Here we go - the "Econo-maran"

MultiHulls General Discussions (MultiHull/MultiOne)
41

I am aware of the boat. [Andy - Nope !] ANTHONY Wright and I communicate a lot, and he made me aware of the idea. While it allows for instant modifications, somehow the asthetics leave a lot to be desired. :wink:

I would try the idea to get the shape right, and then transfer to “traditional” materials. Kind of like pop-bottle boats. Yes, they work, but are kind of ugly - to my eyes anyway.

I suppose the idea of pop bottles and closed cellular foam for floats makes some sense here since we are talking about ways to build economically. Not sure who exactly owns that one, but sure would invited them to post here so some others could give their building ideas a try.

EDIT: I have been taken to task - and rightly so, by the person with whom I have corresponded. It was ANTHONY Wright - NOT Andy Wright. My apologies and I can only point otward a touch of forgetfullness when it came to typing the name. All of you “Should Have Known” whom I was referring to - but now that the “real” person caught up with me - here are my amends - and my sincere apologies. Also for clarification - Andy does indeed sail multihulls, we do correspond, and I believe he also made sails for a while and also lives in the U.K. Mea Culpa !

42

Just another question, Dick how would i go about attaching the mast to the beams?
Just want to get some ideas.
Thnx Shaun

43

ill have a word with the guy who built it im sure you will be interested in his findings !!.i agree on the looks thing to an extendt but if it gets people interested in multis i say its a good thing.im going to be giving it a try before i build the nightmare as im having trouble finding the time to build another boat from scratch.

44

Ah Ha!!! Glad to see that someone else thought of the same concept.
I’d be very interested in hearing more about how it works.
See the previous thread I started some time back:
http://www.rcsailing.net/forum1/showthread.php?t=3083

45

Actually, the mast sits right behind the front beam on a tri, so no problems. The issue with a cat, is you have to be darn sure of your final location of the mast relative to the lateral resistance. Otherwise you will wind up with too much lee or weather helm and will continue fighting where the boat wants to go.

I would fabricate as follows:

  1. Use a long bolt with a round head.
  2. Fill the screwdriver slot with epoxy and when cure smooth off with sandpaper.
  3. Stuff some paper towel into the bottom of the mast to keep epoxy from running and press it down to you have abour 1/2 inch to fill with epoxy.
  4. Thicken epoxy to peanut butter consistency (thick) and fill the bottom of the mast. Let cure.
  5. Use a drill slightly larger than the head of the screw/bolt and BEGIN to drill into the bottom of the epoxy filled mast - making a small “cup” to set on the screw/bolt head.
  6. You can use nuts on top and bottom to raise/lower the bolt head, and if you want to be “sort-of” scale, you can fashion a “dolphin striker” under the mast, much like your big cat. This can be pop-riveted to the underside of the front cross beam out near the inside of each hull. Leave enough slack to allow it to form a diamond wire under the front beam. You can use some shroud wire to make the dolphin striker too. It doesn’t have to be a metal strap. If you decide to do this - fabricate it first so you make sure you have a long enough bolt. If you use the wire idea, simply grind a “V” notch at the other end of the bolt to sit on top of the wire.

Even if you use a round mast that doesn’t rotate, you can use the mast step to adjust tension on your shrouds and forestay - up to tighten them, down to loosen them.

Hope these ideas help.

46

No comment !

47

you cant just post a pic like that then make no comment ,come on give us the details of that thing it looks great.

48

Simply, this thing is a trifoiler as long as a multihull of the class M40 and it goes approximately 1,5 times more quickly than conventional M40.
Of course, its favorite pace is carrying, and not near.
Needs wind, wind…

It is no mine !

49

Thnx Dick
just another question, Do you guys use mast rake and get flex from the masts or is it just plane masts?
I was planning on using carb0n arrow shafts for the mast but i think they will be too thin and flexible.

50

I think you may be right - using arrow shafts for booms are fine, but for a big multihull mast they will bend and then you will need diamonds and shrouds - and perhaps a backstay to tighten up the jib luff.

Try the follow:
Golf club shafts
Off-shore fishing pole blanks
X-C Ski poles
Order standard carbon or glass tubes from kite shops
Wood - 1/2 inch thick, 3/4 inch fore/aft and 60-65 inches (??) in length. Wood is cheap, you cn rip it to size ona table saw, and can maake a bunch of them if they break for the same cost of only one carbon fiber mast.
Do a search on Bill Korsgard’s foam mast that he builds and vaccuum bags for his iceboats - light, sttrong and also inexpensive.

51

I think I’m going with the fishing rod, should get some nice bend outta it!

52

Howzit guys
Finished making the mould and hopefully i should have the hulls done soon!
I decided on using ghost rider but just use outer hulls for the cat.
Just some questions:
What should i use for the rudder?
What is the best material for the sails?

will post pics soon
Shaun RSA

53

Ghost “Rider” - or Ghost “Train” ???

The Ghost ** FREIGHT Train series is a bit “fat” in the cross sections, and the tear-drop shape generates a lot of surface drag. In light air this is not a good idea. Better to flip the hull design upside down - so it is a reverse tear-drop shape. That way inn light air, you have a narrow cross section in the water. As wind increases and pushes hulls deeper, the reserve buoyancy from the wider part of the hull comes into play. This keeps getting bigger/wider as it is pushed deeper. The curved decks and bottom of hull both tend to shed water which is a good thing!

If you are building to F-48/Mini40 size (original plans) I would use some 2-3 mm ply. If you have reduced plans to 1 Meter sizze, balas should work. In either case a “skin” of 1/2 0z. glass cloth is advisable as the rudder along with the daggerboard has some high loads in strong winds.

