TBK

I've begun the construction of a new mini 40 trimaran, following the design plans for the Nightmare MKVII graciously provided to me for free by Ersnt Zemann. There has been a considerable amount of interest again in building rc multihulls and I decided to document the build so that others interested could benefit from my experience (or lack thereof). The hull templates are designed to make a male plug, using foam construction. However I've decided to build the boat using a glass over balsa plank technique, as I am much more familiar with this building method. The first step is to take the templates and "split" them in half so that the bottom half and the top half of the boat will be built separately. Once that is done then the sections are transferred onto a piece of 1/8" masonite and cut out with a scroll saw. Section 0 is cut out of 1/4" balsa and Section 15 has an extra 1/8" balsa piece added so that the planks can be glued directly to them during the build. They will be cut off later when removing the completed hull. Next the pieces are glued to small mounting 2"x2"x1/2" blocks made of maple. Once all the pieces are made then they can be screwed to the building board. I used a 1"x10"x4' piece on melamine shelving for the building board base as it tends to remain flat and is easy to layout the hull spacing. The sections are laid out from Section 0 to 15 on an 80mm spacing. The sections are then screwed to the board making sure to align them vertically and on the center line. Once all the forms are mounted the edges are covered with masking tape to prevent the planks from sticking to the frames as they get glued together. Now you can begin the planking process. You will need to get some 1/8" medium grade balsa sheets at least 48" long. As the only lengths commonly available are 36" I had to scarf a section on to make up the overall 48". This is pretty simple to do- just take one section of 36" sheet, find the center and then cut it in half using a 45 degree angle. Take the other 36" sheet and cut a matching 45 degree angle at one end. Lay both pieces on a flat surface covered in some waxed paper, butt and align the two ends together and the apply some thin CA glue to the joint. The glue will wick into the material bonding both pieces together to form one long sheet. Now you need to strip the sheet into 5/16" strips. I use a little stripping tool made by xacto that holds a standard utility knife. To start the planking take one strip and temporarily pin it in place along the center keeline. This will keep all the frames aligned and ensure that there is no twist or movement on the frame. Now take the first plank and thin CA glue it to the bow frame at the gunwhale, then attach the plank to each susequent frame with a pin until you get to the stern frame. Again glue this plank to the last frame balsa section using thin CA glue. Next add a second plank on top of the first, gluing to the bow section then butting each plank together and applying thin CA glue to the joint. It will wick into the joint and bond immediately. Caution this stuff can glue your skin so be careful. Now repeat the same two planks to the other side. The process gets repeated until the entire frame is covered. As you get to the more curved sections you will need to angle the edges to get the planks to align. This is easy to do with a couple of swipes with a sanding block. The pictures below show the completed building boards and the start of the planking process on the main hull.

bertauy

Very nice start to your build. Looks very meticulous in your process. Good luck, keep us posted.

can you post pictures of how you joined the 2 36" sheets of balsa to cover the 48" length of your build? I am not quite getting from your description how you joined them. I used 2 part foam to fill the space between the sections, but the foam has been contracting over the last few days and distorting the plug for the side hull. I am going to need to build a new plug for the side hull using tried and true balsa planks over sections method.

Yann

TBK

Here are some photos showing the method to make longer planks. Take two 36" sheets and cut one in half with a 45 degree angle and take the other sheet and cut one end with a 45 degree angle. Now take one short piece and CA glue it to the longer piece and you're done. Next take a stripping tool and cut the sheet into strips or planks. As you can see I've now completed the planking of the main hull bottom and it is ready for sanding, fairing and then glassing.

TBK

I have made a little more progress on the build. The main hull bottom is now completed and ready to be glassed. Since I've run out of 2 oz glass, I'm going to begin the planking of the main hull deck and then both pieces will be glassed at the same time.

TBK

Got a chance to get some more progress done on the main hull. Completed planking of the main hull deck. Both hull templates were then sanded and prep'd for glassing.

TBK

Here are the hulls being glassed. I 've used 2 oz cloth, as it drapes very well over just about any shape. I am using epoxy resin as it is much stronger than polyester, shirnks less on curing and has no odour to stink up my shop. Here are photos showing the cloth draped over the hulls before and after the epoxy was added. Once the resin cures I'll sand both hulls lightly to take off any high points, and then trim the excess glass. I'll then appy a topcoat of epoxy resin mixed with a fairing (sanding) filler to finish off the hulls.

