I have found this forum to be one of the best ‘depositories’ of rc yacht building information I have seen - ever!! Seeing I have gathered alot of information from such sources, I thought would give something back.
A bit of background on me - I have spent many miles onboard some of the best racing yachts Oz has to offer - Skandia Wild Thing, Amazon (before she burnt to the waterine) and Brindabella just to name a few. I LOVE flat, powerful looking strns which belong to boats like the open 60’s, VO70’s and TP 52’s. When I saw the thread on Claudio’s AC33 I knew what I had to do…
ClaudioD has been kind enough to send me a copy of his plans for this boat. I will fit into the Marblehead rules which for me is just a bonus. I have no plans to race it against other boats, but if the opportunity comes up I don’t think it will be slow. So far I have cut out the stations from the plans provided (on 6mm plywood) and mounted them on a board. I was lucky to have part of an old laminex-topped kitchen bench available.
Anyway I will jump on here after each time I complete something on the boat. I plan to have some photos on here once I find a new USB cord for my camers (A Leica DLux-3 if anyone has one lying around!!)
I have started planking. Claudio said that he planked his with 3mm samba (ubeche) but being in Oz I don’t have anything like that available. The best I could find was 2.5mm balsa. I don’t think it will be too much of a prob as I will coat the interior of the hull with epoxy prior to sanding.
I mademy own balsa stripper, and I will post some piccies once the camera is working.
I am quite proud of muself - I have completed 3 planks!!
Here are a few more piccies - one of my soopa doopa balsa stripper. Its made from cedar which I had lying around. I cut a strip off to make a channel, then screwed the cut out bit on the side to hold a ‘break-off’ blade in place. Hey presto!!
Make sure you apply pressure to force the balsa into the channel or you will end up with wiggly planks!!
I thought I would share how I was holding the planks in place where its difficult to get the little handy clamps in (which I got for AU$2 per pack of 6 - what a bargain!!) I use some M20 poly cotton thread which is perfect. The poly/cotton thread is easly held in place by the clamps or a clothes peg.
I did start out glueing the planks along the edge of one another but seeing I will be putting epoxy on the inside i have now thought its a waste of time and glue to keep doing it. I have started the bow section which due to the tight radius of the lines coming into the knuckle I have built it with thicker sections of balsa. I have seen others use a block of balsa then shaped it afterwards - gee I wish I did that!! Oh well, they do say that hindsight is 20/20 vision…
Sorry, but may have misunderstood me - I am using CA glue for the construction then once finished with the planking I will apply epoxy on the inside to stiffen the balsa prior to sanding and filling. I fond that the balsa has trouble twisting and forming around the stations if the edges are glued together. Thanks for the advice Hew, I will probably be found to be eating my words down the track!!
Anyways, I completed building up the forefoot area of the bow last night. I used 6mm square balsa and whittled them into fit. It was actually alot of fun!!
I also put a plank in the middle of the hull. This is how I held the plank on for the glue to set. The poly/cotton thread is strong but the cotton won’t adhere to the CA glue. Also, the furryness of the thread enables it to be held tightly by a hobby clamp (I have really little ones which are perfect) or a big clothes peg.
next I plan to install thinner strips over the curves in the hull - the 9mm wide strips are too think and won’t conform to the tight radii of the tumbleholme.
I have finished the balsa planking. I showed my dad who is a Shipwright and he was impressed (he is usually hard to impress!!). After having a chat to him, the next step will be applying epoxy on the inside of the mold then using sandpaper and epoxy/microballoon filler its faring time!! I have the outlaws here at our place for a week so maybe good to secret myself away in the shed for a while!!
I have been thinking about installing twin rudders. After looking at the pictures of Claudio’s AC33 I dont like the way half the rudder is out of the water. Also, I like the challenge of engineering the twin rudders…
Hindsight time. I should have made more of an effort to continue the planks right to the very bow rather than stop at Fr. 1 and use solid balsa in the forefoot. I now have a concave shape in the bow area. It seems to me minor, and it is symetrical on both sides so I will keep it.
I have now completed planking with balsa, and have coated the interior of the mold with epoxy. Dad the shipwright has given me some epoxy - International Epiglass 9000. I was planning on using West system just because it seems to be the most commonly used, but seeing I can get this for ‘free’* I may as well use it. Even though I am using the ‘fast’ hardener, it still took all night to go off!! But it is starting to get warmer and we will have days between 35-40 deg C for the next few weeks…
*I am sure he will ask me to clean out his workshop or scrape off some barnacles on one of his boats in return!!
I sanded the balsa this morning just to get the high areas down, then I used microballoons and epoxy to fill. Dad has assured me it will sand well - but I am doubting him!! Its not his elbow which is going to get a workout…
I have attached a few piccies of the hull waiting for the filler to cure as well as another one of the planking process.
Well I am glad I followed dad’s advice with using micro balloons and epoxy for faring - it sanded very well and easily but not too soft like the plaster filler I did a test on. The plaster filler sanded too easily so it would have been difficult to get a fair hull.
Hindsight time - Next time I don’t think I will use balsa planking. Its difficult to get a fair hull as the planks still bend even after two coats of epoxy on the inside. I will use some pine or cedar and strip it down to 2 - 2.5mm x 8-9mm planks. Then a belt sander will make short work of fairing.
Next I will apply a glass/epoxy layer to the mold. May be a few days as I am waiting on the glass fibre from a supplier.
hi brad. just wondering why you didn’t use glass before fairing it?
to stop the hollowing of where your joins are, you could have used scarf joints.
btw. just to correct one of your posts what you are describing as tumbleholme is really just the turn of the bilge… not trying to offend you.
