Here we go - the "Econo-maran"

The object: Build a multihull in the most cost effective manner, easily able to be replicated by inexperienced builders at the F-48/Mini40 scale size.

The Start:

Econo-maran POST #1
With the holidays over and daughter firmly moved and planted in her new home, thoughts are again turning toward the potential to try a building method incorporating flat slab sides and a curved deck and hull bottom of composite material construction.

To start, I found an interesting build process for a large (and subsequently) inexpensive full size trimaran. I have decided to try the process in the r/c size format. As you may recall from a previous post, the full size boat has slab sides of plywood, and the company furnishes a “pan” or bottom hull fiberglass laid up shape that bonds to the bottom of the slab sides, providing rocker fore/aft and curved underwater sections cross beam. The full size boat uses plywood for a fairly flat deck, but I am thinking of providing a similar “pan” for the curved top deck to help shed water should the deck be forced under. In both cases of these “pans” - I will use extruded household insulation foam to provide a material that can be easily shaped. I suppose, one could lay up balsa strips, but that is tedious and time consuming, and the foam, covered with glass is both cost effective and easy to do for a beginning home builder. Later, if it warrants and easy mould can be made for pure glass hull bottoms and decks - doing away with the added glass weight.

I have attached two photos that represent the start of the project. More photos to come as I move forward with the build. I am starting the project with four pieces of balsa sheet, 48 inches long and 1/8 inch thick. These will make up the two hulls for my proposed Econo-maran. To keep costs down, and make the process easy to construct, I am going ahead with a catamaran design, which is only two hulls to be built - not three. I also will use a piece of 1/4 inch thick balsa for my bulkheads and stations where the shape of the hulls will be derived. The balsa only cost was (gulp) an unexpected $20.00 (US) from a local hobby shop. Next time I will mail order and receive double the number of sheets. Lesson learned. The foam was picked up with approval from a local home building site as a discard. It happens to be 2 inches thick - I think 1 inch thick would work, and will probably cut this down to prevent waste.

The hull you see in the background is one of two resurrected from a first attempt at an F-48 catamaran that was scaled from my real cat. Unfortunately as I began to build it (circa 1998 - 1999), I found there are issues in trying to make a cat “look” good, and still house the radio gear equally balanced in port and starboard hull. Will have to rethink, as I hate the look of a big box sitting under the mainsail housing the radio gear. Since this is a test of a new building process, I will forge ahead and deal with radio control later. I will use the old hull dimensions with modifications to come up with a more modern catamaran design. Hopefully something like the full size Formula/Inter 17 catamaran hulls will emerge. When done, I expect the final platform to be about 48 inches long by about 32 - 38 inches wide. Not sure at this moment if I will use a separate daggerboard in each hull and separate rudders, or center mount the daggerboard and only one center located rudder. Likewise, the rig/sail may come from an existing 36/600 or 1 meter for starters. Can always increase sail area later.

As I move forward, I will try to provide photos as the build progresses. I intend to keep track of total build time if possible to allow others considering the process an idea of time involved. I currently have left-over WEST System epoxy, so for starters, that cost will not be included.

Materials to date:
4 pieces of 1/8 x 48 inch balsa (hull sides)
1 piece of 1/4 x 36 inch balsa (bulkheads, bracing, mounting tabs, etc.)
1 chunk of 2 inch thick foam (deck and bottom of hull)

Great idea!!

I’m really looking forward to seeing the progress of the project.


Econo-maran POST #2

Well, I started in on the project - no need for photos yet, but already indecision (or need for a decision) has raised it’s ugly head. :mad:

I am trying to keep the process simple, and the thought of how to shape the bottom and top of the hull foam covering became clear.

  1. I can cut/shape the internal (minimum) bulkhead/stations to have a flat surface to attach the foam, and shape the “curvature” by eye. This makes cutting the spacers and internal bulkhead forms easy, but shaping the foam a bit hard to replicate on two different hulls.

  2. The other option is to cut the curved shape at the top and bottom of each bulkhead and use that shape as a central guide - filling in between the balsa with foam - then sanding/shaping the foam to match the minimal shape contours of the projecting balsa. In this case, more work (and time) is required, but the general shape will be closely replicated between each hull surface.