TBK

The hulls were sanded and the excess glass was trimmed off. I removed both hulls from the templates and then checked for a mating fit. I put my existing trimaran up against the new hull for a comparision. Similar rocker but obviously more volume. It should be interesting to see how the two boats sail against each other. I put both hulls back onto the templates for a final finish/sanding coat of epoxy mixed with a fairing filler to make it easier to sand. I have decided to use these hulls as male plugs, so I'll be finishing them off with some primer and then get them ready to make some hulls.

TBK

Got some more done on the main hulls plugs. As shown below they are now primed and this will be followed by sanding and final fairing. I used a high quality automotive primer (Dulpi-color)which cures quickly and can be sanded to take out any imperfections in the finish. The plugs will then be prepared for moulding new hulls by applying 4-5 coats of mould release wax, followed by a couple of mist coats of PVA release agent. I plan to make the first set with at least 2 layers of standard 4 oz glass laminated together with a final finish coat of epoxy resin, combined with fairing filler. Once I pull it from the mould I can determine if that combination is strong, yet light enough. If this goes well then I am planning to try to mould another hull in carbon fiber. Given the high cost of this material I wanted to be sure that the process worked first using standard glass. I'm still keeping my option open to use these plugs as one offs for the hulls and that is why they have only one layer of 2 oz cloth on them. This is plenty strong enough to use them as a male plug as long as they remain on the building board with the hull templates acting to prevent deformation during the moulding process. My other trimaran was a glass over balsa one-off build.

martno1fan

They look really good mate but i thought you werent suposed to use matting with epoxy only cloth?.Reason been is that mat has a binder in it to help hold the fibres together and epoxy wont break down the binder so you need to either use poly resins or if you want an epoxy hull then you need to use cloth .You might want to check on that .
Mart

TBK

You are right. You can't use glass matt with epoxy. I am only using woven cloth.

TBK

martno1fan

Sory i took it you meant mat when you said standard glass my mistake,a tip for you google is a great tool for finding out about people especially boat designers [X(].
Mart

Idealist

I think TBK knows what and why he does it - the way he is doing it! - Keep on rocking, TBK!

TBK

Thanks Idealist. Although I consider myself a pretty competent builder I'm always on the lookout for new or easier ways to do things. I hope to cast the first hull off the main hull deck plug tonight. The plug has been prepared with the release wax and PVA. The main hull bottom plug still needed some extra preparation to get it "true" so it still needs to be prepared before I can cast off it. I will use the first cast to determine if I have the right weight cloth, number of layers etc to get a strong yet light result. Most guys are finding that two layers of 4 oz cloth , when used with epoxy resin can yield a good result. I'll have to try it and see. If it isn't strong enough I can always add another layer of either 2oz or 4oz cloth afterwards. I'll post more photos of this when I'm done.

TBK

TBK

Oop's I seem to have hit the post button twice in my reply to Idealist. Stay tuned more photos on this build to come through shortly.

TBK

TBK

More progress photos. The main hull deck plug has been finished and readied for moulding. Notice the blue color which is the PVA coating. The other photos show the first hull being laidup over the plug. I have used 2 layers of 4 oz glass and epoxy resin. When it cures I will pull it from the plug and evaluate it's overall strength vs weight. If it seems to be acceptable I will add a finish coat of epoxy mixed with fairing filler, to cover the weave.

TBK

I pulled the first main hull deck off the mould. With 2 layers of 4 oz cloth and epoxy resin it seemed a bit flimsy so I put it back on the plug and added another layer of 4 oz cloth. That ceratinly made it more solid but it also increased the overall weight. I'm going to try a different combination using 2 layers of 4 oz cloth followed by a layer of 2 oz cloth to see if I can lower the weight without giving up some strength. Since the plug produced a fairly good quality product I will also try to a mould a hull using carbon fiber weave cloth. Photos below show the completed hull with 3 - 4 oz layers of cloth.

tommyeflight89

Work looks great so far. I just got my copy of plans from Ernst and have been looking all over for trimaran info.
I thought you were going to use your plug to make a female mould, but I see you have used a male mould.
How will you be finishing the outer surface of the hulls? Was it difficult to get the cloth to drape on your plug?
Although each half may be a little flimsy, I am sure once you add some bulkheads and epoxy them together, you will have a stiff hull.
I am enjoying your progress so far!
Edit: One more thing. I see you have used high quality automotive paint. Where is the available to you and how do you apply it? Does it need a catalyst etc? I live in London Ont and need a source of some good primer... Do autobody shops sell it by the quart?

