the grass but leave the top as is what you think?might also varnish the hull after painting it to seal it all again .also have you got any plans for your engine and rudder set up sizes etc sorry to be a pain much appreciated .

jasperrc

The general rule of thumb for hull is a ratio between 1:2 and 1 1/2:2, so 15x26 should be plenty wide.

I don't know about a .10 size hull. I would start around 7x14 or 8x16 but someone else may have a better idea.

I've never used waterproof wood glue on a boat, but most of the ones I have seen indicate not to use them underwater or for extended exposure applications. I have used polyurethane glue on the wooden parts of a boat, but then have sealed over with something else. I don't know if varnish will work over glue or not as a finish sealant. The main things to be concerned about are whether or not the bond between the glue and varnish is good, and whether or not the varnish is fuel proof. I have tested polyurethane with the 10% nitro fuel I use without problems.

For running on grass, you want as much surface area as possible to spread out the load and keep the hull fom sinking in to the grass, so I wouldn't do skids for grass. On concrete or pavement, it's just the opposite, skids are good. Reduces the amount of friction.

As for motor mounts, it kind of depends on what you are trying to do, and what your requirements for your design are. My initial requirements were that it must be movable from one hull to another and that the electronics should be protected.

Here are the 3 setups I have used. The first was a full platform that included a remote box for the radio gear. It attached to the hull with 4 screws. This and the hulls it was used on were probably too heavy for the .40 size motor I have, but still a lot of fun.



The second was a lot lighter and had a dual rudder set up. It retained the same remote radio box as the first one. The control cables ran inside the hull, coming out right under the engine mount.



This last one was finished this weekend. Still mobile, this one can be moved a total of 4 inches for and aft to change the CoG. Dual rudders without the remote box. Radio gear is inside the stand itself. Heavier than the second, but lighter than the first one.

martno1fan

thanx for the advice i think ill try it see how it goes in any case im hoping the coro will be water tight that im using to wrap the foam with time will tell !!.liked the angled rudders do they act like ailerons lifting the boat a little in the turn ?looks like a good idea.have you tried them out yet or not.i found some really thin coro looks less than two mill not measured it yet but looks like itll bend easy to wrap the hull !!.im still thinking on that one im sure i read somewhere how someone used cloth and varnish to cover a boat hull ,any ideas on this one?.might be worth a try i have plenty of good varnish marine stuff should be ok .whatever i decide ill keep you posted and thanks for the help.

jasperrc

I actually angled them out on purpose. My flat bottom acts like it wants to flip to the inside on a hard turn, so I angled them out to try to flatten the turns. Haven't tried it yet, but hopefully this week some time. I'l let you know. I have since heard that angling them in will help if it wants to flip to the outside ina turn, so it should work.

Try the cloth and varnish and let us know. I'm interested because I have a good bit of it, and cloth is cheap. If it works for you, I will try it on one of my boats...

martno1fan

what cloth would you use for it mate i might give it a go!!

jasperrc

If you are going to glass the whole thing, I would use Selph-Inflicted's recommendation.
If you are just glassing the seams, I would use 5 oz.

martno1fan

well heres what ive done so far i covered the foam in thin corro using epoxy!!,then covered the sides and deck with some blue and red tape .its like ducktape water proof so shouldnt come off.the coro was sealed where needed with epoxy and bit of silicone in few spots.im gonna put another thin coro skin underneath as a skid so as not to wear the tape on the edges.hows she look for a 1st attempt?.just need to buy some alluminium for the pilons for motor mount im thinking of fixing my servos to it too might try water proofing the servos using silicone i saw a thread on this so might give it a go!!.ill put the rx and battery into a water proof box set into the deck.how far from the transome should i put the engine mount?.do i need to angle the prop upwards a cpl of degrees to keep it from taking off?.thanks for any help on this cant wait to get this thing up and running!!.[img][/img]

martno1fan

another question for ya mate how does that moose can work?ive never seen it done that way before looks interesting have you any plans on how its done?,more importantly does it work i could allways do with more power hehe!!

martno1fan

well heres acpl of pics of my progress ,nearly finnished !![img][/img]

jasperrc

Lookin' good! I like it! How much does she weigh?

A few degrees up angle on the front of the motor is a good idea to help put more downforce on the bow. I hope it's not too late for you to add some.

You generally want a balance point around 1/3 of the boat's length from the stern. On a really light boat, maybe a little further forward.

The mousse can muffler works well. I have the mousse can muffler because my old Fox motor came to me 23 years old but NIB, without the muffler. Since I couldn't easily get a new muffler, I first used the muffler from an old worn out OS 35 that fit with a little adaptation, but it didn't flow enough air. I found these plans [link=http://www.spadtothebone.com/SPAD/Mufflers/] (Mousse can muffler) [/link] on the S.P.A.D. web site and came up with the muffler you see in the pics. At first I did not want to use the OS muffler to make my mousse can muffler, so I Frankensteined the contraption you see on the first 2 engine setups. I got tired of fooling with it getting loose, so I went ahead and started using the OS muffler, and that's what's on there now.

It's nice because you can experiment with different size mousse cans and with different sizes and numbers of tailpipes to get the performance you want.

Keep up the good work, and keep those pics coming!

martno1fan

hi mate glad you like it im not sure on the exact weight as ive only got some electric bathroom scales which i tested it on it says 5lb not sure how acurate that is!!.i will angle it up a cpl of degrees ill stick some washers onder the fron end.i used an old har gell tub for the battery and receiver srew down lid was water tight lets hope itis now ive drilled it and siliconed it ehh!!.not that i intend finding out anytime soonlol.i never did use the varnish and cloth but i will on the next one sounds like it works a guy on here uses it reg and says any man made cloth will do ie nylon polyester !!.might find some snazzy pattern and use that,my daughters into barbie but i think ill stay clear of the pink haha!!she balances right under the spinner which id say is just less than a third of her length,do you think i should add weight to the front or see how she goes 1st?.i just need to alter the rudder servos conection shes binding a bit so ill move it a bit maybe put it right way up instead of on its side apart from that shes ready to go.ill let you know how she goes ,nearly said flies lets hope she dont do that aaahhhggg.lets hope the ponds not frozen either want to see her on the wet stuff.wish me luck i might give her her maiden voyage tomorrow weather permitting .

martno1fan

did i say spinner?oops meant the rear of the engine seems about a third or just less rides nice in the water (garden pond)lol.excuse my spelling on last post guess im getting exited !!.oh yea love the moose can idea so how do they work? on the one you linked for me doesnt show any exaust out is that right?.might sound stupid but i have no clue lol.

martno1fan

i must be losing it forget the last question i see what i do now so what will happen if i drill the outlet hole near the rear of the can?.

martno1fan

right shes done i angled the engine up a cpl of degrees hope you can tell from the pic!![img][/img]

martno1fan

just thought id let ya know i just bought a new engine off ebay well its used but sound like in good condition !!its a sc61 abc motor would you say this is too much engine for this boat ?.[img][/img]heres a pic of it looks good lets hope it runs as good as it looks!!.

jasperrc

I can see the angle, looks good!

Keep us posted if you use the cloth and varnish, love to see the results.

If you get ice to run on, try it. Your boat will fly!

Sounds like you're balanced pretty well. Try that and see before adding any weight.

That .61 will be a lot for your boat, but what a wild ride!

jsmith944

Hey guys!! Im working on a swamp boat right now and needed any advice that anyone can give me. Got some pics here take a look and tell me what u think. Im going to put a .90 on it.