Building a Cedar Strip Canoe: Sanding and Fiberglassing

Updated on May 27, 2016
jimmar profile image

Jim is a retired software/electrical engineer who enjoys the outdoors. He likes to challenge himself with creative projects at home.

a cup full of used staples
a cup full of used staples

The hull is stripped, the stems are attached and it looks pretty rough. Now begins what seems like a never ending process of sanding. You will want to get the hull, especially the outside, as smooth as possible. It will make laying the fiberglass cloth and applying the epoxy less difficult. Not to mention that it will look nice. Where the strips come together when forming the curve of the hull there will be an edge that needs to be taken down. There will be other places where planks don’t fit together perfectly because of inaccurate milling or twisting as they run the length of the hull. These can leave depressions, ridges, gaps or other imperfections that will have to be corrected or compensated for by sanding, planning, filing patching and more sanding.

Starting with the outside of the hull, the first step is to plane down any obvious ridges or high spots. On this boat I did not use a conventional block plane much. I did have many planks that were slightly higher or lower than the neighboring plank. They need to be taken down to the same level. In the past I used a sharp block plane angled across the grain to shave the strips to the same level. Care must be taken not to create a big gouge in the soft cedar. This time I used a sure form plane. It is more controllable but it can leave more scratches that needed to be sanded out. This got the hull shaped into a rough feeling but fairly continuously curved shape.

Next, any knot holes, gaps, cracks, or gouges should be patched with epoxy resin and hardener thickened with sanding dust to a consistency about that of peanut butter. This patching can be fairly significant. The tiny hairline gaps where planks meet and the staple holes, I did not bother to patch. The epoxy will fill those during the application of fiberglass cloth. Sanding will involve several courses of progressively smaller grit. Using a Random Orbital Sander, I started with 40 grit. This is aggressive but helped with any extra shaping. I then followed this sequence:

ROS sand with 60 grit -

Patch any missed areas with thickened epoxy and allow to harden.

ROS sand again with 60 grit.

ROS sand with 80 grit

Hand sand with 80 grit in rough spots that need touch up

ROS sand with 100 grit

Dampen the hull to raise the wood grain then allow to dry

ROS sand with 120 grit.

After you are satisfied or tired of sanding it will be time to apply the fiberglass and epoxy, then flip the hull and repeat the process all over again on the inside once the epoxy on the outside is hard. There are some specialized homemade tools I used for sanding. To help shape the curve of the hull I made a sanding board of ¼” plywood(paneling) about 6 inches wide and 2 feet long, with a handle attached to each end. On the other side I used rubber cement to glue ½ sheets of 60 grit. Using rubber cement allows the worn sandpaper to be replaced with fresh. The board flexes and bends around the curves in the hull. I also made a large flat sanding block from thicker plywood for the bottom and sides with ½ sheets of sander attached the same way. For the inside curvature of the hull I use some sandpaper discs with an adhesive backing wrapped around a Titebond II glue bottle. The inside is more difficult to sand and consequently I reached the “good enough” point much sooner.

Applying the fiberglass.

I first hung the roll of cloth at one end of the hull on a pipe attached with rope to the ceiling. I then pulled enough cloth from the roll to cover the hull and cut it with scissors. Any wrinkles in the cloth were smoothed out with a soft bristle brush. I use epoxy from US Composites (www.uscomposites.com). It is a medium epoxy resin system with the following characteristics:

  • Mixing Ratio by Volume: 3:1
  • Pot Life: 20-25 Min @ 80F
  • Set Time: 3-4 Hours
  • Drying Time: 8-10 Hours

There are other manufacturers that make epoxy resin like West System, RAKA, MAS, East, System Three and others. I have used US Composites on all three of my boats. I chose it because it was less costly than the other systems and I’d heard of other builders using it. From my experience I found that it is best to apply this epoxy in a warm environment, say 70 F and above. For the outside of the hull I started when the temperature was in the low 60’s but I had an electric heater under the hull and the jugs of epoxy. By the time I finished the second coating the temperature was near 80F. The warm temperatures help the epoxy to flow much better and it is easier to work. I started coating the inside of the hull when the temps were in the 50’s and even though I heated the resin and hardener first, it was difficult. The cloth on the inside ended up with several small bubble like welts. I don’t think there is significant air trapped in the bubbles, mostly hardened resin, the defects are mostly cosmetic. I think if I could have waited till it was warmer, the epoxy would have flowed better through the cloth when it expanded from the heat created during curing and allowed the air to escape.