TBK

tommyeflight89

Thanks. I really wasn't intending on making a mould at all, so I laid up the hull for a glass over balsa construction, that is why the male plug is only finished with one thin 2oz cloth coat and epoxy. 2 oz or 4oz cloth will drape readily and will "wet" out without any trouble at all. As you get into heavier material this becomes more problematic. I decided to try using it as a male plug to see if I could make an all glass hull that was strong but lighter than the glass covered balsa. My first attempt did make a strong hull but it weighs more than the glass/balsa version. I am going to try again with a different combination of cloth to see if I can lighten it a bit. The advantage of the glass/balsa is it's light weight and it's overall stiffness and strength, primarily due to the balsa core. I am also going to try a hull in carbon fiber to see how that compares. Ultimately I may end up just using the glass/balsa plugs as the final hulls. I'll wait to see how the next few turn out. Making a female mould is relatively time consuming and probably not warranted unless you plan on making a lot of hulls (more than 5 or so). To finish the outer surface of the hull I cover the cloth with a thin layer of epoxy mixed with fairing filler. That gets sanded smooth with progressively finer sandpaper until the finish is smooth. I use a little bondo filler where needed to address any small gaps. Then it's primed painted and sealed with a clear coat. Finally the finish is wet sanded and then buffed and sealed with an automotive polymer sealer. As far as the paint goes you can get it at the automotive paint section of your local Canadian Tire. You can get the primer and colors in either spray cans or quart cans which you can either spray or brush on. They are predominantly acyrilc laquers that don't need any catalsyts and be thinned to spray readily. I typically brush on the primer in several thin coats and then sand it smooth. I usually spray the color and clear coats so that I can get that mirror finish. I will document these steps as part of the build log. Good luck with your build. Keep us posted on your progress.

Idealist

Sorry for the double posting, but this makes things much easier for this ongoing project!

The name of the original topic is: "RC-Multihulls?"
_________________________________________
Quote:
"I can see the same basic (building technique) questions are asked again and again -
here in this topic most of them have allready been answered by me -
and also explained with lots of pics! - The FAQs, so to say.

As it is very long - which lots of unspecific stuff in between - look out for the "IDEALIST" -
especially pages 2,5,9,11,14! -

I hope this helps."
________________________________________


I also did all my hulls shells outside over male plugs.
For the "carbon copy" I allways used peel ply (about 80gr.) as the first layer over the plug, then two layers of 160 gr. carbon (linen - not twill) - and then one more layer of peel ply (about 80gr.)!

The problem I solved with this technique was the thickness of carbon, as it got a lower specific weight than glass and is therefore thicker than glass for a given weight (160gr./m2). Also the single strains of the cloth are thicker - and it needs more epoxy resin.
The INNER layer of peel ply saves you from all the sanding you would have to do to glue anything on the inside of the shells. -
And the OUTER layer of peel ply presses the two layers of carbon together and also flattens the surface of the cloth! -
It also sucks any excess resin away from the shell - and you don´t need a vacuum pump system at all.
There is one more advantage of this system:
Once the shells are cured and you remove the outer peel ply WITHOUT removing it from the male plug,
you can sand it directly there - as it is - giving you a strong basis that won`t bend or slide around - and best of all, you just need to sand down the "cloth structure" of the peel ply, which is pressed into the hardened resin. -
When you start sanding, it really makes kind of a "screaming" sound due to this cloth structure - when it doesn`t "scream" anymore, you´re done with rough sanding.
I´m using grain 40 for this - then grain 80 and then 120 - then I remove the shell from the plug and remove the inner layer of peel ply.

tommyeflight89

Thanks for answering my questions guys. My build won't be starting until May, but I will be following this thread.