I have coated the hull with epoxy and then used microballoons to fill major bumps and hollows. I have been very busy over xmas and new year so nothing has happened as yet this year!! I have just completed some splicing jobs (this is how i am financing my build!) so once I have the cash from them i plan to put a layer of thick (300gm) FG and epoxy then start fine faring.
Oh yes, thanks for the point - I get confused sometimes as tumblehome is the curve at the deck edge! duh!
hmm, just for your further reference. it might have been better to glass it first before you add any filler, as sometimes when you laminate over your filler, you can actually get delaminations (i know this cause i’ve had it happen to me before). i also find it easier to apply filler after glassing it. if you have used epoxy filler, its better to use epoxy resin over it.
what kind of glass are you using? whatever you do don’t use chop strand mat unless it is specifically for epoxy (if your using epoxy resin to laminate).
don’t forget to use peel ply after you’ve glassed (whilst glass is still wet though) this will give you a much better surface (as well as fairer) to sand and put more putty on.
cheers
rob
I finally conned dad into ‘donating’ some glass woven mat to my project!! Its about 100 gm/m2 so its about perfect for what I am doing. I have now applied that to the mould with epoxy. Its not the first time I have used glass/epoxy, but this is the first time I have made a mould!
I have seen others use garbage bags as a peel ply. It was easy to put on and smooth out, alot more so than I thought! Also, I used white plastic which was much easier to see the bubbles underneath.
Well the moment of truth tonight! I peeled the plastic off (which came of very easily) to see a mixed effect. In some places it was very smooth, yet in others there are ‘creases’ where the plastic wasn’t as smooth as it should have been. Next time I will cut the plasic into strips about 10 cm wide. this should stop these creases. Overall I was pretty happy with it.
I have now painted the mould with cheap enamel which will aid as a marker during the wet sanding. I will give this a few days to dry and also allow the epoxy to fully cure.
hi brad.
i know i am probably being too picky about this, but you can’t use a plastic bag as peel pli cause it has the total opposite effect, it will keep all the resin in the job(doesn’t really matter in a mould or a plug) , it will give you a shiny surface which isn’t anywhere near as easy to sand.
peel pli is really used to get rid of the extra resin from the laminate and give you a surface that is really easy to sand. now using a plastic bag was a good idea for getting a smoothish surface but its not going to give you the best surface to easily sand. i hope you allowed a few days for the epoxy to cure a bit before you put the paint on.
btw, i hope you haven’t taken offence to anything i have said.
cheers
rob PS continue with your blog it is great to help other people out when i can.
Brad -
up here in US, one can purchase plastic strips woven of polypropolene and it is used to repair folding lawn chairs. Comes in strips about 2-3 inches wide and maybe 10-12 feet in length. Because it is polypropolene epoxy will not adhere, yet is is porous between the weave which allows excess epoxy out. For lawn chairs, it is applied in a “basket-weave” fashion. I’ve use a few times and it really lets excess epoxy out - but does leave the surface a bit rough. Only really good part is it is so extremely inexpensive. With the width being narrow, if applied across a hull on diagonal it will lay pretty flat and not have “air bumps”. Apply epoxy, apply strips very tightly, and when epoxy cures, you can pull strips loose taking excess epoxy with you. Once applied, you can also slip into and vaccuum bag the entire thing if so inclined.
Thanks for the advice guys - there is no way you could offend me by offering advice!!
I did consider using Peel Ply, but I am seeing how cheaply I can make this boat. So far it has cost me $68.20 AU!! This keeps the household CFO happy too!! I was thinking of using blue ‘polytarp’ cloth which has tiny holes in it, but it would produce a rougher surface = more sanding!
The plastic bag works well for me - I just take extra care in squeezing the epoxy out once the plastic has been applied. This time I cut the strips about 4" wide, then I could squeeze the excess epoxy out on the edge of the strip, pick it up off the hull using the squeegee, then apply the next bit of plastic. It worked well, the finish was smooth and seemed quite even. Claudio (who built the first AC33) weighed his hull at 325 gm - mine came in at 296 gm and I still have to sand! I guess thats a pretty good weight for an M class made from woven glass!!
Quick Q - should the hull be slightly floppy?? It is like I have made it from cardboard, but it seems quite tough. I guess once I put the deck edge strips and transverse beams in it will be tougher!
Tonight I will finish sanding, then start putting the deck edge in and transverse beams. If ANYONE has some advice / tips / criticism / wants to have a go at me - fire away!!
After sanding I found that in some places I had rubbed too much and put a small hole! This being hull no. 1 I am not too concerned and will use it as a ‘learning point’.
Here are a few piccies of the repair. I used some plastic to get a nice smooth finish. It worked well.
Today I put the reinforcing in the key areas. I decided I would reinforce the bow area where the forestay will be placed, a ‘hoop’ where the keel will be, a strip between the keel and the rudder area and finally where the rudder will be put. I am considering having twin rudders. I have been putting alot of thought into how I will engineer the steering gear, even considering having a set up where I can select twin or single rudder depending on conditions (single for light winds, twin for strong winds).
Also, after sanding and putting the reinforcing in / bow frame, the weight went down to 292 grams!! Coolness…
Once I have put this post in I am building a cradle for the boat, then mounting a bird feeder for the ‘boss’. Any suggestions for the order I should do the jobs in?!?