My 2012 order from U.S. Composites

description
part number
quantitiy
price
units
total
cloth 6 oz E-Glass
FG-C0660
11
$5.95
yard
$65.45
Epoxy with 3:1 Ratio Medium Epoxy Hardener
EPOX-635315
1
$122.00
2GAL, 85 OZ
$122.00
3-1 Ratio Pumps
EPX-P31
1
$6.75
set of 2
$6.75
TOTAL
 
 
 
 
$194.20
Click thumbnail to view full-size

The epoxy is applied in three separate coatings. The first is to wet the cloth and soak into the wood. The second is to fill the weave of the cloth and the third is to bury the cloth. It should be applied in small batches and care must be taken to ensure each batch is mixed properly. Applying resin with no hardener can be disastrous, I know! Each coating should be allow to cure to a tacky feeling but not long enough to be come thoroughly hardened. A few hours is enough, depending on temperature. If you wait too long you will need to sand between coats to create a mechanical bond, as a chemical bond is no longer possible. I applied the first batch about three feet from one end of the boat to anchor the cloth. It was applied with a brush in liberal amounts, alternating from left side to right side or vice versa. It is important not brush with too much pressure trying to force resin into the cloth and to bush from wet side to dry to avoid having the cloth bunch up. Once a small section of cloth was wetted on each side of the hull, I wetted the 3-4 foot section to the end of the boat. The epoxy should then be squeegeed to ensure an even coating and remove any excess resin. The strategy is to allow enough time for the resin to soak in (about 20 minutes) before it is squeegeed. I applied a batch, right side and left, then went back to squeegee the previous application. This worked out to close to 20 minutes. On the initial coating the angle of the squeegee is steep enough so that your thumb is almost dragging on the cloth. Firm pressure should be applied but too much can cause the cloth to pull and bunch up. On the second and third coating I held the squeegee closer to perpendicular. The outside of the hull has 3 coats of epoxy, the inside, two. Once the epoxy is fairly stiff, the extra cloth can be trimmed with a utility knife.


Once you start, be ready for a long day!

Questions & Answers

    Comments

      0 of 8192 characters used
      Post Comment

      • profile image

        John 

        2 weeks ago

        Thanks for the answer. It's back to the ROS for the next few days for me!

      • profile image

        Jim 

        2 weeks ago

        Hi John, I sanded off as much of the excess that I could. Some of it will end up kind of blending in as far as color goes. I did use silica, but not all the time, just where I thought I needed extra toughness.

      • profile image

        John 

        2 weeks ago

        Hi Jim-

        After you did your patching, did you sand off the extra epoxy to clean up the area around the patch? From your pictures it looks like you left some behind, but I can't see any evidence of it in your finished photos. I have just finished up my patching and am now wondering if I made a mistake by being too sloppy with getting excess epoxy on the hull. Also, did you use any silica? I did, and I'm thinking that might also make a difference in how obvious it'll be under the fiberglass. Thanks!!

      • jimmar profile imageAUTHOR

        jimmar 

        6 years ago from Michigan

        Thanks Dan - I'm making a push to get it done by mid-May for a fishing trip in Quetico with my son. I started in Feb. and I'm almost done but I've skipped much of the fine detail just to finish in 3 months.

      • Outbound Dan profile image

        Dan Human 

        6 years ago from Niagara Falls, NY

        Another great Hub in your series and more great pictures of your beautiful boat. Awesome!

      working

      This website uses cookies

      As a user in the EEA, your approval is needed on a few things. To provide a better website experience, skyaboveus.com uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

      For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at: https://skyaboveus.com/privacy-policy#gdpr

      Show Details
      Necessary
      HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
      LoginThis is necessary to sign in to the HubPages Service.
      Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
      AkismetThis is used to detect comment spam. (Privacy Policy)
      HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
      HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
      Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
      CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
      Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the googleapis.com or gstatic.com domains, for performance and efficiency reasons. (Privacy Policy)
      Features
      Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
      Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
      Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
      Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
      Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
      VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
      PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
      Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
      MavenThis supports the Maven widget and search functionality. (Privacy Policy)
      Marketing
      Google AdSenseThis is an ad network. (Privacy Policy)
      Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
      Index ExchangeThis is an ad network. (Privacy Policy)
      SovrnThis is an ad network. (Privacy Policy)
      Facebook AdsThis is an ad network. (Privacy Policy)
      Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
      AppNexusThis is an ad network. (Privacy Policy)
      OpenxThis is an ad network. (Privacy Policy)
      Rubicon ProjectThis is an ad network. (Privacy Policy)
      TripleLiftThis is an ad network. (Privacy Policy)
      Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
      Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
      Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
      Statistics
      Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
      ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
      Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)