The Decision:

I elected to follow option #1 for the following reasons …

a) the cutting of needed internal stations and bulkheads will be quick, since only the hull width and height will vary the dimensions.
b) no need to worry about cutting the protruding curve above the gunwales/shearline, or below the waterline.
c) this also removes the need to cut individual pieces of foam to fit between the balsa protrusions.

Of course, the negative, is that the curved deck and hull bottoms will be shaped “by eye” to look pleasing - but I acknowledge they may of slightly different shapes or radius at the same points on each hull.

While this may seem important, those who follow can decide if time is worth it. For me, I want to keep building time and effort to a minimum, so removing curved bulkheads sticking up/down eliminates time.

I will cut all bulkheads to be flat at deck and waterline levels, saving time. One piece of foam will be cut to span the entire length of the hull and will be attached at various points to the balsa slab side along the total hull length.

With this decision made, I can now layout the individual bulkheads/hull sidewall framer supports. Two of each will be required. These will be constructed from the 1/4 inch thick balsa sheet stock.

Hi Dick im glad you decided to come out of retirement lol just kidding ,sounds like you have the makings of a good idea there ill follow your progress with great interest.if you know anyone with a hot wire cutter you could easyly cut the tops and bottoms of each hull and get the correct shape too.much the same way in which they cut airoplane wings .all you need is the tops of the frames and make a jig and cut away using the wire cutter.yes it means using small blocks of foam but at least you wont need to sand them .ive seen guys make bows from guitar strings and an old battery charger .whichever way you choose good luck and keep the pics coming.

If you can get into RCGroups, sailboats (doesn’t seem to be working at the moment), I think Keven 64 has a hot wire cuter. He lives in Padiham (somewhere up in the Pennines) and his in-laws live in Fleetwood.

OFF TOPIC - hot wire cutting

I used that method to build the foam plug for my MultiONE trimaran! Sections of foam cut to correct length were sandwiched between thin sheet aluminum profiles of cross sections and then cut running hot wire along the template. Once all were cut, it was just a matter of glueing all pieces together to form 1/2 of the hull/ Photo shows top view of main hull, and a bunch of the hull sections cut but before glue up. This is a 1 Meter trimaran design called “IMPULSE” - depending on your own “impulse” it can be configured and built as a trimaran - or - a catamaran.

Again, not to dismiss the thoughts and ideas, but I want to make this for an average “Joe Blow” build in his dining room or kitchen. Someone with space, but not a lot of tools and gadgets. Maybe a guy like WIS :devil2: (if he’s still hanging around here) who has little building skills, but has time and some space where he can work - and defiitely some great finishing skills.

Perhaps I can provide a collection of tips and idea from readers that the builder could consider - depending on skill levels, tools, etc. Remember, the key words here are easy to build and cost effective. I am dreading the epoxy/glass skin process that will be needed as I think I will lose a large group of readers who don’t/can’t mess with fiberglass cloth and epoxy resin.

and now … BACK TO TOPIC

i have to agree with ya. i have a buddy whos is out of work, and doing some little jobs for me. within an hour, his hands, and around his lips, had a good dose of “bog rash” (reaction to the epoxy).

i dont see a problem with epoxy really its the poly resin thats the worse yuk lol.

I agree that polyester resin isn’t real “nice” stuff, but indeed epoxy resin can cause a severe allergic reaction in some individuals who have been sensitized. It can prevent that person from being anywhere near it. Therefore, it’s always advisable to take precautions to minimize exposure by always wearing gloves & having good ventilation.

the poly stuff only smells bad, epoxy tricks you into thinking it’s safer, cause it doesn’t “stink”. but be warned, it’s no good for you!

i wasnt implying epoxy was safe or otherwise ,hey people are allergic to all kinds im allergic to neither of them but i allways wear gloves and mask when i use either out of habbit which i think is a good habbit,as the nun said to the preist!!:slight_smile:

Be carefull though guys…seriously.
I wasn’t allergic for 25 years…now I have to be very careful with this stuff.
Take it from a guy who has used a lot of the stuff.

hi guys heres a video of a guy i know from another site hes just finnished his snapdragon and this is its first outing enjoy!!

Doesn’t look big enough for an F-48/Mini40 - is it built as a one meter?

Also needs a bit of leech control on the main higher up - dumping too much wind when close-hauled to my liking.

Just observations…

Here’s a photo of a Mini40 just to give example of relative size - looking at the video, and the owner carrying his boat - it just looks too small.