Sails - for regular suit - 1/5 oz. coated ripstop nylon or polyester will work. You can also go to the Tri-Spi clear material with scrim threads inside. If building a storm suit, 2 oz. “real boat” Dacron material isn’t out of line - if you can find it, as sail area will be small, and the Dacron is less likely to be stretched. Try local kite shops if possible, since mailing from the States might be prohibitive.

Here’s a couple of links to give you ideas:

http://www.kitebuilder.com/catalog/index.php/cPath/24_108_116?osCsid=0a17b884e2e8b136a68d5e4c5a5da2bc

http://www.kitebuilder.com/catalog/product_info.php/cPath/24_174/products_id/1101?osCsid=ab5e613d34f47d5f7a1f7da5eedb305d

http://www.kitebuilder.com/catalog/product_info.php/cPath/24_110/products_id/1184?osCsid=ab5e613d34f47d5f7a1f7da5eedb305d

While there - look around as there are other items, line, fittings, tubes, etc. that might serve you as you build.

** EDIT - WITH APOLOGIES:

Shaun - GHOST TRAIN - or - FREIGHT TRAIN ???

if you are building GHOST TRAIN … Disregard the stuff above about the Tear-Drop shape. If you are building to FREIGHT TRAIN, then comments stand. Sorry about confusion.

54

sorry yes ghost train, I did flip the the hulls over and i have made it accordingly to plan, I was thinking for the rudders and centre board to use normal wood and shape it then just cover it in epoxy?

55

that will work !

56

“Econo-maran” Update:

Well it’s turning to fall so time to think about indoor and winter projects. This one has been on the shelf calling to me to get back to finish it, so started in tonite with a few minutes working on foam for decks and bottom of hulls.

To refresh so you don’t have to go back (topic was hijacked a few times :scared: ) this is a slab-side balsa sheet hull, with a deck and hull bottom out of foam, shaped and glued to sides. It is planned as a catamaran configuration, and not sure if radio gear will share space inside hulls - or in a “pod” between hulls.

The original purpose was to put together a quick-build very economical set of hulls that while inexpensive would give reasonable performance.

The photos below are a continuation of the process. Once the hulls have had major bulkhead spacers added, they are laid on top of the foam, and outline of top view deck profile traced. These tracing are then rough cut on a bandsaw (very quick - but a handsaw or jigsaw will work just as well)

Once cut to rough shape, they can be sanded to a rounded shape pleasing to the eye. I had originally thought about semi-circular underwater cross sections, but after seeing performance of some of the new “A” Class cats, and the Aussie Formula 16 “BLADE” I may go with flatter underwater sections to the rear to promote a lift condition when sailing fast.

Right now, I am looking at a uni-rig (mainsail only) with mast and board set back quite far.

Also, I only had 2 inch thick foam, so used what I had. Once I get to cutting the slab-side view profile, you will see a lot of waste as much of the balsa and foam is removed to produce small transoms - so 3/4 inch maximum thick foam is sufficient. Again, as noted, I am working on this as time permits - don’t want to get the wife mad this early in the building season.

Next planned step is to cut profile side-view of balsa sheets and then hold foam in place with pieces of masking tape to draw side profile. I can then cut the foam and begin to round over for deck curvature and hull bottoms.

In the meantime, here are some photos -

#1 - top view of hulls with deck and bottom marked by tracing around hull
#2 - the profiles (viewed from above) are rough cut to approximate size
#3 - “exploded” side view showing how foam will be attached for deck and hull. You can see there will be excess foam and balsa needing to be removed to make a small transom.
#4 - foam and balsa slab side hulls in planned position for attachment
#5 - pink lines indicate approximate side profile. Top and bottom foam will attach to this "cut-line and then be shaped and blended in to eye appeal.

57

I’ve just come across a similar construction technique on the West System website which can be found under: Projects/Boat Construction/Developing multihulls. There is a pdf there with images - just thought i’d mention it. :slight_smile:

58

Yup -

I had corresponded with the builder prior to the Gougeon newsletter. Since so many cats and trimarans seem to opt for flat/slab side hulls, it sure makes sense to spend the time only on curved decks and hull bottoms, and just accept the sides “as is”. If worried about “oil can” flex, one could build in a mid level cross-hull sub-structure.

59

Wow - that was sure a meandering, off-topic bunch of posts !

This post, started in 2007, the “Econo-maran” project was shelved when there was a lack of interest in the big boats. Now, there is a renewed interest by some, so I am going back to the original concept for an easy to build set of hulls. What has changed between the start and today, is the shape of multihulls has taken a turn from the tall fine entry bows like “A” Class and Formula18 designs to the low bows to reduce crosswind issues when tacking and the new generation America’s Cup boats, the IACC 45’s and of course, once again the leaders in design - the 'A" and “C” Class boats.

Without having to read the entire thread - but you can - the concept is slab side balsa sheet with decks and hull bottoms from shaped foam. Quick, easy and inexpensive for anyone wanting a big multihull, but not wanting to pay for a kit, or glue up strips of balsa. MY idea can certainly be modified for your own design and cross-sections. It’s the concept of 2 sides, and a foam top and bottom.

In photos below, I have added a slab of pink foam to bottom of hull, held in place with tape on temporary basis, and I’ve free-handed the side view of a hull reflecting the wave piercing, reverse bow design. For right now, you can images all three photos placed next to each other to get an idea of the planned general hull profile.

       Bow profile                      Hull midsection                    Stern profile