I have read about the "German Rubber Method" for moulding with male plugs, sailboat hulls specifically.
You do your normal layup, and instead of leaving it to cure, you stretch latex sheet over the outer surface of your layup + plug. This gets pulle tight and stapled to the plug board. After curing the latex sheet comes right off and you are left with a nice smooth surface on the outside.. not much sanding! It also insures that the cloth is tight against the plug surface while it cures.
As for the latex sheet, I tried a google search.. and came up with a bunch of latex fetish stuff.. lol.
My best idea on where to get it is some Yoga store etc. They sell it in large strips to use as resistance in 'exercising'. It is usually brightly coloured. One strip would be enough for each hull half, considering it is very stretchy.

http://ghmyc.org/German_Rubber_Method.html

TBK

Interesting concept. If you go onto the RG65 build forum you will see the use of ureathane rubber moulding materials called Pour-A-Mould. Basically you paint a layer or two of this stuff onto your finished plug, then cover it with a few additional layers of a hardening mixture and voila you get a perfect female mould. There is a supplier for this stuff in Ontario, in Mississauga if I not mistaken. I gave it some thought but it would require a lot more effort to prepare the plug.

TBK

Well I've done a couple of hulls now with different cloth weights. The two finished hull decks shown are different combos - one is 3 layers of 4oz cloth and the other is 2 layers of 4 oz cloth and one layer of 2 oz cloth. The difference between them is about 50 grams and they are both strong/stiff enough although the 3- 4oz layer one is a little more rigid. I decided to go with the 2- 4oz layer version. I also tried just 2- 4oz layers but determined it wasn't adequate. You can also see the first hull being moulded of the main hull bottom with the layups on the plug. I have also started my first carbon hull using one layer of 6 oz carbon fiber twill and one layer of 2 oz cloth over top. You can see it below on the plug. I look forward to getting it off the plug tommorow to see how strong/light it is compared to the two others. Hopefully that will be the right combo and then I will use it to make the matching carbon main hull bottom.

Idealist

Three times AWESOME!!! - Keep on rocking TBK!

Just for me and all other readers, who are not so familiar with american weight systems:
Would you please give us the relation beween oz and grams?
Is 2oz. glass about the same as 80grams?
And much more important - How "heavy" is the 6oz. cabon in grams?

Shellweights?

TBK

Our fiberglass cloth weights are given in oz/sq yd. I believe that in Europe that measure is in grams/sq metre. One could do the conversion where 1oz = 31.1grams and 1sq yd = .08361sq m and the 2oz cloth is about 75g/sq m equivalent. Similarly the 6oz carbon would be about 225g/sq m equivalent The real measurements however are the overall shell weights, as that will ultimately determine the overall weight of the finished boat. Once I pull the carbon hull off the mould I will put all three on a scale and give you the weights of each. I will also include the weight of the glass-over-balsa shell that I used as a plug, since it could also be used to finish the boat as it was made very light with 3mm or 1/8" balsa planks, 1 layer of 2oz cloth and 1 thin finishing resin/fairing filler layer.

TBK

TBK

Here are the weights.

Main Hull Decks
1) Layup with 3 -4oz cloth layers + one finsh resin coat was 260g or 9oz
2) Layup with 2 -4oz and 1 -2oz cloth layers + one finish resin coat was 240g or 8.5oz
3) Layup with 1 - 6oz carbon fiber twill and 1 -2oz cloth +one finish resin coat was 190g or 6.75oz
4) Original 1/8' thick balsa planked hull with 1 -2oz cloth layer + one external finish resin coat (not internal yet) was 190g or 6.75oz

As you can see the glass over balsa hull is the same weight as the carbon fiber hull and it is noticeably stiffer

Main Hull Bottom
1) Layup with 2 -4oz and 1-2oz coth layers + one finish resin coat was 325g or 11oz
2) Original 1/8" thick balsa planked hull with 1 -2oz colth layer + one external finish resin coat (not internal yet) was 250g or 9oz

I will be moulding a carbon fiber main hull bottom next to see how it compares with the glass over balsa hull.

I am also starting to assemble the float hull templates onto their building boards so that I can begin planking those as well.