I had been very good and close friends with the original designer of the SNAPDRAGON design which was originally scheduled as a 1.2 meter, until his untimely passing away last year (Mike Howell).

nope its a 4 ft boat ,as far as i know its to the plans and he built all the hulls from scratch.i beleive he used a marble head number 2 rig for it with his own sails he made himself.doesnt look small to me from what i saw and seeing as this was its first outing id say it sailed pretty well .i think he was a little scared while sailing her as hed never sailed one before ,any way i thought you guys might be interested to see it .

Great video, really inspires me to get back into a multi.
I enjoyed the music track, is it ENYA?

OK guys - as there is such interest in the video I thought I ought to join you and put a few things straight :slight_smile:

The Tri IS built to the Snapdragon plans and is full size. Dick - when comparing the boats size with the man carrying it - you might not realise it but I am 6ft 4 inches tall - thats what makes the boat look small ! On the water - ALL boats look small on our lake its that big :stuck_out_tongue:

The rig - actually the mast is a temporary one made out of an aluminium expanding curtain rod. The sails are homemade and remember this was its first outing so no fettling had been done. Yes I agree the sail does sag off at the peak- I saw that and noted it for attention - the mast bent a little above the diamond stays and the kicker needed tightening.

I wasn’t scared sailing it - just a little apprehensive :slight_smile:

Glad you liked the music - yes its ENYA - " May it be" from Lord of the Rings

Don B.

Don thanks for clearing that up for him err us lol,i thought you were using the marble head rig ? at least i thought id read that duu!!.either way she sailed well and as i said before it was the first outing so its allways best to take that into account before making negative statements about the sure you will sort it out in no time!! by the way dont lie you were crapping yerself lol!!be honest haha.its a pitty you didnt show the tip over and the retreive that would have been good to see ,i hope you didnt get wet lol its a bit cold this time of year.where is the lake you were on? looks like i mining area .oh and i hope your wife got the curtains back up ok lol .
ps hope you dont mind me stealing your vid!!

Martno1 Ah - they don’t know on here about the pitchpole !!

After sailing for quite some time I relaxed and then an almighty gust off the mountain hit us - the Tri took off like a scalded cat, dug the lee hull and pitchpoled.

It drifted in upside down until about 50 ft off the shore line in an area where there are small mooring posts sticking up from the water. We have no rescue boat and no-one had waders that day. So we sent off an electric powered tugboat towing a line to go round the Tri in order to pull it upright. Going past one of the posts the wind blew the tug round the post and, being poor in reverse it could not unwind the line - it was stuck. I went back to my car and got out my powerful scale Lifeboat and then was able to push the tug with it to unwind the line and rescue that boat at least. :slight_smile:

The Tri had by this time drifted further down the lake. I motored my Lifeboat along to it and with the line attached set off to rescue the Tri. Manouevering the Lifeboat, I went briefly into reverse and picked up the line round the prop :scared:

I was able to pull the Lifeboat ashore with the line but the fuses had blown on the two motors - so back to the car for new fuses. (In the meantime the chap with the Tugboat was trying to push the upturned Tri. This time the superstructure of the Tug came off and drifted away - fortunately it was plywood so it floated and drifted into the bank.)

I fixed the motors and set off again with the Lifeboat.

This time everything went well - the Tri was dragged ashore and the only damage was one of the diamond stay wires had come out of the crimp. easily fixed !

What a pity we did not get that on video - but the clubmate using my video camera had also set off with his power boat to help. However when halfway there he lost all power and eventually his boat ended up on the far shore of the lake so we did not see him again for about half an hour whilst he rescued that too !!!

Tomorrow I am off to sail it again - this time with a pair of chest waders on just in case:)

The lake is Lyn Padarn, at Llanberis at the foot of Snowdon in North Wales. Its about 3 miles long and about 1/2 mile wide where we sail

Don B.

Laugh i nearly cried reading that lot Don i wish id seen that haha!!,get some mast head buoyancy put on the mast it will right itself when the wind gets it.Andy Wright gave me that tip he reckons most times the boat spins round on its side till the wind gets under the sails and up she pops.Certainly saves a fiasco or getting wet lol.Lovely scenery where you sail mate sounds like you wont run out of room either .Good luck with your next trip to the lake :slight_smile: .Dont forget the camera you never know you could make a few quid on youve been framed lol hehe.